Expansion of alloantigen reactive Tregs for transplantation tolerance

描述（由申请人提供）：T淋巴细胞的一小部分表达FoxP3，被称为调节性T细胞或Tregs。许多人类疾病或疾病相关并发症的治疗往往需要各种器官的移植。然而，移植组织需要经受宿主T淋巴细胞的排斥反应。宿主来源的供体特异性treg提供了一种天然的方法来抑制移植器官的排斥反应，没有副作用或与免疫抑制药物相关的脱靶。treg的发现频率非常低，动物模型表明，要达到临床疗效，需要大量treg；因此，阐明Tregs扩增的机制将有助于将这一特定T淋巴细胞亚群用于诱导移植耐受的治疗应用。我们发现持续和聚集的CD3和CD28信号传导诱导效应T细胞凋亡，并允许Tregs在不到2周的时间内扩增。在此条件下培养12天的未分选的人CD4 T细胞（最初为6%的FoxP3+细胞）在Tregs中高度富集（培养结束时为75%的FoxP3+细胞）。因此，该方法对Tregs的临床应用具有很大的前景和潜力。本研究将详细探讨小鼠和人供体反应性Treg扩增诱导移植耐受的机制，并阐明该系统中Treg选择性扩增的机制。Aim 1将验证Treg特异性转录因子FoxP3在该系统中积极抑制细胞凋亡的假设，从而允许Treg选择性增殖和扩增。目的2将采用mhc肽四聚体诱导TCR连接，以验证通过固定化mhc肽四聚体和抗cd28选择性扩增小鼠和人类异体抗原特异性功能treg的持续和聚集信号的假设。这些研究结果将极大地促进Tregs在提高移植耐受性方面的临床应用。

DESCRIPTION (provided by applicant): A small subset of T lymphocytes expresses FoxP3 and is called as regulatory T cells or Tregs. Transplantation of various organs is often required to treat many human diseases or disease-related complications. However, transplanted tissues need to survive rejection by host T lymphocytes. Host-derived donor-specific Tregs offer a natural way of suppressing rejection of transplanted organs without side effects or off targets associated with immunosuppressive drugs. Tregs are found at very low frequency and animal models have shown that large numbers of Tregs are required to achieve clinical efficacy; therefore elucidation of the mechanisms underlying the expansion of Tregs will facilitate the therapeutic application of this specific subset of T lymphocytes for induction of transplantation tolerance. We have found that sustained and clustered CD3 and CD28 signaling induces apoptosis of effector T cells and allows expansion of Tregs in less than 2 weeks. Unsorted human CD4 T cells (initially 6% FoxP3+ cells) cultured for 12 days under this condition were highly enriched for Tregs (>75% cells Foxp3+ cells at end of culture). Therefore, this procedure has great promise and potential for clinical application of Tregs. The proposed study will investigate in detail the expansion of donor reactive Tregs from mice and humans for induction of transplantation tolerance and elucidate the mechanism of selective Treg expansion in this system. Aim 1 will test the hypothesis that Treg specific transcription factor FoxP3 actively suppresses apoptosis in this system, allowing selective proliferation and expansion of Tregs. Aim 2 will employ MHC-peptide tetramers for induction of TCR ligation to test the hypothesis that sustained and clustered signaling by immobilized MHC-peptide tetramers and anti-CD28 selectively expand alloantigen specific functional Tregs from mice and humans. The outcome of these studies will greatly facilitate clinical application of Tregs to improve transplantation tolerance. PUBLIC HEALTH RELEVANCE: Regulatory T cells offer a natural way of inducing longevity of transplanted organs to recipients without side effects. Using a novel system, proposed study aims to expand alloreactive Tregs to facilitate the long term acceptance of transplanted tissue to mismatch recipients.