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Encyclopedia > Superantigen
SEB, A typical bacterial superantigen (PDB:3SEB) The β-grasp domain is shown in red, and the β-barrel in green: The "disulphide loop" is shown in yellow
SEB, A typical bacterial superantigen (PDB:3SEB) The β-grasp domain is shown in red, and the β-barrel in green: The "disulphide loop" is shown in yellow
SEC3 (yellow) complexed with an MHC-II molecule (green & cyan): The SAgs binds adjacent to the antigen (purple) presentation cleft in the MHC-II
SEC3 (yellow) complexed with an MHC-II molecule (green & cyan): The SAgs binds adjacent to the antigen (purple) presentation cleft in the MHC-II
Figure 1. Schematic of Superantigen stimulation compared to normal antigen presentation and activation [2].

Superantigens (SAgs) are secreted proteins (exotoxins) that exhibit highly potent lymphocyte-transforming (mitogenic) activity directed towards T lymphocytes [2,4,6]. Compared to a normal antigen-induced T-cell response where .001-.0001% of the body’s T-cells are activated, SAgs are capable of activating up to 20% of the body’s T-cells [23]. This causes a massive immune response that is not specific to any particular epitope on the SAg. Since one of the fundamental strengths of the adaptive immune system is its ability to target antigens with high specificity, SAgs produce an immune response that is effectively useless. Microbes (including viruses, mycoplasma, and bacteria [2]) produce SAgs as a defense mechanism to aid them in evading the immune system [4]. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... In chemistry, a disulfide is an ion formed by sulfur atoms. ... Image File history File links Size of this preview: 469 × 600 pixelsFull resolution (718 × 918 pixel, file size: 241 KB, MIME type: image/png) Made by Bassophile, using PDB code 1JWU using PyMol I, the creator of this work, hereby grant the permission to copy, distribute and/or modify this... Image File history File links Size of this preview: 469 × 600 pixelsFull resolution (718 × 918 pixel, file size: 241 KB, MIME type: image/png) Made by Bassophile, using PDB code 1JWU using PyMol I, the creator of this work, hereby grant the permission to copy, distribute and/or modify this... An exotoxin is a soluble chemical excreted by a microorganism, including bacteria, fungi, algae, and protozoa. ... A mitogen is a chemical, usually some form of a protein that encourages a cell to commence cell division, triggering mitosis. ... A lymphocyte is a type of white blood cell involved in the human bodys immune system. ... For the server security software, see Microsoft Forefront. ... T cells belong to a group of white blood cells known as lymphocytes and play a central role in cell-mediated immunity. ... An epitope is the part of a macromolecule that is recognized by the immune system, specifically by antibodies, B cells, or cytotoxic T cells. ... The immune system is the collection of organs and tissues involved in the adaptive defense of a body against foreign biological material. ... A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). ... This article is about biological infectious particles. ... Species M. genitalium M. hominis M. pneumoniae etc. ... 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. ...


Types of Superantigens

The most well characterized superantigens are secreted by the bacteria Staphylococcus aureus, and Streptococcus pyogenes [1]. These bacteria produce more than 20 different SAgs [9, 15]. Five groups have been proposed for classifying these toxins based on the specific variable region of the β chain of the human T cell receptor (TCR) to which they bind. Group I, for example, contains Toxic Shock Syndrome Toxin 1 (TSST-1) [1, 2]. Other non-bacterial SAgs have been discovered and are discussed in the section on endogenous superantigens. 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... Binomial name Streptococcus pyogenes Rosenbach 1884 Streptococcus pyogenes is a Gram-positive coccus that grows in long chains depending on the culture method. ... For other uses, see Toxin (disambiguation). ... Antigen presentation stimulates T cells to become either cytotoxic CD8+ cells or helper CD4+ cells. ... Toxic shock syndrome (TSS) is a rare but potentially fatal disease caused by a bacterial toxin. ... Look up Endogenous in Wiktionary, the free dictionary. ...

Most of the genes encoding SAgs are located in close proximity to each other on mobile elements of bacterial genomes such as plasmids or “pathogenicity islands” [15]. An operon known as the enterotoxin gene cluster was found to be common in most SAg-producing bacterial strains [15]. Table 1 illustrates the main groups of enterotoxins and nomenclature used to describe them. This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... Figure 1: Illustration of a bacterium with plasmids enclosed showing chromosomal DNA and plasmids. ... A pathogen or infectious agent is a biological agent that causes disease or illness to its host. ... An operon is a group of key nucleotide sequences including an operator, a common promoter, and one or more structural genes that are controlled as a unit to produce messenger RNA (mRNA). ...

Table 1. Major bacterial SAgs and their characteristics and nomenclature [15].
Toxins Amino acids Molecular weight motifs


Figure 2. Structure of a typical superantigen showing the binding sites for the MHC and TCR [13]

SAgs are produced intracellularly by bacteria and are released upon infection as extracellular mature toxins [5]. The sequences of these toxins are relatively conserved among the different subgroups. More important than sequence homology, the 3D structure is very similar among different SAgs resulting in similar functional effects among different groups [12, 14]. Crystal structures of the enterotoxins reveals that they are compact, ellipsoidal proteins sharing a characteristic two-domain folding pattern comprising an NH2-terminal β barrel globular domain known as the oligosaccharide / oligonucleotide fold, a long α-helix that diagonally spans the center of the molecule, and a COOH terminal globular domain [12]. The domains have binding regions for the Major Histocompatibility Complex Class II (MHC Class II) and the T-cell Receptor (TCR), respectively (see Figure 2) [13]. Enargite crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... Source Four ERS Ellipsoidal, or Ellipsoidal Reflector Spotlight (abbreviated to ERS), is the name for a type of theatrical light, getting the name from the ellipsoidal reflector used to intensify the light of a back-loading lamp through the barrel and lens. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... The Globular Cluster M80 in the constellation Scorpius is located about 28,000 light years from the Sun and contains hundreds of thousands of stars. ... Look up domain in Wiktionary, the free dictionary. ... An oligosaccharide is a saccharide polymer containing a small number (typically three to six) of component sugars, also known as simple sugars. ... Oligonucleotides are short sequences of nucleotides (RNA or DNA), typically with twenty or fewer bases. ... Side view of an α-helix of alanine residues in atomic detail. ... The major histocompatibility complex (MHC) is a large genomic region or gene family found in most vertebrates. ... TCR can mean: Toronto Civic Railways Total Control Racing, a slotless track mini-car racing that lets you control your car Tottenham Court Road, a street in London which Tottenham Court Road tube station is named after TCR (music), the musical project of Robin Moulder and TC of Satiate. ...


Superantigens bind first to the MHC Class II and then coordinate to a T-cell Receptor (TCR) with a specific Variable β motif [4,14,15].

MHC Class II

Figure 4. Ribbon diagrams showing three classes of SAg (red) binding to MHC Class II molecules (blue and yellow). SEB shows binding to α-chain; TSST shows binding at a different location on the α-chain; SPE-C shows binding to the β chain mediated by a zinc ion, which blocks antigen interaction with the TCR [1].

Binding to the MHC class II can involve interactions between the SAg and the peptide in the cleft of the MHC, as is the case with TSST-1 of the Group I SAgs. Group II SAgs exhibit peptide independent binding. Most SAgs bind preferentially to the α-chain of MHC class II molecules in the NH2-terminal domain [1, 15]. There are several different forms of the Human Leukocyte Antigen (HLA) that exhibit some variation on the heavy chains, and most SAgs show preference for the HLA-DQ form of the molecule [15]. Binding to the α-chain puts the SAg in the appropriate position to coordinate to the TCR. Less commonly, SAgs attach to the polymorphic MHC class II β-chain in an interaction mediated by a zinc ion coordination complex between three SAg residues and a highly conserved region of the HLA-DR β chain [14]. The use of a zinc ion in binding leads to a higher affinity interaction [12]. Several staphylococcal SAgs are capable of cross-linking MHC molecules by binding to both the α and β chains [12,14]. This mechanism stimulates cytokine expression and release in antigen presenting cells as well as inducing the production of costimulatory molecules that allow the cell to bind to and activate T cells more effectively [14]. Peptides (from the Greek πεπτος, digestible), are the family of short molecules formed from the linking, in a defined order, of various α-amino acids. ... HLA region of Chromosome 6 The human leukocyte antigen system (HLA) is the name of the human major histocompatibility complex (MHC). ... An antibody molecule. ... HLA DQ is a protein/peptide-antigen receptor and graft-versus-host disease antigen that is composed of 2 subunits DQα and DQβ. DQα and DQβ are encoded by two loci, HLA-DQA1 and HLA-DQB1 which are found in the MHC Class II (or HLA-D) region in the... In general, polymorphism describes multiple possible states for a single property (it is said to be polymorphic). ... 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. ... HLA-DR is a major histocompatibility complex, class II, cell surface receptor encoded by the human leukocyte antigen complex on chromosome 6 region 6p21. ... Vulcanization is an example of cross-linking. ... Cytokines are a group of proteins and peptides that are used in organisms as signaling compounds. ...

T-cell Receptor

Figure 4. Model of a SAg (SEB) linking an MHC Class II and a TCR [23]

The T-cell binding region of the SAg interacts with the Variable region on the Beta chain of the T-cell Receptor. A given SAg can activate a large proportion of the T-cell population because the human T-cell repertoire comprises only about 50 types of Vβ elements and some SAgs are capable of binding to multiple types of VB regions. This interaction varies slightly among the different groups of SAgs [13]. Variability among different people in the types of T-cell regions that are prevalent explains why some people respond more strongly to certain SAgs. Group I SAgs contact the Vβ at the CDR2 and framework region of the molecule [1,9]. SAgs of Group II interact with the Vβ region using mechanisms that are conformation-dependent. These interactions are for the most part independent of specific Vβ amino acid side-chains. Group IV SAgs have been shown to engage all three CDR loops of certain Vβ forms [1,9]. The interaction takes place in a cleft between the small and large domains of the SAg and allows the SAg to act as a wedge between the TCR and MHC. This displaces the antigenic peptide away from the TCR and circumvents the normal mechanism for T-cell activation [14, 23]. A single chain antibody fragment showing the positions of the three complementarity determining regions, CDR1, CDR2 and CDR3 A complementarity determining region (CDR) is a short amino acid sequence found in the variable domains of antigen receptor (e. ... Conformation generally means structural arrangement. ...

The biological strength of the SAg (its ability to stimulate) is determined by its affinity for the TCR. SAgs with the highest affinity for the TCR elicit the strongest response [22]. SPMEZ-2 is the most potent SAg discovered to date [22]. Look up affinity in Wiktionary, the free dictionary. ...

T-cell Signaling

The SAg cross-links the MHC and the TCR inducing a signaling pathway that results in the proliferation of the cell and production of cytokines. Low levels of Zap-70 have been found in T-cells activated by SAgs, indicating that the normal signaling pathway of T-cell activation is impaired [10]. It is hypothesized that Fyn rather than Lck is activated by a tyrosine kinase, leading to the adaptive induction of anergy [18]. Both the protein kinase C pathway and the protein tyrosine kinase pathways are activated, resulting in upregulating production of proinflammatory cytokines [11]. This alternative signaling pathway impairs the calcium/calcineurin and Ras/MAPkinase pathways slightly [18], but allows for a focused inflammatory response. 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. ... ZAP-70 is an abbrevation for Zeta-chain-associated protein kinase 70 (70 is the molecular weight in kDa). ... Funen (Danish: Fyn) is the third largest island of Denmark. ... Rickenbacker International Airport (airport code: LCK) is located in Columbus, Ohio. ... Tyrosine kinases are a subclass of protein kinase, see there for the principles of protein phosphorylation A tyrosine kinase (EC 2. ...

Direct Effects

SAg stimulation of antigen presenting cells and T-cells elicits a response that is mainly inflammatory, focused on the action of Th1 T-helper cells. Some of the major products are IL-1, IL-2, IL-6, TNF-α, gamma interferon (IFN-γ), macrophage inflammatory protein 1α (MIP-1α), MIP-1β, and monocyte chemoattractant protein 1 (MCP-1) [11]. This excessive uncoordinated release of cytokines, (especially TNF-α), overloads the body and results in to rashes, fever, and can lead to multi-organ failure, coma and death [9, 15]. Deletion or anergy of activated T-cells follows infection. This results from production of IL-10 from prolonged exposure to the toxin. IL-10 downregulates production of IL-2, MHC Class II, and costimulatory molecules on the surface of APCs. These effects produce memory cells that are unresponsive to antigen stimulation [8, 19]. One mechanism by which this is possible involves cytokine-mediated suppression of T-cells. MHC crosslinking also activates a signaling pathway that suppresses hematopoiesis and upregulates Fas-mediated apoptosis [21]. IFN-α is another product of prolong SAg exposure. This cytokine is closely linked with induction of autoimmunity [20], and the autoimmune disease Kawasaki Disease is known to be caused by SAg infection [22]. SAg activation in T-cells leads to production of CD40 ligand which activates isotype switching in B cells from to IgG and IgM and IgE [17]. To summarize, the T-cells are stimulated and produce excess amounts of cytokine resulting in cytokine-mediated suppression of T-cells and deletion of the activated cells as the body returns to homeostasis. The toxic effects of the microbe and SAg also damage tissue and organ systems, a condition known as Toxic Shock Syndrome [17]. If the initial inflammation is survived, the host cells become anergic or are deleted, resulting in a severely compromised immune system. This article or section does not adequately cite its references or sources. ... Interleukin-1 (IL-1) is secreted by the macrophages, monocytes and dendritic cells. ... The abbreviation IL-2 can refer to: Interleukin-2, a cytokine responsible for stimulating the growth of T-lymphocytes. ... Interleukin-6 (IL-6) is a pro-inflamatory cytokine secreted by T cells and macrophages to stimulate immune response to trauma, especially burns or other tissue damage leading to inflammation. ... In medicine, tumor necrosis factor alpha (TNFα, cachexin or cachectin) is an important cytokine involved in systemic inflammation and the acute phase 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. ... For the ICAO airport code see Candle Lake Airpark Expression pattern Orthologs Human Mouse Entrez Ensembl Uniprot Refseq Location Chemokine (C-C motif) ligand 2 (CCL2) is a small cytokine belonging to the CC chemokine family that is also known as monocyte chemotactic protein-1 (MCP-1). ... This article needs additional references or sources for verification. ... Anergy is a theory in immunobiology in which there is a lack of reaction by the bodys defence mechanisms when foreign substances come into contact with the body. ... Ilyushin Il-10 was a ground attack aircraft that was an upgrade from the Ilyushin Il-2 developed past the second world war. ... Haematopoiesis is the formation of blood cellular components. ... A section of mouse liver showing an apoptotic cell indicated by an arrow Apoptosis (pronounced apo tō sis) is a process of suicide by a cell in a multicellular organism. ... Kawasaki disease, also known as lymph node syndrome, mucocutaneous node disease, infantile polyarteritis and Kawasaki syndrome, is a poorly understood self-limited vasculitis that affects many organs, including the skin and mucous membranes, lymph nodes, blood vessel walls, and the heart. ... CD40 is a costimulatory protein found on antigen presenting cells. ... 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. ... IGM might be an acronym or abbreviation for: The polymeric immunoglobulin, IgM International Grandmaster, a chess ranking intergalactic medium Intragroup medium - see: Intracluster medium IG Metall - the dominant German metalworkers union IGM is an acronym created by Robinson Technologies for several early BBS door games, including Legend of the Red... IGE (Internet Gaming Entertainment) is the largest MMORPG services company world-wide, with offices in Los Angeles, Hong Kong, and Miami. ... Toxic shock syndrome (TSS) is a rare but potentially fatal disease caused by a bacterial toxin. ...

Superantigenicity independent Effects (Indirect Effects)

Apart from their mitogenic activity, SAgs are able to cause symptoms that are characteristic of infection [as cited by 2].

One such effect is emesis. This effect is felt in cases of food poisoning, when SAg-producing bacteria release the toxin, which is highly resistant to heat. There is a distinct region of the molecule that is active in inducing gastrointestinal toxicity [as cited by 2]. This activity is also highly potent, and quantities as small as 20-35ug of SAg are able to induce vomiting [15]. Vomiting (or emesis) is the forceful expulsion of the contents of ones stomach through the mouth. ... Foodborne illness or food poisoning is caused by consuming food contaminated with pathogenic bacteria, toxins, viruses, prions or parasites. ... 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... To meet Wikipedias quality standards, this article or section may require cleanup. ...

SAgs are able to stimulate recruitment of neutrophils to the site of infection in a way that is independent of T-cell stimulation. This effect is due to the ability of SAgs to activate monocytic cells, stimulating the release of the cytokine TNF-α, leading to increased expression of adhesion molecules that recruit leukocytes to infected regions. This causes inflammation in the lungs, intestinal tissue, and any place that the bacteria have colonized [3]. While small amounts of inflammation are natural and helpful, excessive inflammation can lead to tissue destruction. Neutrophil granulocytes (commonly referred to as neutrophils) are a class of white blood cells and are part of the immune system. ... 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. ... This article refers to a colony in politics and history. ... An abscess on the skin, showing the redness and swelling characteristic of inflammation. ...

One of the more dangerous indirect effects of SAg infection concerns the ability of SAgs to augment the effects of endotoxins in the body. This is accomplished by reducing the threshold for endotoxicity. Schlievert demonstrated that, when administered conjunctively, the effects of SAg and endotoxin are magnified as much as 50 000 times [4]. This could be due to the reduced immune system efficiency induced by SAg infection. Aside from the synergistic relationship between endotoxin and SAg, the “double hit” effect of the activity of the endotoxin and the SAg result in effects more deleterious that those seen in a typical bacterial infection. This also implicates SAgs in the progression of sepsis in patients with bacterial infections [17]. Endotoxin is part of the outer membrane of the cell wall of Gram-negative bacteria. ... This page is a candidate to be copied to Wiktionary. ... Sepsis (in Greek Σήψις, putrefaction) is a serious medical condition, resulting from the immune response to a severe infection. ...

Diseases Associated with Superantigen production [2]

Toxic shock syndrome (TSS) is a rare but potentially fatal disease caused by a bacterial toxin. ... Kawasaki disease, also known as lymph node syndrome, mucocutaneous node disease, infantile polyarteritis and Kawasaki syndrome, is a poorly understood self-limited vasculitis that affects many organs, including the skin and mucous membranes, lymph nodes, blood vessel walls, and the heart. ... For the beetle, see Exema. ... Rheumatoid arthritis (RA) is traditionally considered a chronic, inflammatory autoimmune disorder that causes the immune system to attack the joints. ... For the disease characterized by excretion of large amounts of very dilute urine, see diabetes insipidus. ...


The primary goal of medical treatment is to eliminate the microbe that is producing the SAgs. This is accomplished through the use of vasopressors, fluid resuscitation and antibiotics [2]. The body naturally produces antibodies to some SAgs, and this effect can be augmented by stimulating B-cell production of these antibodies [16]. Immunoglobulin pools are able to neutralize specific antibodies and prevent T-cell activation. Synthetic antibodies and peptides have been created to mimic SAg-binding regions on the MHC class II, blocking the interaction and preventing T cell activation [as cited by 2]. Immunosuppressants are also employed to prevent T-cell activation and the release of cytokines. Corticosteroids are used to reduce inflammatory effects [17]. A vasoconstrictor, also vasopressor or simply pressor, is any substance that acts to cause vasoconstriction (narrowing of the lumena of blood vessels) and usually results in an increase of the blood pressure. ... Fluid replacement or fluid resuscitation is the medical practice of replenishing bodily fluid lost through sweating, bleeding, fluid shifts or other pathologic processes. ... An antibiotic is a drug that kills or slows the growth of bacteria. ... Wikipedia does not yet have an article with this exact name. ... The abbreviation B comes from bursa of Fabricius that is an organ in birds in which avian B cells mature. ... 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. ... Immunosuppressive drugs or immunosuppressants are drugs that are used in immunosuppressive therapy to inhibit or prevent activity of the immune system. ... In physiology, corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. ...

Evolution of Superantigen Production

SAg production effectively corrupts the immune response, allowing the microbe secreting the SAg to be carried and transmitted unchecked. One mechanism by which this is done system is through inducing anergy of the T-cells to antigens and SAgs [8, 10]. Lussow and MacDonald demonstrated this by systematically exposing animals to a streptococcal antigen. They found that exposure to other antigens after SAg infection failed to elicit an immune response [8]. In another experiment, Watson and Lee discovered that memory T-cells created by normal antigen stimulation were anergic to SAg stimulation and that memory T-cells created after a SAg infection were anergic to all antigen stimulation. The mechanism by which this occurred was undetermined [10]. The genes that regulate SAg expression also regulate mechanisms of immune evasion such as M protein and capsule expression, supporting the hypothesis that SAg production evolved primarily as a mechanism of immune evasion [6]. Anergy is a theory in immunobiology in which there is a lack of reaction by the bodys defence mechanisms when foreign substances come into contact with the body. ... A lymphocyte is a shown in the center of this picture 1. ... A paraprotein is an abnormal protein in the urine or blood, most often associated with benign MGUS (monoclonal gammopathy of undetermined significance) and multiple myeloma. ... The word capsule (from the Latin capsula, a small box), has many similar meanings in English: In botany, a capsule is a type of dry fruit as in the poppy, iris, foxglove, etc. ... This article is about biological evolution. ...

When the structure of individual SAg domains has been compared to other immunoglobulin-binding streptococcal proteins (such as those toxins produced by [[E. coli]]) it was found that the domains separately resemble members of these families. This homology suggests that the SAgs evolved through the recombination of two smaller B-strand motifs [24]. Homology is an important concept in several disciplines: Homology (anthropology) in archaeology and anthropology. ...

Endogenous SAgs

Minor lymphocyte stimulating (Mls) exotoxins were originally discovered in the thymic stromal cells of mice. These toxins are encoded by SAg genes that were incorporated into the mouse genome from the mouse mammary tumour virus (MMTV). The presence of these genes in the mouse genome allows the mouse to express the antigen in the thymus as a means of negatively selecting for lymphocytes with a variable Beta region that is susceptible to stimulation by the viral SAg. The result is that these mice are immune to infection by the virus later in life [as cited by 2]. In human anatomy, the thymus is a ductless gland located in the upper anterior portion of the chest cavity. ... Stroma can refer to: 1) The connective supportive framework of a biological cell, tissue, or organ. ... (Veterinary Medicine) Mouse mammary tumor virus (MMTV) is a virus that causes breast cancer in mouse Mus domesticus. ... Thymus, see Thyme. ... A request has been made on Wikipedia for this article to be deleted in accordance with the deletion policy. ...

Similar endogenous SAg-dependent selection has yet to be identified in the human genome, but endogenous SAgs have been discovered and are suspected of playing an integral role in viral infection. Infection by the Epstein-Barr virus, for example, is known to cause production of a SAg in infected cells, yet no gene for the toxin has been found on the genome of the virus. The virus manipulates the infected cell to express its own SAg genes, and this helps it to evade the host immune system. Similar results have been found with rabies, cytomegalovirus, and HIV [as cited by 2]. The Epstein-Barr virus (EBV), also called Human herpesvirus 4 (HHV-4), is a virus of the herpes family (which includes Herpes simplex virus and Cytomegalovirus), and is one of the most common viruses in humans. ... Species see text Cytomegalovirus (CMV) (from the Greek cyto-, cell, and -mega-, large) is a viral genus of the Herpesviruses group: in humans it is commonly known as human herpesvirus 5 (HHV-5). ... 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). ...


Much detailed research has been conducted to determine the specific structures and binding mechanisms of each type of SAg. This paper presents a general overview of some of these that are more common and well-understood mechanisms of SAg infection. Recent research attempts to harness the immunostimulatory properties of these molecules by using specific SAgs to induce inflammatory cytokines that could target and prevent tumour growth [16]. As the microbial population develops more effective ways of infecting other organisms the human population uses intelligence to combat the advancing lines


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  21. Masaki Yamaguchi, Steve Nadler, Jong-Wook Lee, and H. Joachim Deeg. 1999 Induction of negative regulators of hematopoiesis in human bone marrow cells by HLA-DR cross-linking. Transplant Immunology. 7; 159-168.
  22. Vickery L. Arcus, Thomas Proft, Jill A. Sigrell, Heather M. Baker, John D. Fraser and Edward N. Baker. 2000. Conservation and variation in superantigen structure and activity highlighted by the three-dimensional structures of two new superantigens from Streptococcus pyogenes. Journal of Molecular Biology. 299 (1); 157-168
  23. Hongmin Li, Andrea Llera, Daisuke Tsuchiya, Lukas Leder, Xavier Ysern, Patrick M. Schlievert, Klaus Karjalainen, and Roy A. Mariuzza. 1998. Three-Dimensional Structure of the Complex between a T Cell Receptor b Chain and the Superantigen Staphylococcal Enterotoxin B. Immunity, 9; 807–816
  24. C Bachert, P Gevaert, P van Cauwenberge 2002. Staphylococcus aureus enterotoxins: a key in airway disease? Allergy 57 (6), 480–487.

Further reading

  • Superantigen Web Database at Birkbeck College
    • Introduction to SAgs at Superantigen Web Database
  • List of Superantigen Proteins from UniProt
  • MeSH Superantigens

  Results from FactBites:
Reference.com/Encyclopedia/Superantigen (517 words)
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.
Superantigens are secreted as exotoxins by bacteria or protozoa, alternatively viruses hijack our own molecular machinery to generate endotoxin forms of superantigens.
In the Zinc-independent superantigens, both the T-cell receptor and MHC-type II molecules are able to simultaneously bind the β-barrel domain: this simultaneous cross-linking of the molecules and their associated cells leads to the over-activation of T-cells which in turn leads to the over production of cytokines and other cell-signalling molecules.
Superantigen (351 words)
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.
Superantigens are secreted as exotoxins by bacteria, alternatively viruses hijack our own molecular machinery to generate endotoxin forms of superantigens.
Superantigens are also the suspected cause of numerous diseases displaying characteristic symptoms with unknown causes.
  More results at FactBites »



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