C3a, one of the cleavage products of complement component C3, has the following actions:
- anaphylatoxin: it stimulates mast cells and basophils to release histamine, so increasing vascular permeability
- contraction of smooth muscle: particularly of gastrointestinal tract and bronchi
As well as production by the classical and alternative pathways, it can be produced by the action of a variety of C3 cleaving enzymes e.g. bacterial proteases, plasmin.
Last reviewed 01/2018