Immunology USMLE Step 1 Practice Question
A 45-year-old man with rheumatoid arthritis receives an experimental fusion protein that blocks B7-CD28 interaction on antigen-presenting cells. His vital signs are stable (BP 128/82, HR 72, RR 16, Temp 37°C). Recent labs show normal CBC and creatinine. He denies fever or infections. Two weeks post-administration, he develops severely diminished T cell proliferation responses to mitogens (lymphocyte count 1,200/μL). Which of the following best explains this immunologic consequence?
Answer choices
- AIncreased histamine release from mast cells
- BIncreased neutrophil oxidative burst
- CEnhanced membrane attack complex formation
- DFailure of T cell activation leading to anergyCorrect answer
- EExcessive class switching in B lymphocytes
- FReduced thymic output of naive T cells due to impaired central tolerance
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