In sarcoidosis, the granulomas are non-caseating and driven by CD4+ Th1 cells. The key cytokine that drives macrophage fusion into multinucleated giant cells and sustains granuloma formation is:
- A IFN-γ produced by Th1 cells activating macrophages and inducing fusion via CD44 and DC-STAMP ✓
- B IL-4 from Th2 cells inducing alternative macrophage activation
- C IL-17 from Th17 cells recruiting neutrophils to form the granuloma core
- D TGF-β causing macrophage apoptosis and replacement by fibroblasts
Correct answer: A. IFN-γ produced by Th1 cells activating macrophages and inducing fusion via CD44 and DC-STAMP
Explanation
Granuloma formation in sarcoidosis is a CD4+ Th1-driven response. IFN-γ secreted by Th1 cells classically activates macrophages (M1 polarization), upregulates DC-STAMP and CD44 on macrophage surfaces to mediate cell-cell fusion into Langhans-type or foreign-body type giant cells, and sustains TNF-α production necessary for granuloma integrity. IL-4 drives Th2 and M2 polarization (anti-inflammatory/fibrotic). IL-17 drives neutrophilic inflammation. TGF-β promotes fibrosis but is not the primary granuloma driver.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.