IMMUNOLOGY

Detailed explanation-1: -DAF and CR1 can bind to C3b to block formation of the alternative C3 convertase (1) and also accelerate the decay of the C3bBb complex (2).

Detailed explanation-2: -The C3 convertase formed in the classical or lectin pathways is formed of C4b and C2b instead (NB: C2b, the larger fragment of C2 cleavage, was formerly known as C2a). The cleavage of C4 and C2 is mediated by serine proteases.

Detailed explanation-3: -C3 convertase can be used to refer to the form produced in the alternative pathway (C3bBb) or the classical and lectin pathways (C4bC2a). Once formed, both C3 convertases will catalyze the proteolytic cleavage of C3 into C3a and C3b (hence the name “C3-convertase").