[Complement activation by C-reactive protein in various inflammatory diseases (in vitro)].

C-reactive protein (CRP)-mediated complement activation can be tested on cryostat sections of the rat kidney by indirect immunofluorescence (C3-IFT). In contrast to a positive C3-IFT regularly obtained with sera of patients with polymyalgia rheumatica, we found unexpectedly negative C3-IFT results in 5/18 patients with seropositive rheumatoid arthritis and in 11/14 patients with bacterial endocarditis in spite of elevated CRP and normal hemolytic complement in these sera. Differential diagnostic and pathophysiological aspects of these findings are addressed.