Intrinsic Effects of Tim-3 on T cell exhaustion and TCR signaling

描述（由申请人提供）：近年来，T细胞耗竭已被认为是限制免疫病理学的重要机制，尽管可能希望以靶向方式规避该机制，以帮助消除病毒储库或肿瘤。然而，驱动和维持T细胞耗竭的信号仍然没有得到很好的理解。现在已经鉴定了耗尽的T细胞的几种表面蛋白标志物，包括跨膜蛋白PD-1和Tim-3以及其他标志物。尽管大量的相关证据将Tim-3表达与疲劳期间T细胞活化功能障碍联系起来，但关于Tim-3促进疲劳的发展和/或维持的机制知之甚少。这一直是具有挑战性的，部分原因是Tim-3不是由幼稚T细胞表达的，而是仅在多轮激活后才被检测到。因此，需要新的试剂和模型系统，其将允许更直接地定义原代T细胞中的Tim-3功能。 与PD-1或许多其他T细胞活性的负调节因子不同，Tim-3不包含用于募集抑制性磷酸酶的基序。相反，我们最近的工作表明，Tim-3表达实际上通过通常与积极结果相关的途径增加信号传导，即有效的TCR/CD 3介导的T细胞活化，至少在急性条件下。来自其他组的相关数据表明，T细胞耗竭是由慢性抗原刺激引起的，该刺激延长了T细胞活化的效应相，以T细胞记忆为代价。我们假设Tim-3通过最初增强TCR信号通路，导致持续和失调的T细胞活化，从而导致T细胞耗竭。 这一假设将通过两个具体目标进行检验。在目标1中，将开发一种新的小鼠品系，其在T细胞区室中具有Tim-3的诱导型（和可逆的）表达。在目的2中，将确定增强的Tim-3表达是否驱动T细胞耗竭和/或TCR信号传导。后面的实验将利用最近描述的报告小鼠，其中抗原受体衍生的信号传导可以与其他来源区分开。

DESCRIPTION (provided by applicant): T cell exhaustion has been recognized in recent years as an important mechanism for limiting immune pathology, although it may be desirable to circumvent this mechanism in a targeted fashion, to help eliminate viral reservoirs or tumors. However, the signals that drive and maintain exhaustion in T cells are still not well understood. Several surface protein markers of exhausted T cells have now been identified, including the transmembrane proteins PD-1 and Tim-3, among other markers. Despite the extensive amount of correlative evidence linking Tim-3 expression to dysfunction of T cell activation during exhaustion, little is known about the mechanisms by which Tim-3 contributes to the development and/or maintenance of exhaustion. This has been challenging, in part due to the fact that Tim-3 is not expressed by na¿ve T cells, but is only detected after multiple rounds of activation. There is therefore a need for new reagents and model systems that will allow for the more direct definition of Tim-3 function in primary T cells. Unlike PD-1 or many other negative regulators of T cell activity, Tim-3 contains no motifs for the recruitment of inhibitory phosphatases. Rather, our recent work suggests that Tim-3 expression actually increases signaling through pathways that are normally associated with positive outcomes, i.e. efficient TCR/CD3-mediated T cell activation, at least under acute conditions. Correlative data from other groups indicate that T cell exhaustion results from chronic antigenic stimulation that extends the effector phase of T cell activation, at the expense of T cell memory. We hypothesize that Tim-3 contributes to T cell exhaustion by initially enhancing TCR-signaling pathways, leading to sustained and dysregulated T cell activation. This hypothesis will be tested with two Specific Aims. In Aim 1, a novel mouse strain will be developed, with inducible (and reversible) expression of Tim-3 in the T cell compartment. In Aim 2, it will be determined whether enforced Tim-3 expression drives T cell exhaustion and/or TCR signaling. The latter experiments will take advantage of a recently described reporter mouse, in which antigen receptor derived signaling can be distinguished from other sources.