Immunoaffinity purification of human complement component C9 using monoclonal antibodies.

Five monoclonal antibodies to human C9 were produced. Three of the antibodies had affinities from 1.6 to 3.1 X 10(9) M-1 and 2 were of lower affinity, 0.1 to 0.3 X 10(9) M-1. Four distinct antigenic sites on C9 were detected. The lowest affinity antibody was immobilised on Sepharose 4B and used to isolate C9 from human plasma. A 1200-fold purification was obtained with yield of 30-40%. The purified antigen maintained full cytolytic activity.