Now, what exactly happens following the formation of the antibody antigen complex? So usually once the antibody antigen complex is formed, that's when we activate the classical pathway of the complement system. So what triggers the classical pathway is the formation of the antibody antigen complex. So what exactly happens once we form that antibody antigen complex to initiate the classical pathway? Well, as it turns out, the complement system actually consists of over 30 inactivated proteins that are found circulating in the bloodstream of our body. And these proteins are only activated when we actually form the antibody antigen complex.