The terminal complement split product C5a has been described as an important mediator in
inflammatory diseases. C5a is generated upon cleavage of C5 and earlier research
suggests that, besides the known C5 convertases formed upon activation of the complement
pathways, various enzymes could activate C5 directly. We demonstrate that eculizumab
effectively blocks C5 activation when mediated by C5-convertase formation, but fails to block
C5a generation resulting from direct enzymatic cleavage by trypsin and thrombin. C5a …