Role and Mechanism of PDI-PDL Pathway in EAE

描述（由申请人提供）：EAE是由髓磷脂抗原特异性脑源性CD4+ Th1细胞引发的中枢神经系统炎症性疾病。遇到抗原后，T细胞通过TCR接收信号1，通过“正”共刺激分子接收信号2，导致完全激活。其他共刺激分子如CTLA4为T细胞激活提供负信号，可能对终止免疫反应很重要。最近，另一个向T细胞提供负信号的通路被描述为PD1- PDL1/2通路。本研究的主要目的是明确PD1通路在EAE调控中的功能和机制。我们拥有独特的试剂（单克隆抗体和融合蛋白）和动物模型（基因敲除和TCR转基因动物），这将使我们能够在临床相关疾病模型中剖析该途径的作用。我们将利用这些工具研究以下内容：目的1:PD1-PDL通路在体内调控EAE中的作用？我们的假设是PD1-PDL1/PDL2通路负调控体内自身免疫反应。利用阻断性单克隆抗体作为工具，研究这种新途径在急慢性EAE和复发性疾病的自身免疫反应中的功能和作用。我们将定义这一途径在体内调节自身反应性T细胞中的作用。我们还将研究这一新途径在主动疾病和被动诱导疾病中的作用。目的2:pd1 - PDL1在自身抗原耐受中的作用。我们的假设是通过PD1的信号传导促进了自身反应性T细胞的耐受性。我们将使用靶向PDL1的信号融合蛋白诱导EAE的耐受。我们将使用独特的体外和体内实验，包括MOG TCR转基因动物，以更好地了解体内靶向PD1共刺激途径的机制。PDL1和PDL2在专业骨髓来源的抗原呈递细胞和实质细胞上均有表达，通过使用PD1、PDL1和PDL2缺陷小鼠，我们将研究这些配体在实质细胞和淋巴样细胞表达中对这一途径调节自身免疫反应功能的作用。目的3:PD1-PDL1/PDL2通路与其他“正”和“负”调节通路之间的相互作用。我们的假设是PD1-PDL通路在调节EAE中起重要作用，特别是在缺乏CD28的情况下。我们将定义PD1通路与其他CD28同源物（CD28, CTLA4， ICOS）在调节EAE中的相互作用。

DESCRIPTION (provided by applicant): EAE is an inflammatory disease of the central nervous system initiated by myelin antigen-specific encephalitogenic CD4+ Th1 cells. After encountering antigen, T cells receive signal 1 through the TCR and signal 2 through "positive" costimulatory molecules leading to full activation. Other costimulatory molecules such as CTLA4 provide a negative signal for T cell activation and may be important for terminating immune responses. Recently, another pathway that provides negative signaling to T cells has been described, the PD1- PDL1/2 pathway. The main goal of this proposal is to define the functions and mechanisms of the PD1 pathway in regulating EAE. We have unique reagents (monoclonal antibodies and fusion proteins) and animal models (gene knockout and TCR transgenic animals) that will enable us to dissect the role of this pathway in a clinically relevant disease model. We will use these tools to study the following: Aim 1: What is the function of PD1-PDL pathway in regulating EAE in vivo? Our hypothesis is that the PD1-PDL1/PDL2 pathway negatively regulates autoimmune responses in vivo. Using blocking monoclonal antibodies as tools to investigate the functions and of this new pathway in autoimmune responses in acute and chronic EAE, and in relapsing disease. We will define the role of this pathway in regulating autoreactive T cells in vivo. We will also study the functions of this new pathway in active disease and passively induced disease. Aim 2: Role of PD 1- PDL1 in tolerance to autoantigens. Our hypothesis is that signaling through PD1 promotes tolerance in autoreactive T cells. We will use a signaling fusion protein targeting PDL1 to induce tolerance in EAE. We will use unique in vitro and in vivo assays including MOG TCR transgenic animals to better understand the mechanisms of targeting the PD1 costimulatory pathway in vivo. PDL1 and PDL2, are expressed on both professional bone marrow derived antigen-presenting cells and on parenchymal cells, by using PD1, PDL1, and PDL2 deficient mice we will investigate the role of parenchymal versus lymphoid cell expression of the ligands on the function of this pathway in regulating autoimmune responses. Aim 3: Interactions between PD1-PDL1/PDL2 pathway and other "positive" and "negative" regulatory pathways. Our hypothesis is that PD1-PDL pathway plays an important role in regulating EAE particularly in the absence of CD28. We will define the interactions between the PD1 pathway and other CD28 homologues (CD28, CTLA4, ICOS) in regulating EAE.