Regulation Of Suppressor T Cells by PTEN

描述（由申请人提供）： 越来越清楚的是，对器官和组织同种异体移植物的耐受性的维持需要调节性/抑制性T细胞（T细胞）的参与。虽然小鼠和人类中存在几种类型的TcB，但最具特征的集合是CD 4 + CD 25 + TcB，其对于免疫系统的稳态是必需的。CD 4 + CD 25 + T细胞最显著的特征之一是，与效应CD 4 + T细胞不同，CD 4 + CD 25 + T细胞不能响应于单独的IL-2刺激而增殖，尽管它们表达IL-2 R的所有3条链。最近，我们已经开始研究这种功能的T细胞，推理，这种独特的调节控制下游IL-2 R信号将是重要的了解个体发育和生长/扩展的要求T细胞作为一个前奏，他们的发展作为移植治疗工具。我们的数据表明，CD 4 + CD 25 + T细胞通过以下方式对IL-2产生应答：（1）经历胚细胞转化而无细胞分裂;（2）获得对凋亡的抗性并诱导Bcl-xL蛋白。在CD 4 + CD 25 + T细胞中IL-2 R信号转导的详细生物化学研究表明STAT-5的完整和正常磷酸化，但PI-3 K靶Akt或p70 S6激酶的磷酸化缺失。令人惊讶的是，我们发现PI-3 K本身被IL-2激活，这表明PI-3 K靶点在TcB中的下游调节。另外的数据表明，TcR组成型表达高水平的脂质磷酸酶PTEN，这是PI-3 K信号转导的调节，并且TcR的TCR刺激（已知其诱导IL-2应答性）完全阻断了相关的PTEN表达，并且新地使IL-2介导的PI-3 K下游信号传导成为可能。这些数据表明，T细胞中的IL-2 R信号传导与“正常”T效应细胞的IL-2 R信号传导明显不同，并且强烈暗示PTEN是该过程的组成部分。基于这些数据，我们有三个目标：在目标#1中，我们将确定TCR活化后PTEN下调的动力学。药理学抑制剂以及TCR信号传导缺陷的小鼠和细胞系将用于确定调节该过程的信号传导机制。在目标#2中，我们将使用T细胞中PTEN部分和完全缺陷以及诱导缺陷的小鼠，以确定PTEN在调节细胞发育和体外功能中的作用，特别是对IL-2需求和反应性的作用。最后，在目标#3中，我们将采用移植模型来研究PTEN在Treg生物学中的体内作用。总的来说，我们相信这些研究将在CD 4 + CD 25 + T细胞生物学中定义一个重要的范例，为它们作为治疗剂的发展提供重要的信息，并在PI-3 K偶联信号传导领域具有更广泛的意义，PI-3 K偶联信号传导是T细胞应答的关键控制器。

DESCRIPTION (provided by applicant): It is increasingly clear that the maintenance of tolerance to organ and tissue allografts requires the participation of regulatory/suppressor T cells (Tregs). While several types of Tregs exist in mice and man, the best characterized set are CD4+CD25+ Tregs, which are essential for homeostasis of the immune system. One of the most striking features of CD4+CD25+ Tregs is that unlike effector CD4+ T cells, CD4+CD25+ T regs fail to proliferate in response to IL-2 stimulation alone, although they express all 3 chains of the IL-2R. Recently, we have begun to study this feature of Tregs, reasoning that this unique regulatory control of downstream IL-2R signals would be important for understanding ontogeny and growth/expansion requirements of T regs as a prelude to their development as therapeutic tools in transplantation. Our data show that CD4+CD25+ T regs are responsive to IL-2 by: (1) undergoing blast transformation without cell division; and (2) acquiring resistance to apoptosis with induction of Bcl-xL protein. Detailed biochemical studies of IL-2R signal transduction in CD4+CD25+ T regs demonstrate intact and normal phosphorylation of STAT-5 but absence of phosphorylation of the PI-3K targets Akt or p70S6 kinase. Surprisingly, we find that PI-3K itself is activated by IL-2, suggesting downstream regulation of PI-3K targets in Tregs. Additional data demonstrate that Tregs constitutively express high levels of the lipid phosphatase PTEN, a regulation of PI-3K signal transduction, and that TCR stimulation of Tregs, which is known to induce IL-2 responsiveness, completely blocks PTEN expression in association and newly enables IL-2 mediated PI-3K downstream signaling. These data show that IL-2R signaling in T regs is distinctly different from that of "normal" T effector cells, and strongly implicates PTEN as an integral part of that process. Based on these data we have three aims: In aim #1, we will determine the kinetics of PTEN downregulation following TCR activation. Pharmacologic inhibitors as well as mice and cell lines with defects in TCR signaling will next be used to determine the signaling mechanisms which regulate this process. In aim #2 we will use mice with partial and complete deficiencies of PTEN in T cells, as well as with inducible deficiencies, to determine the role of PTEN in regulatory cell development and in vitro function, in particular on IL-2 requirements and responsiveness. Finally, in aim #3, we will employ transplantation models to study the in vivo role of PTEN in Treg biology. Collectively, we believe these studies will define an important paradigm in the biology of CD4+CD25+ T regs, provide information important for their development as therapeutics, and have broader implications in the field of PI-3K coupled signaling, which is a key controller of T cell responses.