Anaphylatoxin
From Biocrawler, the free encyclopedia.
Anaphylatoxin, or anaphylotoxin, is a fragment (C3a, C4a or C5a) of the complement system that triggers degranulation of (release of substances from) mast cells or basophils, which is an important part of the immune system in all kinds of inflammation and especially as part of defense against parasites. If the degranulation is too strong, it can cause allergic reactions.
Anaphylatoxins indirectly mediate:
- spasms of smooth muscle cells, for example bronchospasms
- increase in the permeability of blood capillaries
- chemotaxis — receptor-mediated movement of leukocytes in the direction of the increasing concentration of anaphylatoxins
Although some drugs (morphine, codeine, synthetic ACTH) and some neurotransmitters (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.
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