Complement Component 3a

Complement component 3a is the anaphylatoxin released from the N-terminal region of the C3 alpha chain when C3 convertases of any activation pathway cleave C3. This small cationic peptide signals through the G protein-coupled receptor C3aR, which is expressed on mast cells, eosinophils, monocytes, and other immune cells. C3a triggers mediator release, smooth-muscle contraction, chemotaxis, and amplification of the inflammatory response, and it modulates adaptive immunity and regeneration processes. C3a is rapidly inactivated by carboxypeptidase cleavage to C3adesArg. Recombinant C3a supports receptor-binding assays, anaphylatoxin signaling studies, and complement-inflammation research. Compared with C5a, C3a is a weaker but broadly acting inflammatory mediator.