CD4+ T-helper cell subsets are distinguished by their cytokine profiles. A patient with disseminated Mycobacterium avium infection is found to have a specific deficiency of the cytokine essential for macrophage activation and granuloma formation. Which Th subset is deficient in its function?

• A Th2 secreting IL-4 and IL-13
• B Th1 secreting IFN-γ ✓
• C Th17 secreting IL-17
• D Treg secreting IL-10 and TGF-β

Explanation

Th1 cells secrete IFN-γ, which activates macrophages to kill intracellular organisms, including mycobacteria, by upregulating reactive oxygen and nitrogen intermediates and promoting granuloma formation. Defects in the IL-12/IFN-γ axis (Mendelian susceptibility to mycobacterial disease, MSMD) result in disseminated non-tuberculous mycobacterial infections. Th2 cytokines drive allergic/helminthic responses, Th17 drives neutrophilic tissue inflammation, and Tregs suppress immune responses. IFN-γ is the central macrophage-activating cytokine for intracellular killing.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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