Epigenetic Control of T cell Autoimmunity

有效控制系统性自身免疫性疾病，如类风湿性关节炎(RA)，目前依赖于使用强烈的全身性免疫抑制，因此增加了感染和恶性肿瘤的风险。治疗自身免疫性疾病的一个更好的理论方法是诱导抗原特异性耐受，只针对危险的自我反应性T和B细胞。然而，由于我们无法在完整的免疫系统中可视化和研究那些自身抗原特异性的多克隆淋巴细胞，这种有可能治愈自身免疫性疾病的有效疗法的设计受到了阻碍。此外，我们对患者体内已对自身抗原有反应的淋巴细胞中克隆性无能的诱导缺乏足够的知识。最后，我们识别新的治疗靶点的典型候选方法是一个固有的缓慢过程，可能会受到对诱导无能的重要分子机制的先入为主的不利影响。我们现在提出一系列临床前研究，将利用新兴的抗原/II类四聚体技术来追踪打破免疫耐受和引起自身免疫的多克隆CD4T细胞。具体目标1将研究NT5‘E和Foxp3在外周免疫系统中多克隆CD4T细胞与自身抗原相遇后克隆性无能的形成和维持中的单独作用。ECTO-5‘-核苷酸酶(NT5’E)是一种新的候选无能因子，它是通过全基因组筛选发现的与基因表达变化相关的染色质修饰，它在控制克隆性无能发育和维持抗原无应答中的作用将被评估。具体目标2将确定克隆性无能在表观遗传学改变中的作用，以防止CD4T细胞介导性关节炎的发展。在这一目标下的实验将通过过继转移对天然自身抗原葡萄糖-6-磷酸异构酶(GPI)起反应的KRN TCR转基因T细胞来建立RA模型，并在全身性炎症或淋巴细胞减少的背景下探讨NT5‘E和Foxp3 CD4T调节细胞在克隆性无能诱导的表观遗传学控制中的作用。除了增加我们关于NT5‘E诱导无能的调节和体内免疫调节的基础知识外，使用II类四聚体获得的结果也将作为开发生物标记物的范例，用于人体试验，旨在针对自身反应性CD4T细胞进行克隆性无能诱导。此外，我们正在进行的关于CD4T细胞对自身抗原反应过程中基因表达的表观遗传控制的研究，为确定其他新的治疗靶点提供了机会。

Effective control of systemic autoimmune diseases such as rheumatoid arthritis (RA) currently relies on the use of intense generalized immunosuppression, thus increasing the risk of infection and malignancy. A better theoretical approach to the treatment of autoimmune disease is the induction of an antigen-specific tolerance that targets only the dangerous self-reactive T and B cells. The design of such effective therapies with the potential to cure autoimmune disease, however, is hampered by our inability to visualize and study those self antigen-specific polyclonal lymphocytes within the intact immune system. Furthermore, we lack sufficient knowledge regarding the induction of clonal anergy in lymphocytes that are already responding to self antigens within the diseased individual. Finally, our typical candidate approach to the identification of new therapeutic targets is an inherently slow process that can be adversely influenced by preconceived notions about the molecular mechanisms that are important to the induction of anergy. We now propose a series of pre-clinical studies that will make use of emerging antigen/class II tetramer technologies to track polyclonal CD4+ T cells that break immune tolerance and cause autoimmunity. Specific Aim 1 will investigate the individual roles of NT5'E and Foxp3 in the development and maintenance of clonal anergy following initial self antigen encounter by polyclonal CD4+ T cells in the peripheral immune system. Ecto-5'-nucleotidase (NT5'E), a novel candidate anergy factor discovered using a genome-wide screen for chromatin modifications in association with changes in gene expression, will be evaluated for its role in the control of clonal anergy development and maintenance of antigen unresponsiveness. Specific Aim 2 will establish the role of clonal anergy in the epigenetic changes that protect against the development of CD4+ T cell-mediated arthritis. Experiments under this aim will model RA using an adoptive transfer of KRN TCR-transgenic T cells reactive to the natural autoantigen glucose-6-phosphate isomerase (GPI), and investigate in the setting of systemic inflammation or lymphopenia the roles of NT5'E and Foxp3+CD4+ T regulatory cells in the epigenetic control of clonal anergy induction. In addition to increasing our fundamental knowledge about the regulation of anergy induction by NT5'E and immunoregulation in vivo, the results obtained with the class II tetramers will also serve as a paradigm for the development of biomarkers for use in human trials designed to target autoreactive CD4+ T cells for clonal anergy induction. Furthermore, our ongoing investigation of the epigenetic control of gene expression during CD4+ T cell responses to self antigen offers the opportunity to identify additional novel therapeutic targets.