The gut epithelium is populated by intraepithelial lymphocytes (IELs), a heterogeneous T cell population with cytotoxic and regulatory properties, which can be acquired at the epithelial layer. However, the role of T cell receptor (TCR) in this process remains unclear. Single-cell transcriptomic analyses revealed distinct clonal expansions between cell states, with CD4⁺CD8αα⁺ IELs being one of the least diverse populations. Conditional deletion of TCR on differentiating CD4⁺ T cells or of major histocompatibility complex (MHC) class II on intestinal epithelial cells prevented CD4⁺CD8αα⁺ IEL differentiation. However, TCR ablation on differentiated CD4⁺CD8αα⁺ IELs or long-term cognate antigen withdraw did not affect their maintenance. TCR re-engagement of antigen-specific CD4⁺CD8αα⁺ IELs by Listeria monocytogenes did not alter their state but correlated with reduced bacterial invasion. Thus, local antigen recognition is an essential signal for differentiation of CD4⁺ T cells at the epithelium, yet differentiated IELs are able to preserve an effector program in the absence of TCR signaling.

肠道上皮由上皮内淋巴细胞 (IEL) 组成，这是一种具有细胞毒性和调节特性的异质 T 细胞群，可以在上皮层获得。然而，T细胞受体（TCR）在此过程中的作用仍不清楚。单细胞转录组分析揭示了细胞状态之间明显的克隆扩张，其中 CD4 ⁺ CD8αα ⁺ IEL 是多样性最差的群体之一。条件性删除分化 CD4 ⁺ T 细胞上的 TCR 或肠上皮细胞上主要组织相容性复合物 (MHC) II 类可阻止 CD4 ⁺ CD8αα ⁺ IEL 分化。然而，分化的 CD4 ⁺ CD8αα ⁺ IEL 上的 TCR 消融或长期同源抗原撤回并不影响其维持。单核细胞增生李斯特菌对抗原特异性 CD4 ⁺ CD8αα ⁺ IEL 的 TCR 重新接合并没有改变它们的状态，但与细菌入侵减少相关。因此，局部抗原识别是上皮 CD4 ⁺ T 细胞分化的重要信号，但分化的 IEL 能够在缺乏 TCR 信号传导的情况下保留效应程序。