In granuloma formation, which cytokine produced by sensitized T lymphocytes is MOST critical for inducing and maintaining macrophage differentiation into epithelioid cells and giant cells?

• A IL-4 (activating M2 macrophage polarisation)
• B IL-10 (suppressing macrophage activation)
• C IL-17 (recruiting neutrophils to granuloma center)
• D IFN-γ (activating M1 macrophage polarisation) ✓

Explanation

IFN-γ, produced primarily by CD4+ Th1 lymphocytes and NK cells, is the key cytokine that drives classical (M1) macrophage activation, inducing transformation into epithelioid cells with enhanced secretory function and reduced phagocytic capacity. Continued IFN-γ stimulation also drives multinucleated giant cell formation through macrophage fusion. This IFN-γ-dependent macrophage activation is central to the host defense against intracellular pathogens like Mycobacterium tuberculosis, and its genetic deficiency (IL-12/IFN-γ axis mutations) results in severe susceptibility to atypical mycobacterial and Salmonella infections (Mendelian susceptibility to mycobacterial disease).

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.