A 28-year-old man presents with recurrent sino-pulmonary infections since childhood and is found to have very low serum IgG but normal T-cell counts. Nitroblue tetrazolium (NBT) test is normal. Which immunoglobulin class is MOST important in providing long-term immunological memory after vaccination?
- A IgM
- B IgA
- C IgG ✓
- D IgE
Correct answer: C. IgG
Explanation
IgG is the predominant immunoglobulin in serum and the principal mediator of long-term humoral memory; it undergoes class switching after primary IgM response and persists for years. IgM is the first antibody produced in a primary response but does not confer durable memory. IgA is critical at mucosal surfaces, while IgE mediates allergic responses and anti-helminthic immunity.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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