Distinct requirements for T-bet in gut innate lymphoid cells

Interleukin (IL)-22-producing innate lymphoid cells (ILCs; ILC22) comprise a heterogeneous population of cells that are dependent on the transcription factor retinoid-related orphan γt (RORγt) and are critical for barrier function of the intestinal mucosa. A distinct ILC22 subset expresses the natural cytotoxicity receptor NKp46 (NKp46⁺ ILC22); however, the factors that contribute to the generation of this population versus other subsets are largely unknown. Herein, we show that T-bet (encoded by Tbx21) was highly expressed in NKp46⁺ ILC22,a feature shared by all NKp46⁺ cells present in the intestine but not by other IL-22-producing populations. Accordingly, the absence of T-bet resulted in loss of NKp46⁺ ILC22 in the intestinal lamina propria. The residual NKp46⁺ ILC22 present in Tbx21^-/- mice showed a marked reductionof Rorγt expression and impairment in IL-22 production. Generation and functions of gut NK1.1⁺ cells were also altered. Bone marrow chimera experiments revealed a cell-intrinsic requirement for T-bet in thesesubsets and competitive reconstitution experiments revealed roles for T-bet in multiple ILC subsets. Thus, T-bet has a general importance for ILC in the gut and plays a selective and critical role in the generation of NKp46⁺ ILC22.