Fig. 2.
In the alternative pathway of complement activation, C3 convertase is spontaneously produced by hydrolysis of C3 to form C3(H2O) in a process referred to as ‘tickover’. If CFH is not sufficient to inhibit cell surface binding, then C3(H2O) will bind with Bb to form C3 convertase resulting in the activation of the downstream complement cascade. MAC= Membrane attack complement.