Role of CX3CR1 in adaptive immunity during autoimmune encephalomyelitis

描述(申请人提供)：存在于神经元和外周内皮细胞上的跨膜趋化因子Fractalk1(CX3CL1)作为一种黏附分子或一种可溶的趋化物质。CX3CL1通过其受体CX3CR1传递信号，CX3CR1表达于小胶质细胞、单核/巨噬细胞、树突状细胞、NK细胞和T细胞。值得注意的是，与健康对照组相比，多发性硬化症患者外周血NK细胞中CX3CR1的表达降低，并且外周血中缺乏与疾病活动相关的CX3CR1细胞。然而，CX3CR1在抗原提呈细胞和T细胞中的作用以及它们在中枢神经系统病理中的作用仍然是个谜。这项研究的假设是CX3CR1/CX3CL1调节抗原提呈细胞(APC)效应器功能，影响实验性自身免疫性脑脊髓炎(EAE)中致病T细胞的发育。这一假说基于下列假设：1)EAE症状更严重，CNS脱髓鞘增强CX3CR1缺陷小鼠；2)CX3CR1缺失与CD115 CD11c树突状细胞选择性聚集到CNS组织相关；3)骨髓嵌合小鼠揭示骨髓中CX3CR1缺失导致了一种不寻常的、严重的、慢性的、持续瘫痪的EAE疾病。这项建议的总体目标是阐明CX3CR1在EAE过程中的功能以及它如何调节致病性中枢神经系统炎症。其具体目的是：1.确定CX3CR1通过调节抗原提呈和T细胞启动在EAE发病中的作用。我们将验证这一假设，即CX3CR1控制外周DC成熟，影响抗原递呈，并随后影响外周T细胞极化。我们将研究CX3CR1抗原转运和树突状细胞动员的作用以及CX3CR1缺陷在脑源性T细胞生成中的作用。2.探讨CX3CR1缺乏在EAE效应相中的作用及对神经元损伤和脱髓鞘的保护作用。我们推测，骨髓中CX3CR1的缺失对于维持EAE脑内T细胞介导的炎症和组织损伤至关重要。我们将研究CX3CR1在疾病高峰期和恢复期中枢神经系统组织内致病和调节性T细胞亚群的抑制信号、激活和存活中的作用。3.明确人CX3CR1I249/M280信号的减弱如何复制EAE过程中CX3CR1-/-小鼠的病理改变。我们假设表达I249/M280的细胞将表现出与CX3CR1缺陷细胞相当的效应功能。我们将使用表达人类变异体的敲入小鼠作为低亲和力模型，研究I249/M280在中枢神经系统自身免疫期间体内APC激活和T细胞极化中的作用。

DESCRIPTION (provided by applicant): The transmembrane chemokine fractalkine (CX3CL1) present on neurons and peripheral endothelial cells acts as an adhesion molecule or as a soluble chemoattractant. CX3CL1 signals through its receptor CX3CR1 which is expressed in microglia, monocytes/macrophages and dendritic cells, NK cells and T cells. Notably, multiple sclerosis patients revealed lower expression of CX3CR1 in peripheral NK cells when compared to healthy controls and lack of CX3CR1+ cells in peripheral blood correlated with disease activity. However, the role of CX3CR1 in antigen presenting cells and T cells, and their contribution to CNS pathology are still enigmatic. The hypothesis behind the proposed research is that CX3CR1/CX3CL1 regulates antigen presenting cell (APC) effector functions influencing the development of pathogenic T cells during experimental autoimmune encephalomyelitis (EAE). This hypothesis is based on the following: 1) EAE symptoms are more severe and CNS demyelination is enhanced CX3CR1-deficient mice, 2) absence of CX3CR1 correlated with a selective accumulation of CD115+CD11c+ dendritic cells to CNS tissues, and 3) Bone marrow chimeric mice revealed that absence of CX3CR1 in bone marrow induced an unusual, severe and chronic non-remitting EAE disease with sustained paralysis. The overall goal of this proposal is to elucidate the function of CX3CR1 during EAE and how it regulates pathogenic CNS inflammation. The specific aims are: 1. to determine the role of CX3CR1 for the initiation of EAE via modulation of antigen presentation and T cell priming. We will test the hypothesis that CX3CR1 controls peripherally DC maturation affecting antigen presentation and subsequently peripheral T cell polarization. We will investigate the role of CX3CR1 antigen trafficking and dendritic cell mobilization and effects of CX3CR1-deficiency in generation of encephalitogenic T cells. 2. To determine the role of CX3CR1 deficiency in the effector phase of EAE and protection from neuronal damage and demyelination. We hypothesize that absence of CX3CR1 in bone marrow is critical for the maintenance of T cell mediated inflammation and tissue damage in the EAE brain. We will investigate the role of CX3CR1 in inhibitory signaling, activation, and survival of pathogenic and regulatory T cell subsets within CNS tissues at peak of disease and at time of recovery. 3. To define address how weaker signaling through human CX3CR1I249/M280 replicates the pathology of Cx3cr1-/- mice during EAE. We hypothesize that I249/M280 expressing cells will exhibit effector functions comparable to CX3CR1-deficient cells. We will use knock-in mice expressing the human variant as a low affinity model to investigate the role of the I249/M280 in APC activation and T cell polarization in vivo during CNS autoimmunity.