Abstract

Programmed cell death-1 (PD-1) is a co-inhibitory receptor that dampens immune responses upon interaction with PD-L1 and PD-L2. Although PD-1 expression on T cells is known to be activation-dependent, how cytokines modify its regulation is not fully resolved. Using polyclonal T-cell activation to study cytokine-dependent PD-1 regulation, we found that IL-2 inhibited transcriptional up-regulation of PD-1 despite the promotion of T-cell activation. The IL-2-mediated reduction in PD-1 expression augmented CD8⁺ T-cell activities against PD-L1-expressing target cells. To study the mechanism of PD-1 reduction, we focused on STAT5 activation in the IL-2 signaling pathway. Bioinformatic analysis suggested a novel conserved PD-1 promoter domain where NFAT and STAT5 can potentially compete with each other for binding. NFAT1 interaction with this domain revealed substantial potency in PD-1 transcription compared to STAT5A, and STAT5A overexpression could quench NFAT1-dependent PD-1 up-regulation in a sequence-specific manner. Chromatin immunoprecipitation analysis of activated T cells showed that IL-2 treatment significantly diminished the binding of NFAT1 and NFAT2 in the hypothesized competition site, while STAT5 binding to the same region was increased. These results raise the possibility that the competition of transcriptional factors might be involved in the fine-tuning of PD-1 expression by cytokines such as IL-2.

中文翻译：

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STAT5 干扰 PD-1 转录激活并影响 CD8+ T 细胞对 PD-1 依赖性免疫调节的敏感性

摘要

程序性细胞死亡-1 (PD-1) 是一种共抑制受体，可在与 PD-L1 和 PD-L2 相互作用时抑制免疫反应。尽管已知 T 细胞上的 PD-1 表达是激活依赖性的，但细胞因子如何改变其调节尚未完全解决。使用多克隆 T 细胞活化来研究细胞因子依赖性 PD-1 调节，我们发现尽管促进 T 细胞活化，IL-2 仍抑制 PD-1 的转录上调。IL-2 介导的 PD-1 表达减少增强了 CD8 ⁺T 细胞对表达 PD-L1 的靶细胞的活性。为了研究 PD-1 减少的机制，我们专注于 IL-2 信号通路中的 STAT5 激活。生物信息学分析提出了一个新的保守 PD-1 启动子结构域，其中 NFAT 和 STAT5 可以潜在地相互竞争以进行结合。与 STAT5A 相比，NFAT1 与该结构域的相互作用揭示了 PD-1 转录的显着效力，并且 STAT5A 过表达可以以序列特异性方式抑制 NFAT1 依赖性 PD-1 上调。活化 T 细胞的染色质免疫沉淀分析表明，IL-2 处理显着降低了假设竞争位点中 NFAT1 和 NFAT2 的结合，而 STAT5 与同一区域的结合增加。