In leprosy, the Ridley-Jopling classification defines the lepromatous pole (LL) as immunologically anergic to M. leprae antigens. Which T-cell subset dominance characterizes the lepromatous pole as compared to the tuberculoid pole?

• A Tuberculoid: CD8+ cytotoxic T cell dominance; Lepromatous: CD4+ helper T cell dominance
• B Tuberculoid: CD4+ Th1 dominance; Lepromatous: CD4+ Th2 dominance with suppressed cell-mediated immunity ✓
• C Tuberculoid: natural killer cell dominance; Lepromatous: B cell dominance
• D Tuberculoid: regulatory T cell (Treg) dominance; Lepromatous: Th17 dominance

Explanation

At the tuberculoid pole (TT), a robust CD4+ Th1 response (IFN-γ, IL-2, IL-12) activates macrophages to kill M. leprae, resulting in few, well-defined, AFB-negative lesions with granuloma formation. At the lepromatous pole (LL), CD4+ Th2 responses dominate (IL-4, IL-5, IL-10), suppressing macrophage killing; bacterial load is high, lesions are numerous and widespread, and lepromin test is negative. This Th1/Th2 paradigm is the immunological basis of the clinical spectrum of leprosy.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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