In type 1 diabetes (T1D) autoreactive CD8 T cells infiltrate pancreatic islets and destroy insulin-producing β cells. Progression to T1D onset is a chronic process, which suggests that the effector activity of β-cell autoreactive CD8 T cells needs to be maintained throughout the course of disease development. The mechanism that sustains diabetogenic CD8 T cell effectors during the course of T1D progression has not been completely defined. Here we used single-cell RNA sequencing to gain further insight into the phenotypic complexity of islet-infiltrating CD8 T cells in NOD mice. We identified two functionally distinct subsets of activated CD8 T cells, CD44^highTCF1⁺CXCR6⁻ and CD44^highTCF1⁻CXCR6⁺, in islets of prediabetic NOD mice. Compared with CD44^highTCF1⁺CXCR6⁻ CD8 T cells, the CD44^highTCF1⁻CXCR6⁺ subset expressed higher levels of inhibitory and cytotoxic molecules and was more prone to apoptosis. Adoptive cell transfer experiments revealed that CD44^highTCF1⁺CXCR6⁻ CD8 T cells, through continuous generation of the CD44^highTCF1⁻CXCR6⁺ subset, were more capable than the latter population to promote insulitis and the development of T1D. We further showed that direct IL-27 signaling in CD8 T cells promoted the generation of terminal effectors from the CD44^highTCF1⁺CXCR6⁻ population. These results indicate that islet CD44^highTCF1⁺CXCR6⁻ CD8 T cells are a progenitor-like subset with self-renewing capacity, and, under an IL-27–controlled mechanism, they differentiate into the CD44^highTCF1⁻CXCR6⁺ terminal effector population. Our study provides new insight into the sustainability of the CD8 T cell response in the pathogenesis of T1D.

在 1 型糖尿病 (T1D) 中，自身反应性 CD8 T 细胞浸润胰岛并破坏产生胰岛素的 β 细胞。进展为 T1D 发病是一个慢性过程，这表明 β 细胞自身反应性 CD8 T 细胞的效应活性需要在整个疾病发展过程中保持。在 T1D 进展过程中维持致糖尿病 CD8 T 细胞效应器的机制尚未完全确定。在这里，我们使用单细胞 RNA 测序来进一步了解 NOD 小鼠胰岛浸润 CD8 T 细胞的表型复杂性。我们鉴定了两个功能不同的活化 CD8 T 细胞亚群，CD44^高TCF1 ⁺ CXCR6 ^-和 CD44^高TCF1 ^- CXCR6 ⁺，在糖尿病前期 NOD 小鼠的胰岛中。与 CD44^高TCF1 ⁺ CXCR6 ^- CD8 T 细胞相比，CD44^高TCF1 ^- CXCR6 ⁺子集表达更高水平的抑制性和细胞毒性分子，更容易发生细胞凋亡。过继细胞转移实验表明，CD44^高TCF1 ⁺ CXCR6 ⁻ CD8 T 细胞，通过持续产生 CD44^高TCF1 ⁻ CXCR6 ⁺子集，比后者更有能力促进胰岛炎和 T1D 的发展。我们进一步表明，CD8 T 细胞中的直接 IL-27 信号传导促进了来自 CD44^高TCF1 ⁺ CXCR6 ^-群体的末端效应子的产生。这些结果表明胰岛 CD44^高TCF1 ⁺ CXCR6 ^- CD8 T 细胞是具有自我更新能力的祖细胞亚群，并且在 IL-27 控制的机制下，它们分化为 CD44^高TCF1 ^- CXCR6 ⁺末端效应细胞群. 我们的研究为 CD8 T 细胞反应在 T1D 发病机制中的可持续性提供了新的见解。