Inflammation and Immune Pathology USMLE Step 1 Practice Question
A 52-year-old man with a 40 pack-year smoking history presents to the clinic with progressive dyspnea on exertion over the past 2 years and a chronic productive cough. He denies hemoptysis, weight loss, or fever. Vital signs show mild tachypnea at 22 breaths/min; oxygen saturation is 94% on room air. Chest X-ray demonstrates hyperinflation with flattened diaphragms and loss of vascular markings. High-resolution CT confirms centrilobular emphysema predominantly affecting the upper lung lobes. Pulmonary function tests show an FEV1/FVC ratio of 0.58 with minimal response to bronchodilators. Laboratory studies reveal a serum alpha-1 antitrypsin level of 187 mg/dL (normal >200 mg/dL). A transbronchial lung biopsy shows extensive alveolar septal destruction with elastic fiber fragmentation, but minimal lymphocytic infiltration or granulomatous inflammation. Which of the following mechanisms best explains the observed alveolar destruction in this patient?
Answer choices
- AChronic Th1 cell-mediated destruction of type I pneumocyte antigens
- BFibroblast hyperproliferation leading to obliterative fibrosis and bronchiolar narrowing
- CImbalance between neutrophil-derived serine protease activity and antiprotease defenseCorrect answer
- DIgE-mediated mast cell and eosinophil activation causing airway remodeling
- ECirculating immune complex deposition with complement-mediated alveolar wall injury
- FInfectious bronchiolitis obliterans with progressive small airway obliteration
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