Mechanisms Controlling Regulatory T cell Effector Function in IBD

项目摘要 IBD中调节性T细胞效应器功能的控制机制。炎症性肠病的发病机制 IBD的特征在于对肠道微生物群组分的免疫失调。小鼠发现 IBD模型和最近的人类遗传学研究强调了免疫调节蛋白的关键，非冗余作用。 细胞因子IL-10在维持肠道免疫稳态中的作用。我们的实验室已经证明Foxp 3+调节T Treg细胞是肠道中IL-10的主要来源。然而，IL-10仅产生于 由Treg细胞的亚群-定义为“效应”（e）Treg细胞。在使用IL-10的初步研究中 转基因报告小鼠模型，以探索分离的T细胞转录组之间的差异。 在IL-10表达的基础上，我们鉴定了DNA结合因子Gfi 1是IL-10基因的中心阻遏物 在所有CD 4 T细胞亚群中的表达，包括Treg细胞。Gfi 1似乎通过相互作用， 通过抑制Prdm 1（Blimp 1）的转录，间接地与IL 10基因座，这是一种反式激活因子， Treg细胞中的IL 10。此外，Gfi 1抑制其他似乎对eTreg功能至关重要的基因， 提示Gfi 1可能在调控eTreg细胞分化中起关键作用。我们终于有 鉴定了诱导Foxp 3 + Treg细胞表达IL-10的细胞因子信号。本质上，IL-10 Treg细胞的表达是潜伏的，需要激活抑制Gfi 1的细胞因子信号以解除抑制 作为eTreg细胞编程的一部分的IllO转录。这可以解释为什么T细胞的IL-10表达 在很大程度上局限于处于体内平衡的肠道，在那里对微生物群的持续反应提供了一种状态， 控制炎症和促炎细胞因子的来源，促进IL-10的发展， 表达eTreg细胞。我们假设肠道中的炎症信号超过了Gfi 1介导的抑制， Gfi 1表达的调节将影响Treg细胞的保护能力 炎症环境中的细胞-在很大程度上通过调节IL-10的表达。此外，我们 Gfi 1通过抑制IL-10在CD 4 T效应细胞中维持致病性表型，从而抑制IL-10的表达。 Gfi 1将致病性T细胞转化为产生IL-10的保护性T细胞，从而改善肠道免疫功能。 疾病在此，我们将定义Gfi 1在鼠和人Treg细胞中抑制IL-10的机制， 我们将进行原理验证研究，以检查失调的炎症因子对IBD发病机制的影响。 通过T细胞表达Gfi 1。阐明细胞因子调节Gfi 1-Blimp 1的机制 轴控制T细胞表达IL-10将导致更好地理解稳态网络， 预防IBD，并将为发现新的治疗方法提供基础， 10的表达上调，增强eTreg细胞的分化和功能，从而治疗IBD。

PROJECT SUMMARY Mechanisms Controlling Regulatory T Cell Effector Function in IBD. The pathogenesis of inflammatory bowel disease (IBD) is characterized by immune dysregulation to components of the enteric microbiota. Findings from mouse models of IBD and recent human genetic studies highlight a critical, non-redundant role for the immunoregulatory cytokine IL-10 in the maintenance of intestinal immune homeostasis. Our lab has shown that Foxp3+ regulatory T (Treg) cells are, overwhelmingly, the major source of IL-10 in the intestines. However, IL-10 is only produced by a subset of Treg cells—defined as ‘effector’ (e)Treg cells. In preliminary studies that used an IL-10 transgenic reporter mouse model to explore differences between transcriptomes of T cells separated on the basis of expression of IL-10, we identified the DNA-binding factor Gfi1 as a central repressor of Il10 gene expression in all subsets of CD4 T cells, including Treg cells. Gfi1 appears to act both directly, via interactions with the Il10 locus, and indirectly, by repressing transcription of Prdm1 (Blimp1), which is a trans-activator of Il10 in Treg cells. Additionally, Gfi1 represses other genes that appear to be central to eTreg function, suggesting that Gfi1 may play a key role in regulating the differentiation of eTreg cells. Finally, we have identified cytokine signals that induce the expression of IL-10 by Foxp3+ Treg cells. In essence, IL-10 expression by Treg cells is Iatent and requires activating cytokine signals that repress Gfi1 to derepress transcription of Il10 as part of eTreg cell programming. This could explain why IL-10 expression by T cells is largely restricted to the intestines at homeostasis, where on-going responses to the microbiota provide a state of controlled inflammation and a source of pro-inflammatory cytokines that promote the development of IL-10– expressing eTreg cells. We hypothesize that inflammatory signals in the gut override Gfi1-mediated repression of eTreg cell development and that modulation of Gfi1 expression will impact the protective capabilities of Treg cells in an inflammatory environment—in large part through modulation of IL-10 expression. Further, we posit that Gfi1 maintains a pathogenic phenotype in CD4 T effector cells by repressing IL-10, such that inhibition of Gfi1 will convert pathogenic T cells to IL-10–producing protective T cells, thereby ameliorating intestinal disease. Herein, we will define mechanisms by which Gfi1 represses IL-10 in murine and human Treg cells and we will perform proof-of-principle studies to examine the impact on IBD pathogenesis of dysregulated expression of Gfi1 by T cells. The delineation of mechanisms by which cytokines modulate the Gfi1–Blimp1 axis to control IL-10 expression by T cells will lead to a better understanding of homeostatic networks that prevent IBD, and will provide a basis for discovery of novel therapeutic approaches by which endogenous IL- 10 can be up-regulated, and the differentiation and function of eTreg cells enhanced, to treat IBD.