In granulomatous inflammation, epithelioid macrophages fuse to form Langhans giant cells. The key cytokine driving macrophage differentiation into epithelioid cells and their fusion is:
- A IFN-gamma from Th1 lymphocytes ✓
- B IL-4 and IL-13 from Th2 lymphocytes
- C IL-17 from Th17 lymphocytes
- D TNF-alpha from innate immune cells
Explanation
IFN-gamma produced by antigen-activated CD4+ Th1 lymphocytes (and NK cells) is the master activator of macrophages into epithelioid cells in granulomatous inflammation; it upregulates MHC II, lysosomal enzyme production, and the capacity for intracellular killing. Continued IFN-gamma signalling also drives giant cell formation through macrophage fusion. TNF-alpha maintains the integrity of established granulomas (hence anti-TNF therapy can reactivate latent tuberculosis). IL-4/IL-13 promote alternative macrophage activation (M2/anti-inflammatory phenotype) and fibrosis, not granuloma formation.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.