Molecular Biology/Genetics USMLE Step 1 Practice Question
A 19-year-old man presents with recurrent bacterial infections and impaired wound healing. Vital signs show BP 118/76 mmHg, HR 88/min, RR 16/min, temp 37.2°C, SpO2 98%. Laboratory studies reveal normal total white blood cell count but absent neutrophil chemotaxis on flow cytometry. Complement panel shows markedly decreased C5 levels. He denies recent antibiotic use. Loss of which complement fragment would most directly impair neutrophil recruitment to infection sites?
Answer choices
- AC1q
- BC3b
- CC2b
- DC5aCorrect answer
- EC9
- FC4b
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