Molecular mechanisms of Th17 plasticity in MS

描述（由申请人提供）：多发性硬化症（MS）及其小鼠模型（实验性自身免疫性脑脊髓炎; EAE）是由自身反应性CD 4 + T细胞引发和传播的中枢神经系统自身免疫性疾病。两个亚群的CD 4 + T细胞，Th 1和Th 17细胞已被牵连在自身免疫性疾病，特别是MS的致病性。然而，髓鞘特异性Th 1和Th 17细胞在中枢神经系统（CNS）自身免疫性的发展中的相对贡献仍然存在争议，因为无论是IL-17 F，IL-17 A，也没有IFN-γ缺陷的小鼠是完全保护免受CNS自身免疫性的发展。相比之下，IL-23 p19和IL-23受体（IL-23 R）缺陷型小鼠对EAE的发展具有高度抗性。此外，在患有自身免疫性疾病的患者的发炎组织中，已经鉴定出大量共表达IFN-g和IL-17的Th细胞。在自身免疫过程中，它们在靶组织中的频率增加表明这些细胞在疾病过程中的重要作用。然而，这些细胞在自身免疫中的起源、稳定性和功能仍然是个谜。我们已经确定，在EAE过程中，大多数CNS浸润性T细胞表达IL-23 R，而不管它们的细胞因子产生（IL-17和/或IFN-g）如何，因为它们起源于Th 17细胞。我们进一步表明IL-23在Th 17可塑性中起关键作用，因为它促进IL-17+ IFN-g+ T细胞（Th 17/g）从Th 17细胞中出现。虽然Th 17/g细胞表达T-bet，但这些细胞中IFN-g的产生不受T-bet或其他IFN-g促进转录因子的控制。相比之下，我们确定AhR作为一个关键的转录因子驱动IFN-γ的生产由Th 17细胞响应IL-23。我们还证实了IL-23对于在人CD 4 + T细胞中产生这些细胞的重要性。此外，我们已经启动了一个全基因组分析的DNA酶超敏位点在人类Th 1和Th 17细胞亚群使用Solexa测序。我们的研究结果表明，我们可以确定转录因子的结合位点，并区分表观遗传标记在个别T细胞亚群使用该技术。在这项提案中，我们将测试我们的总体假设，即TH 17/g细胞是CNS特异性自身免疫中的致病细胞，由IL-23通过AhR依赖性机制驱动，并在MS患者中存在选择性遗传改变。总之，这项研究的完成不仅将描绘Th 17/g细胞在自身免疫中的功能，而且还将确定这些细胞在小鼠和人类中产生和调节的机制。

DESCRIPTION (provided by applicant): Multiple sclerosis (MS) and its mouse model (experimental autoimmune encephalomyelitis; EAE) are autoimmune diseases of the central nervous system initiated and propagated by auto-reactive CD4+ T cells. Two subsets of CD4+ T cells, Th1 and Th17 cells have been implicated in the pathogenicity of autoimmune diseases and in particular MS. However, the relative contribution of myelin specific Th1 and Th17 cells in the development of central nervous system (CNS) autoimmunity remains controversial since neither IL-17F, IL- 17A, nor IFN-g deficient mice are fully protected from the development of CNS autoimmunity. In contrast, IL- 23p19- and IL-23 receptor (IL-23R) deficient mice are highly resistant to the development of EAE. Furthermore, in inflamed tissues of patients with autoimmune diseases, Th cells co-expressing IFN-g and IL-17 have been identified in significant number. Their increase frequency in target tissues during autoimmunity suggests an important role of these cells in the disease process. However, the genesis, stability and function of these cells in autoimmunity remain enigmatic. We have determined that most CNS-infiltrating T cells during the course of EAE express the IL-23R irrespective of their cytokine production (IL-17 and/or IFN-g) because they originate from Th17 cells. We further show that IL-23 plays a critical role in Th17 plasticity as it promotes the emergence of IL-17+ IFN-g+ T cells (Th17/g) from Th17 cells. Although Th17/g cells expressed T-bet, IFN-g production in these cells was not controlled by T-bet or other IFN-g-promoting transcription factors. In contrast, we identified AhR as a key transcription factor driving the production of IFN-g by Th17 cells in response to IL-23. We have also confirmed the importance of IL-23 for the generation of these cells in human CD4+ T cells. In addition, we have initiated a genome-wide analysis of DNase hypersensitivity sites in human Th1 and Th17 cells subsets using Solexa sequencing. Our results show that we can identify transcription factors binding sites and distinguish epigenetic marks in individual T cell subsets using this technique. In this proposal, we will test our overarching hypothesis that TH17/g cells are pathogenic cells in CNS-specific autoimmunity, are driven by IL-23 through an AhR-dependent mechanism and present with selective genetic alterations in MS patients. Together the completion of this study will not only delineate the function of Th17/g cells in autoimmunity but also determine the mechanisms by which these cells are generated and can be regulated in mice and humans.