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Encyclopedia > Adaptive immune system

The immune system is the collection of organs and tissues involved in the adaptive defense of a body against foreign biological material. It may be broken down into the adaptive immune system (only found in vertebrates [1] (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9297968)), composed of four lymphoid organs (thymus, lymph nodes, spleen and submucosal lymphoid nodules) and the group motile cells that are involved in the body's defense against foreign bodies. The term may also be used to refer to the totality of a body's defense systems, encompassing both the adaptive immune system and other passive defenses, such as the skin. Thymus, see Thyme. ... Lymph nodes are components of the lymphatic system. ... The spleen is a ductless, vertebrate gland that is not necessary for life but is closely associated with the circulatory system, where it functions in the destruction of old red blood cells and removal of other debris from the bloodstream, and also in holding a reservoir of blood. ...


In multicellular organisms, the immune system is an organ system that acts as a defense against foreign pathogens (such as viruses, bacteria, parasites), some poisons, as well as cancer. Components of the immune system also function in the return of extracellular fluid to the blood. In biology and ecology, an organism (in Greek organon = instrument) is a living being. ... A pathogen (literally birth of pain from the Greek παθογένεια) is a biological agent that can cause disease to its host. ... A common alternate meaning of virus is computer virus. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus_Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... A parasite is an organism that lives in or on the living tissue of a host organism at the expense of it. ... The skull and crossbones symbol traditionally used to label a poisonous substance. ... When normal cells are damaged or old they undergo apoptosis; cancer cells, however, avoid apoptosis. ...


Bacteria and monocellular organisms have an "immune system" (under the broader of the two definitions above) designed to combat bacteriophages (viruses that infect bacteria). They do this by simultaneously expressing restriction enzymes that cut DNA at certain sequences, and enzymes that protect their own DNA from this enzyme by methylating the same sequence. Therefore, the bacterium's DNA will not be damaged by the first enzyme because of the presence of the second enzyme. However, when a bacteriophage attempts to infect this bacterium, the viral DNA has not been protected, and gets degraded by the first enzyme. While study of the bacterial immune system provides useful insights into immunology, the remainder of this article will focus on higher organisms' immune systems, particularly the human immune system. A phage (also called bacteriophage) (in Greek phageton = food/consumption) is a small virus that infects only bacteria. ... A restriction enzyme (or restriction endonuclease) is an enzyme that cuts double-stranded DNA. The enzyme makes two incisions, one through each of the phosphate backbones of the double helix without damaging the bases. ... Space-filling model of a section of DNA molecule Deoxyribose nucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and many viruses). ...

Contents

Recognizing self and non-self

The immune system defends the body by recognizing agents that represent self and those that represent non-self, and launching attacks against harmful members of the latter group. Distinguishing between self and non-self and between harmful non-self and harmless non-self is a difficult problem, and a variety of human disorders arise from failures of discriminatory systems (see Disorders of the human immune system). A request has been made on Wikipedia for this article to be deleted in accordance with the deletion policy. ...


Some self/non-self discrimination is effected by hard-wired mechanisms that recognize features displayed only by pathogens. The MBL pathway of the complement system, for instance, recognizes mannose sugars, which appear only in the polysaccharide coats of bacterium. The most interesting mechanisms of discrimination, however, are not hard-wired --- rather, they involve the immune system learning to recognize non-self. The complement system is a complex biochemical cascade of the immune system, leading to cytolysis, chemotaxis, opsonization and inflammation, it can mark pathogens for phagocytosis. ...


For instance, the plasma membrane of every nucleated cell contains molecules of a large glycoprotein called the major histocompatibility complex (MHC). These proteins have configurations and amino acid sequences that are unique to every individual. T cells, a group that encompasses cytotoxic T lymphocytes (CTLs), the cells that kill virally-infected cells, contain surface-mounted receptors that they use to determine if a given cell is virally infected by reading the peptides displayed on its MHC molecules. During their development, T cells are tested for self-reactivity. If a given cell contains receptors that bind strongly to an existing molecule in the body, it is destroyed by forced apoptosis, leaving behind T cells that can be safely released into the body. (This is a much-truncated picture of T cell development; see the article on T cells for more). Drawing of a cell membrane A component of every biological cell, the cell membrane (or plasma membrane) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... A glycoprotein is a macromolecule composed of a protein and a carbohydrate (a sugar). ... The major histocompatibility complex (MHC) is a large genomic region or gene family found in most vertebrates containing many genes with important immune system roles. ... CTL can refer to: Computational tree logic Cut-to-length logging This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Peptides (from the Greek πεπτος, digestable), are the family of molecules formed from the linking, in a defined order, of various amino acids. ... In health care, managed health care is the idea that the service that is provided by a hospital or other group of clinics may be managed by an external company. ... T cells are a subset of lymphocytes that play a large role in the immune response. ... In biology, apoptosis (from the Greek words apo = from and ptosis = falling, pronounced ap-a-tow-sis[1]) is one of the main types of programmed cell death (PCD). ... T cells are a subset of lymphocytes that play a large role in the immune response. ...


Structure of the immune system

Most multicellular organisms possess an immune system consisting of innate immunity which generally consists of a set of genetically-encoded responses to pathogens and does not change during the lifetime of the organism. Adaptive immunity, in which the response to pathogens changes during the lifetime of an individual, appeared somewhat abruptly in evolutionary time with the appearance of cartilaginous (jawed) fish. Organisms that possess an adaptive immunity also possess an innate immunity and many of the mechanisms between the systems are common, so it not always possible to draw a hard and fast boundary between the individual components involved in each, despite the clear difference in operation. Higher vertebrates and all mammals have both an innate and an adaptive immune system. This timeline outlines the major events in the development of life on planet Earth. ... Orders see text The Chondrichthyes or cartilaginous fishes are jawed fish with paired fins, paired nostrils, scales, two-chambered hearts, and skeletons made of cartilage. ... Typical classes Petromyzontidae (lampreys) Placodermi - extinct Chondrichthyes (cartilaginous fish) Acanthodii - extinct Actinopterygii (ray-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) Amphibia (amphibians) Reptilia (reptiles) Aves (birds) Mammalia (mammals) Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary...


Innate immune system

The adaptive immune system may take days or weeks after an initial infection to have an effect. However, most organisms are under constant assault from pathogens, which must be kept in check by the faster-acting innate immune system. Innate immunity fights pathogens using defenses that are quickly mobilized and triggered by receptors that recognize a broad spectrum of pathogens. Plants and many lower animals do not possess an adaptive immune system and instead rely on innate immunity.


The study of the innate immune system has recently flourished. Earlier studies of innate immunity utilized model organisms that lack adaptive immunity such as the plant Arabidopsis thaliana, the fly Drosophila melanogaster, and the worm Caenorhabditis elegans. Recent advances have been made in the field of innate immunology with the discovery of the toll-like receptors, which are the receptors in mammals that are responsible for a large proportion of the innate immune recognition of pathogens. There is strong evidence that these toll-like receptors are responsible for sensing the "pathogen-associated molecular patterns" and/or providing the "danger signal" as speculated by Janeway and Matzinger, respectively. Binomial name Arabidopsis thaliana (L.) Heynh. ... Binomial name Drosophila melanogaster Drosophila melanogaster (Black-bellied Dew-lover) a dipteran (two-winged) insect, is the species of fruit fly that is commonly used in genetic experiments; it is among the most important model organisms. ... Binomial name Caenorhabditis elegans Caenorhabditis elegans () is a free_living nematode (a roundworm), about 1 mm in length, which lives in a temperate soil environment. ... Toll-like receptors (TLRs) are primary transmembrane proteins of immune cells that serve as a key part of the innate immune system; in addition they show a link between the innate and adaptive immune systems in vertebrates. ...


Physical barrier

The first defense includes barriers to infection such as skin and mucus coating of the gut and airways, physically preventing the interaction between the host and pathogen. Pathogens which penetrate these barriers encounter constitutively expressed anti-microbial molecules that restrict the infection.


Phagocytic cells

The second-line defense includes phagocytic cells, which includes macrophages and neutrophil granulocytes (polymorphonuclear leukocytes, PMN) that can engulf (phagocytose) foreign substances. Macrophages are thought to mature continuously from circulating monocytes. Macrophages (Greek: big eaters) are cells found in tissues that are responsible for phagocytosis of pathogens, dead cells and cellular debris. ... Neutrophil granulocytes (commonly referred to as neutrophils) are a class of white blood cells and are part of the immune system. ... Granulocytes are a category of white blood cells, characterised by the fact that all types have differently staining granules in their cytoplasm on light microscopy. ... In phagocytosis (literally, cell eating), large particles are enveloped by the cell membrane of a (usually larger) cell and internalized to form a food vacuole. ...


Phagocytosis involves chemotaxis, where phagocytic cells are attracted to microorganisms by means of chemotactic chemicals like microbial products, complements, damaged cells and white blood cell fragments; chemotaxis is followed by adhesion, where the phagocyte sticks to the microorganism. Adhesion is enhanced by opsonization, where proteins like opsonins are coated on the surface of the bacterium. This is followed by ingestion, in which the phagocyte extends projections, forming pseudopods that engulf the foreign organism. Finally the bacterium is digested by the enzymes in the lysosome. Chemotaxis is the phenomenon in which bacteria, other organisms, or single cells of multicellular organisms direct their movements according to certain chemicals in their environment. ... Schematic of cell adhesion The study of cell adhesion is part of cell biology. ... An opsonin is any molecule that acts as a binding enhancer for the process of phagocytosis. ... Ingestion is the action of consuming something orally, whether it be food, drink, medicine, or other substance. ... Pseudopods or pseudopodia (false feet) are temporary projections of eukaryotic cells. ...


Anti-microbial proteins

In addition, anti-microbial proteins may be activated if a pathogen pass through the barrier offered by skin. There are several class of antimicrobial proteins, such as acute phase proteins (C-reactive protein, for example, binds to the C-protein of S. pneumoniae - enhances phagocytosis and activates complement), lysozyme and the complement system. Acute phase proteins are a class of proteins that are synthetized in the liver in response to inflammation. ... C-reactive protein (CRP) is a plasma protein, an acute phase protein produced by the liver. ... Binomial name Streptococcus pneumoniae Streptococcus pneumoniae is a species of Streptococcus that is a major human pathogen. ... Categories: Stub | EC 3. ... The complement system is a complex biochemical cascade of the immune system, leading to cytolysis, chemotaxis, opsonization and inflammation, it can mark pathogens for phagocytosis. ...


Complement system

The complement system is a very complex group of serum proteins which is activated in a cascade fashion. Three different pathways, the classical, alternative, and mannose-binding lectin pathways, are involved in complement activation. The first recognizes antigen-antibody complexes, the second spontaneously activates on contact with pathogenic cell surfaces, the third recognizes mannose sugars, which tend to appear only on pathogenic cell surfaces. A cascade of protein activity follows complement activation; this cascade can result in a variety of effects including opsonization of the pathogen, destruction of the pathogen by formation and activation of the membrane attack complex, and inflammation. The complement system is a complex biochemical cascade of the immune system, leading to cytolysis, chemotaxis, opsonization and inflammation, it can mark pathogens for phagocytosis. ... The word cascade can have many meanings: In biochemistry, a cascade is a consecutive series of chemical reactions. ... The classical pathway of activation of the complement system is a group of blood proteins that mediate the specific antibody response. ... The alternative pathway of the complement system is a humoral component of the immune systems natural defence against infections which can operate without antibody participation. ... Fischer projection of D-mannose Mannose is a sugar, one of the hexose series of carbohydrates. ... An opsonin is any molecule that acts as a binding enhancer for the process of phagocytosis. ...


Adaptive immune system

The adaptive immune system, also called the acquired immune system, ensures that most mammals that survive an initial infection by a pathogen are generally immune to further illness caused by that same pathogen. Vaccination exploits this mechanism to produce immunity by way of introducion of an attenuated pathogen. The adaptive immune system is based on immune cells called leukocytes (or white blood cells) that are produced by stem cells in the bone marrow. In many species, including mammals, the adaptive immune system can be divided into two major sections: Vaccination is a term coined by Edward Jenner for the process of administering a weakened form of a disease to patients as a means of giving them immunity to a more serious form of the disease. ... White Blood Cells is also the name of a White Stripes album. ... Mouse embryonic stem cells. ... Bone marrow is the tissue comprising the center of large bones. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary...

  • The humoral immune system, which acts against bacteria and viruses in the body liquids (such as blood). Its primary means of action are proteins called immunoglobulins, also called antibodies, which are produced by B cells
  • The cellular immune system, which (among other duties) destroys virus-infected cells. The functions of CMI are performed by T cells, also called T lymphocytes (T means they develop in the thymus). There are two major types of T cells:
    • Cytotoxic T cells (TC cells) recognize infected cells by using T-cell receptors to probe the surface of other cells. If they recognize an infected cell, they release granzymes to signal that cell to become apoptotic ("commit suicide"), thus killing that cell and any viruses it is in the process of creating.
    • Helper T cells (TH cells) activate infected macrophages (cells that ingest dangerous material), and also produce cytokines (interleukins) that induce the proliferation of B and T cells.
    • In addition, there are Regulatory T cells (Treg cells) which are important in regulating cell-mediated immunity.

Humoral immunity is mediated by secreted antibodies, produced in cells of the B lymphocyte lineage (B cell). ... Red blood cells (erythrocytes) are present in the blood and help carry oxygen to the rest of the cells in the body Blood is a circulating tissue composed of fluid plasma and cells (red blood cells, white blood cells, platelets). ... Schematic of antibody binding to an antigen An antibody is a protein complex used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ... Schematic of antibody binding to an antigen An antibody is a protein used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ... B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response). ... 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. ... T cells are a subset of lymphocytes that play a large role in the immune response. ... Thymus, see Thyme. ... A cytotoxic (or TC) T cell is a T cell (a type of white blood cell) which has on its surface antigen receptors that can bind to fragments of antigens displayed by the Class I MHC molecules of virus infected somatic cells and tumor cells. ... Granzymes are exogenous serine proteases that are released by cytoplasmic granules within cytotoxic T cells and natural killer cells. ... In biology, apoptosis (from the Greek words apo = from and ptosis = falling, pronounced ap-a-tow-sis[1]) is one of the main types of programmed cell death (PCD). ... A helper (or TH) T cell is a T cell (a type of white blood cell) which has on its surface antigen receptors that can bind to fragments of antigens displayed by the Class II MHC molecules found on professional antigen-presenting cells (APCs). ... Macrophages (Greek: big eaters) are cells found in tissues that are responsible for phagocytosis of pathogens, dead cells and cellular debris. ... Cytokines are small protein molecules that are the core of communication between immune system cells, and even between immune system cells and cells belonging to other tissue types. ... Interleukins are a group of cytokines that are expressed by white blood cells (leukocytes, hence the -leukin) as a means of communication (inter-). The function of the immune system depends in a large part on interleukins, and rare deficiencies of a number of them have been described, all featuring autoimmune... The word proliferation can refer to: Nuclear proliferation Chemical weapon proliferation the spread in use of other weapons systems Cell proliferation According to Gloria Anzaldúa (1990), the difference between appropriation and proliferation is that the first steals and harms; the second helps heal breaches of knowledge. ... Regulatory T cells (also known as suppressor T cells) are a specialized subpopulation of T cells that act to suppress activation of the immune system and there by maintain immune system homeostasis and tolerance to self. ...

The intersection between innate and adaptive immune systems

Splitting the innate and adaptive immunity has served to simplify discussions of immunology. However, the systems are quite intertwined in a number of important respects.


One of the most important examples are the mechanisms of antigen presentation. After they leave the thymus, T cells require activation to proliferate and differentiate into "killer" T cells (CTLs). Activation is provided by antigen presenting cells (APCs). A major category of APCs involved in T cell activation, the dendritic cells, are part of the innate immune system. Activation occurs when a DC simulatenously binds to a T "helper" cell's antigen receptor and to its CD28 receptor, which provides the "second signal" needed for DC activation. This signal is a means by which the DC conveys that the antigen is indeed dangerous, and the next encountered T "killer" cells need to be activated. This mechanism is based on antigen danger evaluation by T cells that are all belonging to the adaptive immune system. But the dendritic cells are often directly activated by engaging their toll like receptors, getting their "second signal" directly from the antigen. In this way they actually recognize in "first person" the danger and direct the T killer attack. In this way, the innate immune system plays a critical role in the activation of the adaptive immune system. Dendritic cells (DC) are immune cells and form part of the mammal immune system. ... Dendritic cells (DC) are immune cells and form part of the mammal immune system. ... Toll-like receptors (TLRs) are primary transmembrane proteins of immune cells that serve as a key part of the innate immune system; in addition they show a link between the innate and adaptive immune systems in vertebrates. ...


Adjuvants, or chemicals that stimulate an immune response, provide artificially this "second signal" in procedures when an antigen that would not normally raise an immune response is artificially introduced into a host. With the adjuvant, the response is much more robust. Historically, a commonly used formula Freund's Complete Adjuvant, an emulsion of oil and mycobacterium. It was later discovered that toll-like receptors, expressed on innate immune cells, are critical in the activation of adaptive immunity. In medicine, adjuvants are agents which modify the effect of other agents while having few if any direct effects when given by themselves. ... Species see text Mycobacterium is the a genus of actinobacteria, given its own family, the Mycobacteriaceae. ...


Disorders of the human immune system

Many disorders of the human immune system fall into two broad categories: those characterized by attenuated immune response and those characterized by overzealous immune response.


Immunodeficiency is characterized by an attenuated response. There are congenital (inborn) and acquired forms of immune deficiency. Chronic granulomatous disease, in which phagocytes have trouble destroying pathogens, is an example of the former. AIDS ("Acquired Immune Deficiency Syndrome"), an infectious disease, caused by the HIV virus that destroys CD4+ T cells, is an example of the latter. Immunosuppressive medication intentionally induces an immunodeficiency in order to prevent rejection of transplanted organs. In medicine, immune deficiency (or immunodeficiency) is a state where the immune system is incapable of defending the organism from infectious disease. ... In medicine (genetics and pediatrics) chronic granulomatous disease (CGD) is a hereditary disease where neutrophil granulocytes are unable to destroy ingested pathogens. ... A phagocyte is a cell that ingests (and destroys) foreign matter, such as microorganisms or debris via a process known as phagocytosis, in which these cells ingest and kill offending cells by cellular digestion. ... AIDS (Acquired Immunodeficiency Syndrome or Acquired Immune Deficiency Syndrome, sometimes written Aids) is a global, human epidemic. ... In medicine, infectious disease or communicable disease is disease caused by a biological agent (e. ... HIV (Human Immunodeficiency Virus) is a retrovirus that infects cells of the human immune system. ... Transplant rejection is a process by which the immune system of the recipient of a transplant attacks the transplanted organ or tissue. ... An organ transplant is the transplantation of an organ (or part of one) from one body to another, for the purpose of replacing the recipients damaged or failing organ with a working one from the donor. ...


On the other end of the scale, an overactive immune system figures in a number of other disorders, particularly autoimmune disorders such as lupus erythematosus, type I diabetes (sometimes called "juvenile onset diabetes"), multiple sclerosis, psoriasis, and rheumatoid arthritis. In these the immune system fails to properly distinguish between self and non-self and attacks a part of the patient's own body. Other examples of overzealous immune responses in disease include hypersensitivities such as allergies and asthma. Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. ... Diabetes mellitus is a medical disorder characterized by varying or persistent hyperglycemia (elevated blood sugar levels), especially after eating. ... Rheumatoid arthritis (RA) is a chronic, inflammatory autoimmune disorder that causes the immune system to attack the joints. ... Hypersensitivity is the name given to a state in which an immune response damages the bodys own tissues. ... This article needs cleanup. ...


Further reading

  • A standard textbook on the immune system is Immunobiology, by Charles Janeway, et al. The paperback of the sixth edition is ISBN 0815341016. NCBI makes the 5th edition availiable electronically at [2] (http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=imm.TOC&depth=10).

The National Center for Biotechnology Information (NCBI) is part of the US National Library of Medicine (NLM), which is a branch of the US National Institutes of Health. ...

See also


An antigen is any molecule that is recognized by antibodies. ... An epitope is the part of a foreign organism (or its proteins) that is being recognised by the immune system and targeted by antibodies, cytotoxic T cells or both. ... 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. ... Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. ... Perforin is a cytolytic protein found in the granules of CD8 T-cells and NK cells. ... In biology, apoptosis (from the Greek words apo = from and ptosis = falling, pronounced ap-a-tow-sis[1]) is one of the main types of programmed cell death (PCD). ... Immunosuppression is the medical suppression of the immune system. ... Immunosuppressive drugs suppress the immune system, blocking the bodys ability to fight infection or foreign substances that enter the body. ... Immunotherapy is a disease treatment based upon the concept of triggering the bodys own natural defenses to fight off the disease, usually by stimulating the immune system either locally or systemically. ... 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 lymphocyte is a type of white blood cell involved in the human bodys immune system. ... Macrophages (Greek: big eaters) are cells found in tissues that are responsible for phagocytosis of pathogens, dead cells and cellular debris. ... The major histocompatibility complex (MHC) is a large genomic region or gene family found in most vertebrates containing many genes with important immune system roles. ... MHC class I molecules are cell surface proteins found on most cells of the body. ... Monoclonal antibodies (mAb) are antibodies that are identical because they were produced by one type of immune cell, all clones of a single parent cell. ... Polyclonal antibodies are antibodies that are derived from different cell lines. ...

Immune system
Humoral immune system - Cellular immune system - Lymphatic system
White blood cells - B cells - Antibodies - Antigen (MHC)
Lymphocytes: T cells (Cytotoxic & Helper) - B cells (Plasma cells & Memory B cells)


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. ... 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. ... White Blood Cells is also the name of a White Stripes album. ... B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response). ... Schematic of antibody binding to an antigen An antibody is a protein used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ... An antigen is any molecule that is recognized by antibodies. ... The major histocompatibility complex (MHC) is a large genomic region or gene family found in most vertebrates containing many genes with important immune system roles. ... A lymphocyte is a type of white blood cell involved in the human bodys immune system. ... T cells are a subset of lymphocytes that play a large role in the immune response. ... A cytotoxic (or TC) T cell is a T cell (a type of white blood cell) which has on its surface antigen receptors that can bind to fragments of antigens displayed by the Class I MHC molecules of virus infected somatic cells and tumor cells. ... A helper (or TH) T cell is a T cell (a type of white blood cell) which has on its surface antigen receptors that can bind to fragments of antigens displayed by the Class II MHC molecules found on professional antigen-presenting cells (APCs). ... B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response). ... Plasma cells are B lymphocytes that secrete immunoglobulins (antibodies). ... Memory B cells are B cells that although activated by the immune system, they are stored inside the circulatory system for later use, for long periods of time, possibly a whole lifetime. ...

Human organ systems
Cardiovascular system - Digestive system - Endocrine system - Immune system - Integumentary system - Lymphatic system - Muscular system - Nervous system - Skeletal system - Reproductive system - Respiratory system - Urinary system

  Results from FactBites:
 
Immune system - Wikipedia, the free encyclopedia (2743 words)
The Immune System (also known as the Immunlological System) is made up of all the mechanisms through which a multicellular organism defends itself from internal invaders such as bacteria, virus or parasites.
The innate system is comprised of all the mechanisms that defend an organism in non-specific form, against an invader, responding in the same fashion, regardless of what it is. It constitutes older defense strategies, some of these being found in primitive multicellular forms, in plant and fungi.
Suppression of the immune system is often used to control autoimmune disorders or inflammation when this causes excessive tissue damage, and to prevent transplant rejection after an organ transplant.
  More results at FactBites »

 
 

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