Induration at a tuberculin skin test site is read 48 to 72 hours after intradermal injection of purified protein derivative. Histology of the indurated area shows perivascular accumulation of CD4+ T cells and activated macrophages. The cytokine principally responsible for macrophage activation in this lesion is:

• A IFN-gamma ✓
• B IL-4
• C IL-17
• D TNF-beta alone, acting directly on bacilli

Explanation

The Mantoux reaction is the classic example of type IV delayed-type hypersensitivity. Sensitized CD4+ Th1 cells recognize processed tuberculin presented on APCs and secrete IFN-gamma, which is the key activator of macrophages, driving classical M1 activation, increased phagolysosomal killing, and granuloma formation. IL-4 (option B) defines the Th2 pathway involved in immediate hypersensitivity regulation, and IL-17 mediates neutrophil recruitment in extracellular bacterial defense rather than macrophage activation.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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