What process increases the affinity of antibodies during an immune response?

• A. V(D)J recombination
• B. Isotype switching
• C. Somatic hypermutation
• D. Antigen presentation

Answer: (C)

Affinity maturation during an immune response occurs through somatic hypermutation in the variable regions of immunoglobulin genes within proliferating B cells in germinal centers. Activation-induced cytidine deaminase creates point mutations in the V regions of both heavy and light chains as B cells divide. B cells that acquire mutations yielding higher antigen affinity are selected by binding to antigen on follicular dendritic cells and receiving help from T follicular helper cells; these high-affinity cells then expand and differentiate into plasma cells and memory B cells, producing antibodies with increasingly higher affinity over time.

V(D)J recombination happens earlier in B cell development to create a diverse BCR repertoire, not during the ongoing response. Isotype switching changes the antibody’s constant region to alter effector function, not its affinity. Antigen presentation is about displaying peptide fragments to T cells and does not directly increase antibody affinity.