A pathologist examines a liver biopsy from a patient with Schistosoma mansoni infection and finds non-necrotizing granulomas with central eosinophilic material surrounding schistosome eggs, with surrounding eosinophils, giant cells, and concentric fibrosis ('pipe-stem fibrosis'). Which cytokine drives the granulomatous response and periportal fibrosis in this context?

• A IFN-gamma from Th1 cells — primary driver of classical protective granulomas
• B IL-13 from Th2 cells — driving alternatively activated macrophages and TGF-beta-mediated fibrosis ✓
• C TNF-alpha from macrophages — the central cytokine for granuloma maintenance and fibrosis
• D IL-17 from Th17 cells — neutrophilic inflammation preceding granuloma formation

Explanation

Schistosome egg-induced granulomas in the liver are driven by a Th2 immune response. The eggs release soluble egg antigens (SEA) that polarize CD4+ T cells toward Th2, producing IL-4, IL-5, and IL-13. IL-13 is the key cytokine driving alternatively activated (M2) macrophage polarization, which promotes fibrogenesis through TGF-beta and collagen deposition — leading to the characteristic 'Symmer's pipe-stem' periportal fibrosis causing portal hypertension. IFN-gamma-driven Th1 responses characterize TB/sarcoid granulomas; blocking IL-13 signaling in animal models reduces liver fibrosis.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.