The timing of differentiation and potency of CD8 effector function is set by RNA binding proteins

CD8 T cell differentiation into effector cells is initiated early after antigen encounter by signals from the T cell antigen receptor and costimulatory molecules. The molecular mechanisms that determine the timing and rate of differentiation however are not defined. Here we show that the RNA binding proteins (RBP) ZFP36 and ZFP36L1 limit the rate of differentiation of activated naïve CD8 T cells and the potency of the resulting cytotoxic lymphocytes. The RBP act in an early and short temporal window to enforce dependency on costimulation via CD28 for full T cell activation and effector differentiation by directly binding mRNA of NF-kB, IRF8 and NOTCH1 transcription factors and IL2. Their absence in T cells, or the adoptive transfer of a small numbers of CD8 T cells lacking the RBP, promotes resilience to influenza A virus infection without immunopathology. These findings highlight ZFP36 and ZFP36L1 as nodes for the integration of the early T cell activation signals determining the speed and quality of the CD8 response. Overall design: ZFP36L1 iCLIP libraries were prepared from OT-I transgenic cytotoxic T lymphocytes, with three biological replicates in control cells, and three biological replicates in Zfp36/Zfp36l1 conditional knockout cells as a negative control.

CD8 T细胞向效应细胞的分化在抗原接触后早期便由T细胞抗原受体与共刺激分子的信号启动。然而，决定分化时序与速率的分子机制仍未明确。本研究证实，RNA结合蛋白（RNA binding protein, RBP）ZFP36与ZFP36L1可限制活化的初始CD8 T细胞的分化速率，以及最终形成的细胞毒性淋巴细胞的功能效能。这类RNA结合蛋白在早期且短暂的时间窗口内发挥作用，通过直接结合NF-κB、IRF8与NOTCH1转录因子以及IL2的mRNA，使T细胞完全活化及效应分化依赖于CD28介导的共刺激信号。若T细胞中缺乏这类RNA结合蛋白，或过继转移少量缺失该类RNA结合蛋白的CD8 T细胞，可增强机体对甲型流感病毒感染的抵抗力，且不会引发免疫病理损伤。上述研究结果表明，ZFP36与ZFP36L1是整合早期T细胞活化信号的关键节点，这些信号决定了CD8 T细胞应答的速度与质量。整体实验设计：从OT-I转基因细胞毒性T淋巴细胞中制备ZFP36L1 iCLIP文库，对照组设置3次生物学重复，以Zfp36/Zfp36l1条件性敲除细胞作为阴性对照，同样设置3次生物学重复。