This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: general microbiology, Subject name: Microbiology
A child is suffering from recurrent chronic infections with encapsulated bacteria; Which subclass of IgG does the child has deficiency 
Select and explain. 
A. IgG1, B. IgG2, C. IgG3, D. IgG4
B: IgG2
Answer: B: IgG2 
Explanation: * IgG has four subclasses: IgG1, IgG2, IgG3 and IgG4 * IgG2 antibody is directed against polysaccharide antigens and hence it is most impoant defence against encapsulated bacteria. Ref:- Review of medical microbiology and immunology 13th ed; pg num:- 1127