Overproduction of IFNg by Cbl-b deficient CD8+ T cells provides resistance against regulatory T cells and induce potent anti-tumor immunity. Overproduction of IFNg by Cbl-b deficient CD8+ T cells provides resistance against regulatory T cells and induce potent anti-tumor immunity

Regulatory T cells are one of the integral components of the adaptive immune system that contribute to the regulation of anti-tumor T cell responses. However, studies have suggested that alterations in T cell signaling networks can result in T cells that are resistant to the suppressive effects of Treg cells. Here, we investigated the role of Cbl-b, an E3 ubiquitin ligase and a negative regulator of TCR signaling pathways, in establishing CD8+ T cell resistance to Treg cell-mediated suppression. First, the absence of Cbl-b rendered CD8+ T cells refractory to the suppressive effects of Treg cells in vitro. Transcriptomic analyses suggested that pathways associated with cellular proliferation and cytokine production likely contribute to the observed phenotype. In particular, hyper-secretion of IFN-g by Cbl-b deficient CD8+ T cells served as a novel mechanism which selectively renders CD8+ T cells less sensitive to suppression by Treg cells. To explore our findings in vivo, we utilized tumor-bearing FoxP3DTR-eGFP mice to confirm that the adoptively transferred tumor-specific CD8+ T cells were susceptible to regulation by Treg cells in the tumor. Unlike the wildtype counterpart, Cbl-b deficient CD8+ T cells were resistant to the suppressive effects of Treg cells in the tumor, and the therapeutic benefit of Cbl-b deficiency was abrogated upon IFN-g blockade. Collectively, our data highlight the role of Cbl-b deficiency and subsequent hyper-secretion of IFN-g as a key mechanism which renders CD8+ T cells resistant to Treg cell-mediated suppression. Overall design: CD8+ T-cells, either CBLB wildtype (WT) or knockout (KO), some stimulated with either anti-CD3 or anti-CD3 + anti-CD28

调节性T细胞（Regulatory T cells）是适应性免疫系统不可或缺的组成部分之一，参与调控抗肿瘤T细胞应答。已有研究表明，T细胞信号网络的异常可使T细胞对调节性T细胞的抑制效应产生抵抗。本研究旨在探究E3泛素连接酶Cbl-b——T细胞受体（TCR）信号通路的负调控因子——在赋予CD8+ T细胞抵抗调节性T细胞介导抑制作用中的功能。首先，体外实验证实，Cbl-b缺失可使CD8+ T细胞摆脱调节性T细胞的抑制效应。转录组分析显示，细胞增殖与细胞因子产生相关通路或与该实验表型密切相关。其中，Cbl-b缺陷型CD8+ T细胞的干扰素-γ（IFN-γ）过度分泌，是一种全新的机制，可选择性降低CD8+ T细胞对调节性T细胞抑制作用的敏感性。为在体内验证上述研究发现，我们使用携带肿瘤的FoxP3DTR-eGFP小鼠，证实过继转移的肿瘤特异性CD8+ T细胞在肿瘤微环境中可被调节性T细胞调控。与野生型对照不同，Cbl-b缺陷型CD8+ T细胞在肿瘤内可抵抗调节性T细胞的抑制效应；且干扰素-γ阻断实验可抵消Cbl-b缺失带来的治疗益处。综上，本研究数据表明，Cbl-b缺失及其后续的干扰素-γ过度分泌，是赋予CD8+ T细胞抵抗调节性T细胞介导抑制作用的关键机制。总体实验设计：分别获取CBLB野生型（WT）或敲除型（KO）的CD8+ T细胞，其中部分细胞用抗CD3抗体刺激，其余部分同时用抗CD3与抗CD28抗体刺激。