Treg suppression of islet allograft rejection

描述（由申请人提供）：调节性T （Treg）细胞抑制同种异体移植排斥反应，对外周耐受至关重要。尽管在动物模型中对Treg细胞和同种异体移植物存活进行了广泛的研究，但在正常野生型（WT）动物中，单独过继移植Treg细胞在诱导同种异体移植物长期存活或耐受方面仍然无效，因为只有一小部分全身给药的Treg细胞可以到达同种异体移植物。此外，移植的Treg细胞有限的寿命也可能抑制了它们的抑制作用。这些问题可能严重阻碍了Treg细胞治疗抑制同种异体移植排斥反应或自身免疫性疾病的临床试验进展。本研究的重点是利用新方法优化Treg对胰岛异体移植排斥反应的抑制，并了解其作用机制。我们已经开发了一种系统，在该系统中，供体胰岛被激活并与CD4+CD25+ Treg细胞孵育，导致移植前胰岛内Treg细胞的募集。我们发现“treg占据”的同种异体胰岛移植比“空的”胰岛存活时间长得多。此外，该系统内肝内胰岛移植比肾包膜下或经门静脉移植存活时间更长。我们首次选择肝实质作为移植部位，这是基于肝脏是一个具有免疫特权的部位，而通过门静脉输注的胰岛容易发生即时血液介导的炎症反应（IBMIR）。因此，在肝实质中移植Treg占据的胰岛是通过优化Treg抑制来延长同种异体胰岛存活的一种新颖而实用的方法。然后，我们提出研究是否以抗凋亡Treg细胞为主的胰岛异体移植物或过度表达IDO的Treg-为主的胰岛异体移植物在肝脏中长期存活，是否修改Treg细胞中的MAPK和STAT信号通路增强其抑制作用，以及Treg-为主的胰岛移植物是否也在轻度免疫抑制的糖尿病NOD小鼠中长期存活。我们还建议进一步研究肝实质中Treg抑制增强的机制。在这项研究中，将在化学诱导的糖尿病WT和NOD小鼠中实施一种独特的肝内胰岛移植模型。抗凋亡Treg细胞和过表达IDO的胰岛细胞也将被用来最大限度地抑制Treg。此外，MAPK和STAT信号通路将被修改以增强Treg功能。综上所述，本研究旨在将转移的Treg细胞定位到异体胰岛移植物中，促进Treg细胞的存活、扩增和/或功能，使其发挥最佳的抑制作用。这一建议揭示了一种诱导胰岛移植长期存活的新方法，并可能有助于设计一种促进1型糖尿病患者胰岛移植接受的临床方案。

DESCRIPTION (provided by applicant): Regulatory T (Treg) cells suppress allograft rejection and are critical for peripheral tolerance. Despite the extensive studies on Treg cells and allograft survival in animal models, adoptive transfer of Treg cells alone remains ineffective in inducing long-term allograft survival or tolerance in normal wild-type (WT) animals, because only a small fraction of systemically administered Treg cells can reach an allograft. Moreover, the limited life span of transferred Treg cells also likely restrains their suppression. These problems may have severely hampered the progress in clinical trial using Treg cell therapies for suppressing allograft rejection or autoimmune diseases. This proposal will focus on optimizing Treg suppression of islet allograft rejection using novel approaches, and understanding the mechanisms of their action. We have developed a system in which donor islets are activated and incubated with CD4+CD25+ Treg cells, resulting in intra-islet recruitment of Tregs before transplantation. We found that "Treg-preoccupied" islet allografts survived much longer than "empty" islets. In addition, intra-hepatic islet transplantation in the system resulted in even longer survival than that under kidney capsule or via the portal vein. We for the first time have selected the hepatic parenchyma as a grafting site based on the facts that the liver is an immune privileged site but that islets infused via the portal vein are subject to instant blood-mediated inflammatory reaction (IBMIR). Hence, transplanting Treg-preoccupied islets in the hepatic parenchyma is a novel and practical approach to prolonging islet allograft survival by optimizing Treg suppression. We then propose to investigate whether islet allografts that are preoccupied with apoptosis-resistant Treg cells or Treg- preoccupied islet allografts that over-express IDO survive long term in the liver, whether modifying MAPK and STAT signaling pathways in Treg cells enhances their suppression, and whether Treg-preoccupied islet allografts also survive long-term in diabetic NOD mice in the presence of mild immunosuppression. We also propose to further study the mechanisms underlying the enhanced Treg suppression in the hepatic parenchyma. In this study, a unique model of intra-hepatic islet transplantation in both chemical-induced diabetic WT and NOD mice will be implemented. Apoptosis-resistant Treg cells and islets over-expressing IDO will also be utilized to maximize Treg suppression. Moreover, MAPK and STAT signaling pathways will be modified to enhance Treg function. Taken together, this study is to localize transferred Treg cells to islet allografts and promote the survival, expansion, and/or function of Treg cells so that they can optimally exert suppression. This proposal reveals a novel approach to inducing long-term islet allograft survival and may help design a clinical protocol to promote islet allograft acceptance in patients with type 1 diabetes. PUBLIC HEALTH RELEVANCE: Despite extensive studies on Treg cells related to graft survival in many animal models, adoptive transfer of Treg cells alone remains ineffective in inducing long-term graft survival in normal wild-type animals, because only a small fraction of systemically administered Treg cells can reach a graft. These problems have severely hampered the progress in clinical trial using Treg cell therapies for suppressing transplant rejection. This proposal will utilize novel strategies to optimize Treg suppression of islet graft rejection by localizing Treg cells to islet grafts and promoting the survival, expansion and function of Treg cells, leading to a potential cure for patients with type 1 diabetes via islet transplantation.