Bacterial Infections USMLE Step 1 Practice Question
A 6-year-old unvaccinated girl presents with severe paroxysmal coughing spells followed by inspiratory whooping and posttussive vomiting for 3 weeks. Vital signs: BP 98/62, HR 112, RR 38, Temp 37.8°C, SpO2 94% on room air. CBC reveals WBC 18,500/μL with marked lymphocytosis (78%). Chest X-ray shows no infiltrates. She denies fever or rhinorrhea. Which mechanism best explains the lymphocytosis observed in this patient?
Answer choices
- AActivation of the Gs protein leading to increased cyclic AMP
- BDirect destruction of ciliated epithelium by endotoxin
- CInterference with folate metabolism
- DSuppression of neutrophil oxidative burst
- EInhibition of the Gi protein leading to increased cyclic AMPCorrect answer
- FBacterial lipopolysaccharide-induced apoptosis of T regulatory cells
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