In granuloma formation, the conversion of macrophages into epithelioid cells requires sustained stimulation by which cytokine, produced primarily by activated CD4+ Th1 lymphocytes?

• A IL-4
• B IL-13
• C IFN-gamma ✓
• D TNF-alpha

Explanation

IFN-gamma produced by Th1 CD4+ T cells and NK cells is the critical mediator that transforms macrophages into epithelioid cells and promotes their fusion into multinucleated giant cells. IFN-gamma activates macrophage killing mechanisms (reactive oxygen/nitrogen species, lysosomal enzymes) and upregulates antigen presentation. TNF-alpha is also important for granuloma maintenance (which is why TNF inhibitors predispose to granulomatous infection reactivation), but the primary driver of macrophage-to-epithelioid conversion is IFN-gamma.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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