Inflammation and Immune Pathology USMLE Step 1 Practice Question
A 19-year-old male college student presents to the emergency department with a 12-hour history of fever, severe frontal headache, photophobia, and neck stiffness. On examination, temperature is 39.5°C, heart rate 124/min, blood pressure 88/56 mmHg, respiratory rate 24/min. A petechial rash is noted on his trunk and lower extremities. Lumbar puncture reveals CSF with WBC 1,400/μL (92% neutrophils), protein 210 mg/dL, glucose 22 mg/dL, and opening pressure 38 cm H₂O. Gram stain demonstrates gram-negative diplococci, and blood cultures subsequently grow Neisseria meningitidis. Which of the following best explains the acute inflammatory cascade and CNS pathology in this patient's infection?
Answer choices
- ABacterial capsular polysaccharide directly invades epithelial cells, triggering apoptosis-mediated barrier breakdown without innate immune activation
- BToll-like receptor recognition of bacterial lipopolysaccharide activates NF-κB signaling, leading to excessive TNF-α and IL-1β production by resident microglia and infiltrating neutrophilsCorrect answer
- CIgG-mediated immune complex deposition at the blood-brain barrier causes complement-independent vasculitis and increased vascular permeability
- DBacterial neuraminidase enzymatically strips sialic acid from meningeal endothelial glycoproteins, directly compromising tight junction integrity
- ECD8+ cytotoxic T lymphocytes recognize bacterial peptides on infected meningeal cells and induce localized tissue necrosis via perforin release
- FMast cell degranulation triggered by IgE cross-linking releases histamine and tryptase, causing selective meningeal vasodilation without neutrophilic infiltration
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