Galectin-1 regulation of T cell activation and tolerance

描述（由申请人提供）：该提案代表了一系列旨在评估内源性半乳糖凝集素-1在调节T细胞发育、激活和耐受性诱导中的潜在作用的研究。本实验的基本原理源于我们的研究，将半乳糖凝集素-1定义为一种新型的T细胞调节剂，能够调节TCR信号以选择性地调节功能结果。通过涉及T细胞突触内T细胞糖蛋白重组的独特分子机制，我们提出半乳糖凝集素-1反对共刺激剂诱导的脂质筏募集到突触和持续的TCR信号转导。我们的初步研究结果预测内源性半乳糖凝集素-1可能在T细胞发育过程中设置TCR信号阈值，并防止T细胞过度活跃和自身免疫。半乳糖凝集素-1在整个胸腺中大量表达，并可与TCR结合诱导胸腺细胞凋亡。因此，我们建议分析半乳糖凝集素-1在TCR介导的胸腺细胞阳性和阴性选择中的作用（Aim 1）。半乳糖凝集素-1也由激活的T细胞亚群表达。在一些成熟的T细胞群中，半乳糖凝集素-1可以与TCR结合促进细胞凋亡，同时拮抗IL-2的产生。此外，半凝集素-1可以使Th1反应扭曲为Th2反应。因此，我们建议研究凝集素- 1在成熟T细胞活化、分化和凋亡中的作用（Aim 2）。最后，在静止的CD4+CD25+调节性T细胞（Treg）中，galectin- 1的表达相对较高，在活化的Treg细胞中，其表达水平甚至更高。像假定的Treg细胞效应物一样，半乳糖凝集素-1可以反式发挥作用，拮抗抗原反应性T细胞产生的IL-2。因此，我们建议研究半乳糖凝集素-1在Treg细胞活性、炎症性肠病和组织特异性自身免疫的诱导和调节中的作用（Aim 3）。虽然以前的研究主要评估了T细胞暴露于重组半乳糖凝集素-1的活性，但在这里我们评估了其内源性活性。为了解决这些问题，我们将分析野生型和TCR转基因T细胞的发育和反应，其中半乳糖凝集素-1基因已被切除。在替代方法中，我们将在新开发的半乳糖凝集素-1抑制剂L2hmda或重组半乳糖凝集素-1存在的情况下，通过分化或激活T细胞来表征半乳糖凝集素-1的活性。这些研究将有助于我们对T细胞调控、功能命运决定和自身免疫性疾病预防的基本理解。此外，他们可能会发现新的治疗靶点，旨在诱导自身耐受性，以阻断自身免疫和移植物排斥或逆转对肿瘤抗原的耐受性。

DESCRIPTION (provided by applicant): This proposal represents a series of studies designed to assess a potential role for endogenous galectin-1 in regulating T cell development, activation, and tolerance induction. The rationale for the proposed experiments stems from our studies defining galectin-1 as novel T cell regulator, capable of tuning TCR signals to selectively modulate functional outcome. Through a unique molecular mechanism involving reorganization of T cell glycoproteins within the T cell synapse, we propose that galectin-1 opposes costimulator-induced lipid raft recruitment to the synapse and processive and sustained TCR signal transduction. Our preliminary findings predict that endogenous galectin-1 might function in setting TCR signaling thresholds during T cell development and in preventing T cell hyperactivity and autoimmunity. Galectin-1 is expressed abundantly throughout the thymus and can cooperate with TCR engagement to induce thymocyte apoptosis. Therefore, we propose to analyze the role of galectin-1 in TCR mediated thymocyte positive and negative selection (Aim 1). Galectin-1 is also expressed by a subset of activated T cells. In some mature T cell populations, galectin-1 can cooperate with TCR engagement to enhance apoptosis, while antagonizing IL-2 production. Furthermore, galectin-1 can skew a Th1 response to a Th2 response. Therefore, we propose to examine the role of galectin- 1 in mature T cell activation, differentiation and apoptosis (Aim 2). Finally, galectin- 1 expression is relatively high in resting CD4+CD25+ regulatory T cells (Treg) and its expression is increased to even higher levels in activated Treg cells. Like the putative Treg cell effector, galectin-1 can function in trans to antagonize IL-2 production by antigen responsive T cells. Therefore, we propose to examine the role of galectin-1 in Treg cell activity and the induction and the regulation of inflammatory bowel disease and tissue specific autoimmunity (Aim 3). While previous studies have primarily assessed the activity of T cell exposure to recombinant galectin-1, here we assess its endogenous activity. To address these issues we will analyze T cell development and responses of wild type and TCR transgenic T cells in which the galectin-1 gene has been ablated. In alternate approaches, we will characterize galectin-1 activity by differentiating or activating T cells in the presence of the newly developed galectin-1 inhibitor, L2hmda, or recombinant galectin-1. These studies will contribute to our basic understanding of T cell regulation, functional fate determination, and autoimmune disease prevention. Furthermore, they may identify novel targets for therapeutics aimed at inducing self tolerance for blocking autoimmunity and graft rejection or reversing tolerance to tumor antigens.