Interleukin (IL-)23 is a major mediator and therapeutic target in chronic inflammatory diseases that also elicits tissue protection in the intestine at homeostasis or following acute infection^1,2,3,4. However, the mechanisms that shape these beneficial versus pathological outcomes remain poorly understood. To address this gap in knowledge, we performed single-cell RNA sequencing on all IL-23 receptor-expressing cells in the intestine and their acute response to IL-23, revealing a dominance of T cells and group 3 innate lymphoid cells (ILC3s). Unexpectedly, we identified potent upregulation of the immunoregulatory checkpoint molecule cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) on ILC3s. This pathway was activated by gut microbes and IL-23 in a FOXO1- and STAT3-dependent manner. Mice lacking CTLA-4 on ILC3s exhibited reduced regulatory T cells, elevated inflammatory T cells and more-severe intestinal inflammation. IL-23 induction of CTLA-4⁺ ILC3s was necessary and sufficient to reduce co-stimulatory molecules and increase PD-L1 bioavailability on intestinal myeloid cells. Finally, human ILC3s upregulated CTLA-4 in response to IL-23 or gut inflammation and correlated with immunoregulation in inflammatory bowel disease. These results reveal ILC3-intrinsic CTLA-4 as an essential checkpoint that restrains the pathological outcomes of IL-23, suggesting that disruption of these lymphocytes, which occurs in inflammatory bowel disease^5,6,7, contributes to chronic inflammation.

白细胞介素 (IL-)23 是慢性炎症性疾病的主要介质和治疗靶点，在稳态时或急性感染后还可引起肠道组织保护^1,2,3,4 。然而，形成这些有益与病理结果的机制仍然知之甚少。为了解决这一知识空白，我们对肠道中所有表达 IL-23 受体的细胞及其对 IL-23 的急性反应进行了单细胞 RNA 测序，揭示了 T 细胞和第 3 组先天淋巴细胞 (ILC3) 的主导地位。出乎意料的是，我们发现 ILC3 上免疫调节检查点分子细胞毒性 T 淋巴细胞相关抗原 4 (CTLA-4) 的有效上调。该通路由肠道微生物和 IL-23 以 FOXO1 和 STAT3 依赖性方式激活。 ILC3 上缺乏 CTLA-4 的小鼠表现出调节性 T 细胞减少、炎症 T 细胞升高和更严重的肠道炎症。 IL-23 对 CTLA-4 ⁺ ILC3 的诱导对于减少共刺激分子并增加肠骨髓细胞上的 PD-L1 生物利用度是必要且充分的。最后，人类 ILC3 上调 CTLA-4 以响应 IL-23 或肠道炎症，并与炎症性肠病的免疫调节相关。这些结果表明，ILC3 固有的 CTLA-4 是抑制 IL-23 病理结果的重要检查点，表明炎症性肠病中发生的这些淋巴细胞的破坏^5,6,7会导致慢性炎症。