Complement C4,a component of the classical complement pathway,has an important role in innate immune function. C4 protein is expressed as a single chain precursor which is proteolytically cleaved into a trimer of alpha,beta,and gamma chains (molecular wights 95,78,and 31 kDa) prior to secretion. The alpha chain is cleaved to release C4 anaphylatoxin,an antimicrobial peptide and a mediator of local inflammation. This antibody raised against 1543-1744aa of human C4A protein recognize C4 gamma chain.