BIOL 2050U Lecture Notes - Eosinophil, Mast Cell, Monocyte
Document Summary
Complement cascade 2 parts (enzymatic and lytic/pore forming) C1 binds antibody via q domain (c1q) must bind multiple antibodies fc"s for protease activity (igm, 2 igg"s) C1s cleaves c4 into a and b c4b attaches to bacterial surface attracts c2. C1s cleaves c2 into a and b fragments c4b + c2a = Mbl (mannose-binding lectin) same process except mbl substitutes c1 complex binds mannose via its lectin heads then cleaves c4 and c2 to make classical c3 convertase. **no antibody recognition necessary; bacteria is directly recognized** C3 binds bacterial surface spontaneously then binds factor b which is cleaved by factor d into a and b. **both convertases have same function: cleave c3 into c3b** both also have sim. structure (c4b:c3b::c2a:bb) Amplification presence of one c3b leads to activation of 250+ others some bind bacteria covalently (thioester); most are hydrolyzed by water. Fcr, c1qr, cr1 (for c3b), cr3 (for i-c3b) C5b, c6, 7, 8, 9 form pore on bacterial surface.
