Role of CX3CR1 in adaptive immunity during autoimmune encephalomyelitis

描述（由申请人提供）：存在于神经元和外周内皮细胞上的跨膜趋化因子fractalkine （CX3CL1）作为粘附分子或可溶性趋化剂。CX3CL1通过其受体CX3CR1发出信号，CX3CR1在小胶质细胞、单核/巨噬细胞和树突状细胞、NK细胞和T细胞中表达。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中CX3CR1+细胞的表达较低，外周血中CX3CR1+细胞的缺乏与疾病活动相关。然而，CX3CR1在抗原提呈细胞和T细胞中的作用及其对中枢神经系统病理的贡献仍然是谜。本研究提出的假设是CX3CR1/CX3CL1调节实验性自身免疫性脑脊髓炎（EAE）期间影响致病性T细胞发育的抗原呈递细胞（APC）效应功能。该假说基于：1)EAE症状更严重，CX3CR1缺失小鼠中枢神经系统脱髓鞘增强；2)CX3CR1缺失与CD115+CD11c+树突状细胞向中枢神经系统组织的选择性积累相关；3)骨髓嵌合小鼠发现骨髓中CX3CR1缺失诱导了一种罕见的、严重的、慢性非缓解性EAE疾病，并伴有持续瘫痪。本提案的总体目标是阐明CX3CR1在EAE中的功能及其如何调节致病性CNS炎症。具体目标是：1。通过调节抗原呈递和T细胞启动来确定CX3CR1在EAE启动中的作用。我们将验证CX3CR1控制外周DC成熟影响抗原呈递和随后的外周T细胞极化的假设。我们将研究CX3CR1抗原转运和树突状细胞动员的作用，以及CX3CR1缺乏对脑源性T细胞产生的影响。2. 探讨CX3CR1缺失在EAE效应期的作用，以及对神经元损伤和脱髓鞘的保护作用。我们假设骨髓中CX3CR1的缺失对于EAE脑中T细胞介导的炎症和组织损伤的维持至关重要。我们将研究CX3CR1在疾病高峰和恢复时中枢神经系统组织中致病性和调节性T细胞亚群的抑制信号、激活和存活中的作用。3. 通过人CX3CR1I249/M280的弱信号如何在EAE期间复制Cx3cr1-/-小鼠的病理。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体的敲入小鼠作为低亲和力模型来研究I249/M280在中枢神经系统自身免疫过程中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. PUBLIC HEALTH RELEVANCE: More than 20% of the population carries a variant fractalkine receptor (CX3CR1) with defective functions. This research will address the role of CX3CR1 during the immune response associated with experimental autoimmune encephalomyelitis as a model of multiple sclerosis (MS). Defining the beneficial or detrimental effects of CX3CR1 will advance prevention and treatment strategies for patients living with MS.