Immunology USMLE Step 1 Practice Question
A 29-year-old man received antivenom following a rattlesnake bite 10 days ago. He now presents with fever (38.5°C), diffuse urticaria, and arthralgias. Vital signs show BP 128/82, HR 98, RR 16, SpO2 98% on room air. Physical examination reveals tender, swollen wrists and knees. Urinalysis shows 2+ proteinuria. He denies prior antivenom exposure. Which of the following best explains the immunologic mechanism underlying this patient's delayed clinical presentation?
Answer choices
- AImmediate mast cell degranulation caused by allergen cross linking of IgE
- BCytotoxic antibodies directed against host cell surface antigens
- CDonor lymphocytes recognizing host HLA antigens
- DDirect T cell mediated injury without antibody involvement
- EDeposition of circulating antigen antibody complexes with complement activationCorrect answer
- FDelayed-type hypersensitivity reaction mediated by CD8+ T cells recognizing antigen-presenting cells
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