Bacteriology USMLE Step 1 Practice Question
A 35-year-old healthcare worker with no respiratory symptoms undergoes TB exposure screening. Forty-eight hours after intradermal PPD placement, she develops a 16 mm area of induration without vesiculation. Vital signs are normal (BP 118/76, HR 82, RR 16, Temp 37°C). Chest X-ray shows no infiltrates. She takes no immunosuppressive medications. Which immune mechanism produces this delayed-type hypersensitivity reaction?
Answer choices
- AIgG mediated opsonization
- BIgE mediated mast cell degranulation
- CImmune complex deposition
- DComplement mediated cytolysis
- EMemory T cell mediated delayed hypersensitivityCorrect answer
- FB cell mediated antibody production against tuberculin antigen
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