compliment system why the name is complement because it complements the ability of antibodies to do their job three different pathways depending on who pulls the trigger who will start the Cascade if it's antigen-antibody complex this is the classical pathway if it's the bacterial endotoxin this is the alternative pathway if mannose binding lectin this is the lectin pathway in PNH the problem is usually in the alternative pathway so let's elaborate now alternative pathway of the complement what triggers the Cascade is bacterial endotoxin which is a lipo polysaccharide in the outer membrane of gram-negative bacteria that was nice microbiology there we start with factor c3 hydrolysis in the presence of water into factor C 3 B it will bind with factor B and then factor D will convert factor B into B a and B B factor BB will combine with 3 3 B to form c3 convertase this is a big deal c3 convertase will convert c3 into c3a and c3b c3b will bind with c3 convertase to form c5 convertase c5 convertase will do what converts c5 into c 5a and c5 b c 5b together with c6 7 8 and 9 will form something called the Mac this is not anti microsoft and this is not MacDonald's either this is the membrane attack complex it will form a pore in the cell membrane of the bacteria which will disrupt the ionic and osmotic environment of the cell and now the bacteria will die go to hell