Function of a novel subset of dendritic cells in EAE

描述(申请人提供)：实验性自身免疫性脑脊髓炎(EAE)是以中枢神经系统炎症和脱髓鞘为特征的多发性硬化症(MS)的动物模型。CD4+T细胞的两个亚群Th1和Th17与MS和EAE的致病有关。在外周和中枢神经系统(CNS)中，CD4+T细胞与主要组织相容性II类(MHCII)+抗原提呈细胞(APC)之间的相互作用是诱导自身免疫所必需的。EAE的临床表现不仅需要外周免疫系统中原始的自身反应性CD4+T细胞的初始启动，而且关键依赖于中枢神经系统内神经抗原特异性的CD4+T细胞的重新激活才能发育为效应性T细胞。树突状细胞是一类异质性的专职抗原提呈细胞，能够启动、放大和调节免疫反应。在持续的EAE和MS期间，在中枢神经系统中发现大量的树突状细胞(DC)，支持其积极参与疾病的病理生理。传统的树突状细胞参与了EAE致病T细胞应答的启动和放大。另一方面，树突状细胞的另一个亚群，浆样树突状细胞已被证明在疾病中具有调节作用。因此，了解树突状细胞不同亚群的功能和调节非常重要，因为这些细胞可以作为一种手段来调节或加剧EAE和MS的自身免疫反应。使用追踪视黄醇相关孤儿受体-GT(RORgt)表达细胞的报告小鼠，我们发现了一种新的树突状细胞群体，其特征是RORgt的表达，RORgt是对Th17细胞的发育至关重要的转录因子。我们没有在幼鼠的淋巴器官或中枢神经系统中检测到这些细胞。然而，我们在活动期EAE小鼠的中枢神经系统中观察到了这些新的CD11c+RORgt+树突状细胞。在这项提议中，我们将检验这一创新假设，即RORgt+CD11c+树突状细胞(DC)的这一亚群代表着独特的树突状细胞亚群，对于EAE的发展和中枢神经系统致病Th17细胞的重新刺激非常重要。我们将(1)通过流式细胞术、组织学和RNA-SEQ对这些RORgt+树突状细胞进行鉴定，(2)确定RORgt+DC在EAE中的功能。这些研究的完成将为新发现的表达RORgt的树突状细胞亚群在诱导和调节致病T细胞反应中的作用提供新的见解。解决这些问题将有助于我们理解树突状细胞的个体发育，树突状细胞是免疫系统中重要的细胞亚群，并有望找到新的策略，旨在防止自身免疫期间致病细胞在中枢神经系统中的激活和进入。

DESCRIPTION (provided by applicant): Experimental autoimmune encephalomyelitis (EAE) is an animal model of multiple sclerosis (MS) characterized by inflammation and demyelination of the CNS. Two subsets of CD4+ T cells, Th1 and Th17 cells, have been implicated in the pathogenicity of MS and EAE. The interactions between CD4+ T cells and major histocompatibility class II (MHCII)+ antigen presenting cells (APCs) are necessary in both the periphery and central nervous system (CNS) to elicit autoimmunity. Clinical manifestations of EAE do not only require the initial priming of naive autoreactive CD4+ T cells in the peripheral immune system but critically depends on the reactivation of neuroantigen-specific CD4+ T cells within the CNS to develop into effector T cells. Dendritic cells are a heterogeneous class of professional antigen-presenting cells (APCs) capable of initiating, amplifying and regulating immune responses. During ongoing EAE and MS, a substantial accumulation of dendritic cells (DC) has been found in the CNS supporting their active participation in the pathophysiology of the diseases. Conventional DCs have been implicated in priming and the amplification of the pathogenic T cell response in EAE. On the other hand, another subset of dendritic cells, plasmatoid DC have been shown to have regulatory roles in the disease. Understanding the function and regulation of different subsets of dendritic cells is therefore important because these cells could serve as a means to regulate or exacerbate autoimmune responses in EAE and MS. Using a reporter mouse, which tracks retinoid-related orphan receptor-gt (RORgt)- expressing cells, we discovered a new population of dendritic cells characterized by the expression of RORgt, the transcription factor important for the development of Th17 cells. We did not detect these cells in the lymphoid organs or CNS of naive mice. However, we observed these new CD11c+ RORgt+ dendritic cells in the CNS of mice with active EAE. In this proposal, we will test the innovative hypothesis that this subset of RORgt+ CD11c+ dendritic cells (DCs) represents a unique subset of dendritic cells and is important for the development of EAE and the restimulation of pathogenic Th17 cells in the CNS. We will (1) characterize these RORgt + dendritic cells by flow cytometry, histology and RNA-seq, and (2) determine the function of RORgt+ DCs in EAE. The completion of these studies will provide novel insights on the role of a newly identified subset of dendritic cells that expresses RORgt in the induction and modulation of pathogenic T cell responses. Addressing these questions will significantly contribute to our understanding of the ontogeny of dendritic cells an important cell subset of the immune system and hopefully identify new strategies aimed at preventing the activation and entry of pathogenic cell in the CNS during autoimmunity.