A laboratory measures antibody affinity maturation during a secondary immune response. Which of the following molecular processes in germinal centres is primarily responsible for generating antibodies with progressively higher affinity for antigen?
- A VDJ recombination of heavy chain genes
- B Somatic hypermutation of variable region genes followed by antigen-driven selection ✓
- C Class switch recombination from IgM to IgG
- D Activation-induced cytidine deaminase (AID)-mediated deletion of constant region genes
Explanation
Affinity maturation occurs in germinal centres of secondary lymphoid organs during T-dependent immune responses. Activation-induced cytidine deaminase (AID) introduces point mutations in the variable (V) region genes (somatic hypermutation); B cells expressing higher-affinity BCRs capture more antigen and receive survival signals from follicular helper T cells, while lower-affinity cells undergo apoptosis. VDJ recombination occurs in primary lymphoid organs during development, not in germinal centres. Class switching changes effector function but not antigen-binding affinity.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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