USMLE Step 1 · USMLE Step 1: Medical Sciences
Microbiology, Immunology and Infectious Pathogens
6 practice questions, each with the answer and an explanation.
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Random questions from this topic, one at a time. You see the answer and the explanation straight after each one.
All 6 questions
- A 19-year-old college student presents with high fever, neck stiffness, and a petechial skin rash. Lumbar puncture demonstrates cloudy CSF with abundant polymorphonuclear leukocytes and intracellular…
- Which class of cell surface molecules is recognized by CD8+ cytotoxic T lymphocytes, presenting endogenous cytoplasmic antigens processed by the proteasome?
- A 55-year-old man treated with broad-spectrum clindamycin for cellulitis develops watery, foul-smelling diarrhea, abdominal cramping, and leukocytosis. Colonoscopy reveals yellowish-white pseudomembra…
- Which cytokine secreted by activated Th1 lymphocytes is the principal activator of macrophages and promotes granuloma formation in Mycobacterium tuberculosis infections?
- A 7-year-old boy develops facial puffiness, dark cola-colored urine, and hypertension two weeks after recovering from a skin infection (impetigo). Complement C3 levels are markedly depressed. Renal bi…
- An 8-month-old infant with recurrent pyogenic bacterial infections (otitis media, pneumonia) is evaluated. Flow cytometry shows absent CD19+ and CD20+ B cells, with normal numbers of CD3+ T cells. Ser…
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