Human anaphylatoxin CD88 is a 74-residue glycopolypeptide which is generated by proteolytic cleavage of the complement factor C5 in the course of complement activation. A variety of biological effects evoked by CD88 could be demonstrated, rendering this molecule an important mediator of inflammation, with granulocytes and macrophages as the main target cells. All cellular responses to CD88 are specifically mediated by interactions with the membrane bound C5a receptor, a seven transmembrane GTP-binding-protein-coupled receptor that belongs to the rhodopsin supergene family.