The complement component C4 plays a central role in the activation of the classical pathway of the complement system. C4 is cleaved by activated C1 which removes the C4a anaphylato, Xenopus/Amphibian,in from the alpha chain. The remaining active C4b fragment becomes a subunit of the C3 convertase (C4b2a) and the C5 convertase (C3bC4b2a) enzymes of the classical complement pathway. The C4a anaphylato, Xenopus/Amphibian,in is a mediator of local inflammatory process. The C4A6 allotype is totally deficient in hemolytic activity. This antibody recognizes the human complement C4 in ELISA.