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Encyclopedia > Immune system
A scanning electron microscope image of a single neutrophil (yellow), engulfing anthrax bacteria (orange).
A scanning electron microscope image of a single neutrophil (yellow), engulfing anthrax bacteria (orange).

An immune system is a collection of mechanisms within an organism that protects against infection by identifying and killing pathogens and tumor cells. It detects a wide variety of pathogens, such as viruses and parasitic worms and distinguishes them from the organism's normal cells and tissues. Detection is complicated as pathogens adapt and evolve new ways to successfully infect the host organism. Image File history File links Size of this preview: 575 × 600 pixel Image in higher resolution (2304 × 2403 pixel, file size: 2. ... Image File history File links Size of this preview: 575 × 600 pixel Image in higher resolution (2304 × 2403 pixel, file size: 2. ... SEM Cambridge S150 at Geological Institute, University Kiel, 1980 SEM opened sample chamber The scanning electron microscope (SEM) is a type of electron microscope capable of producing high-resolution images of a sample surface. ... Neutrophil granulocytes (commonly referred to as neutrophils) are a class of white blood cells and are part of the immune system. ... “Life on Earth” redirects here. ... An infection is the detrimental colonization of a host organism by a foreign species. ... A pathogen or infectious agent is a biological agent that causes disease or illness to its host. ... Tumor or tumour literally means swelling, and is sometimes still used with that meaning. ... This article is about biological infectious particles. ... This article or section does not cite any references or sources. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the... Biological tissue is a collection of interconnected cells that perform a similar function within an organism. ... This article is about evolution in biology. ...


To survive this challenge, several mechanisms have evolved that recognize and neutralize pathogens. Even simple unicellular organisms such as bacteria possess enzyme systems that protect against viral infections. Other basic immune mechanisms evolved in ancient eukaryotes and remain in their modern descendants, such as plants, fish, reptiles, and insects. These mechanisms include antimicrobial peptides called defensins, pattern recognition receptors, and the complement system. More sophisticated mechanisms, however, developed relatively recently, with the evolution of vertebrates.[1] The immune systems of vertebrates such as humans consist of many types of proteins, cells, organs, and tissues, which interact in an elaborate and dynamic network. As part of this more complex immune response, the vertebrate system adapts over time to recognize particular pathogens more efficiently. The adaptation process creates immunological memories and allows even more effective protection during future encounters with these pathogens. This process of acquired immunity is the basis of vaccination. A cluster of Escherichia coli bacteria magnified 10,000 times. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... A bacteriophage (from bacteria and Greek phagein, to eat) is a virus that infects bacteria. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... For other uses, see Plant (disambiguation). ... For other uses, see Fish (disambiguation). ... Subclasses Anapsida Diapsida Synonyms Reptilia Laurenti, 1768 Reptiles are tetrapods and amniotes, animals whose embryos are surrounded by an amniotic membrane, and members of the class Sauropsida. ... Orders Subclass Apterygota Archaeognatha (bristletails) Thysanura (silverfish) Subclass Pterygota Infraclass Paleoptera (Probably paraphyletic) Ephemeroptera (mayflies) Odonata (dragonflies and damselflies) Infraclass Neoptera Superorder Exopterygota Grylloblattodea (ice-crawlers) Mantophasmatodea (gladiators) Plecoptera (stoneflies) Embioptera (webspinners) Zoraptera (angel insects) Dermaptera (earwigs) Orthoptera (grasshoppers, etc) Phasmatodea (stick insects) Blattodea (cockroaches) Isoptera (termites) Mantodea (mantids) Psocoptera... Antimicrobial peptides (also called host defence peptides) are an evolutionarily conserved component of the innate immune response and are found among all classes of life. ... Defensins are small (30-35 residue) cysteine rich cationic proteins found in vertebrate phagocytes (notably the azurophil granules of neutrophils) and active against bacteria, fungi and enveloped viruses. ... Pattern recognition receptors, or PRRs, are a class of cell surface receptors which are employed by the cells of the immune system to identify foreign (disease-associated) biomolecules in the body. ... A complement protein attacking an invader. ... This article does not cite any references or sources. ... This article is about modern humans. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... In biology, an organ is a group of tissues which perform some function. ... Immunity is a medical term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. ... The immune system is the collection of organs and tissues involved in the adaptive defense of a body against foreign biological material. ... A vial of the vaccine against influenza. ...


Disorders in the immune system can cause disease. Immunodeficiency diseases occur when the immune system is less active than normal, resulting in recurring and life-threatening infections. Immunodeficiency can either be the result of a genetic disease, such as severe combined immunodeficiency, or be produced by pharmaceuticals or an infection, such as the acquired immune deficiency syndrome (AIDS) that is caused by the retrovirus HIV. In contrast, autoimmune diseases result from a hyperactive immune system attacking normal tissues as if they were foreign organisms. Common autoimmune diseases include rheumatoid arthritis, diabetes mellitus type 1 and lupus erythematosus. These critical roles of immunology in health and disease are areas of intense scientific study. In medicine, immune deficiency (or immunodeficiency) is a state where the immune system is incapable of defending the organism from infectious disease. ... A genetic disorder, or genetic disease is a disease caused, at least in part, by the genes of the person with the disease. ... Severe combined immunodeficiency, or SCID, is a genetic disorder in which both arms (B cells and T cells) of the adaptive immune system are crippled, due to a defect in one of several possible genes. ... Acquired Immune Deficiency Syndrome or acquired immunodeficiency syndrome (AIDS or Aids) is a collection of symptoms and infections resulting from the specific damage to the immune system caused by the human immunodeficiency virus (HIV). ... Genera Alpharetrovirus Betaretrovirus Gammaretrovirus Deltaretrovirus Epsilonretrovirus Lentivirus Spumavirus A retrovirus is any virus belonging to the viral family Retroviridae. ... Species Human immunodeficiency virus 1 Human immunodeficiency virus 2 Human immunodeficiency virus (HIV) is a retrovirus that causes acquired immunodeficiency syndrome (AIDS, a condition in humans in which the immune system begins to fail, leading to life-threatening opportunistic infections). ... Autoimmunity is the failure of an organism to recognize its own constituent parts (down to the sub-molecular levels) as self, which results in an immune response against its own cells and tissues. ... Rheumatoid arthritis (RA) is traditionally considered a chronic, inflammatory autoimmune disorder that causes the immune system to attack the joints. ... Diabetes mellitus type 1 (Type 1 diabetes, Type I diabetes, T1D, IDDM) is a form of diabetes mellitus. ... Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. ...

Contents

Layered defense in immunity

The immune system protects organisms from infection with layered defenses of increasing specificity. Most simply, physical barriers prevent pathogens such as bacteria and viruses from entering the body. If a pathogen breaches these barriers, the innate immune system provides an immediate, but non-specific response. Innate immune systems are found in all plants and animals.[2] However, if pathogens successfully evade the innate response, vertebrates possess a third layer of protection, the adaptive immune system. Here, the immune system adapts its response during an infection to improve its recognition of the pathogen. This improved response is then retained after the pathogen has been eliminated, in the form of an immunological memory, and allows the adaptive immune system to mount faster and stronger attacks each time this pathogen is encountered.[3] An infection is the detrimental colonization of a host organism by a foreign species. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... This article is about biological infectious particles. ... The innate immune system comprises the cells and mechanisms that defend the host from infection by other organisms, in a non-specific manner. ... For other uses, see Plant (disambiguation). ... For other uses, see Animal (disambiguation). ... The immune system is the collection of organs and tissues involved in the adaptive defense of a body against foreign biological material. ... Immunity is medical term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. ...

Components of the immune system
Innate immune system Adaptive immune system
Response is non-specific Pathogen and antigen specific response
Exposure leads to immediate maximal response Lag time between exposure and maximal response
Cell-mediated and humoral components Cell-mediated and humoral components
No immunological memory Exposure leads to immunological memory
Found in nearly all forms of life Found only in jawed vertebrates

Both innate and adaptive immunity depend on the ability of the immune system to distinguish between self and non-self molecules. In immunology, self molecules are those components of an organism's body that can be distinguished from foreign substances by the immune system.[4] Conversely, non-self molecules are those recognized as foreign molecules. One class of non-self molecules are called antigens (short for antibody generators) and are defined as substances that bind to specific immune receptors and elicit an immune response.[5] This article does not cite any references or sources. ... Cell-mediated immunity is an immune response that does not involve antibodies but rather involves the activation of macrophages and NK-cells, the production of antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen. ... Humoral immunity is mediated by secreted antibodies, produced in cells of the B lymphocyte lineage (B cell). ... Cell-mediated immunity is an immune response that does not involve antibodies but rather involves the activation of macrophages and NK-cells, the production of antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen. ... Humoral immunity is mediated by secreted antibodies, produced in cells of the B lymphocyte lineage (B cell). ... Classes Placodermi Chondrichthyes Acanthodii Osteichthyes Gnathostomata is the group of vertebrates with jaws. ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. ... This article does not cite any references or sources. ... A immune receptor (or immunologic receptor) is a receptor, usually on a cell membrane, which binds to a substance (for example, a cytokine) and causes a response in the immune system. ...


Surface barriers

Several barriers protect organisms from infection, including mechanical, chemical and biological barriers. The waxy cuticle of many leaves, the exoskeleton of insects, the shells and membranes of externally deposited eggs, and skin are examples of the mechanical barriers that are the first line of defense against infection.[5] However, as organisms cannot be completely sealed against their environments, other systems act to protect body openings such as the lungs, intestines, and the genitourinary tract. In the lungs, coughing and sneezing mechanically eject pathogens and other irritants from the respiratory tract. The flushing action of tears and urine also mechanically expels pathogens, while mucus secreted by the respiratory and gastrointestinal tract serves to trap and entangle microorganisms.[6] Plant cuticles are a protective waxy covering produced only by the epidermal cells (Kolattukudy, 1996) of leaves, young shoots and all other aerial plant organs. ... Look up foliage in Wiktionary, the free dictionary. ... An exoskeleton is an external anatomical feature that supports and protects an animals body, in contrast to the internal endoskeleton of, for example, a human. ... Orders Subclass Apterygota Archaeognatha (bristletails) Thysanura (silverfish) Subclass Pterygota Infraclass Paleoptera (Probably paraphyletic) Ephemeroptera (mayflies) Odonata (dragonflies and damselflies) Infraclass Neoptera Superorder Exopterygota Grylloblattodea (ice-crawlers) Mantophasmatodea (gladiators) Plecoptera (stoneflies) Embioptera (webspinners) Zoraptera (angel insects) Dermaptera (earwigs) Orthoptera (grasshoppers, etc) Phasmatodea (stick insects) Blattodea (cockroaches) Isoptera (termites) Mantodea (mantids) Psocoptera... The term eggshell is a term for the outer covering of a hard-shelled egg, and some forms of eggs with soft outer coats. ... In most birds and reptiles, an egg (Latin ovum) is the zygote, resulting from fertilization of the ovum. ... Beyond overall skin structure, refer below to: See-also. ... Human respiratory system The lungs flank the heart and great vessels in the chest cavity. ... In anatomy, the intestine is the segment of the alimentary canal extending from the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine (or colon). ... In anatomy, the genitourinary system is the organ system of all the reproductive organs and the urinary system. ... This article does not cite any references or sources. ... This article or section is not written in the formal tone expected of an encyclopedia article. ... In humans the respiratory tract is the part of the anatomy that has to do with the process of respiration or breathing. ... The tear system. ... This article or section is in need of attention from an expert on the subject. ... Mucus is a slippery secretion of the lining of various membranes in the body (mucous membranes). ... Upper and Lower gastrointestinal tract The gastrointestinal tract (GI tract), also called the digestive tract, or the alimentary canal, is the system of organs within multicellular animals that takes in food, digests it to extract energy and nutrients, and expels the remaining waste. ... A cluster of Escherichia coli bacteria magnified 10,000 times. ...


Chemical barriers also protect against infection. The skin and respiratory tract secrete antimicrobial peptides such as the β-defensins.[7] Enzymes such as lysozyme and phospholipase A in saliva, tears, and breast milk are also antibacterials.[8][9] Vaginal secretions serve as a chemical barrier following menarche, when they become slightly acidic, while semen contains defensins and zinc to kill pathogens.[10][11] In the stomach, gastric acid and proteases serve as powerful chemical defenses against ingested pathogens. Antimicrobial peptides (also called host defence peptides) are an evolutionarily conserved component of the innate immune response and are found among all classes of life. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... Lysozyme single crystal. ... Phospholipases A2 (PLA2s) (PDB 1CJY, EC 3. ... Saliva is the watery and usually frothy substance produced in the mouths of humans and some animals. ... It has been suggested that the section Benefits for the infant from the article Breastfeeding be merged into this article or section. ... An antiseptic solution of Povidone-iodine applied to an abrasion Antiseptics (Greek αντί, against, and σηπτικός, putrefactive) are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction. ... The vagina, (from Latin, literally sheath or scabbard ) is the tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. ... Menarche (IPA: ) is the first menstrual period, or first menstrual bleeding in the females of human beings. ... Acidity redirects here. ... Horse semen being collected for breeding purposes. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Standard atomic weight 65. ... In anatomy, the stomach is a bean-shaped hollow muscular organ of the gastrointestinal tract involved in the second phase of digestion, following mastication. ... Gastric acid is, together with several enzymes and the intrinsic factor, one of the main secretions of the stomach. ... Proteases (proteinases, peptidases, or proteolytic enzymes) are enzymes that break peptide bonds between amino acids of proteins. ...


Within the genitourinary and gastrointestinal tracts, commensal flora serve as biological barriers by competing with pathogenic bacteria for food and space and, in some cases, by changing the conditions in their environment, such as pH or available iron.[12] This reduces the probability that pathogens will be able to reach sufficient numbers to cause illness. However, since most antibiotics non-specifically target bacteria and do not affect fungi, oral antibiotics can lead to an “overgrowth” of fungi and cause conditions such as a vaginal candidiasis (yeast infection).[13] There is good evidence that re-introduction of probiotic flora, such as pure cultures of the lactobacilli normally found in yoghurt, helps restore a healthy balance of microbial populations in intestinal infections in children and encouraging preliminary data in studies on bacterial gastroenteritis, inflammatory bowel diseases, urinary tract infection and post-surgical infections.[14][15][16] Commensalism is an interaction between two living organisms, where one organism benefits and the other is neither harmed nor helped. ... Escherichia coli, one of the many species of bacteria present in the human gut. ... The correct title of this article is . ... Staphylococcus aureus - Antibiotics test plate. ... Subkingdom/Phyla Chytridiomycota Blastocladiomycota Neocallimastigomycota Glomeromycota Zygomycota Dikarya (inc. ... Candidiasis, commonly called yeast infection or thrush, is a fungal infection of any of the Candida species, of which Candida albicans is probably the most common. ... Probiotics are dietary supplements containing potentially beneficial bacteria or yeast, with lactic acid bacteria (LAB) as the most common microbes used. ... Species L. acidophilus L. brevis L. delbrueckii subsp. ... Yoghurt or yogurt, less commonly yoghourt or yogourt (see spelling below), is a dairy product produced by bacterial fermentation of milk. ... Bacterial gastroenteritis is an inflammation of the stomach and intestines caused by bacteria or bacterial toxins. ... In medicine, inflammatory bowel disease (IBD) is a group of inflammatory conditions of the large intestine and, in some cases, the small intestine. ... A urinary tract infection (UTI) is a bacterial infection that affects any part of the urinary tract. ...


Innate immunity

For more details on this topic, see Innate immune system.

Microorganisms that successfully enter an organism will encounter the cells and mechanisms of the innate immune system. Innate immune defenses are non-specific, meaning these systems recognize and respond to pathogens in a generic way.[5] This system does not confer long-lasting immunity against a pathogen. The innate immune system is the dominant system of host defense in most organisms.[2] The innate immune system comprises the cells and mechanisms that defend the host from infection by other organisms, in a non-specific manner. ... Immunity is a medical term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. ...


Humoral and chemical barriers

Inflammation

For more details on this topic, see Inflammation.

Inflammation is one of the first responses of the immune system to infection.[17] The symptoms of inflammation are redness and swelling, which are caused by increased blood flow into a tissue. Inflammation is produced by eicosanoids and cytokines, which are released by injured or infected cells. Eicosanoids include prostaglandins that produce fever and the dilation of blood vessels associated with inflammation, and leukotrienes that attract certain white blood cells (leukocytes).[18][19] Common cytokines include interleukins that are responsible for communication between white blood cells; chemokines that promote chemotaxis; and interferons that have anti-viral effects, such as shutting down protein synthesis in the host cell.[20] Growth factors and cytotoxic factors may also be released. These cytokines and other chemicals recruit immune cells to the site of infection and promote healing of any damaged tissue following the removal of pathogens.[21] An abscess on the skin, showing the redness and swelling characteristic of inflammation. ... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... In biochemistry, eicosanoids are a class of oxygenated hydrophobic molecules that largely function as autocrine and paracrine mediators. ... Cytokines are a group of proteins and peptides that are used in organisms as signaling compounds. ... Chemical structure of prostaglandin E1 (PGE1). ... This article needs additional references or sources for verification. ... Vasodilation is where blood vessels in the body become wider following the relaxation of the smooth muscle in the vessel wall. ... Leukotrienes are autocrine and paracrine eicosanoid lipid mediators derived from arachidonic acid by 5-lipoxygenase. ... “White Blood Cells” redirects here. ... Interleukins are a group of cytokines that were first seen to be expressed by white blood cells (leukocytes, hence the -leukin) as a means of communication (inter-). The name is sort of a relic though; it has since been found that interleukins are produced by a wide variety of bodily... Chemokines are a family of pro-inflammatory activation-inducible cytokines, or small protein signals secreted by cells. ... Chemotaxis is a kind of taxis, in which bodily cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. ... Interferons (IFNs) are natural proteins produced by the cells of the immune system of most vertebrates in response to challenges by foreign agents such as viruses, bacteria, parasites and tumor cells. ... An overview of protein synthesis. ... Growth factor is a protein that acts as a signaling molecule between cells (like cytokines and hormones) that attaches to specific receptors on the surface of a target cell and promotes differentiation and maturation of these cells. ...


Complement system

For more details on this topic, see Complement system.

The complement system is a biochemical cascade that attacks the surfaces of foreign cells. It contains over 20 different proteins and is named for its ability to “complement” the killing of pathogens by antibodies. Complement is the major humoral component of the innate immune response.[22][23] Many species have complement systems, including non-mammals like plants, fish, and some invertebrates.[24] A complement protein attacking an invader. ... A Biochemical Cascade is a series of chemical reactions in which the products of one reaction are consumed in the next reaction. ... Each antibody binds to a specific antigen; an interaction similar to a lock and key. ... Humoral immunity is the aspect of immunity that is mediated by secreted antibodies, produced in the cells of the B lymphocyte lineage (B cell). ... Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria Mammals (class Mammalia) are warm-blooded, vertebrate animals characterized by the production of milk in female mammary glands and by the presence of: hair, three middle ear bones used in hearing, and a neocortex region in... Invertebrate is an English word that describes any animal without a spinal column. ...


In humans, this response is activated by complement binding to antibodies that have attached to these microbes or the binding of complement proteins to carbohydrates on the surfaces of microbes. This recognition signal triggers a rapid killing response.[25] The speed of the response is a result of signal amplification that occurs following sequential proteolytic activation of complement molecules, which are also proteases. After complement proteins initially bind to the microbe, they activate their protease activity, which in turn activates other complement proteases, and so on. This produces a catalytic cascade that amplifies the initial signal by controlled positive feedback.[26] The cascade results in the production of peptides that attract immune cells, increase vascular permeability, and opsonize (coat) the surface of a pathogen, marking it for destruction. This deposition of complement can also kill cells directly by disrupting their plasma membrane.[22] Lactose is a disaccharide found in milk. ... A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). ... Cell signaling is part of a complex system of communication that governs basic cellular activities and coordinates cell actions. ... Proteolysis is the directed degradation (digestion) of proteins by cellular enzymes called proteases or by intramolecular digestion. ... Proteases (proteinases, peptidases, or proteolytic enzymes) are enzymes that break peptide bonds between amino acids of proteins. ... In chemistry and biology, catalysis is the acceleration (increase in rate) of a chemical reaction by means of a substance, called a catalyst, that is itself not consumed by the overall reaction. ... Positive feedback is a feedback system in which the system responds to the perturbation in the same direction as the perturbation (It is sometimes referred to as cumulative causation). ... Vascular permeability characterizes the capacity of a blood vessel wall to pass through small molecules (ions, water, nutrients) or even whole cells (lymphocytes on their way to the site of inflammation). ... An opsonin is any molecule that acts as a binding enhancer for the process of phagocytosis, for example, by coating the negatively-charged molecules on the membrane. ... The cell membrane (also called the plasma membrane, plasmalemma or phospholipid bilayer) is a semipermeable lipid bilayer common to all living cells. ...


Cellular barriers of the innate system

A scanning electron microscope image of normal circulating human blood. One can see red blood cells, several knobby white blood cells including lymphocytes, a monocyte, a neutrophil, and many small disc-shaped platelets.
A scanning electron microscope image of normal circulating human blood. One can see red blood cells, several knobby white blood cells including lymphocytes, a monocyte, a neutrophil, and many small disc-shaped platelets.

Leukocytes (white blood cells) act like independent, single-celled organisms and are the second arm of the innate immune system.[5] The innate leukocytes include the phagocytes (macrophages, neutrophils, and dendritic cells), mast cells, eosinophils, basophils, and natural killer cells. These cells identify and eliminate pathogens, either by attacking larger pathogens through contact or by engulfing and then killing microorganisms.[24] Innate cells are also important mediators in the activation of the adaptive immune system.[3] Image File history File links Download high-resolution version (1800x2239, 1365 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system Scanning electron microscope White blood cell Platelet Neutrophil granulocyte Lymphocyte Monocyte ... Image File history File links Download high-resolution version (1800x2239, 1365 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system Scanning electron microscope White blood cell Platelet Neutrophil granulocyte Lymphocyte Monocyte ... SEM Cambridge S150 at Geological Institute, University Kiel, 1980 SEM opened sample chamber The scanning electron microscope (SEM) is a type of electron microscope capable of producing high-resolution images of a sample surface. ... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... Human red blood cells Red blood cells are the most common type of blood cell and the vertebrate bodys principal means of delivering oxygen from the lungs or gills to body tissues via the blood. ... A scanning electron microscope (SEM) image of a single human lymphocyte. ... Monocyte A monocyte is a leukocyte, part of the human bodys immune system that protect against blood-borne pathogens and move quickly to sites of infection in the tissues. ... Neutrophil granulocytes (commonly referred to as neutrophils) are a class of white blood cells and are part of the immune system. ... A 250 ml bag of newly collected platelets. ... “White Blood Cells” redirects here. ... A phagocyte is a cell that ingests and destroys foreign matter such as microorganisms or debris via a process known as phagocytosis. ... A macrophage of a mouse stretching its arms to engulf two particles, possibly pathogens Macrophages (Greek: big eaters, makros = long, phagein = eat) are white blood cells, more specifically phagocytes, acting in the nonspecific defense as well as the specific defense system of vertebrate animals. ... This article does not cite any references or sources. ... Dendritic cells (DC) are immune cells and form part of the mammal immune system. ... Mast cells A mast cell (or mastocyte) is a resident cell of areolar connective tissue (loose connective tissue) that contains many granules rich in histamine and heparin. ... Image of an eosinophil Eosinophil granulocytes, commonly referred to as eosinophils (or less commonly as acidophils), are white blood cells of the immune system that are responsible for combating infection by parasites in vertebrates. ... This article or section does not cite its references or sources. ... Natural NK cells are cytotoxic; small granules in their cytoplasm contain special proteins such as perforin and proteases known as granzymes. ... The immune system is the collection of organs and tissues involved in the adaptive defense of a body against foreign biological material. ...


Phagocytosis is an important feature of cellular innate immunity performed by cells called 'phagocytes' that engulf, or eat, pathogens or particles. Phagocytes generally patrol the body searching for pathogens, but can be called to specific locations by cytokines.[5] Once a pathogen has been engulfed by a phagocyte, it becomes trapped in an intracellular vesicle called a phagosome, which subsequently fuses with another vesicle called a lysosome to form a phagolysosome. The pathogen is killed by the activity of digestive enzymes or following a respiratory burst that releases free radicals into the phagolysosome.[27][28] Phagocytosis evolved as a means of acquiring nutrients, but this role was extended in phagocytes to include engulfment of pathogens as a defense mechanism.[29] Phagocytosis probably represents the oldest form of host defense, as phagocytes have been identified in both vertebrate and invertebrate animals.[30] Steps of a macrophage ingesting a pathogen: a. ... A phagocyte is a cell that ingests and destroys foreign matter such as microorganisms or debris via a process known as phagocytosis. ... Cytokines are a group of proteins and peptides that are used in organisms as signaling compounds. ... This article or section is in need of attention from an expert on the subject. ... In cell biology, a vacuole formed around a particle absorbed by phagocytosis. ... Organelles. ... A phagolysosome is a membrane-bound organelle which is formed from the fusing of a lysosome and a phagosome. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... Respiratory burst is the rapid release of reactive oxygen species (superoxide radical and hydrogen peroxide) from different types of cells. ... In chemistry, radicals (often referred to as free radicals) are atomic or molecular species with unpaired electrons on an otherwise open shell configuration. ... Link title {{portal|Food} A nutrient is either a chemical element or compound used in an organisms metabolism or physiology. ...


Neutrophils and macrophages are phagocytes that travel throughout the body in pursuit of invading pathogens.[31] Neutrophils are normally found in the bloodstream and are the most abundant type of phagocyte, normally representing 50% to 60% of the total circulating leukocytes.[32] During the acute phase of inflammation, particularly as a result of bacterial infection, neutrophils migrate toward the site of inflammation in a process called chemotaxis, and are usually the first cells to arrive at the scene of infection. Macrophages are versatile cells that reside within tissues and produce a wide array of chemicals including enzymes, complement proteins, and regulatory factors such as interleukin 1.[33] Macrophages also act as scavengers, ridding the body of worn-out cells and other debris, and as antigen-presenting cells that activate the adaptive immune system.[3] Diagram of the human circulatory system. ... A complement protein attacking an invader. ... Interleukin-1 (IL-1) is secreted by the macrophages, monocytes and dendritic cells. ... An antigen-presenting cell (APC) is a cell that displays foreign antigen complexed with MHC on its surface. ...


Dendritic cells (DC) are phagocytes in tissues that are in contact with the external environment; therefore, they are located mainly in the skin, nose, lungs, stomach, and intestines.[34] They are named for their resemblance to neuronal dendrites, as both have many spine-like projections, but dendritic cells are in no way connected to the nervous system. Dendritic cells serve as a link between the innate and adaptive immune systems, as they present antigen to T cells, one of the key cell types of the adaptive immune system.[34] Beyond overall skin structure, refer below to: See-also. ... For the article about nose in humans, see human nose. ... Human respiratory system The lungs flank the heart and great vessels in the chest cavity. ... In anatomy, the stomach is a bean-shaped hollow muscular organ of the gastrointestinal tract involved in the second phase of digestion, following mastication. ... In anatomy, the intestine is the segment of the alimentary canal extending from the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine (or colon). ... Drawing by Santiago Ramón y Cajal of neurons in the pigeon cerebellum. ... Dendrites (from Greek dendron, “tree”) are the branched projections of a neuron that act to conduct the electrical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project. ... The nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and also stops input from the senses, and initiates actions. ... Antigen presentation is a process in the bodys immune system by which macrophages, dendritic cells and leukocytes capture antigens and then carry those antigens to T-cells. ... T cells are a subset of lymphocytes that play a large role in the immune response. ...


Mast cells reside in connective tissues and mucous membranes, and regulate the inflammatory response.[35] They are most often associated with allergy and anaphylaxis.[32] Basophils and eosinophils are related to neutrophils. They secrete chemical mediators that are involved in defending against parasites and play a role in allergic reactions, such as asthma.[36] Natural killer (NK cells) cells are leukocytes that attack and destroy tumor cells, or cells that have been infected by viruses.[37] Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, muscle, and nervous tissue. ... The mucous membranes (or mucosae; singular: mucosa) are linings of mostly endodermal origin, covered in epithelium, and are involved in absorption and secretion. ... Low Temperature Scanning Electron Microscope (LTSEM) image of Varroa destructor on a honey bee host Mites parasitising a harvestman Parasitism is one version of symbiosis (living together), a phenomenon in which two organisms which are phylogenetically unrelated co-exist over a prolonged period of time, usually the lifetime of one... Natural killer cells (NK) are a type of lymphocyte (a white blood cell) and a component of nonspecific immune defense. ... Tumor or tumour literally means swelling, and is sometimes still used with that meaning. ...


Adaptive immunity

For more details on this topic, see Adaptive immune system.

The adaptive immune system evolved in early vertebrates and allows for a stronger immune response as well as immunological memory, where each pathogen is "remembered" by a signature antigen.[38] The adaptive immune response is antigen-specific and requires the recognition of specific “non-self” antigens during a process called antigen presentation. Antigen specificity allows for the generation of responses that are tailored to specific pathogens or pathogen-infected cells. The ability to mount these tailored responses is maintained in the body by "memory cells". Should a pathogen infect the body more than once, these specific memory cells are used to quickly eliminate it. The immune system is the collection of organs and tissues involved in the adaptive defense of a body against foreign biological material. ...


Lymphocytes

The cells of the adaptive immune system are special types of leukocytes, called lymphocytes. B cells and T cells are the major types of lymphocytes and are derived from hematopoietic stem cells in the bone marrow.[24] B cells are involved in the humoral immune response, whereas T cells are involved in cell-mediated immune response. A scanning electron microscope (SEM) image of a single human lymphocyte. ... B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response). ... T cells are a subset of lymphocytes that play a large role in the immune response. ... Sketch of bone marrow and its cells Pluripotential hemopoietic stem cells (PHSCs) are stem cells found in the bone marrow. ... This article does not cite any references or sources. ... Humoral immunity is the aspect of immunity that is mediated by secreted antibodies, produced in the cells of the B lymphocyte lineage (B cell). ... Cell-mediated immunity is an immune response that does not involve antibodies but rather involves the activation of macrophages and NK-cells, the production of antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen. ...

Association of a T cell with MHC class I or MHC class II, and antigen (in red)
Association of a T cell with MHC class I or MHC class II, and antigen (in red)

Both B cells and T cells carry receptor molecules that recognize specific targets. T cells recognize a “non-self” target, such as a pathogen, only after antigens (small fragments of the pathogen) have been processed and presented in combination with a “self” receptor called a major histocompatibility complex (MHC) molecule. There are two major subtypes of T cells: the killer T cell and the helper T cell. Killer T cells only recognize antigens coupled to Class I MHC molecules, while helper T cells only recognize antigens coupled to Class II MHC molecules. These two mechanisms of antigen presentation reflect the different roles of the two types of T cell. A third, minor subtype are the γδ T cells that recognize intact antigens that are not bound to MHC receptors.[39] Image File history File links TCR-MHC_bindings. ... Image File history File links TCR-MHC_bindings. ... MHC I (1hsa) vs MHC II (1dlh) (more details. ... A cytotoxic T cell (also known as TC, CTL or killer T cell) belongs to a sub-group of T lymphocytes (a type of white blood cell) which are capable of inducing the death of infected somatic or tumor cells; they kill cells that are infected with viruses (or other... This article or section does not cite its references or sources. ... MHC I (1hsa) vs MHC II (1dlh) (more details. ... MHC I (1hsa) vs MHC II (1dlh) (more details. ... γδ T cells represent a small subset of T cells that possess a distinct T cell receptor (TCR) on their surface. ...


In contrast, the B cell antigen-specific receptor is an antibody molecule on the B cell surface, and recognizes whole pathogens without any need for antigen processing. Each lineage of B cell expresses a different antibody, so the complete set of B cell antigen receptors represent all the antibodies that the body can manufacture.[24] Each antibody binds to a specific antigen; an interaction similar to a lock and key. ... Two methods exist for an antigen to be processed and presented on the cell surface. ...


Killer T cells

Killer T cells directly attack other cells carrying foreign or abnormal antigens on their surfaces.
Killer T cells directly attack other cells carrying foreign or abnormal antigens on their surfaces.[40]

Killer T cell are a sub-group of T cells that kill cells infected with viruses (and other pathogens), or are otherwise damaged or dysfunctional.[41] As with B cells, each type of T cell recognises a different antigen. Killer T cells are activated when their T cell receptor (TCR) binds to this specific antigen in a complex with the MHC Class I receptor of another cell. Recognition of this MHC:antigen complex is aided by a co-receptor on the T cell, called CD8. The T cell then travels throughout the body in search of cells where the MHC I receptors bear this antigen. When an activated T cell contacts such cells, it releases cytotoxins that form pores in the target cell's plasma membrane, allowing ions, water and toxins to enter. This causes the target cell to undergo apoptosis.[42] T cell killing of host cells is particularly important in preventing the replication of viruses. T cell activation is tightly controlled and generally requires a very strong MHC/antigen activation signal, or additional activation signals provided by "helper" T cells (see below).[42] Image File history File links Cytotoxic_T_cell. ... Image File history File links Cytotoxic_T_cell. ... A cytotoxic T cell (also known as TC, CTL or killer T cell) belongs to a sub-group of T lymphocytes (a type of white blood cell) which are capable of inducing the death of infected somatic or tumor cells; they kill cells that are infected with viruses (or other... Antigen presentation stimulates T cells to become either cytotoxic CD8+ cells or helper CD4+ cells. ... This page is a candidate to be copied to Wiktionary. ... CD8 (cluster of differentiation 8) is a molecule that is expressed on the surface of cytotoxic T cells. ... Cytotoxicity is the quality of being poisonous to cells. ... The cell membrane (also called the plasma membrane, plasmalemma or phospholipid bilayer) is a semipermeable lipid bilayer common to all living cells. ... This article is about the electrically charged particle. ...


Helper T cells

Helper T cells regulate both the innate and adaptive immune responses and help determine which types of immune responses the body will make to a particular pathogen.[43][44] These cells have no cytotoxic activity and do not kill infected cells or clear pathogens directly. They instead control the immune response by directing other cells to perform these tasks. This article or section does not cite its references or sources. ...


Helper T cells express T cell receptors (TCR) that recognize antigen bound to Class II MHC molecules. The MHC:antigen complex is also recognized by the helper cell's CD4 co-receptor, which recruits molecules inside the T cell (e.g. Lck) that are responsible for T cell's activation. Helper T cells have a weaker association with the MHC:antigen complex than observed for killer T cells, meaning many receptors (around 200–300) on the helper T cell must be bound by an MHC:antigen in order to activate the helper cell, while killer T cells can be activated by engagement of a single MHC:antigen molecule. Helper T cell activation also requires longer duration of engagement with an antigen-presenting cell.[45] The activation of a resting helper T cell causes it to release cytokines that influence the activity of many cell types. Cytokine signals produced by helper T cells enhance the microbicidal function of macrophages and the activity of killer T cells.[5] In addition, helper T cell activation causes an upregulation of molecules expressed on the T cell's surface, such as CD40 ligand (also called CD154), which provide extra stimulatory signals typically required to activate antibody-producing B cells.[46] CD4 (cluster of differentiation 4) is a molecule that is expressed on the surface of T helper cells (as well as regulatory T cells and dendritic cells). ... Rickenbacker International Airport (airport code: LCK) is located in Columbus, Ohio. ... CD154, also called CD40 ligand or CD40L, is a protein that is expressed on T cell surfaces. ...


γδ T cells

γδ T cells possess an alternative T cell receptor (TCR) as opposed to CD4+ and CD8+ (αβ) T cells and share the characteristics of helper T cells, cytotoxic T cells and NK cells. The conditions that produce responses from γδ T cells are not fully understood. Like other 'unconventional' T cell subsets bearing invariant TCRs, such as CD1d-restricted Natural Killer T cells, γδ T cells straddle the border between innate and adaptive immunity.[47] On one hand, γδ T cells are a component of adaptive immunity as they rearrange TCR genes to produce receptor diversity and can also develop a memory phenotype. On the other hand, the various subsets are also part of the innate immune system, as restricted TCR or NK receptors may be used as pattern recognition receptors. For example, large numbers of human Vγ9/Vδ2 T cells respond within hours to common molecules produced by microbes, and highly restricted Vδ1+ T cells in epithelia will respond to stressed epithelial cells.[48] γδ T cells represent a small subset of T cells that possess a distinct T cell receptor (TCR) on their surface. ... Antigen presentation stimulates T cells to become either cytotoxic CD8+ cells or helper CD4+ cells. ... CD1d is a member of the CD1 (cluster of differentiation 1) family of glycoproteins expressed on the surface of various human antigen-presenting cells. ... Natural killer T cells (NK T cells) are a type of lymphocyte, or white blood cell. ... The immune system is the collection of organs and tissues involved in the adaptive defense of a body against foreign biological material. ... V(D)J recombination is a mechanism of DNA recombination used by humans and other vertebrates for immunological protection against attacks by bacterial, viral, and parasitic invaders. ... Pattern recognition receptors, or PRRs, are a class of cell surface receptors which are employed by the cells of the immune system to identify foreign (disease-associated) biomolecules in the body. ... Non-peptidic antigens are low molecular weight compounds that stimulate human Vγ9/Vδ2 T cells. ... Types of epithelium In biology and medicine, epithelium is a tissue composed of a layer of cells. ...

An antibody is made up of two heavy chains and two light chains. The unique variable region allows an antibody to recognize its matching antigen.
An antibody is made up of two heavy chains and two light chains. The unique variable region allows an antibody to recognize its matching antigen.[40]

Image File history File links Antibody. ... Image File history File links Antibody. ...

B lymphocytes and antibodies

A B cell identifies pathogens when antibodies on its surface bind to a specific foreign antigen.[49] This antigen/antibody complex is taken up by the B cell and processed by proteolysis into peptides. The B cell then displays these antigenic peptides on its surface MHC class II molecules. This combination of MHC and antigen attracts a matching helper T cell, which releases lymphokines and activates the B cell.[50] As the activated B cell then begins to divide, its offspring (plasma cells) secrete millions of copies of the antibody that recognizes this antigen. These antibodies circulate in blood plasma and lymph, bind to pathogens expressing the antigen and mark them for destruction by complement activation or for uptake and destruction by phagocytes. Antibodies can also neutralize challenges directly, by binding to bacterial toxins or by interfering with the receptors that viruses and bacteria use to infect cells.[51] B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response). ... Proteolysis is the directed degradation (digestion) of proteins by cellular enzymes called proteases or by intramolecular digestion. ... Lymphokines are a subset of Cytokines that are produced by immune cells. ... This does not adequately cite its references or sources. ... Plasma cells are B lymphocytes that secrete immunoglobulins (antibodies). ... Secretion is the process of segregating, elaborating, and releasing chemicals from a cell, or a secreted chemical substance or amount of substance. ... This article does not cite its references or sources. ...


Alternative adaptive immune system

Although the classical molecules of the adaptive immune system (e.g. antibodies and T cell receptors) exist only in jawed vertebrates, a distinct lymphocyte-derived molecule has been discovered in primitive jawless vertebrates, such as the lamprey and hagfish. These animals possess a large array of molecules called variable lymphocyte receptors (VLRs) that, like the antigen receptors of jawed vertebrates, are produced from only a small number (one or two) of genes. These molecules are believed to bind pathogenic antigens in a similar way to antibodies, and with the same degree of specificity.[52] Antigen presentation stimulates T cells to become either cytotoxic CD8+ cells or helper CD4+ cells. ... A scanning electron microscope (SEM) image of a single human lymphocyte. ... Idealized agnatha. ... Subfamilies Geotriinae Mordaciinae Petromyzontinae A lamprey (sometimes also called lamprey eel) is a jawless fish with a toothed, funnel-like sucking mouth. ... Genera Eptatretus Myxine Nemamyxine Neomyxine Notomyxine Paramyxine Quadratus This article is about the Hagfish. ... For a non-technical introduction to the topic, see Introduction to Genetics. ... This article does not cite any references or sources. ...


Immunological memory

For more details on this topic, see Immunity (medical).

When B cells and T cells are activated and begin to replicate, some of their offspring will become long-lived memory cells. Throughout the lifetime of an animal, these memory cells will remember each specific pathogen encountered and can mount a strong response if the pathogen is detected again. This is "adaptive" because it occurs during the lifetime of an individual as an adaptation to infection with that pathogen and prepares the immune system for future challenges. Immunological memory can either be in the form of passive short-term memory or active long-term memory. Immunity is a medical term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. ...


Passive memory

Passive immunity is usually short-term, lasting between a few days and several months. Newborn infants have no prior exposure to microbes and are particularly vulnerable to infection. Several layers of passive protection are provided by the mother. During pregnancy, a particular type of antibody, called IgG, is transported from mother to baby directly across the placenta, so human babies have high levels of antibodies even at birth, with the same range of antigen specificities as their mother.[53] Breast milk also contains antibodies that are transferred to the gut of the infant and protect against bacterial infections until the newborn can synthesize its own antibodies.[54] This is passive immunity because the fetus does not actually make any memory cells or antibodies, it only borrows them. In medicine, protective passive immunity can also be transferred artificially from one individual to another via antibody-rich serum.[55] A human infant In basic English usage, an infant is defined as a human child at the youngest stage of life, especially before they can walk or simply a child before the age of one[1] (see also child and adolescent). ... A pregnant woman near the end of her term Pregnancy is the carrying of one or more offspring in an embryonal or fetal stage of development by female mammals, including humans, inside their bodies, between the stages of conception and birth. ... The placenta is an ephemeral (temporary) organ present in female placental vertebrates during gestation (pregnancy), but a placenta has evolved independently also in other animals as well, for instance scorpions and velvet worms. ... It has been suggested that the section Benefits for the infant from the article Breastfeeding be merged into this article or section. ... Passive immunity occurs when high levels of human (or horse) antibodies specific for a pathogen or toxin are transferred to non-immune individuals. ... “Unborn child” redirects here. ... Intravenous immunoglobulin (IVIG) is a blood product administered intravenously. ... Blood plasma is the liquid component of blood, in which the blood cells are suspended. ...

The time-course of an immune response begins with the initial pathogen encounter, (or initial vaccination) and leads to the formation and maintenance of active immunological memory.
The time-course of an immune response begins with the initial pathogen encounter, (or initial vaccination) and leads to the formation and maintenance of active immunological memory.

Image File history File links Download high-resolution version (1136x704, 75 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system Immunity (medical) ... Image File history File links Download high-resolution version (1136x704, 75 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system Immunity (medical) ...

Active memory and immunization

Long-term active memory is acquired following infection by activation of B and T cells. Active immunity can also be generated artificially, through vaccination. The principle behind vaccination (also called immunization) is to introduce an antigen from a pathogen in order to stimulate the immune system and develop specific immunity against that particular pathogen without causing disease associated with that organism.[5] This deliberate induction of an immune response is successful because it exploits the natural specificity of the immune system, as well as its inducibility. With infectious disease remaining one of the leading causes of death in the human population, vaccination represents the most effective manipulation of the immune system mankind has developed.[56][24] A vial of the vaccine against influenza. ... A child being immunized against polio. ... This article does not cite any references or sources. ...


Most viral vaccines are based on live attenuated viruses, while many bacterial vaccines are based on acellular components of micro-organisms, including harmless toxin components.[5] Since many antigens derived from acellular vaccines do not strongly induce the adaptive response, most bacterial vaccines are provided with additional adjuvants that activate the antigen-presenting cells of the innate immune system and maximize immunogenicity.[57] A vaccine is an antigenic preparation used to establish immunity to a disease. ... The attenuator plays an important regulatory role in prokaryotic cells because of the absence of the nucleus in prokaryotic organisms. ... Non-cellular life is life that exists without cells. ... This article or section does not cite any references or sources. ... In medicine, adjuvants are agents which modify the effect of other agents while having few if any direct effects when given by themselves. ... An antigen-presenting cell (APC) is a cell that displays foreign antigen complexed with MHC on its surface. ... This page is a candidate to be copied to Wiktionary using the Transwiki process. ...


Disorders of human immunity

The immune system is a remarkably effective structure that incorporates specificity, inducibility and adaptation. Failures of host defense do occur, however, and fall into three broad categories: immunodeficiencies, autoimmunity, and hypersensitivities.


Immunodeficiencies

Immunodeficiencies occur when one or more of the components of the immune system are inactive. The ability of the immune system to respond to pathogens is diminished in both the young and the elderly, with immune responses beginning to decline at around 50 years of age.[58][59] In developed countries, obesity, alcoholism, and illegal drug abuse are common causes of poor immune function.[59] However, malnutrition is the most common cause of immunodeficiency in developing countries.[59] Diets lacking sufficient protein are associated with impaired cell-mediated immunity, complement activity, phagocyte function, IgA antibody concentrations, and cytokine production. Deficiency of single nutrients such as zinc; selenium; iron; copper; vitamins A, C, E, and B6; and folic acid (vitamin B9) also reduces immune responses.[59] In medicine, immune deficiency (or immunodeficiency) is a state where the immune system is incapable of defending the organism from infectious disease. ... Paul Kruger in his old age. ... // [[Media:Media:Example. ... This article needs cleanup. ... Drug abuse has a wide range of definitions related to taking a psychoactive drug or performance enhancing drug for a non-therapeutic or non-medical effect. ... Percentage of population affected by malnutrition by country, according to United Nations statistics. ... It has been suggested that Underdevelopment be merged into this article or section. ... ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Standard atomic weight 65. ... For other uses, see Selenium (disambiguation). ... General Name, symbol, number iron, Fe, 26 Chemical series transition metals Group, period, block 8, 4, d Appearance lustrous metallic with a grayish tinge Standard atomic weight 55. ... For other uses, see Copper (disambiguation). ... Retinol (Vitamin A) For the record label, see Vitamin Records A vitamin is an organic compound required in tiny amounts for essential metabolic reactions in a living organism. ... Retinol, the animal form of vitamin A, is a yellow fat-soluble, antioxidant vitamin important in vision and bone growth. ... For other uses, see Vitamin C (disambiguation). ... Tocopherol, or vitamin E, is a fat-soluble vitamin in eight forms that is an important antioxidant. ... Pyridoxine Pyridoxal phosphate Vitamin B6 is a water-soluble vitamin. ... Folic acid and folate (the anion form) are forms of the water-soluble Vitamin B9. ...


Immunodeficiencies can also be inherited or 'acquired'.[5] Chronic granulomatous disease, where phagocytes have a reduced ability to destroy pathogens, is an example of an inherited, or congenital, immunodeficiency. AIDS and some types of cancer cause acquired immunodeficiency.[60][61] In medicine, immune deficiency (or immunodeficiency) is a state where the immune system is incapable of defending the organism from infectious disease. ... ]] compounds (most importantly, the superoxide radical) used to kill certain ingested pathogens. ... A phagocyte is a cell that ingests and destroys foreign matter such as microorganisms or debris via a process known as phagocytosis. ... Primary immunodeficiencies are disorders in which part of the bodys immune system is missing or does not function properly. ... Acquired Immune Deficiency Syndrome or acquired immunodeficiency syndrome (AIDS or Aids) is a collection of symptoms and infections resulting from the specific damage to the immune system caused by the human immunodeficiency virus (HIV). ... Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ...


Autoimmunity

Overactive immune responses comprise the other end of immune dysfunction, particularly the autoimmune disorders. Here, the immune system fails to properly distinguish between self and non-self, and attacks part of the body. Under normal circumstances, many T cells and antibodies react with “self” peptides.[62] One of the functions of specialized cells (located in the thymus and bone marrow) is to present young lymphocytes with self antigens produced throughout the body and to eliminate those cells that recognize self-antigens, preventing autoimmunity.[49] Autoimmunity is the failure of an organism to recognize its own constituent parts (down to the sub-molecular levels) as self, which results in an immune response against its own cells and tissues. ... Thymus, see Thyme. ... This article does not cite any references or sources. ...


Hypersensitivity

Hypersensitivity is an immune response that damages the body's own tissues. They are divided into four classes (Type I – IV) based on the mechanisms involved and the time course of the hypersensitive reaction. Type I hypersensitivity is an immediate or anaphylactic reaction, often associated with allergy. Symptoms can range from mild discomfort to death. Type I hypersensitivity is mediated by IgE released from mast cells and basophils.[63] Type II hypersensitivity occurs when antibodies bind to antigens on the patient's own cells, marking them for destruction. This is also called antibody-dependent (or cytotoxic) hypersensitivity, and is mediated by IgG and IgM antibodies.[63] Immune complexes (aggregations of antigens, complement proteins, and IgG and IgM antibodies) deposited in various tissues trigger Type III hypersensitivity reactions.[63] Type IV hypersensitivity (also known as cell-mediated or delayed type hypersensitivity) usually takes between two and three days to develop. Type IV reactions are involved in many autoimmune and infectious diseases, but may also involve contact dermatitis (poison ivy). These reactions are mediated by T cells, monocytes, and macrophages.[63] Hypersensitivity refers to undesirable (damaging, discomfort-producing and sometimes fatal) reactions produced by the normal immune system. ... Anaphylaxis is an acute systemic (multi-system) and severe Type I Hypersensitivity allergic reaction in humans and other mammals. ... An allergy is an abnormal, acquired sensitivity to a given substance, including pollen, drugs, or numerous environmental triggers. ... Immunoglobulin E (IgE) is an antibody subclass (known as isotypes), found only in mammals. ... Mast cells A mast cell (or mastocyte) is a resident cell of areolar connective tissue (loose connective tissue) that contains many granules rich in histamine and heparin. ... This article or section does not cite its references or sources. ... Molecular surface of an IgG molecule Immunoglobulin G(IgG) is a monomeric immunoglobulin, built of two heavy chains γ and two light chains. ... IgM (Immunglobulin M) antibody molecule consisting of 5 base units. ... Immune Complex Diseases An immune complex is the combination of an epitope with an antibody directed against that epitope. ... Contact dermatitis is a term for a skin reaction resulting from exposure to allergens or irritants. ... Binomial name Toxicodendron radicans (L.) Kuntze Poison-ivy (Toxicodendron radicans or Rhus toxicodendron), in the family Anacardiaceae, is a woody vine that is well-known for its ability to produce urushiol, a skin irritant which for most people will cause an agonizing, itching rash. ... T cells are a subset of lymphocytes that play a large role in the immune response. ... Monocyte A monocyte is a leukocyte, part of the human bodys immune system that protect against blood-borne pathogens and move quickly to sites of infection in the tissues. ... A macrophage of a mouse stretching its arms to engulf two particles, possibly pathogens Macrophages (Greek: big eaters, makros = long, phagein = eat) are white blood cells, more specifically phagocytes, acting in the nonspecific defense as well as the specific defense system of vertebrate animals. ...


Other mechanisms of host defense

For more details on this topic, see Innate immune system#Other forms of innate immunity.

It is likely that a multicomponent, adaptive immune system arose with the first vertebrates, as invertebrates do not generate lymphocytes or an antibody-based humoral response.[1] Many species, however, utilize mechanisms that appear to be precursors of these aspects of vertebrate immunity. Immune systems appear even in the most structurally-simple forms of life, with bacteria using a unique defense mechanism, called the restriction modification system to protect themselves from viral pathogens, called bacteriophages.[64] The innate immune system comprises the cells and mechanisms that defend the host from infection by other organisms, in a non-specific manner. ... This article does not cite any references or sources. ... Invertebrate is an English word that describes any animal without a spinal column. ... The restriction modification system is used by prokaryotic organisms (i. ... A bacteriophage (from bacteria and Greek phagein, to eat) is a virus that infects bacteria. ...


Pattern recognition receptors are proteins used by nearly all organisms to identify molecules associated with microbial pathogens. Antimicrobial peptides called defensins are an evolutionarily conserved component of the innate immune response found in all animals and plants, and represent the main form of invertebrate systemic immunity.[1] The complement system and phagocytic cells are also utilized by most forms of invertebrate life. Ribonucleases and the RNA interference pathway are conserved across all eukaryotes, and are thought to play a role in the immune response to viruses and other foreign genetic material.[65] Pattern recognition receptors, or PRRs, are a class of cell surface receptors which are employed by the cells of the immune system to identify foreign (disease-associated) biomolecules in the body. ... Antimicrobial peptides (also called host defence peptides) are an evolutionarily conserved component of the innate immune response and are found among all classes of life. ... Invertebrate is an English word that describes any animal without a spinal column. ... Immunity is a medical term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. ... A complement protein attacking an invader. ... Ribonuclease (RNase) is an enzyme that catalyzes the breakdown of RNA into smaller components. ... Cells use dicer to trim double stranded RNA to form small interfering RNA or microRNA. An exogenous dsRNA or endogenous pre-miRNA can be processed by dicer and incorporated into the RNA-induced silencing complex (RISC), which targets single-stranded messenger RNA molecules and triggers translational repression;[1] incorporation into... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ...


Unlike animals, plants lack phagocytic cells, and most plant immune responses involve systemic chemical signals that are sent through a plant.[66] When a part of a plant becomes infected, the plant produces a localized hypersensitive response, whereby cells at the site of infection undergo rapid apoptosis to prevent the spread of the disease to other parts of the plant. Systemic acquired resistance (SAR) is a type of defensive response used by plants that renders the entire plant resistant to a particular infectious agent.[66] RNA silencing mechanisms are particularly important in this systemic response as they can block virus replication.[67] The hypersensitive response (HR) is a mechanism, used by plants, to prevent the spread of infection by microbial pathogens. ... A section of mouse liver showing an apoptotic cell indicated by an arrow // Apoptosis is a process of deliberate life relinquishment by a cell in a multicellular organism. ... In plants, the transpiration stream is the uninterrupted stream of water which is taken up by the roots and, via the xylem vessels, transported to the leaves where it will eventually evaporate at the air/apoplast-interface of the substomatal cavity. ... Disease resistance in fruit and vegetables; There are a number of lines of defence against pests (that is, those animals that cause damage to the plants we grow) and diseases in the organic garden, principle among these being the practice of good husbandry, creating healthy soil and ensuring high standards... Cells use dicer to trim double stranded RNA to form small interfering RNA or microRNA. An exogenous dsRNA or endogenous pre-miRNA can be processed by dicer and incorporated into the RNA-induced silencing complex (RISC), which targets single-stranded messenger RNA molecules and triggers translational repression;[1] incorporation into...


Tumor immunology

Macrophages have identified a cancer cell (the large, spiky mass). Upon fusing with the cancer cell, the macrophages (smaller white cells) will inject toxins that kill the tumor cell. Immunotherapy for the treatment of cancer is an active area of medical research.
Macrophages have identified a cancer cell (the large, spiky mass). Upon fusing with the cancer cell, the macrophages (smaller white cells) will inject toxins that kill the tumor cell. Immunotherapy for the treatment of cancer is an active area of medical research.[68]

Another important role of the immune system is to identify and eliminate tumors. The transformed cells of tumors express antigens that are not found on normal cells. To the immune system, these antigens appear foreign, and their presence causes immune cells to attack the transformed tumor cells. The antigens expressed by tumors have several sources;[69] some are derived from oncogenic viruses like human papillomavirus, which causes cervical cancer,[70] while others are the organism's own proteins that occur at low levels in normal cells but reach high levels in tumor cells. One example is an enzyme called tyrosinase that, when expressed at high levels, transforms certain skin cells (e.g. melanocytes) into tumors called melanomas.[71][72] A third possible source of tumor antigens are proteins normally important for regulating cell growth and survival, that commonly mutate into cancer inducing molecules called oncogenes.[69][73][74] Image File history File links Download high-resolution version (2289x1669, 1101 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system ... Image File history File links Download high-resolution version (2289x1669, 1101 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system ... A macrophage of a mouse stretching its arms to engulf two particles, possibly pathogens Macrophages (Greek: big eaters, makros = long, phagein = eat) are white blood cells, more specifically phagocytes, acting in the nonspecific defense as well as the specific defense system of vertebrate animals. ... The term immunotherapy incorporates an array of strategies of treatment based upon the concept of modulating the immune system to achieve a prophylactic and/or therapeutic goal. ... Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ... Tumor or tumour literally means swelling, and is sometimes still used with that meaning. ... This article does not cite any references or sources. ... An oncogenic process which is any tumor-forming process. ... Species See text Papillomaviruses are viruses that commonly cause warts. ... Cervical cancer is a malignant cancer of the cervix. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... Tyrosinase (monophenol monooxygenase) (EC 1. ... This article or section does not cite its references or sources. ... Melanoma is a malignant tumor of melanocytes which are found predominantly in skin but also in the bowel and the eye (see uveal melanoma). ... The term cell growth is used in two different ways in biology. ... An oncogene is a modified gene that increases the malignancy of a tumor cell. ...


The main response of the immune system to tumors is to destroy the abnormal cells using killer T cells, sometimes with the assistance of helper T cells.[72][75] Tumor antigens are presented on MHC class I molecules in a similar way to viral antigens. This allows killer T cells to recognize the tumor cell as abnormal.[76] NK cells also kill tumorous cells in a similar way, especially if the tumor cells have fewer MHC class I molecules on their surface than normal; this is a common phenomenon with tumors.[77] Sometimes antibodies are generated against tumor cells allowing for their destruction by the complement system.[73] A complement protein attacking an invader. ...


Clearly, some tumors evade the immune system and go on to become cancers.[78] Tumor cells often have a reduced number of MHC class I molecules on their surface, thus avoid detection by killer T cells.[76] Some tumor cells also release products that inhibit the immune response; for example by secreting the cytokine TGF-β, which suppresses the activity of macrophages and lymphocytes.[79] In addition, immunological tolerance may develop against tumor antigens, so the immune system no longer attacks the tumor cells.[78] Transforming Growth Factor beta (TGF beta) is a biological protein. ... A macrophage of a mouse stretching its arms to engulf two particles, possibly pathogens Macrophages (Greek: big eaters, makros = long, phagein = eat) are white blood cells, more specifically phagocytes, acting in the nonspecific defense as well as the specific defense system of vertebrate animals. ... A scanning electron microscope (SEM) image of a single human lymphocyte. ... Immune or immunological tolerance is the process by which the immune system does not attack an antigen. ...


Paradoxically, macrophages can promote tumor growth [80] when tumor cells send out cytokines that attract macrophages which then generate cytokines and growth factors that nurture tumor development. In addition, a combination of hypoxia in the tumor and a cytokine produced by macrophages induces tumor cells to decrease production of a protein that blocks metastasis and thereby assists spread of cancer cells. Metastasis (Greek: change of the state) is the spread of cancer from its primary site to other places in the body. ...


Physiological regulation

Hormones can modulate the sensitivity of the immune system. For example, female sex hormones are known to stimulate both adaptive[81] and innate immune responses.[82] Some autoimmune diseases such as lupus erythematosus strike women preferentially, and their onset often coincides with puberty. By contrast, androgens such as testosterone seem to suppress the immune system.[83] Other hormones appear to regulate the immune system as well, most notably prolactin, growth hormone and vitamin D.[84][85] It is conjectured that a progressive decline in hormone levels with age is partially responsible for weakened immune responses in aging individuals.[86] Conversely, some hormones are regulated by the immune system, notably thyroid hormone activity.[87] Norepinephrine A hormone (from Greek όρμή - to set in motion) is a chemical messenger from one cell (or group of cells) to another. ... Sex steroids, also known as gonadal steroids, are steroid hormones which interact with vertebrate androgen or estrogen receptors. ... Puberty refers to the process of physical changes by which a childs body becomes an adult body capable of reproduction. ... Androgen is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates by binding to androgen receptors. ... Testosterone is a steroid hormone from the androgen group. ... Prolactin (PRL) is a peptide hormone primarily associated with lactation. ... Growth hormone (GH or somatotropin) is a 191-amino acid, single chain polypeptide hormone which is synthesised, stored and secreted by the somatotroph cells within the lateral wings of the anterior pituitary gland, which stimulates growth and cell reproduction in humans and other animals. ... Vitamin D is a fat soluble vitamin that contributes to the maintenance of normal levels of calcium and phosphorus in the bloodstream. ... The thyroid hormones, thyroxine (T4) and triiodothyronine (T3), are tyrosine-based hormones produced by the thyroid gland. ...


The immune system is enhanced by sleep and rest,[88] and is impaired by stress.[89]


Diet may affect the immune system; for example, fresh fruits, vegetables, and foods rich in certain fatty acids may foster a healthy immune system.[90] Likewise, fetal undernourishment can cause a lifelong impairment of the immune system.[91] In traditional medicine, some herbs are believed to stimulate the immune system, such as echinacea, licorice, ginseng, astragalus, sage, garlic, elderberry, shitake and lingzhi mushrooms, and hyssop, as well as honey. Studies have suggested that such herbs can indeed stimulate the immune system,[92] although their mode of action is complex and difficult to characterize. For other uses, see Fruit (disambiguation). ... A plate of vegetables Vegetable is a culinary term which generally refers to an edible part of a plant. ... In chemistry, especially biochemistry, a fatty acid is a carboxylic acid often with a long unbranched aliphatic tail (chain), which is either saturated or unsaturated. ... Prenatal development is the process in which an embryo or fetus (or foetus) gestates during pregnancy, from the times of fertilization until birth. ... The term describes medical knowledge systems, which developed over centuries within various societies before the era of modern medicine; traditional medicines include medicines such as herbal medicine, Ayurvedic medicine, Unani medicine, Acupuncture, Traditional Chinese medicine, Traditional Ayurvedic Medicine, South African Muti, Yoruba Ifá, as well as other medical knowledge and... Species See text Echinacea commonly called the Purple coneflowers, is a genus of nine species of herbaceous plants in the Family Asteraceae. ... Species Glycyrrhiza acanthocarpa Glycyrrhiza aspera Glycyrrhiza astragalina Glycyrrhiza bucharica Glycyrrhiza echinata Glycyrrhiza eurycarpa Glycyrrhiza foetida Glycyrrhiza glabra Glycyrrhiza iconica Glycyrrhiza korshinskyi Glycyrrhiza lepidota Glycyrrhiza pallidiflora Glycyrrhiza triphylla Glycyrrhiza uralensis Glycyrrhiza yunnanensis Ref: ILDIS Version 6. ... Not to be confused with ginger. ... Species See text. ... Binomial name L. Sage leaves - first variety Sage leaves - second variety Common sage (Salvia officinalis) is a small evergreen subshrub, with woody stems, grayish leaves, and blue to purplish flowers native to southern Europe and the Mediterranean region. ... Binomial name L. Allium sativum L., commonly known as garlic, is a species in the onion family Alliaceae. ... Species See text Elder or Elderberry (Sambucus) is a genus of between 5–30 species of shrubs or small trees (two species herbaceous), formerly treated in the honeysuckle family Caprifoliaceae, but now shown by genetic evidence to be correctly classified in the moschatel family Adoxaceae. ... Shiitake mushroom lentinus edodes (=lentinula edodes) Shiitake mushrooms (椎茸) are an edible mushroom typically cultivated on the shii tree (Pasania cuspidata--a relative of the oak). ... Binomial name (Curtis) P. Karst LíngzhÄ« (traditional Chinese: 靈芝; simplified Chinese: 灵芝; Japanese: reishi; Korean: yeongji, hangul: 영지) is the name for one form of the mushroom Ganoderma lucidum, and its close relative Ganoderma tsugae, which grows in the northern Eastern Hemlock forests. ... Species See text Hyssop (Hyssopus) is a genus of about 10-12 species of herbaceous or semi-woody plants in the family Lamiaceae, native from the Mediterranean east to central Asia. ... A jar of honey, shown with a wooden honey server and scones/biscuits. ...


Manipulation in medicine

The immune response can be manipulated to suppress unwanted responses resulting from autoimmunity, allergy, and transplant rejection, and to stimulate protective responses against pathogens that largely elude the immune system (see immunization). Immunosuppressive drugs are used to control autoimmune disorders or inflammation when excessive tissue damage occurs, and to prevent transplant rejection after an organ transplant.[24][93] Image File history File links Download high-resolution version (1100x846, 45 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Dexamethasone ... Image File history File links Download high-resolution version (1100x846, 45 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Dexamethasone ... For a list of immunosuppressive drugs, see the transplant rejection page. ... Dexamethasone is a potent synthetic member of the glucocorticoid class of steroid hormones. ... Transplant rejection occurs when the immune system of the recipient of a transplant attacks the transplanted organ or tissue. ... For a list of immunosuppressive drugs, see the transplant rejection page. ... An abscess on the skin, showing the redness and swelling characteristic of inflammation. ... Transplant rejection occurs when the immune system of the recipient of a transplant attacks the transplanted organ or tissue. ... “Transplant” redirects here. ...


Anti-inflammatory drugs are often used to control the effects of inflammation. The glucocorticoids are the most powerful of these drugs; however, these drugs can have many undesirable side effects (e.g., central obesity, hyperglycemia, osteoporosis) and their use must be tightly controlled.[94] Therefore, lower doses of anti-inflammatory drugs are often used in conjunction with cytotoxic or immunosuppressive drugs such as methotrexate or azathioprine. Cytotoxic drugs inhibit the immune response by killing dividing cells such as activated T cells. However, the killing is indiscriminate and other organs and cell types are affected, which causes toxic side effects.[93] Immunosuppressive drugs such as cyclosporin prevent T cells from responding to signals correctly by inhibiting signal transduction pathways.[95] Anti-inflammatory refers to the property of a substance or treatment that reduces inflammation. ... Glucocorticoids are a class of steroid hormones characterised by an ability to bind with the cortisol receptor and trigger similar effects. ... Central obesity (or apple-shaped or masculine obesity) occurs when the main deposits of body fat are localised around the abdomen and the upper body. ... Hyperglycemia or High Blood Sugar is a condition in which an excessive amount of glucose circulates in the blood plasma. ... Osteoporosis is a disease of bone in which the bone mineral density (BMD) is reduced, bone microarchitecture is disrupted, and the amount and variety of non-collagenous proteins in bone is altered. ... Cytotoxicity is the quality of being poisonous to cells. ... For a list of immunosuppressive drugs, see the transplant rejection page. ... Methotrexate (rINN) (IPA: ), abbreviated MTX and formerly known as amethopterin, is an antimetabolite and antifolate drug used in treatment of cancer and autoimmune diseases. ... Azathioprine is a chemotherapy drug, now rarely used for chemotherapy but more for immunosuppression in organ transplantation, autoimmune disease such as rheumatoid arthritis or inflammatory bowel disease such as Crohns disease. ... Chemotherapy is the use of chemical substances to treat disease. ... ... Overview of signal transduction pathways In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another, most often involving ordered sequences of biochemical reactions inside the cell, that are carried out by enzymes and linked through second messengers resulting in...


Larger drugs (>500 Da) can provoke a neutralizing immune response, particularly if the drugs are administered repeatedly, or in larger doses. This limits the effectiveness of drugs based on larger peptides and proteins (which are typically larger than 6000 Da). In some cases, the drug itself is not immunogenic, but may be co-administered with an immunogenic compound, as is sometimes the case for Taxol. Computational methods have been developed to predict the immunogenicity of peptides and proteins, which are particularly useful in designing therapeutic antibodies, assessing likely virulence of mutations in viral coat particles, and validation of proposed peptide-based drug treatments. Early techniques relied mainly on the observation that hydrophilic amino acids are overrepresented in epitope regions than hydrophobic amino acids;[96] however, more recent developments rely on machine learning techniques using databases of existing known epitopes, usually on well-studied virus proteins, as a training set.[97] A publicly accessible database has been established for the cataloguing of epitopes from pathogens known to be recognizable by B cells.[98] The emerging field of bioinformatics-based studies of immunogenicity is referred to as immunoinformatics.[99] The unified atomic mass unit (u), or Dalton (Da), is a small unit of mass used to express atomic and molecular masses. ... Paclitaxel is a drug used in the treatment of cancer. ... Hydrophile, from the Greek (hydros) water and φιλια (philia) friendship, refers to a physical property of a molecule that can transiently bond with water (H2O) through hydrogen bonding. ... Phenylalanine is one of the standard amino acids. ... Hydrophobe (from the Greek (hydros) water and (phobos) fear) in chemistry refers to the physical property of a molecule that is repelled by water. ... As a broad subfield of artificial intelligence, machine learning is concerned with the design and development of algorithms and techniques that allow computers to learn. At a general level, there are two types of learning: inductive, and deductive. ... A training set is used in artificial intelligence, together with a supervised training method, and it consists of an input vector and an answer vector. ... Map of the human X chromosome (from the NCBI website). ...


Manipulation by pathogens

The success of any pathogen is dependent on its ability to elude host immune responses. Therefore, pathogens have developed several methods that allow them to successfully infect a host, while evading immune-mediated destruction.[100] Bacteria often overcome physical barriers by secreting enzymes that digest the barrier — for example, by using a type II secretion system.[101] Alternatively, using a type III secretion system, they may insert a hollow tube into the host cell, which provides a direct conduit for proteins to move from the pathogen to the host; the proteins transported along the tube are often used to shut down host defenses.[102] Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ...


An evasion strategy used by several pathogens to circumvent the innate immune system is intracellular replication (also called intracellular pathogenesis). Here, a pathogen spends a majority of its life-cycle inside host cells, where it is shielded from direct contact with immune cells, antibodies and complement. Some examples of intracellular pathogens include viruses, the food poisoning bacterium Salmonella and the eukaryotic parasites that cause malaria (Plasmodium falciparum) and leishmaniasis (Leishmania spp.). Other bacteria, such as Mycobacterium tuberculosis, live inside a protective capsule that prevents lysis by complement.[103] Many pathogens secrete compounds that diminish or misdirect the host's immune response.[100] Some bacteria form biofilms to protect themselves from the cells and proteins of the immune system. Such biofilms are present in many successful infections, e.g., the chronic Pseudomonas aeruginosa and Burkholderia cenocepacia infections characteristic of cystic fibrosis.[104] Other bacteria generate surface proteins that bind to antibodies, rendering them ineffective; examples include Streptococcus (protein G), Staphylococcus aureus (protein A), and Peptostreptococcus magnus (protein L).[105] In cell biology, molecular biology and related fields, the word intracellular means inside the cell. It is used in contrast to extracellular (outside the cell). ... Pathogenesis is the mechanism by which a certain etiological factor causes disease (pathos = disease, genesis = development). ... A foodborne illness (also foodborne disease) is any illness resulting from the consumption of food. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... Species Salmonella bongori Salmonella enterica Salmonella arizonae Salmonella enteritidis Salmonella typhi Salmonella typhimurium Salmonella is a genus of rod-shaped Gram-negative enterobacteria that causes typhoid fever, paratyphoid fever, and foodborne illness. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... Malaria is a vector-borne infectious disease caused by protozoan parasites. ... Binomial name Plasmodium falciparum Welch, 1897 Plasmodium falciparum is a protozoan parasite, one of the species of Plasmodium that cause malaria in humans. ... This does not cite any references or sources. ... Binomial name Mycobacterium tuberculosis Zopf 1883 Mycobacterium tuberculosis is the bacterium that causes most cases of tuberculosis[1]. It was first described on March 24, 1882 by Robert Koch, who subsequently received the Nobel Prize in physiology or medicine for this discovery in 1905. ... Lysis (Greek lusis from luein = to separate) refers to the death of a cell by bursting, often by viral or osmotic mechanisms that compromise the integrity of the cellular membrane. ... Staphylococcus aureus biofilm on an indwelling catheter. ... Binomial name Pseudomonas aeruginosa (Schroeter 1872) Migula 1900 Synonyms Bacterium aeruginosum Schroeter 1872 Bacterium aeruginosum Cohn 1872 Micrococcus pyocyaneus Zopf 1884 Bacillus aeruginosus (Schroeter 1872) Trevisan 1885 Bacillus pyocyaneus (Zopf 1884) Flügge 1886 Pseudomonas pyocyanea (Zopf 1884) Migula 1895 Bacterium pyocyaneum (Zopf 1884) Lehmann and Neumann 1896 Pseudomonas polycolor... Burkholderia cenocepacia is a Gram-negative bacteria that is common in the environment and may cause disease in plants. ... Streptococcus is a genus of spherical shaped Gram-positive bacteria, belonging to the phylum Firmicutes[1] and the lactic acid bacteria group. ... Binomial name Rosenbach 1884 Staphylococcus aureus , (literally Golden Cluster Seed) the most common cause of staph infections, is a spherical bacterium, frequently living on the skin or in the nose of a person, that can cause a range of illnesses from minor skin infections (such as pimples, boils, and cellulitis... Peptostreptococci, anaerobic streptococci, are Gram-positive cocci, a type of bacteria. ...


The mechanisms used by viruses to evade the adaptive immune system are more complicated. The simplest approach is to rapidly change non-essential epitopes (amino acids and/or sugars) on the invader's surface, while keeping essential epitopes concealed. HIV, for example, regularly mutates the proteins on its viral envelope that are essential for entry into its host target cell. These frequent changes in antigens may explain the failures of vaccines directed at these proteins.[106] Masking antigens with host molecules is another common strategy for avoiding detection by the immune system. In HIV, the envelope that covers the viron is formed from the outermost membrane of the host cell; such "self-cloaked" viruses make it difficult for the immune system to identify them as "non-self".[107] An epitope is the part of a macromolecule that is recognized by the immune system, specifically by antibodies, B cells, or cytotoxic T cells. ... Phenylalanine is one of the standard amino acids. ... Many viruses (e. ... A vaccine is an antigenic preparation used to establish immunity to a disease. ... This article is about biological infectious particles. ...


History of immunology

For more details on this topic, see History of immunology.

Immunology is a science that examines the structure and function of the immune system. It originates from medicine and early studies on the causes of immunity to disease. The earliest known mention of immunity was during the plague of Athens in 430 BC. Thucydides noted that people who had recovered from a previous bout of the disease could nurse the sick without contracting the illness a second time.[108] This observation of acquired immunity was later exploited by Louis Pasteur in his development of vaccination and his proposed germ theory of disease.[109] Pasteur's theory was in direct opposition to contemporary theories of disease, such as the miasma theory. It was not until Robert Koch's 1891 proofs, for which he was awarded a Nobel Prize in 1905, that microorganisms were confirmed as the cause of infectious disease.[110] Viruses were confirmed as human pathogens in 1901, with the discovery of the yellow fever virus by Walter Reed.[111] Timeline of immunology: 1798 - smallpox vaccination (Edward Jenner) 1862 - phagocytosis (Ernst Haeckel) 1877 - mast cells (Paul Ehrlich) 1879 - development by Louis Pasteur of attenuated chicken cholera, anthrax and rabies vaccines development (Louis Pasteur) 1883 - Cellular theory of vaccination (Elie Metchnikoff) 1885 - first application of rabies vaccine in treatment of a... Image File history File links Paul_Ehrlich. ... Paul Ehrlich Paul Ehrlich in his workroom Paul Ehrlich (March 14, 1854 – August 20, 1915) was a German scientist who won the 1908 Nobel Prize in Physiology or Medicine. ... Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. ... Medicine is the science and art of maintaining andor restoring human health through the study, diagnosis, and treatment of patients. ... The city-state of Athens in ancient Greece was hit by a devastating epidemic, known as the Plague of Athens, during the second year of the Peloponnesian War (430 BC) when an Athenian victory still seemed within reach. ... Centuries: 6th century BC - 5th century BC - 4th century BC Decades: 480s BC 470s BC 460s BC 450s BC 440s BC - 430s BC - 420s BC 410s BC 400s BC 390s BC 380s BC Years: 435 BC 434 BC 433 BC 432 BC 431 BC - 430 BC - 429 BC 428 BC... Bust of Thucydides residing in the Royal Ontario Museum, Toronto. ... Louis Pasteur (December 27, 1822 – September 28, 1895) was a French chemist best known for his remarkable breakthroughs in microbiology. ... A vial of the vaccine against influenza. ... The germ theory of disease, also called the pathogenic theory of medicine, is a theory that proposes that microorganisms are the cause of many diseases. ... The miasmatic theory of disease held that diseases such as cholera or the Black Death were caused by a miasma (Greek language: pollution), a noxious form of bad air. In general, this concept has been supplanted by the more scientifically founded germ theory of disease. ... For the American lobbyist, see Bobby Koch. ... Kochs postulates (or Henle-Koch postulates) are four criteria designed to establish a causal relationship between a causative microbe and a disease. ... List of Nobel Prize laureates in Physiology or Medicine from 1901 to the present day. ... A cluster of Escherichia coli bacteria magnified 10,000 times. ... This false-colored electron micrograph shows a malaria sporozoite migrating through the midgut epithelia. ... Major Walter Reed, M.D., (September 13, 1851 - November 23, 1902) was a U.S. Army physician who in 1900 led the team which confirmed the theory (first set forth in 1881 by Cuban doctor/scientist Carlos Finlay) that yellow fever is transmitted by mosquitoes, rather than by direct contact. ...


Immunology made a great advance towards the end of the 19th century, through rapid developments, in the study of humoral immunity and cellular immunity.[112] Particularly important was the work of Paul Ehrlich, who proposed the side-chain theory to explain the specificity of the antigen-antibody reaction; his contributions to the understanding of humoral immunity were recognized by the award of a Nobel Prize in 1908, which was jointly awarded to the founder of cellular immunology, Elie Metchnikoff.[113] Humoral immunity is the aspect of immunity that is mediated by secreted antibodies, produced in the cells of the B lymphocyte lineage (B cell). ... Cell-mediated immunity is an immune response that does not involve antibodies but rather involves the activation of macrophages and natural killer cells, the production of antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen. ... Paul Ehrlich Paul Ehrlich in his workroom Paul Ehrlich (March 14, 1854 – August 20, 1915) was a German scientist who won the 1908 Nobel Prize in Physiology or Medicine. ... Side-chain theory is a theory proposed by Paul Ehrlich (1854 - 1915) to explain the immune response living cells. ... Eli Metchnikoff (1845-1916) was a Russian scientist, pivotal in starting the relatively modern discipline of probiotics. ...


See also

Wikimedia Commons has media related to:

Image File history File links Commons-logo. ... The clonal selection theory has become a widely accepted model for how the immune system responds to infection and how certain types of B and T lymphocytes are selected for destruction of specific antigens invading the body. ... An epitope is the part of a macromolecule that is recognized by the immune system, specifically by antibodies, B cells, or cytotoxic T cells. ... A hapten is a small molecule which can elicit an immune response only when attached to a large carrier such as a protein; the carrier may be one which also does not elicit an immune response by itself. ... Immunostimulators are the drugs which stimulate the immune system by inducing activation or increasing activity of any of its components. ... The major systems of the human body consist of: Circulatory system Digestive system Endocrine system Immune system Integumentary system Lymphatic system Muscular system Nervous system Reproductive system Respiratory system Skeletal system Urinary system Category: ... // Monoclonal antibodies (mAb) are antibodies that are identical because they were produced by one type of immune cell and are all clones of a single parent cell. ... Original antigenic sin (first described in 1960 by Thomas Francis, Jr. ... Polyclonal antibodies are antibodies that are derived from different B-cell lines. ... This article does not cite any references or sources. ...

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PDF is an abbreviation with several meanings: Portable Document Format Post-doctoral fellowship Probability density function There also is an electronic design automation company named PDF Solutions. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 1st day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 1st day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 1st day of the year in the Gregorian calendar. ... Charles Alderson Janeway, Jr. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 1st day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 4th day of the year in the Gregorian calendar. ... PDF is an abbreviation with several meanings: Portable Document Format Post-doctoral fellowship Probability density function There also is an electronic design automation company named PDF Solutions. ... National Institute of Allergy and Infectious Diseases (NIAID) is a component of the National Institutes of Health (NIH), which is an agency of the United States Department of Health and Human Services. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 1st day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 4th day of the year in the Gregorian calendar. ... The World Health Organization (WHO) is a specialized agency of the United Nations (UN) that acts as a coordinating authority on international public health. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 1st day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 1st day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 1st day of the year in the Gregorian calendar. ... Science is the journal of the American Association for the Advancement of Science (AAAS). ... PDF is an abbreviation with several meanings: Portable Document Format Post-doctoral fellowship Probability density function There also is an electronic design automation company named PDF Solutions. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 1st day of the year in the Gregorian calendar. ... January 8 is the 8th day of the year in the Gregorian calendar. ... January 8 is the 8th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... Eli Metchnikoff (1845-1916) was a Russian scientist, pivotal in starting the relatively modern discipline of probiotics. ... January 8 is the 8th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ...

External links

  • How Your Immune System Works - from HowStuffWorks
  • Immune System - from the University of Hartford
  • Immunobiology; Fifth Edition – Online version of the textbook by Charles Janeway (Advanced undergraduate/graduate level)
  • Immunology - BioMed Central (free content) scientific journal
  • The Inner Life of a Cell - Rendering of the inner functions of the human body
  • The Microbial World - Animal defenses against microbes - Chapter in on-line microbiology textbook
  • Microbiology and Immunology On-Line Textbook - from the University of South Carolina School of Medicine
  • Plant Immunity - Institute of Biochemical Plant Pathology at the GSF-National Research Center for Environment and Health

HowStuffWorks is a website created by Marshall Brain but now owned by the Convex Group. ... The University of Hartford, often called UHA or UHart, was founded in 1877, and is a private, independent, and nonsectarian coeducational university located in West Hartford, Connecticut. ... Charles Alderson Janeway, Jr. ... BioMed Central (BMC) is a UK-based scientific publisher specializing in open access publication. ... The University of South Carolina, Columbia (USC or Carolina) is a public, co-educational, research university located in Columbia, South Carolina, United States. ... Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. ... The immune system is the collection of organs and tissues involved in the adaptive defense of a body against foreign biological material. ... The innate immune system comprises the cells and mechanisms that defend the host from infection by other organisms, in a non-specific manner. ... Humoral immunity is the aspect of immunity that is mediated by secreted antibodies, produced in the cells of the B lymphocyte lineage (B cell). ... Cell-mediated immunity is an immune response that does not involve antibodies but rather involves the activation of macrophages and NK-cells, the production of antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen. ... A complement protein attacking an invader. ... Anaphylatoxins, or anaphylotoxins, are fragments (C3a, C4a or C5a) that are produced during the pathways of the complement system. ... Each antibody binds to a specific antigen; an interaction similar to a lock and key. ... // Monoclonal antibodies (mAb) are antibodies that are identical because they were produced by one type of immune cell and are all clones of a single parent cell. ... Polyclonal antibodies are antibodies that are derived from different B-cell lines. ... An autoantibody is an antibody (a type of protein) manufactured by the immune system that is directed against one or more of the individuals own proteins. ... The allotype affects the constant region (labeled CL and CH1-3 in the diagram. ... In immunology, the immunoglobulin isotype refers to the type of chain. ... The idiotype affects the variable region (labeled VL and VH in the diagram. ... This article does not cite any references or sources. ... Superantigens (SAgs) are a group of virulent toxins that indiscriminately activate T-cells of the immune system causing system-wide inflammation and other serious, potentially fatal symptoms. ... “White Blood Cells” redirects here. ... T cells are a subset of lymphocytes that play a large role in the immune response. ... B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response). ... Natural killer cells (NK) are a type of lymphocyte (a white blood cell) and a component of nonspecific immune defense. ... Mast cells A mast cell (or mastocyte) is a resident cell of areolar connective tissue (loose connective tissue) that contains many granules rich in histamine and heparin. ... Categories: Wikipedia cleanup | Biology stubs | Blood and immune system cells ... Eosinophils are white blood cells that are responsible for combating infection by parasites in the body. ... A phagocyte is a cell that ingests and destroys foreign matter such as microorganisms or debris via a process known as phagocytosis. ... Neutrophil granulocytes (commonly referred to as neutrophils) are a class of white blood cells and are part of the immune system. ... A macrophage of a mouse stretching its arms to engulf two particles, possibly pathogens Macrophages (Greek: big eaters, makros = long, phagein = eat) are white blood cells, more specifically phagocytes, acting in the nonspecific defense as well as the specific defense system of vertebrate animals. ... Dendritic cells (DC) are immune cells and form part of the mammal immune system. ... An antigen-presenting cell (APC) is a cell that displays foreign antigen complexed with MHC on its surface. ... The reticuloendothelial system (RES), part of the immune system, consists of the phagocytic cells located in reticular connective tissue, primarily monocytes and macrophages. ... Immunity is a medical term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. ... Autoimmunity is the failure of an organism to recognize its own constituent parts (down to the sub-molecular levels) as self, which results in an immune response against its own cells and tissues. ... An allergy is an abnormal, acquired sensitivity to a given substance, including pollen, drugs, or numerous environmental triggers. ... Immune or immunological tolerance is the process by which the immune system does not attack an antigen. ... Central tolerance is a condition caused by tumor cells caused by tumor antigens inhibiting the immune system which has no reaction. ... In medicine, immune deficiency (or immunodeficiency) is a state where the immune system is incapable of defending the organism from infectious disease. ... Immunogenetics is the branch of medical research that explores the relationship between the immune system and genetics. ... This article needs to be cleaned up to conform to a higher standard of quality. ... V(D)J recombination is a mechanism of DNA recombination used by humans and other vertebrates for immunological protection against attacks by bacterial, viral, and parasitic invaders. ... Immunoglobulin class switching (or isotype switching) is a mechanism by which the constant region of a heavy chain changes. ... MHC I (1hsa) vs MHC II (1dlh) (more details. ... HLA region of Chromosome 6 The human leukocyte antigen system (HLA) is the name of the human major histocompatibility complex (MHC). ... Cytokines are a group of proteins and peptides that are used in organisms as signaling compounds. ... An abscess on the skin, showing the redness and swelling characteristic of inflammation. ... An opsonin is any molecule that acts as a binding enhancer for the process of phagocytosis, for example, by coating the negatively-charged molecules on the membrane. ... This article does not cite its references or sources. ... In mammals including humans, the lymphatic vessels (or lymphatics) are a network of thin tubes that branch, like blood vessels, into tissues throughout the body. ... A scanning electron microscope (SEM) image of a single human lymphocyte. ... This article does not cite any references or sources. ... Thymus, see Thyme. ... Hassalls corpuscles (or thymic corpuscles) are structures in the thymus gland, composed of epithelial reticular cells. ... The spleen is an organ located in the abdomen, where it functions in the destruction of old red blood cells and holding a reservoir of blood. ... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... The Splenic hilum is a location on the surface of the spleen. ... The fibroelastic coat of the spleen invests the organ, and at the hilum is reflected inward upon the vessels in the form of sheaths. ... The red pulp (also called splenic pulp, but should not be confused with white pulp) is a soft mass of a dark reddish-brown color, resembling grumous blood It consists of a fine reticulum of fibers, continuous with those of the splenic trabeculae, to which are applied flat, branching cells. ... The Cords of Billroth (also known as splenic cords or red pulp cords) are found in the red pulp of the spleen between the sinusoids, consisting of fibrils and connective tissue cells with a large population of monocytes and macrophages. ... The marginal zone is a portion of the spleen. ... The altered coat of the arterioles, consisting of adenoid tissue, presents here and there thickenings of a spheroidal shape, the white pulp (Malpighian bodies of the spleen, splenic lymphoid nodules). ... Periarteriolar lymphoid sheaths (or periarterial lymphatic sheaths, or PALS) are a portion of the white pulp of the spleen. ... Lymph nodes are components of the lymphatic system. ... In some animals, including mammals, the two types of extracellular fluids are interstitial fluid and blood plasma. ... The pulp of the lymph gland does not, completely fill the spaces, but leaves, between its outer margin and the enclosing trabeculae, a channel or space of uniform width throughout. ... There are very few or no other articles that link to this one. ... In anatomy, lymph vessels are thin walled, valved structures that carry lymph away from the tissues, through the lymph nodes and thoracic duct back to the general circulation. ... High endothelial venules, or HEVs, are a subtype of blood endothelium present within lymph nodes; used by various leukocytes to gain entry into the lymph node via the blood. ... The mucosa-associated lymphoid tissue (MALT) is the diffuse system of small concentrations of lymphoid tissue found in various sites of the body such as the gastrointestinal tract, thyroid, breast, lung, salivary glands, eye, and skin. ... The mucous membranes (or mucosa) are linings of ectodermic origin, covered in epithelium, that line various body cavities and internal organs. ... Overview About 70% of the bodys immune system is found in the digestive tract. ... Peyers patches are secondary lymphoid organs named after the 17th-century Swiss anatomist Hans Conrad Peyer. ... List of bones of the human skeleton Human anatomy is primarily the scientific study of the morphology of the adult human body. ... Diagram of the human circulatory system. ... For the Physics term GUT, please refer to Grand unification theory The gastrointestinal or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and... This article does not cite any references or sources. ... In zootomy, the integumentary system is the external covering of the body, comprised of the skin, hair, feathers, scales, nails, sweat glands and their products (sweat and mucus). ... This article does not cite its references or sources. ... The muscular system is the biological system of an organism that allows it to move. ... The nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and also stops input from the senses, and initiates actions. ... The reproductive system is the ensembles and interactions of organs and/or substances within an organism that strictly pertain to reproduction. ... The Respiratory System Among four-legged animals, the respiratory system generally includes tubes, such as the bronchi, used to carry air to the lungs, where gas exchange takes place. ... A human skeleton The human skeleton consists of both fused and individual bones supported and supplemented by ligaments, tendons, muscles and cartilage. ... It has been suggested that this article or section be merged into Excretory system. ...


  Results from FactBites:
 
Immune System - NIAID Net News (979 words)
The immune system is a complex of organs--highly specialized cells and even a circulatory system separate from blood vessels--all of which work together to clear infection from the body.
The organs of the immune system, positioned throughout the body, are called lymphoid organs.
The spleen, at the upper left of the abdomen, is also a staging ground and a place where immune system cells confront foreign microbes.
The Immune System (2025 words)
The immune system is a complex network of organs containing cells that recognize foreign substances in the body and destroy them.
Immune responses are normally directed against the antigen that provoked them and are said to be antigen-specific.
Immunologic memory is the ability of the adaptive immune system to mount a stronger and more effective immune response against an antigen after its first encounter with that antigen, leaving the organism better able to resist it in the future.
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