A2a receptor engagement promotes T cell tolerance

描述（由申请人提供）：腺苷A2 a受体最近已显示在体内负调节免疫应答中起关键作用。我们的实验室一直有兴趣剖析促进TCR诱导的活化与耐受的信号。在我们的研究过程中，我们发现腺苷A2 a受体在T细胞无反应性的诱导过程中高度上调。基于初步数据，我们假设T细胞上的A2 a受体接合促进T细胞耐受的诱导。使用体外T细胞克隆，我们将确定A2 a受体激动剂促进T细胞耐受性的能力，即使在共刺激的情况下。使用A2 a基因敲除小鼠，我们将确定A2 a受体在促进耐受性中的特异性和内源性腺苷在促进耐受性中的作用。此外，我们将确定A2 a受体对抗原呈递细胞（APC）和靶组织的作用。使用T细胞介导的自身免疫的体内模型，我们将证明A2 a受体接合通过促进无反应性和抗原特异性Lag-3+ T调节细胞来防止T细胞介导的死亡的能力。有趣的是，肿瘤微环境含有高水平的腺苷。因此，我们提出肿瘤来源的腺苷促进肿瘤特异性T细胞耐受的诱导。我们将使用A2 a特异性拮抗剂和来自A2 a敲除小鼠的T细胞在明确的前列腺癌小鼠模型中检验这一假设。我们预测，通过抑制A2 a受体结合，我们将能够预防/克服肿瘤诱导的耐受性，从而增强肿瘤疫苗的功效。我们还将确定A2 a诱导耐受的机制。先前，我们已经表明CREB和CREM与IL-2启动子的-180位点的结合在抑制无能T细胞中的IL-2转录中起重要作用。由于A2 a接合导致cAMP的产生，我们将测试A2 a接合部分通过增强CREB/CREM在该位点的结合来介导其抑制作用的假设。此外，基于初步数据，我们将检验新的cAMP激活的靶点EPAC是关键下游效应子的假设。了解A2 a受体促进T细胞耐受性的作用和机制应该为设计特定的临床靶点提供见解。

DESCRIPTION (provided by applicant): The adenosine A2a receptor has recently been shown to play a critical role in negatively regulating immune responses in vivo. Our laboratory has been interested in dissecting the signals that promote TCR-induced activation versus tolerance. During the course of our studies we have found that the adenosine A2a receptor is highly upregulated during the induction of T cell anergy. Based upon preliminary data we hypothesize that A2a receptor engagement on T cells promotes the induction of T cell tolerance. Using T cell clones in vitro we will define the ability of A2a receptor agonists to promote T cell tolerance even in the setting of costimulation. Using A2a knockout mice we will define the specificity of the A2a receptor in promoting tolerance and the role of endogenous adenosine in promoting tolerance. Further we will define the role of the A2a receptor on antigen presenting cells (APCs) and target tissues. Using an in vivo model of T cell mediated autoimmunity we will demonstrate the ability of A2a receptor engagement to prevent T cell mediated death by promoting anergy and antigen specific Lag-3+ T regulatory cells. Interestingly, the tumor microenvironment contains high levels of adenosine. As such, we propose that tumor-derived adenosine facilitates the induction of tumor-specific T cell tolerance. We will test this hypothesis using A2a specific antagonists and T cells from the A2a knockout mice in a well defined murine model of prostate cancer. We predict that by inhibiting A2a receptor engagement, we will be able to prevent/overcome tumor-induced tolerance and thus enhance the efficacy of tumor vaccines. We will also define the mechanism of A2a-induced tolerance. Previously, we have shown that the binding of CREB and CREM to the -180 site of the IL-2 promoter plays an important role in repressing IL-2 transcription in anergic T cells. In as much as A2a engagement leads to the generation of cAMP, we will test the hypothesis that A2a engagement mediates its inhibitory effect in part by enhancing the binding of the CREB/CREM at this site. Furthermore, based on preliminary data we will test the hypothesis that the novel cAMP activated target EPAC is a critical downstream effector. Understanding the role and mechanism by which the A2a receptor promotes T cell tolerance should provide insight in terms of devising specific clinical targets.