A Novel Tolergenic Dendritic Cell: Biology & Therapeutic Potential

描述(申请人提供)：我们的总体目标是确定一个新的耐受性DC群体在外周和中枢免疫耐受中的作用(S)；描述他们用来调节T细胞免疫的细胞和分子机制；并测试他们在移植和免疫模型中的治疗潜力。树突状细胞(DC)向T细胞递呈自身或外源抗原，调节免疫反应。CCR9的表达定义了一个独特但广泛的DC亚群，它迁移到CCR9配体CCL25，CCL25是一种趋化因子，与T祖细胞归巢到胸腺和淋巴细胞归巢到肠道有关。初步研究表明，CCR9+DC是未成熟浆细胞样树突状细胞(PDC)的一个亚群，初步提出如下假设：1.CCR9+PDC作为强大的内源性耐受原诱导外周调节性T细胞，并能以CCR9依赖的方式将外周自身抗原携带到胸腺，在胸腺中介导中枢耐受；2.CCR9+PDC在移植中具有抑制GVHD和同种免疫反应的潜力。目的：1.进一步研究CCR9+pDC的特性，确定其耐受潜能，明确CCR9+pDC调节T细胞免疫的细胞和分子机制。体外实验将证实和评估CCR9+(vs.CCR9-)PDC诱导Tregs的机制，包括调节细胞因子的表达和对TLR配体的反应。对CCR9+(耐受性)和CCR9-(免疫原性)PDC的基因和蛋白质表达进行比较分析，将有助于从机制上深入了解它们的特殊作用。体内实验将证实CCR9+PDC在体内调节免疫反应的能力。2：明确CCR9在胸腺归巢和耐受性pDC蓄积中的作用。短期归巢和重建分析将检验我们的假设，即CCR9+pDC比CCR9-pDC对胸腺的归巢更好。CCR9对这种归巢的机制重要性将通过CCR9配体CCL25的抗体以及来自野生型和CCR9缺陷供者的PDC的比较研究来确定。3：明确CCR9+pDC和PDC表达的CCR9在中枢耐受中的作用。体内建立的方法将确定胸腺归巢CCR9+PDC调节胸腺细胞发育(克隆缺失、Treg诱导)的能力，以及CCR9在PDC介导的中枢耐受中的作用。4.评价CCR9+DC在组织移植模型中的治疗潜力，并探讨其体内免疫抑制机制：将采用移植物抗宿主病(GVHD)模型和胰岛细胞移植模型，检测CCR9+PDC介导的免疫耐受形成的治疗潜力，并探讨其相关机制。 与公共健康相关：这些研究定义了一种内源性细胞，似乎可以控制我们的免疫系统。他们将测试一种使用这些细胞进行移植免疫治疗的新方法，并可能导致对自身免疫、过敏和其他免疫系统疾病的新见解和治疗方法。

DESCRIPTION (provided by applicant): Our overall goal is to define the role(s) of a novel tolerogenic DC population in peripheral and central immune tolerance; to characterize the cellular and molecular mechanisms they employ to regulate T cell immunity; and to test their therapeutic potential in models of transplantation and immunity. Dendritic cells (DCs) present self or foreign antigen to T cells, and regulate immune responses. CCR9 expression defines a unique but widespread DC subset that migrates to the CCR9 ligand CCL25, a chemokine implicated in T progenitor cell homing to the thymus and in lymphocyte homing to the intestines. Preliminary studies show that CCR9+ DCs are a subset of immature plasmacytoid DC (pDC), and have provided initial insights leading to the following general hypotheses: 1. CCR9+ pDC act as potent endogenous tolerogens that induce peripheral regulatory T cells, and that can carry peripheral self antigens in a CCR9-dependent manner to the thymus where they may mediate central tolerance; and 2. CCR9+ pDC have the potential to suppress GVHD and allo-immune responses in transplantation. AIMS: 1: To further characterize CCR9+ pDC, confirm their tolerogenic potential, and define the cellular and molecular mechanisms CCR9+ pDCs employ to regulate T cell immunity. In vitro assays will confirm and assess mechanisms by which CCR9+ (vs. CCR9-) pDC induce Tregs, including regulatory cytokine expression and responses to TLR ligands. Comparative gene and protein expression analysis of CCR9+ (tolerogenic) vs CCR9- (immunogenic) pDC will lead to mechanistic insights into their specialized roles. In vivo approaches will confirm the ability of CCR9+ pDC to regulate immune responses in vivo. 2: To define the role of CCR9 in thymic homing and accumulation of tolerogenic pDCs. Short term homing and reconstitution assays will test our hypothesis that CCR9+ pDCs home better than CCR9- pDC to the thymus. The mechanistic importance of CCR9 to this homing will be defined with antibodies to the CCR9 ligand CCL25 and in comparative studies of pDC from wild type vs. CCR9-deficient donors. 3: To define the role of CCR9+ pDCs, and of pDC-expressed CCR9, in central tolerance. Established in vivo methods will define ability of thymic-homing CCR9+ pDC to regulate thymocytes development (clonal deletion, Treg induction), and the role of CCR9 in pDC mediated central tolerance. 4: To assess the therapeutic potential of CCR9+ DCs in models of tissue transplantation and to characterize their immunosuppressive mechanisms in vivo: Models of GVHD and pancreatic islet cell transplantation will be used to test the therapeutic potential of CCR9+ pDC mediated tolerogenesis, and to define the mechanisms involved. PUBLIC HEALTH RELEVANCE: These studies define an endogenous cell that appears to keep our immune system in check. They will test a novel approach using these cells for transplantation immunotherapy, and may lead to new insights and treatments for autoimmune, allergic and other disorders of the immune system.