A patient with recurrent bacterial and fungal infections has absent T cells but normal B cell counts. Genetic analysis reveals a mutation affecting the common gamma chain (γc) of cytokine receptors. This mutation affects signaling through which interleukins?

• A IL-1, IL-6, IL-11, IL-17
• B IL-3, IL-5, IL-13, IL-25
• C IL-10, IL-12, IL-18, IL-27
• D IL-2, IL-4, IL-7, IL-9, IL-15, IL-21 ✓

Explanation

The common gamma chain (CD132) is shared by receptors for IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21. Mutations in the gene encoding γc cause X-linked SCID (X-SCID), the most common form of SCID, because IL-7 signaling through γc is essential for T cell development. IL-15 is needed for NK cell maturation. The other interleukins listed use different shared receptor subunits (gp130 for group B, βc for group C, IL-12Rβ1 for group D).

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

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