This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
A child present with recurrent episodes of sinopulmonary infection by bacteria with polysacharide rich capsule. Deficiency of which of the following immunoglobulin subclasses should be specifically investigated - 
Select and explain. 
A. IgA, B. IgG1, C. IgG2, D. IgA + IgG2
D: IgA + IgG2
Answer: D: IgA + IgG2 
Explanation: Ans. is 'd' i.e., IgA+IgG2 Primary Immunodeficiency Diseases, Defination, Diagnosis and Management . IgG2 dificiency is the most common subclass disorder associated with recurrent infections by polysaccharide-encapsulated bacteria. Such infections are more frequent in patients with associated IgA deficiency.