Immunology USMLE Step 1 Practice Question
A 17-year-old girl receives a tetanus booster immunization. Within 48 hours, she develops localized arm erythema (BP 118/76, HR 82, RR 16, Temp 38.2°C, SpO2 98%). Serum analysis shows elevated IgG titers with significantly higher affinity antibodies compared to her primary vaccination response five years prior. She denies fever or systemic symptoms. Which of the following processes most directly explains the increased antibody affinity observed during this secondary immune response?
Answer choices
- ARandom assortment of heavy and light chains during fetal development
- BActivation of complement by immune complexes
- CSomatic hypermutation and selection of B cells in germinal centersCorrect answer
- DRearrangement of V, D, and J gene segments in thymocytes
- ENegative selection of autoreactive T cells in the thymic medulla
- FJunctional diversity from N-nucleotide addition during V(D)J recombination
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