Epigenetic programming of T follicular helper cell differentiation

项目摘要 T滤泡辅助细胞(TFH)是T细胞的一个特殊亚群，直接帮助B细胞形成 生发中心。在生发中心内，B细胞经历抗体的亲和力成熟、类别转换、 以及长寿浆细胞和记忆B细胞的分化。T卵泡辅助反应对 长寿抗体介导的免疫保护，表现为没有长寿抗体 Tfh缺陷个体和动物的反应和免疫缺陷的表现。跟随 病毒感染或免疫激活幼稚的CD4T细胞，这些新激活的T细胞解释不同的 诱导转录因子的信号，这些转录因子指导特定基因表达的变化。与……协调 这些基因表达的变化发生在T辅助细胞分化过程中，基因经历DNA甲基化 控制表达或相关基因的调控元件中CpG基序的变化。DNA甲基化行为 作为一种抑制性表观遗传标记，去甲基化过程与表达能力有关 对细胞功能很重要的基因。甲基化的变化是由Tet双加氧酶催化的，它参与了 去甲基化过程和DNA甲基转移酶促进新的(从头)甲基化转变为 去除了无关的基因。这项提案中具体目标的广泛目标是了解如何 T滤泡辅助细胞经历DNA甲基化程序，要么去甲基化，要么从头开始 甲基化，以及这种编程的操作是否可以增强或损害T滤泡辅助细胞 从而影响对疫苗接种或感染的抗体反应。这项建议的具体目的是 目的：1)确定TET2在调节T滤泡辅助性T细胞和Th1细胞与记忆平衡中的作用 细胞分化；目的2)确定从头甲基化在调节Tfh和Th1记忆细胞中的作用 分化和谱系承诺；以及目的3)确定DNA甲基转移酶抑制是否 促进Tfh分化和增强抗体介导的免疫保护 流感挑战。这些研究将利用细胞免疫学方法，基因表达和整体 基因组DNA甲基化分析，免疫和传染病挑战评估 DNA甲基化编程在T滤泡辅助细胞分化、功能和记忆中的重要性 队形。这些目标结合在一起，将提供对T卵泡助手如何 细胞分化并识别和表征可靶向产生更有效的新途径 可以提高长期免疫力的疫苗接种策略。

Project Summary T follicular helper cells (Tfh) are a specialized subset of T cells that directly provide help to B cells to form germinal centers. Within germinal centers, B cells undergo affinity maturation of antibodies, class switching, and differentiation of long-lived plasma cells and memory B cells. T follicular helper responses are vital to long-lived antibody-mediated immune protection, which is demonstrated by the absence of long-lived antibody responses and the presentation of immune deficiency in Tfh-deficient individuals and animals. Following activation of naïve CD4 T cells by viral infection or immunization, these newly activated T cells interpret various signals that induce transcription factors that direct specific gene expression changes. In coordination with these gene expression changes that occur during T helper cell differentiation, genes undergo DNA methylation changes at CpG motifs in regulatory elements that control expression or relevant genes. DNA methylation acts as a repressive epigenetic mark, and the process of demethylation is associated with the ability to express genes important for cell function. Changes in methylation are catalyzed by Tet dioxygenases that participate in the processes of demethylation, and DNA methyltransferases that promote new (de novo) methylation to turn off irrelevant genes. The broad objectives of the specific aims in this proposal are to gain understanding of how T follicular helper cells undergo DNA methylation programing, either through demethylation or de novo methylation, and whether manipulation of such programing can enhance or impair T follicular helper cell function and thus influence antibody responses to vaccination or infection. The specific aims for this proposal are: Aim 1) Determine the role of Tet2 in regulating the balance of T follicular helper and Th1 cell and memory cell differentiation; Aim 2) Define the role of de novo methylation in regulating Tfh and Th1 memory cell differentiation and lineage commitment; and Aim 3) Determine whether DNA methyltransferase inhibition can promote Tfh differentiation and enhance antibody-mediated immune protection following immunization against influenza challenge. These studies will utilize cellular immunology approaches, gene expression and whole genome DNA methylation analyses, and immunization and infectious disease challenge to evaluate the importance of DNA methylation programing in T follicular helper cell differentiation, function, and memory formation. Together, these aims will combine to provide a mechanistic evaluation of how T follicular helper cells differentiate and identify and characterize novel pathways that can be targeted to generate more effective vaccination strategies that can improve long-lasting immunity.