Which subtype of IgG activates alternate complement system.

Ans. id 'd' i.e. IgG4 * Four subclasses oflgG are there with IgG{ is found in greatest amount and IgG4 in least amount.IgG,-65%IgG3-8%IgG2-23%IgG4-4%* Ig G1, Ig G3 and sometimes Ig G2 activate classical complement pathway.* Ig G4 activates alternate complement pathway.* IgG2 is directed against polysaccharide antigen so it is important in defence against encapsulated bacteria.