Figure 5.

The effect of inhibitors on classical pathway C3 and C5 conversion. Conversion of C3 (50 nM) or C5 (2.5 nM) in the CP model in the absence or presence of 1 µM complement-binding molecule measured by calcium mobilization in U937-C3aR and U937-C5aR cells, respectively. Conversion is shown as a percentage relative to the control without inhibitor. (A) C5-binding molecules OmCI and eculizumab inhibit CP C5 but not C3 conversion. SSL7 inhibits C5 conversion, as well, but less efficiently. C4b-binding protein (C4BP) inhibits both CP C3 and C5 convertases. (B) None of the C3b-binding molecules, except for Cp40, affect CP C3 conversion, whereas all inhibit C5 conversion. Mutant Efb-C and mutant Ecb are unable to bind C3b and thus do not exhibit inhibition. (A,B) Data of three independent experiments, presented as mean ± SD.