TCR signaling control of thymic Treg selection and immune homeostasis

摘要： -- 新生儿胸腺来源的Foxp3+T调节细胞(TTregs)是免疫发育所必需的 动态平衡和限制器官特有的自身免疫性疾病。TCR-pMHC的分子细节 相互作用，以及允许新生儿tTregs发育的特定下游信号通路，种子 外周组织和调节急性炎症的机制还不是很清楚。我们假设有一个子集 新生儿TTregs通过表达具有自身配体特异性的TCR来区分健康和疾病 在炎症条件下表达上调。此tTreg TCR识别属性显示为已分级 免疫抑制程度取决于炎症环境的背景和程度。初步 数据进一步表明，这些tTreg克隆在新生儿选择窗口内的发育情况 时间上受到负选择的限制，并基于动态校对，带有TCR-self-pMHC 在常规绑定模式内停留时间作为指定tTreg开发的关键。测试我们的 假设，我们将首先确定Foxp3+CD4tTreg细胞亚群识别的内源性自身配体。我们的 这种方法是基于我们被证实的识别T细胞识别的自身配体的能力，并与质量配对 从不同解剖位置分离的APC上呈现的MHC-II结合自肽的光谱 以及用于确定单个T细胞克隆类型的识别特性的高通量管道。vbl.使用 配对的TCR-self-pMHC组合我们的第二个目标是直接检查新生儿tTreg 选择是基于互动的停留时间，并评估“非常规”TCR/自我的影响 PMHC结合模式在新生儿tTreg谱系选择中的应用目标3将确定自我和自我之间的协同效应 胸腺APC的pMHC递呈和胸腺细胞产生的TCR信号的质量 新生儿tTreg选择窗口。通过Tec家族的信号通路，ITK被认为是调节信号的途径。 通过扩增支持生存的TCR信号来区分Foxp3 Treg选择和晚期删除的阈值 来源于中等停留时间的配体，通过NFAT和NF-κB信号通路。最后，在成熟的树上， 我们认为ITK的功能是放大微弱的TCR反应，从而允许成熟的Treg识别 显示出自身抗原的梯度。这些研究将为T细胞的微调提供重要的见解 反应和区分效应细胞和调节细胞的信号通路，导致理性 用于癌症和癌症治疗的操纵免疫反应的疗法设计方法 自身免疫性疾病。

Abstract    Neonatal thymic-derived Foxp3+ T regulatory cells (tTregs) are required for the development of immune homeostasis and limiting organ specific autoimmune disease. The molecular details of TCR-pMHC interactions, and the specific downstream signaling pathways that allow neonatal tTregs to develop, seed peripheral tissues and regulate acute inflammation are not well understood. We hypothesize that a subset of neonatal tTregs distinguishes health from disease via the expression of TCR with specificity for self-ligands that are upregulated during inflammatory conditions. This tTreg TCR recognition property manifests as graded levels of immune suppression based on the context and magnitude of the inflammatory setting. Preliminary data further suggest that the development of these tTreg clones within the neonatal selection window is temporally constrained by negative selection, and is predicated on kinetic proofreading, with TCR-self-pMHC dwell times within a conventional binding mode as a key to specifying tTreg development. To test our hypothesis, we will first identify endogenous self-ligands recognized by Foxp3+ CD4 tTreg cell subsets. Our approach is based on our proven ability to identify self-ligands recognized by T cells, paired with mass spectrometry of MHC-II bound self-peptides presented on APC isolated from different anatomical locations, as well as high-throughput pipelines for determining recognition properties of individual T cell clonotypes. Using paired sets of TCR-self-pMHC combinations our second aim will directly examine whether neonatal tTreg selection is based the dwell time of the interaction, and assess the influence of “unconventional” TCR/self- pMHC binding modes in selecting the neonatal tTreg repertoire. Aim 3 will identify synergies between self- pMHC presentation by thymic APCs and the quality of TCR signals generated by thymocytes that define the neonatal tTreg selection window. Signaling by the Tec family kinase, Itk, is proposed to regulate a signaling threshold that separates Foxp3 Treg selection from late stage deletion by amplifying pro-survival TCR signals derived from moderate dwell-time ligands via NFAT and NF-κB signaling pathways. Finally, in mature tTregs, we propose that Itk functions to amplify weak TCR responses, thereby allowing mature Tregs to recognize gradients in self-antigen displayed. These studies will provide important insights into the fine-tuning of T cell responses and the signaling pathways that discriminate effector cells from regulatory cells, leading to rational approaches in the design of therapeutics to manipulate immune responses for treatments of cancer and autoimmune diseases.