Inhibition of immune complex-mediated activation of complement. Effects of agents modulating activation of, and the activated C1 complex.

Several known chemical compounds were shown to selectively inhibit the interaction between immune aggregates and C1q, the activation of C1r-C1s complex by immune aggregate-bound C1q, and the esterolytic activity of the activated C1s, C1s. These reactions are relevant to the functions of the first complement component, C1, and its activation induced by immune complexes. The effects of these inhibitors on tissue injury mediated by immune complex-induced complement activation, such as immune hemolysis, passive cutaneous anaphylaxis, and experimental glomerulonephritis were examined. The results suggest an approximate correlation between the activity shown on the molecular level and that obtained in vivo. One such compound, suramin, was shown to be an effective inhibitor of PCA and the proteinuria manifestation of EGN while not affecting antibody fixation to tissue or histamine-mediated skin reaction. These results suggest that effective suppression of the initial steps of complement activation may be of value of controlling immune complex-mediated tissue injuries in disease.