In granulomatous inflammation, the conversion of macrophages to epithelioid cells and their subsequent fusion into multinucleated giant cells is driven primarily by:

• A IL-4 and IL-13 from Th2 cells promoting alternative macrophage activation
• B TNF-α released by mast cells causing macrophage dedifferentiation
• C IFN-γ secreted by activated CD4+ Th1 cells ✓
• D M-CSF from fibroblasts driving macrophage proliferation

Explanation

IFN-γ produced by activated Th1 lymphocytes is the principal macrophage-activating cytokine that promotes classical (M1) macrophage activation, differentiation into epithelioid cells, and fusion into Langhans-type giant cells. IL-4/IL-13 drive alternative (M2) macrophage activation associated with fibrosis, not granuloma formation. TNF-α augments granuloma formation but does not directly transform macrophages into epithelioid cells. M-CSF governs monocyte-macrophage differentiation, not epithelioid transformation.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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