Behavior of regulatory CD25+ CD4 T cells in vivo

描述（申请人提供）：调节性CD25+CD4 T细胞是免疫耐受的重要介质，可能成为治疗靶点。然而，它们在体内的机制仍然很大程度上是未知的，这是本提案的主要焦点。本文所述的初步工作总结表明：1)我们能够从野生型TCR Tg小鼠和表达单一已知TCR的抗原特异性调节性CD25+CD4 T细胞中纯化出足够数量的抗原特异性调节性CD25+CD4 T细胞；2)我们建立了两个互补的体内系统来测量CD25+CD4 T细胞对非淋巴减少动物应答T细胞的抑制作用；3)我们能够同时可视化抗原特异性CD25+CD4 T细胞、抗原特异性应答T细胞和抗原呈递树突状细胞的行为和细胞相互作用；4) CD25+CD4 T细胞减少应答抗原的T细胞群的大小，抑制效应th1和Th2细胞因子的产生；5) CD25+CD4 T细胞抑制淋巴细胞减少小鼠初始T细胞的稳态增殖。该实验室现在特别准备实现提案中的两个具体目标。在第一个目标中，我们将定义CD25+CD4 T细胞抑制次级淋巴组织中抗原特异性T细胞反应的细胞机制。我们将确定呈递抗原的树突状细胞以及抗原特异性CD25+CD4 T细胞和应答T细胞的命运。在第二个目标中，我们将确定CD25+CD4 T细胞如何通过稳态增殖在免疫重建过程中塑造T细胞室的发育。特别是，我们将测试CD25+CD4 T细胞如何在淋巴细胞减少的条件下调节潜在的自身侵袭性T细胞克隆。尽管细胞机制构成了本提案的主要焦点，但所描述的实验系统是稳健的，并且非常适合于测试特定分子在CD25+CD4 T细胞介导的免疫调节中的作用。

DESCRIPTION (provided by applicant): Regulatory CD25+CD4 T cells are important mediators of immunologic tolerance and are likely to become a therapeutic target. However, their mechanisms in vivo remain largely unknown, and are the main focus of this proposal. The summary of the preliminary work described here shows that 1) we are able to purify in numbers sufficient for the proposed experiments antigen-specific regulatory CD25+CD4 T cells from wild-type TCR Tg mice and antigen-specific regulatory CD25+CD4 T cells expressing a single known TCR; 2) we have established two complementary in vivo systems to measure suppressive effects of CD25+CD4 T cells on responder T cells in non-lymphopenic animals; 3) we are able to simultaneously visualize the behavior and cellular interactions of antigen-specific CD25+CD4 T cells, antigen-specific responder T cells, and antigen-presenting dendritic cells; 4) CD25+CD4 T cells reduce the size of the T cell population responding to antigen and inhibit production of effector Th1and Th2 cytokines; and 5) CD25+CD4 T cells inhibit homeostatic proliferation of naive T cells in lymphopenic mice. The laboratory is now exceptionally poised to pursue the two specific aims in the proposal. In the first aim we will define the cellular mechanisms of by which CD25+CD4 T cells inhibit the antigen-specific T cell responses within the secondary lymphoid tissues. We will determine the fates of the dendritic cells presenting the antigen as well the antigen-specific CD25+CD4 T cells and responder T cells. In the second aim we will determine how CD25+CD4 T cells shape the development of the T cell compartment during immune reconstitution by homeostatic proliferation. In particular, we will test how CD25+CD4 T cells may regulate potentially auto-aggressive T cell clones under conditions of lymphopenia. Although cellular mechanisms constitute the main focus of this proposal, the experimental systems described are robust and are ideally suited for testing roles of specific molecules in CD25+CD4 T cell-mediated immune regulation.