In a granuloma from a patient with sarcoidosis, the central collection of epithelioid macrophages is surrounded by CD4+ T lymphocytes. The epithelioid macrophages are characterized by which functional change compared to normal macrophages?

• A Enhanced phagocytic capacity with increased lysosomal enzyme activity
• B Reduced phagocytic capacity with increased secretory function and fusion tendency ✓
• C Conversion to dendritic cells with upregulation of MHC class II
• D Increased oxidative burst capacity via enhanced NADPH oxidase

Explanation

Epithelioid macrophages represent a specialized differentiation state driven by prolonged IFN-gamma stimulation in chronic granulomatous inflammation. They are characterized by reduced phagocytic capacity (fewer lysosomes, reduced NADPH oxidase activity) but greatly enhanced secretory function, including secretion of ACE, lysozyme, 1-alpha-hydroxylase (explaining hypercalcemia in sarcoidosis), and various cytokines. They also tend to fuse with each other to form multinucleated giant cells. This 'secretory' phenotype explains the serum biomarkers used to monitor sarcoidosis activity (ACE, soluble IL-2R).

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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