RORγt expression in mature T<sub>H</sub>17 cells safeguards their lineage specification by inhibiting conversion to T<sub>H</sub>2 cells.

Chi, Xinxin; Jin, Wei; Zhao, Xiaohong; Xie, Tian; Shao, Jing; Bai, Xue; Jiang, Yu; Wang, Xiaohu et al. · Sci Adv · 2022

basic_science · Level V

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Abstract

RORγt is the lineage-specific transcription factor for T helper 17 (T<sub>H</sub>17) cells and an attractive drug target for treating T<sub>H</sub>17-associated diseases. Although the critical role of RORγt in early T<sub>H</sub>17 cell differentiation has been well recognized, its function in mature T<sub>H</sub>17 cell maintenance remains largely unknown. Here, we show that genetic deletion of <i>Rorc</i> in mature T<sub>H</sub>17 cells inhibited their pathogenic functions. Mechanistically, loss of RORγt led to a closed chromatin configuration at key T<sub>H</sub>17-specific gene loci, particularly at the "super-enhancer" regions. Unexpectedly, RORγt directly bound and inhibited <i>Il4</i> transcription, whereas pharmaceutically or genetically targeting RORγt caused spontaneous conversion of T<sub>H</sub>17 cells to T<sub>H</sub>2-like cells in vitro and in vivo. Our results thus reveal dual crucial functions of RORγt in effector T<sub>H</sub>17 cells in maintaining T<sub>H</sub>17 cell program and constraining T<sub>H</sub>2 cell conversion, offering previously unidenified considerations in therapeutic targeting of RORγt.

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