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Encyclopedia > Innate immune system

The innate immune system comprises the cells and mechanisms that defend the host from infection by other organisms, in a non-specific manner. This means that the cells of the innate system recognize, and respond to, pathogens in a generic way, but unlike the adaptive immune system, it does not confer long-lasting or protective immunity to the host.[1] Innate immune systems provide immediate defense against infection, and are found in all classes of plant and animal life. The immune system is the collection of organs and tissues involved in the adaptive defense of a body against foreign biological material. ... Divisions Green algae Chlorophyta Charophyta Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta—liverworts Anthocerotophyta—hornworts Bryophyta—mosses Vascular plants (tracheophytes) †Rhyniophyta—rhyniophytes †Zosterophyllophyta—zosterophylls Lycopodiophyta—clubmosses †Trimerophytophyta—trimerophytes Pteridophyta—ferns and horsetails Seed plants (spermatophytes) †Pteridospermatophyta—seed ferns Pinophyta—conifers Cycadophyta—cycads Ginkgophyta—ginkgo Gnetophyta—gnetae Magnoliophyta—flowering plants... Animalia redirects here. ...

Contents

Functions

The innate system is thought to constitute an evolutionarily older defense strategy, and is the dominant immune system found in plants, fungi, insects, and in primitive multicellular organisms (see Other forms of innate immunity).[2] Divisions Green algae Chlorophyta Charophyta Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta—liverworts Anthocerotophyta—hornworts Bryophyta—mosses Vascular plants (tracheophytes) †Rhyniophyta—rhyniophytes †Zosterophyllophyta—zosterophylls Lycopodiophyta—clubmosses †Trimerophytophyta—trimerophytes Pteridophyta—ferns and horsetails Seed plants (spermatophytes) †Pteridospermatophyta—seed ferns Pinophyta—conifers Cycadophyta—cycads Ginkgophyta—ginkgo Gnetophyta—gnetae Magnoliophyta—flowering plants... Divisions Chytridiomycota Zygomycota Ascomycota Basidiomycota The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. ... Orders See taxonomy Insects (Class Insecta) are a major group of arthropods and the most diverse group of animals on the Earth, with over a million described species—more than all other animal groups combined. ... Multicellular organisms are those organisms containing more than one cell, and having differentiated cells that perform specialized functions. ...


The major functions of the vertebrate innate immune system include: Classes and Clades See below Male and female Superb Fairy-wren Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns. ...

Cytokines are a group of proteins and peptides that are used in organisms as signaling compounds. ... 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. ... An immune complex is the combination of an epitope with an antibody directed against that epitope. ... The immune system is the collection of organs and tissues involved in the adaptive defense of a body against foreign biological material. ... 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. ...

Inflammation

Main article: Inflammation

Inflammation is one of the first responses of the immune system to infection or irritation. Inflammation is stimulated by chemical factors released by injured cells and serves to establish a physical barrier against the spread of infection, and to promote healing of any damaged tissue following the clearance of pathogens.[3] An abscess on the skin, showing the redness and swelling characteristic of inflammation. ... An abscess on the skin, showing the redness and swelling characteristic of inflammation. ...


The chemicals factors produced during inflammation (histamine, bradykinin, serotonin, leukotrienes) sensitize pain receptors, cause vasodilation of the blood vessels at the scene, and attract phagocytes, especially neutrophils.[3] Neutrophils then trigger other parts of the immune system by releasing factors that summon other leukocytes and lymphocytes. The inflammatory response is characterized by the following symptom quintet: redness (rubor), heat (calor), swelling (tumor), pain (dolor) and possible dysfunction of the organs or tissues involved (functio laesa). This article or section does not cite its references or sources. ... Spacefilling model of bradykinin Bradykinin is a physiologically and pharmacologically active peptide of the kinin group of proteins, consisting of nine amino acids. ... Serotonin (5-hydroxytryptamine, or 5-HT) is a monoamine neurotransmitter synthesized in serotonergic neurons in the central nervous system (CNS) and enterochromaffin cells in the gastrointestinal tract of animals including humans. ... Leukotrienes are autocrine and paracrine eicosanoid lipid mediators derived from arachidonic acid by 5-lipoxygenase. ... A nociceptor is a sensory receptor that sends signals that cause the perception of pain in response to potentially damaging stimulus. ... The blood vessels are part of the circulatory system and function to transport blood throughout the body. ... f you all The blood vessels are part of the circulatory system and function to transport blood throughout the body. ...


Complement system

Main article: Complement system

The complement system is a biochemical cascade of the immune system that helps, or “complements”, the ability of antibodies to clear pathogens or mark them for destruction by other cells. The cascade is composed of many plasma proteins, synthesized in the liver, primarily by hepatocytes. The proteins work together to: A complement protein attacking an invader. ... 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. ... The liver is an organ present in vertebrates and some other animals. ... Hepatocytes make up 60-80% of the cytoplasmic mass of the liver. ...

  • trigger the recruitment of inflammatory cells.
  • "tag" pathogens for destruction by other cells by opsonizing, or coating, the surface of the pathogen.
  • disrupt the plasma membrane of an infected cell, resulting in cytolysis of the infected cell, causing the death of the pathogen.
  • rid the body of neutralized antigen-antibody complexes.

Elements of the complement cascade can be found in many species evolutionarily older than mammals including plants, birds, fish and some species of invertebrates.[4] Cytolysis is the lysis, or death, of cells due to the rupture of the cell membrane. ... Divisions Green algae Chlorophyta Charophyta Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta—liverworts Anthocerotophyta—hornworts Bryophyta—mosses Vascular plants (tracheophytes) †Rhyniophyta—rhyniophytes †Zosterophyllophyta—zosterophylls Lycopodiophyta—clubmosses †Trimerophytophyta—trimerophytes Pteridophyta—ferns and horsetails Seed plants (spermatophytes) †Pteridospermatophyta—seed ferns Pinophyta—conifers Cycadophyta—cycads Ginkgophyta—ginkgo Gnetophyta—gnetae Magnoliophyta—flowering plants... “Aves” redirects here. ... A giant grouper at the Georgia Aquarium Fish are aquatic vertebrates that are typically cold-blooded; covered with scales, and equipped with two sets of paired fins and several unpaired fins. ... Invertebrate is a term that describes any animal without a spinal column. ...


Cells of the innate immune response

Main article: Leukocyte
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.

All white blood cells (WBC) are known officially as leukocytes. Leukocytes are unlike other cells of the body, and are not exclusively associated with any organ or tissue- in fact they effectively act like independent, single-celled organisms. Leukocytes are able to move, interact, and even capture things on their own. Unlike many other cells in the body, most innate immune leukocytes cannot divide or reproduce on their own, but rely on the pluripotential hemopoietic stem cells present in the bone marrow to produce new cells.[1] White Blood Cells is also the name of a White Stripes album. ... 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. ... A 250 ml bag of newly collected platelets. ... White Blood Cells is also the name of a White Stripes album. ... Note that some complexity is omitted from the diagram. ...


The innate leukocytes include: Natural killer cells, mast cells, eosinophils, basophils; and the phagocytic cells including macrophages, neutrophils and dendritic cells, and function within the immune system by identifying and eliminating pathogens that might cause infection.[2]


Mast cells

Main article: Mast cell

Mast cells are a type of innate immune cell that resides in the connective tissue and in the mucous membranes, and are intimately associated with pathogen defense, wound healing, and are often associated with allergy and anaphylaxis.[3] When activated, mast cells rapidly release characteristic granules, rich in histamine and heparin, along with various hormonal mediators, and chemokines, or chemotactic cytokines into the environment. Histamine dilates blood vessels, causing the characteristic signs of inflammation, and recruits neutrophils and macrophages.[3] 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 deals specifically with IgE-mediated hypersensitivity. ... }} In medicine, anaphylaxis is a severe and rapid multi-system allergic reaction. ... This article or section does not cite its references or sources. ... Heparin is a highly sulfated glycosaminoglycan widely used as an injectable anticoagulant. ... Chemokines are a family of pro-inflammatory activation-inducible cytokines, or small protein signals secreted by cells. ... Cytokines are a group of proteins and peptides that are used in organisms as signaling compounds. ... f you all The blood vessels are part of the circulatory system and function to transport blood throughout the body. ...


Phagocytes

Main article: Phagocytosis

The word 'phagocyte' literally means 'eating cell'. These are immune cells that engulf, or eat, pathogens or particles. To engulf a particle or pathogen, a phagocyte extends portions of its plasma membrane, wrapping the membrane around the particle until it is enveloped (i.e. the particle is now inside the cell). Once inside the cell, the invading pathogen is contained inside an endosome which merges with a lysosome.[2] The lysosome contains enzymes and acids that kill and digest the particle or organism. Phagocytes generally patrol the body searching for pathogens, but are also able to react to a group of highly specialized molecular signals produced by other cells, called cytokines. The phagocytic cells of the immune system include Macrophages, Neutrophils and Dendritic cells. Phagocytosis is a form of endocytosis wherein large particles are enveloped by the cell membrane of a (usually larger) cell and internalized to form a phagosome, or food vacuole. ... 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. ... In biology an endosome is a membrane-bound compartment inside cells. ... Organelles. ... 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. ...


Phagocytes often engulf the hosts’ own cells. When cells die, either during normal processes (called apoptosis) or due to a bacterial or viral infection of the cell, phagocytic cells are responsible for their removal from the system.[1] By helping to remove dead cells, to make room for the new healthy cells, phagocytosis is an important part of the healing process following tissue injury. A cell undergoing apoptosis. ... Phagocytosis is a form of endocytosis wherein large particles are enveloped by the cell membrane of a (usually larger) cell and internalized to form a phagosome, or food vacuole. ...

A macrophage
A macrophage

Image File history File linksMetadata Download high resolution version (1280x1024, 279 KB) Summary A macrophage of a mouse stretching itself to eat two smaller particles, possibly pathogens. ... Image File history File linksMetadata Download high resolution version (1280x1024, 279 KB) Summary A macrophage of a mouse stretching itself to eat two smaller particles, possibly pathogens. ...

Macrophages

Macrophages, from the Greek, meaning "large eating cell", are large phagocytic leukocytes, which are able to travel outside of the circulatory system by moving across the cell membrane of capillary vessels and entering the areas between cells in pursuit of invading pathogens. In tissues, organ specific macrophages are differentiated from phagocytic cells present in the blood called monocytes. Macrophages are the most efficient phagocytes, and can eat substantial numbers of bacteria or other cells.[2] The binding of bacterial molecules to receptors on the surface of a macrophage triggers it to engulf and destroy the bacteria through the generation of a “respiratory burst”. Pathogens also stimulate the macrophage to produce chemokines, which summons cells to the site of infection.[2] Macrophages (Greek: big eaters) are cells found in tissues that are responsible for phagocytosis of pathogens, dead cells and cellular debris. ... This article or section does not adequately cite its references or sources. ... 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. ... Respiratory burst is the rapid release of reactive oxygen species (superoxide radical and hydrogen peroxide) from different types of cells. ...


Neutrophils

A neutrophil
A neutrophil

Neutrophils, along with two other cell types; eosinophils and basophils (see below), are known as granulocytes due to the presence of granules in their cytoplasm, or as polymorphonuclear cells (PMNs) due to their distinctive lobed nuclei. Neutrophil granules contain a variety of toxic substances that act to kill or inhibit bacteria and fungi. Similar to macrophages, neutrophils attack pathogens by activating a "respiratory burst". The main products of the neutrophil respiratory burst are strong oxidizing agents including hydrogen peroxide, free oxygen radicals and hypochlorite. Neutrophils are the most abundant type of phagocyte, normally representing 50 to 60% of the total circulating leukocytes, and are usually the first cells to arrive at the scene of infection.[3] The bone marrow of a normal healthy adult produces more than 100 billion neutrophils per day, and more than 10 times that many per day during acute inflammation.[3] Image File history File links PBNeutrophil. ... Image File history File links PBNeutrophil. ... Neutrophil granulocytes (commonly referred to as neutrophils) are a class of white blood cells and are part of the immune system. ... Eosinophil granulocyte Basophil granulocyte Granulocytes are a category of white blood cells characterised by the presence of granules in their cytoplasm. ... The eukaryotic cell nucleus. ... European Union Chemical hazard symbol for oxidizing agents Dangerous goods label for oxidising agents An oxidizing agent (also called an oxidant or oxidizer) is referred to as A chemical compound that readily transfers oxygen atoms or A substance that gains electrons in a redox chemical reaction. ... Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colourless in a dilute solution, slightly more viscous than water. ... The hypochlorite ion The hypochlorite ion is OCl−. A hypochlorite compound is a chemical compound containing this group, with chlorine in oxidation state +1. ... Look up acute in Wiktionary, the free dictionary. ...


Dendritic cells

Dendritic cells (DC) are phagocytic cells present in tissues that are in contact with the external environment, mainly the skin (where they are often called Langerhans cells), the inner lining of the nose, lungs, stomach and intestines.[1] They are named for their resemblance to neuronal dendrites, but dendritic cells are in no way connected to nervous system function. Dendritic cells are very important in the process of antigen presentation, and serve as a link between the innate and adaptive immune systems. Dendritic cells (DC) are immune cells and form part of the mammal immune system. ... In zootomy and dermatology, skin is the largest organ of the integumentary system made up of multiple layers of epithelial tissues that guard underlying muscles and organs. ... Langerhans cells are immature dendritic cells containing large granules called Birbeck granules. ... For the article about nose in humans, see human nose Human nose in profile Elephants have prehensile noses Dogs have very sensitive noses Anatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for respiration. ... 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 portion 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). ... Neurons (also called nerve cells) are the primary cells of the nervous system. ... 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 Human Nervous System 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. ... The immune system is the collection of organs and tissues involved in the adaptive defense of a body against foreign biological material. ...

An eosinophil
An eosinophil

Image File history File links PBEosinophil. ... Image File history File links PBEosinophil. ...

Basophils and Eosinophils

Basophils and Eosinophils are cells related to the neutrophil (see above). When activated by a pathogen encounter, basophils release histamine, are important in defense against parasites, and play a role in allergic reactions (such as asthma).[2] Upon activation, eosinophils secrete a range of highly toxic proteins and free radicals that are highly effective against bacteria and parasites, but are also responsible for most tissue damage occurring during allergic reactions. Activation and toxin release by eosinophils is tightly regulated to prevent any inappropriate tissue destruction.[3] This article or section does not cite its references or sources. ... Eosinophil granulocyte Image of an eosinophil Eosinophil Eosinophil Eosinophil granulocytes, commonly referred to as eosinophils (or less commonly as acidophils), are white blood cells that are responsible for combating infection by parasites in the body. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Eosinophil granulocyte Eosinophil granulocytes, commonly referred to as eosinophils (or less commonly as acidophils), are white blood cells that are responsible for combating infection by parasites in the body. ... This article or section does not cite its references or sources. ... A parasite is an organism that spends a significant portion of its life in or on the living tissue of a host organism and which causes harm to the host without immediately killing it. ... This article needs cleanup. ... Toxic redirects here, but this is also the name of a song by Britney Spears; see Toxic (song) Look up toxic and toxicity in Wiktionary, the free dictionary. ...


Natural killer cells

Main article: Natural killer cell

Natural killer cells, or NK cells, are a component of the innate immune system, and are distinctive in that NK cells attack host cells that have been infected by microbes, but do not attack microbes themselves. NK cells attack and destroy tumor cells, and virally infected cells, through a process known as "missing-self", a term used to describe cells with low levels of a cell-surface marker called MHC I (major histocompatibility complex)—a situation which can arise due to viral infection of host cells.[4] They were named "natural killer" because of the initial notion that they do not require activation in order to kill cells that are "missing self." Natural NK cells are cytotoxic; small granules in their cytoplasm contain special proteins such as perforin and proteases known as granzymes. ... 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. ... MHC I (1hsa) vs MHC II (1dlh) (more details. ...


γδ T cells

Main article: gamma/delta T cells

Like other 'unconventional' T cell subsets bearing invariant T cell receptors (TCRs), such as CD1d-restricted Natural Killer T cells, γδ T cells exhibit characteristics that place them at the border between innate and adaptive immunity. One on hand, γδ T cells may be considered a component of adaptive immunity in that they rearrange TCR genes to produce junctional diversity and develop a memory phenotype. However, the various subsets may also be considered part of the innate immune system where a restricted TCR and/or NK receptors may be used as a pattern recognition receptor. For example, according to this paradigm, large numbers of Vγ9/Vδ2 T cells respond within hours to common molecules produced by microbes, and highly restricted intraepithelial Vδ1 T cells will respond to stressed epithelial cells. γδ T cells represent a small subset of T cells that possess a distinct T cell receptor (TCR) on their surface. ... The T cell receptor or TCR is responsible for recognizing antigen bound to Major histocompatibility complex (MHC). ... 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. ...


Innate immune evasion

Cells of the innate immune system effectively prevent free growth of bacteria within the body, however many pathogens have evolved mechanisms allowing them to evade the innate immune system.[5][6]


Evasion strategies that circumvent the innate immune system include intracellular replication, such as in Salmonella or a protective capsule that prevents lysis by complement and by phagocytes, as in Mycobacterium tuberculosis.[7] Bacteroides species are normally commensal bacteria, making up a substantial portion of the mammalian gastrointestinal flora.[8] Some species (B. fragilis, for example) are opportunistic pathogens, causing infections of the peritoneal cavity. These species evade the immune system by affecting the receptors that phagocytes use to engulf bacteria and inhibiting phagocytosis, or by mimicking host cells so that the immune system does not recognize them as foreign. Staphylococcus aureus inhibits the ability of the phagocyte to respond to chemokine signals. Other organisms such as M. tuberculosis, Streptococcus pyogenes and Bacillus anthracis utilize mechanisms that directly kill the phagocyte. 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. ... 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. ... Species etc. ... Common Clownfish (Amphiprion ocellaris) in their magnificent sea anemone (Heteractis magnifica) home. ... Escherichia coli, one of the many species of bacteria present in the human gut. ... Opportunistic infections are infections caused by organisms and usually do not cause disease in a person with a healthy immune system, but can affect people with a poorly functioning or suppressed immune system. ... In higher vertebrates, the peritoneum is the membrane that forms the lining of the abdominal cavity - it covers most of the intra-abdominal organs. ... Binomial name Staphylococcus aureus Rosenbach 1884 Staphylococcus aureus, the most common cause of staph infections, is a spherical bacterium, frequently living on the skin or in the nose of a healthy person, that can cause a range of illnesses from minor skin infections (such as pimples, boils, and cellulitis) and... Binomial name Streptococcus pyogenes Rosenbach 1884 Streptococcus pyogenes is a Gram-positive coccus that grows in long chains depending on the culture method. ... Binomial name Bacillus anthracis Cohn 1872 Bacillus anthracis is a Gram-positive, facultatively anaerobic, rod-shaped bacterium of the genus Bacillus. ...


Bacteria may also form biofilms to protect themselves from the cells and proteins of the immune system; recent studies indicate that such biofilms are present in many successful infections, including the chronic Pseudomonas aeruginosa and Burkholderia cenocepacia infections characteristic of cystic fibrosis.[9] 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. ...


Other forms of innate immunity

Host defense in prokaryotes

Bacteria (and perhaps other prokaryotic organisms), utilize a unique defense mechanism, called the restriction modification system to protect themselves from pathogens, such as bacteriophages. In this system, bacteria produce enzymes, called restriction endonucleases, that attack and destroy specific regions of the viral DNA of invading bacteriophages. Methylation of the host's own DNA marks it as "self" and prevents it from being attacked by endonucleases.[10] Restriction endonucleases and the restriction modification system exist exclusively in prokaryotes. 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. ... Prokaryotes are unicellular (in rare cases, multicellular) organisms without a nucleus. ... 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. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... 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. ... The structure of part of a DNA double helix Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions for the development and function of living organisms. ... Methylation is a term used in the chemical sciences to denote the attachment or substitution of a methyl group on various substrates. ...


Host defense in invertebrates

Invertebrates do not possess lymphocytes or an antibody-based humoral immune system, and it is likely that a multicomponent, adaptive immune system arose with the first vertebrates.[11] Nevertheless, invertebrates possess mechanisms that appear to be precursors of these aspects of vertebrate immunity. Pattern recognition receptors are proteins used by nearly all organisms to identify molecules associated with microbial pathogens. Toll-like receptors are a major class of pattern recognition receptor, that exists in all coelomates (animals with a body-cavity), including humans.[12] The complement system, as discussed above, is a biochemical cascade of the immune system that helps clear pathogens from an organism, and exists in most forms of life. Some invertebrates; including various insects, crabs, and worms utilize a modified form of the complement response known as the prophenoloxidase (proPO) system.[11] Invertebrate is a term that describes any animal without a spinal column. ... 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. ... Toll-like receptors (TLRs) are type I transmembrane proteins that serve as a key part of the innate immune system. ... Coelomates (Pronounced Seel-uh-mates) are animals with a true Body Cavity. ... A complement protein attacking an invader. ... Superfamilies Dromiacea Homolodromioidea Dromioidea Homoloidea Eubrachyura Raninoidea Cyclodorippoidea Dorippoidea Calappoidea Leucosioidea Majoidea Hymenosomatoidea Parthenopoidea Retroplumoidea Cancroidea Portunoidea Bythograeoidea Xanthoidea Bellioidea Potamoidea Pseudothelphusoidea Gecarcinucoidea Cryptochiroidea Pinnotheroidea * Ocypodoidea * Grapsoidea * An asterisk (*) marks the crabs included in the clade Thoracotremata. ... Click here for Computer worm For other uses, see Worm (disambiguation). ...


Antimicrobial peptides are an evolutionarily conserved component of the innate immune response found among all classes of life and represent the main form of invertebrate systemic immunity. Several species of insect produce antimicrobial peptides known as defensins and cecropins. 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. ... Systemic Relating to, or affecting a particular body system; especially the nervous system. ... Immunity is medical term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. ... Orders See taxonomy Insects (Class Insecta) are a major group of arthropods and the most diverse group of animals on the Earth, with over a million described species—more than all other animal groups combined. ... 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. ...


Host defense in plants

Members of every class of pathogen which infect humans also infect plants. Although the exact pathogenic species vary with the infected species, bacteria, fungi, viruses, nematodes and insects can all cause plant disease. As with animals, plants attacked by insects and/or diseases use a set of complex metabolic responses that lead to the formation of defensive chemical compounds which fight infection or make the plant less attractive to insects and other herbivores.[13] (see: plant defense against herbivory). Phytopathology (plant pathology) is the scientific study of plant diseases caused by pathogens (infectious diseases) and environmental conditons (non-infectiousness). ... Santorio Santorio (1561-1636) in his steelyard balance, from Ars de statica medecina, first published 1614 Metabolism (from μεταβολισμος(metavallo), the Greek word for change), in the most general sense, is the ingestion and breakdown of complex compounds, coupled... A deer and two fawns feeding on some foliage A herbivore is often defined as any organism that eats only plants[1]. By that definition, many fungi, some bacteria, many animals, about 1% of flowering plants and some protists can be considered herbivores. ... Plants have evolved an enormous array of mechanical and chemical defenses against the animals that eat them. ...


Like invertebrates, plants do not generate antibody or T cell responses, nor do their cells circulate to detect pathogens. In addition, some parts of some plants are treated as disposable and replaceable, in ways that very few animals do. Walling off or discarding a part of a plant help stop spread of an infection.[13]


Most plant immune responses involve systemic chemical signals sent throughout a plant. Plants use pattern recognition receptors to identify pathogens and to start a basal response, which produces chemical signals that fight infection. When a part of a plant becomes infected, the plant produces a localized hypersensitive response (HR), in which cells at the site of infection undergo rapid programmed cell death to prevent the spread of the disease to other parts of the plant. HR has some similarities to animal pyroptosis, such as a requirement of caspase-1-like proteolytic activity of VPEγ, a cysteine protease, that regulates cell disassembly during cell death.[14] The hypersensitive response (HR) is a mechanism, used by plants, to prevent the spread of infection by microbial pathogens. ... Programmed cell death (PCD) is the deliberate suicide of an unwanted cell in a multicellular organism. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... Caspases are a group of cysteine proteases, enzymes with a crucial cysteine residue that can cleave other proteins after an aspartic acid residue, a specificity which is unusual among proteases. ... Proteases are enzymes that degrade polypeptides. ...


"Resistance" (R) proteins, encoded by R genes, are widely present in plants and detect pathogens. These proteins contain domains similar to the NOD Like Receptors and Toll-like receptors utilized in animal innate immunity. Systemic acquired resistance (SAR) is a type of defensive response that renders the entire plant resistant to a broad spectrum of infectious agents. SAR involves the production of chemical messengers, such as salicylic acid. Some of these travel through the plant and signal other cells to produce defensive compounds to protect uninfected parts, eg leaves. Salicylic acid itself, although indispensable for expression of SAR, is not the translocated signal responsible for the systemic response. Recent evidence indicates a role for jasmonates in transmission of the signal to distal portions of the plant. RNA silencing mechanisms are also important in the plant systemic response as they can block virus replication.[15] The jasmonic acid response, is stimulated in leaves damaged by insects, and involves the production of methyl jasmonate.[13] 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. ... Toll-like receptors (TLRs) are type I transmembrane proteins that serve as a key part of the innate immune system. ... 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. ... ... Salicylic acid is the chemical compound with the formula C6H4(OH)CO2H, where the OH group is adjacent to the carboxylic acid group. ... Figure 1. ... Jasmonic Acid is released by plants when wounded and helps organize healing and defense. ... Methyl jasmonate is a substance used in plant defense. ...


See also

A cell undergoing apoptosis. ...

References

  1. ^ a b c d Alberts, Bruce; Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walters (2002). Molecular Biology of the Cell; Fourth Edition. New York and London: Garland Science. ISBN 0-8153-3218-1. 
  2. ^ a b c d e f Janeway, Charles; Paul Travers, Mark Walport, and Mark Shlomchik (2001). Immunobiology; Fifth Edition. New York and London: Garland Science. ISBN 0-8153-4101-6. .
  3. ^ a b c d e f g Stvrtinová, Viera; Ján Jakubovský and Ivan Hulín (1995). Inflammation and Fever from Pathophysiology: Principles of Disease. Computing Centre, Slovak Academy of Sciences: Academic Electronic Press. 
  4. ^ a b Janeway CA, Jr. et al (2005). Immunobiology., 6th ed., Garland Science. ISBN 0-443-07310-4. 
  5. ^ Kennedy, Alan. Immune Evasion by bacteria.
  6. ^ Finlay B, McFadden G (2006). "Anti-immunology: evasion of the host immune system by bacterial and viral pathogens". Cell 124 (4): 767-82. PMID 16497587. 
  7. ^ Finlay B, Falkow S (1997). "Common themes in microbial pathogenicity revisited". Microbiol Mol Biol Rev 61 (2): 136-69. PMID 9184008. 
  8. ^ Dorland WAN (editor) (2003). Dorland's Illustrated Medical Dictionary, 30th, W.B. Saunders. ISBN 0-7216-0146-4. 
  9. ^ Kobayashi H (2005). "Airway biofilms: implications for pathogenesis and therapy of respiratory tract infections". Treat Respir Med 4 (4): 241-53. PMID 16086598. 
  10. ^ Restriction Enzymes Access Excellence Classic Collection Background Paper.
  11. ^ a b Beck, Gregory and Habicht, Gail S. Immunity and the Invertebrates Scientific American. November 1996:60-66.
  12. ^ Imler JL, Hoffmann JA. (2001) Toll receptors in innate immunity. Trends Cell Biol. Jul;11(7):304-11. Review. PMID 11413042
  13. ^ a b c Schneider, David (2005) Plant immune responses Stanford University Department of Microbiology and Immunology.
  14. ^ Rojo, E. et. al. (2004). "VPEgamma exhibits a caspase-like activity that contributes to defense against pathogens.". Curr Biol. 14 (21): 1897-1906. PMID 15530390. 
  15. ^ Baulcombe D (2004). "RNA silencing in plants". Nature 431 (7006): 356-63. PMID 15372043. 

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The innate immune system is able to eradicate many microbial pathogens directly, or innate immunity may indirectly facilitate the removal of pathogens by activation of specific elements of the adaptive immune response (cell-mediated and humoral immunity by T cells and B cells).
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