anaphylatoxin /an′əfī′lətok″sin/ , a fragment (C3a, C4a, or C5a) that is produced during the pathways of the complement system. Along with other mechanisms, it mediates changes in mast cells leading to the release of histamine and other immunoreactive or inflammatory reactive substances. If the degranulation of mast cells is too strong, it can cause allergic reactions.
