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CD4+ T细胞引发和传播的中枢神经系统自身免疫性疾病。CD4+ T细胞的两个亚群Th1和Th17细胞与自身免疫性疾病，特别是ms的致病性有关。然而，髓磷脂特异性Th1和Th17细胞在中枢神经系统自身免疫发展中的相对贡献仍然存在争议，因为IL- 17f、IL- 17A和IFN-g缺陷小鼠都不能完全保护其免受中枢神经系统自身免疫的发展。相反，IL- 23p19-和IL-23受体（IL- 23r）缺陷小鼠对EAE的发展具有高度抗性。此外，在自身免疫性疾病患者的炎症组织中，已发现大量共表达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起重要作用。然而，这些细胞在自身免疫中的发生、稳定性和功能仍然是一个谜。我们已经确定，在EAE过程中，大多数cns浸润T细胞表达IL-23R，而不考虑其细胞因子（IL-17和/或IFN-g）的产生，因为它们起源于Th17细胞。我们进一步表明，IL-23在Th17可塑性中起关键作用，因为它促进了Th17细胞中IL-17+ IFN-g+ T细胞（Th17/g）的出现。虽然Th17/g细胞表达T-bet，但这些细胞中IFN-g的产生不受T-bet或其他促IFN-g转录因子的控制。相反，我们发现AhR是Th17细胞响应IL-23产生IFN-g的关键转录因子。我们还证实了IL-23在人类CD4+ T细胞中产生这些细胞的重要性。此外，我们已经使用Solexa测序启动了人类Th1和Th17细胞亚群dna酶超敏位点的全基因组分析。我们的研究结果表明，我们可以使用这种技术识别转录因子结合位点并区分单个T细胞亚群中的表观遗传标记。在本提案中，我们将验证我们的总体假设，即TH17/g细胞是cns特异性自身免疫的致病细胞，通过ahr依赖机制由IL-23驱动，并在MS患者中出现选择性遗传改变。总之，这项研究的完成不仅将描述Th17/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.