 The C4b fragments can then bind to the surface of the bacterium, and initiate the formation of a C3-convertase.The subsequent complement cascade catalyzed by C3-convertase results in creating a membrane attack complex, which causes lysis of the pathogen as well as altered-self in the context of apoptotic and necrotic cells.MBL/MASP-1 complex also has thrombin-like activity (thrombin clots fibrin to initiate blood clots).