Mechanisms of T cell inhibitory pathways

描述(申请人提供)：本K08奖的主要目标是研究B7：CD28共刺激分子家族中调节T细胞激活和耐受的一种新的T细胞抑制途径。PI将在哈佛医学院由T细胞共刺激领域的专家Arlene Sharpe博士指导。我们已经发现T细胞上的程序性死亡-1配体1(PD-L1)可以与B7-1相互作用，这种相互作用可以抑制T细胞的反应。我们将检验这一假设，即T细胞上的PD-L1在控制T细胞激活、效应反应和自身免疫方面发挥重要作用。我们有许多独特的工具，包括基因缺陷小鼠和PD-L1抗体，使我们能够剖析PD-L1信号在T细胞上的分子机制，并研究其在体内控制反应中的作用。我们的具体目标是：1.建立PD-L1对T细胞的抑制作用机制。为此，我们将测试PD-L1对T细胞的抑制作用是否通过1)改变TCR信号通路，和/或2)利用信号伙伴或第二链来实施抑制作用。我们还将测试PD-L1与人类T细胞的连接是否具有抑制作用。这些分目标将为深入了解T细胞上的PD-L1抑制反应的机制以及PD-L1在人类T细胞上的治疗操作的可能性提供依据。2.确定PD-L1在免疫突触(IS)中对T细胞及其伴侣的作用。T细胞通过与IS中的APC接触而被激活和调节。APC上的B7-1可以与T细胞上的CD28、CTLA-4或PD-L1相互作用，这提出了一个问题：PD-L1如何与CD28和CTLA-4竞争B7-1相互作用？我们将关注T细胞上的PD-L1如何在早期突触(微簇)和晚期突触(T细胞-DC突触)与CD28竞争结合B7-1。这些研究将补充目标1中的研究，以探索PD-L1对T细胞发挥抑制作用的另一种方式。3.研究PD-L1对T细胞的体内激活和自身免疫作用。我将研究PD-L1在体内对CD4和CD8T细胞在激活和效应性反应中的作用。这一目标将利用糖尿病的自身免疫模型来检验PD-L1通路可能在体内自身免疫反应期间控制自身反应性T细胞的假设。在这项提议中，我计划在T细胞生物学领域获得新的技能，包括显微镜和自身免疫的体内研究。我的长期目标是将我在基础科学和临床医学方面的背景结合起来，成为一名学术内科科学家和独立研究员，研究抑制性T细胞途径在调节自身免疫和传染病方面的基础作用。 相关性：阻断PD-L1已成为重要的治疗靶点。这些研究将为控制微生物免疫、肿瘤免疫和自身免疫中的T细胞反应提供新的机制，并将为抑制T细胞的机制提供基本的见解。

DESCRIPTION (provided by applicant): The main goal of this K08 Award is to study a new T cell inhibitory pathway in the B7:CD28 family of costimulatory molecules that regulates T cell activation and tolerance. The PI will be mentored at Harvard Medical School by Dr. Arlene Sharpe, an expert in the area of T cell costimulation. We have found that Programmed Death-1 Ligand 1 (PD-L1) on T cells can interact with B7-1, and that this interaction can inhibit T cell responses. We will test the hypothesis that PD-L1 on T cells plays an important role in controlling T cell activation, effector responses, and autoimmunity. We have a number of unique tools, including gene-deficient mice and PD-L1 antibodies that enable us to dissect the molecular mechanisms of PD-L1 signaling on T cells and investigate its roles in controlling in vivo responses. Our specific aims are: 1. Establish the mechanisms by which PD-L1 on T cells exerts inhibitory effects in mice and humans. In this Aim, we will test whether PD-L1 on T cells exerts an inhibitory effect by 1) modifying TCR signaling pathways, and/or by 2) utilizing a signaling partner or second chain to enact inhibitory effects. We will also test if ligation of PD-L1 on human T cells is inhibitory. These subaims will provide insight into the mechanisms by which PD-L1 on T cells inhibits responses and the potential for therapeutic manipulation of PD-L1 on human T cells. 2. Determine the roles of PD-L1 on T cells and its partners at the immunological synapse (IS). T cells are activated and regulated by contact with APCs at the IS. B7-1 on APCs can interact with CD28, CTLA-4, or PD-L1 on the T cell, raising the question: how does PD-L1 compete with CD28 and CTLA-4 for B7-1 interactions? We will focus on how PD-L1 on T cells competes with CD28 for binding to B7-1 in the early synapse (microclusters) and the late synapse (T cell-DC synapse). These studies will complement those in Aim 1 to investigate another means by which PD-L1 on T cells may exert its inhibitory effects. 3. Characterize in vivo effects of PD-L1 on T cells: activation and autoimmunity. I will examine the in vivo role of PD-L1 on CD4 and CD8 T cells during activation and effector responses. This aim will test the hypothesis that the PD-L1 pathway may control self-reactive T cells during autoimmune responses in vivo, using an autoimmune model of diabetes. In this proposal, I plan to acquire new skills in areas of T cell biology, including microscopy and in vivo studies of autoimmunity. My long-term goal is to combine my background in basic science and clinical medicine to be an academic physician-scientist and independent investigator, examining the fundamental roles of inhibitory T cell pathways as they regulate autoimmunity and infectious diseases. RELEVANCE: Blockade of PD-L1 has become an important therapeutic target. These studies will provide insights into new mechanisms to control T cell responses in microbial immunity, tumor immunity, and autoimmunity, and will provide fundamental insights into mechanisms of inhibition of T cells.