Detection and quantification of the terminal C5b-9 complex of human complement by a sensitive enzyme-linked immunosorbent assay.

An enzyme-linked immunosorbent assay for detection and quantification of the terminal complexes (SC5b-9 and membrane attack complex) of human complement is described. We separate the complex from the native complement components, to use antibodies against the native components in a 'double-antibody sandwich' technique. It is thereby possible to detect the terminal complement complex in solution without the requirement of specific antibodies against the neoantigens. The results show that the assay is both sensitive and specific. Evidence is presented that a terminal complement complex occurs in a normal plasma pool. The terminal complement complex may be valuable for evaluating both the physiology and pathophysiology of the complement system in vivo.