In the formation of a tuberculous granuloma, which cytokine secreted by sensitized CD4+ T cells (Th1 cells) is most critical for maintaining macrophage activation and granuloma integrity?

• A IFN-γ, activating macrophages to kill intracellular mycobacteria and maintain granuloma ✓
• B IL-4, driving M2 macrophage polarization
• C IL-17, recruiting neutrophils to contain mycobacteria
• D IL-10, suppressing excessive macrophage activation

Explanation

IFN-γ secreted by antigen-specific Th1 CD4+ T cells is the master cytokine for granuloma formation and maintenance in tuberculosis. It activates macrophages (M1 polarization) to upregulate iNOS (generating NO), lysosomal enzymes, and reactive oxygen species necessary for killing intracellular M. tuberculosis and forming the granuloma. TNF-α from macrophages works synergistically with IFN-γ. IL-4 drives Th2/M2 polarization which is ineffective against TB. IL-10 can suppress protective Th1 responses and promote chronicity.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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