Immunology USMLE Step 1 Practice Question
A 33-year-old man received equine-derived antitoxin following a snakebite. Eight days later, he presents with fever (38.8°C), diffuse arthralgias, urticarial rash, and mild dyspnea. Vital signs show HR 102/min, BP 128/76 mmHg, RR 20/min, SpO2 98% on room air. Urinalysis reveals 2+ proteinuria. He denies previous antitoxin exposure. Which of the following best explains the pathophysiologic mechanism of this reaction?
Answer choices
- APreexisting antibodies against donor endothelial antigens
- BDirect T cell cytotoxicity against skin keratinocytes
- CIgE mediated mast cell degranulation
- DAntibody dependent cellular cytotoxicity by natural killer cells
- EImmune complex deposition with complement activationCorrect answer
- FDelayed-type hypersensitivity mediated by sensitized CD4+ T cells
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