So what exactly is the major difference between these two pathways? Well, as we saw previously, to initiate and activate the classical path pathway, an antibody must find and must bind to its complementary antigen to form the antibody antigen complex. And then that antibody antigen complex goes on to the C One protein of the classical pathway and activates it. And then the C One protein can go on to activate the C two and C four. And that forms a complex known as C four B, C two B complex. And then that activates C Three, which in turn activates C five and that produces our membrane attack complex mac mac.