Regulation of effector T cell function by Blimp-1 in a murine model of colitis

描述(申请人提供)：肠粘膜的动态平衡是通过生理和病理生理炎症之间的微妙平衡来维持的，确保对病原体的有效反应和避免对共生菌的高反应性。这种平衡的破坏会导致慢性炎症性疾病的发展，如溃疡性结肠炎和克罗恩病，统称为炎症性肠病(IBD)。T淋巴细胞是IBD的主要效应细胞，干预T细胞功能可能成为治疗IBD的潜在策略。然而，IBD中不受控制的T细胞反应的确切机制尚不清楚。我们和其他人最近发现转录抑制因子B淋巴细胞诱导成熟蛋白-1(Blimp-1)是T细胞内稳态和功能的重要调节因子。BLIMP-1最初被认为在抗体分泌浆细胞的终末分化中起关键作用。最近的研究表明，Blimp-1在活化的T细胞中也有高表达。带有Blimp-1 T细胞特异性缺失的小鼠会在外周积累“抗原经验”细胞，并自发发展为结肠炎，而不会损害其他器官，这表明Blimp-1是肠道粘膜正常T细胞功能所必需的。基于这些发现以及之前对其他细胞系的研究，证实Blimp-1控制数个遗传程序，我们假设在T细胞中，Blimp-1调节对控制肠粘膜反应性至关重要的遗传程序，并且识别T细胞中Blimp-1的遗传靶点将揭示与粘膜内稳态有关的新的分子途径。在目前的提案中，我们将通过以下具体目标来检验这一假说：1)鉴定Blimp-1CKO小鼠的结肠炎特征，以深入了解在缺乏Blimp-1的情况下中断的效应机制；以及2)生成并比较Blimp-1充足和缺陷的结肠炎T细胞，以确定和验证这些细胞中受Blimp-1调控的基因。为了实现这些目标，我们将使用我们之前培育的Blimp-1 CKO小鼠。首先，我们将进行表型和功能分析，以确定导致这些小鼠疾病的T细胞亚群。其次，我们将使用过继转移实验来产生Blimp-1充足和缺陷的致瘤T细胞，用于基因表达研究(包括RNA微阵列)，以确定Blimp-1控制的分子通路。我们预计，在完成这里提出的实验后，我们将在T细胞中发现Blimp-1的新的遗传靶点，并发现对调节肠道粘膜中的效应性T细胞功能至关重要的新途径。对这些途径的进一步探索可以导致开发新的治疗方法来治疗IBD和潜在的其他炎症性疾病。与公共卫生相关：肠道内T细胞反应失衡导致胃肠道慢性炎症。我们试图阐明在肠道粘膜中控制T细胞效应器功能的调节机制。这些机制的确定将有助于开发新的治疗IBD的方法。

DESCRIPTION (provided by applicant): Homeostasis in the intestinal mucosa is maintained by a delicate balance between physiological and pathophysiological inflammation that assures efficient response against pathogenic organisms and avoidance of hyperresponsiveness to the commensal flora. Disruption of this balance results in the development of chronic inflammatory conditions, such as ulcerative colitis and Crohn's disease, collectively termed Inflammatory Bowel Disease (IBD). T lymphocytes are major effector cells in IBD, thus, interfering with T cell function could be a potential strategy to treat IBD. However, the precise mechanisms underlying the uncontrolled T cell responses in IBD are not well understood. We and others have recently identified the transcriptional repressor B Lymphocyte Induced Maturation Protein-1 (Blimp-1) as an important regulator of T cell homeostasis and function. Blimp-1 was first known for its crucial role in the terminal differentiation of antibody-secreting plasma cells. Recent studies show that Blimp-1 is also highly expressed in activated T cells. Mice with a T cell-specific deletion of Blimp-1 accumulate "antigen-experienced" cells in the periphery and spontaneously develop colitis, without compromising other organs, indicating that Blimp-1 is required for proper T cell function at the intestinal mucosal. Based on these findings and previous studies in other cell lineages, which established that Blimp- 1 controls several genetic programs, we hypothesize that in T cells Blimp-1 regulates genetic programs crucially important to control responsiveness in the intestinal mucosa, and identification of genetic targets of Blimp-1 in T cells should reveal new molecular pathways implicated in mucosal homeostasis. In the current proposal we will test this hypothesis through the following specific aims: 1) characterize the colitis in the Blimp-1CKO mice to gain insight into the effector mechanisms disrupted in the absence of Blimp-1; and 2) generate and compare Blimp-1 sufficient and deficient colitogenic T cells to identify and validate genes regulated by Blimp-1 in these cells. To accomplish these aims we will use the Blimp-1 CKO mice we have previously generated. First, we will conduct phenotypical and functional analysis to identify the T cell subpopulations causing disease in these mice. Second, we will use adoptive transfer experiments to generate Blimp-1sufficient and deficient colitogenic T cells to be used in gene expression studies (including RNA microarray) to identify molecular pathways controlled by Blimp-1. We anticipate that upon completion of the experiments proposed here, we will have identified new genetic targets of Blimp-1 in T cells and uncovered new pathways important for the regulation of effector T cell function in the intestinal mucosal. Further exploration of these pathways can lead to the development of new therapeutic approaches to treat IBD and potentially other inflammatory disorders. PUBLIC HEALTH RELEVANCE: Unbalanced T cell responses in the intestines result in chronic inflammation of the GI tract. We are seeking to elucidate regulatory mechanisms that control T cell effector function in the intestinal mucosa. Identification of these mechanisms will contribute to development of new therapeutic approaches to treat IBD.