Interleukin-2 receptor signaling acts as a checkpoint that shapes the distribution of regulatory T cell subsets (RNA-Seq). Interleukin-2 receptor signaling acts as a checkpoint that shapes the distribution of regulatory T cell subsets (RNA-Seq)

Regulatory T cells (Tregs) require IL-2 for survival in the periphery, yet how IL-2 shapes Treg heterogeneity remains poorly defined. Here we found that inhibition of IL-2R signaling in post-thymic Tregs leads to a preferential early loss of central Tregs (cTregs). Gene expression of cTregs was more dependent on IL-2R signaling than effector Tregs (eTregs). Unexpectedly, ablation of IL-2R signaling in cTregs resulted in increased proliferation, expression of eTreg genes, and enhanced capacity to develop into eTregs. These findings indicate that physiological amounts of IL-2 act as a checkpoint to maintain cTreg homeostasis and tolerance while restraining their development into eTregs. Nevertheless, direct evaluation of eTregs revealed that loss of IL-2R signaling alters the distribution of eTreg subsets, with increased IFNgR1+ eTregs and CXCR5+ PD-1+ T follicular regulatory (TFR) cells but decreased intestinal RORgt+ TR17 cells. Thus, IL-2R signaling also shapes the development of specialized eTregs subsets. Overall design: Treg-specific CD25 knockout was induced with tamoxifen and splenocytes were harvested 10 days later. Tregs were FACS purified from the spleen using viability, CD4, GFP and tdTtomato reporters. cTregs were gated on CD62Lhi and eTregs were gated on CD62Llo. CD25iKO Tregs were gated on CD25lo cells. Each biological replicate includes pooled spleen and lymph nodes from 2-3 mice.

调节性T细胞（Regulatory T cells, Tregs）在外周存活依赖于白细胞介素2（Interleukin-2, IL-2），但IL-2如何塑造Tregs的异质性仍不甚明确。本研究发现，在胸腺后Tregs中抑制IL-2受体（IL-2R）信号通路，会导致中枢记忆性调节性T细胞（central Tregs, cTregs）出现优先的早期丢失。相较于效应性调节性T细胞（effector Tregs, eTregs），cTregs的基因表达更依赖于IL-2R信号通路。出乎意料的是，在cTregs中敲除IL-2R信号通路，会导致增殖增强、eTreg相关基因表达上调，且向eTregs分化的能力提升。上述研究结果表明，生理剂量的IL-2可作为免疫检查点，在维持cTregs稳态与免疫耐受的同时，抑制其向eTregs分化。不过，对eTregs的直接评估显示，IL-2R信号通路缺失会改变eTreg亚群的分布：干扰素γ受体1阳性（IFNγR1+）eTregs与CXCR5+ PD-1+ T滤泡调节性（T follicular regulatory, TFR）细胞比例升高，而肠道RORγt+ 17型调节性T（TR17）细胞比例降低。由此可见，IL-2R信号通路同样可塑造特异性eTreg亚群的分化。

总体实验设计：采用他莫昔芬诱导Treg特异性CD25敲除，于造模10天后收获脾脏细胞。通过活力标记、CD4、GFP及tdTtomato报告基因，利用荧光激活细胞分选（FACS）从脾脏中纯化Tregs。其中，cTregs以CD62L高表达设门，eTregs以CD62L低表达设门，CD25条件性敲除Tregs以CD25低表达设门。每个生物学重复混合2-3只小鼠的脾脏与淋巴结组织。