Anaphylatoxin
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2008-06-22T19:26:49Z
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{{Unreferenced|date=November 2007}}
'''Anaphylatoxins''', or '''anaphylotoxins''', are fragments ([[C3 (complement)|C3a]], [[C4a]] and [[C5a]]) that are produced during the pathways of the [[complement system]].<ref name="pmid3542363">{{cite journal | author = Hugli TE | title = Biochemistry and biology of anaphylatoxins | journal = Complement | volume = 3 | issue = 3 | pages = 111–27 | year = 1986 | pmid = 3542363 | doi = | url = | accessdate = }}</ref>
==Functions==
Anaphylatoxin is able to trigger [[degranulation]] of (release of substances from) [[mast cells]] or [[basophil]]s, which is an important part of the [[immune system]] in all kinds of [[inflammation]] and especially as part of defense against [[parasite]]s. If the degranulation is too strong, it can cause [[allergic reaction]]s.
Anaphylatoxins indirectly mediate:
*spasms of [[smooth muscle|smooth muscle cells]], for example [[bronchospasm]]s
*increase in the permeability of [[capillary|blood capillaries]]
*[[chemotaxis]] — [[receptor (biochemistry)|receptor]]-mediated movement of [[leukocyte]]s in the direction of the increasing concentration of anaphylatoxins
==Examples==
Important anaphylatoxins:
* C3a is not as strong as C5a, but stronger than C4a and can trigger degranulation of Mast-cells and serve as a chemotactic targeting molecule for eosinophile granulocytes.
* C4a is the least active anaphylatoxin
* C5a is the strongest toxin in the row, it is a very strong mediator of inflammation.
** [[co-stimulation]] of C3b at times of phagocytosis (not possible without C5a).
** Chemotactor and activator for granulocytes in general and macrophages
** stimulates respiratory burst in Neutrophils
** increases vascular permeability
** contracts smooth muscle cells
** activates mast cells to release Histamine and TNF-Alpha
==Terminology==
Although some drugs ([[morphine]], [[codeine]], synthetic [[ACTH]]) and some [[neurotransmitter]]s ([[norepinephrine]], [[substance P]]) are important mediators of degranulation of mast cells or basophils, they are generally not called anaphylatoxins. This term is reserved only for fragments of the complement.
== See also ==
*[[Allergy]]
*[[Anaphylatoxin receptors]]
*[[Anaphylaxis]]
*[[Complement system]]
*[[Inflammation]]
*[[Immune system]]
*[[Nervous system]]
==References==
{{Reflist}}
==External links==
* {{MeshName|Anaphylatoxin}}
* {{eMedicineDictionary|Anaphylatoxin}}
{{Immune system}}
[[Category:Complement system]]
[[de:Anaphylatoxin]]
[[pl:Anafilotoksyny]]
[[pt:Anafilatoxina]]