Inflammation and T Cell Memory: Inter-related Barriers to Allograft Tolerance

描述（由申请人提供）：尽管在过去的二十年中早期移植后存活率有所提高，但在先前成功的同种异体肾移植受者中，每年3- 5%的持续损失率继续限制长期预后。胰岛移植的长期结果是完全不可接受的，只有10%的受者在5年内保持无胰岛素。在胰岛中，由于胰岛细胞质量不足引起的代谢衰竭可能是长期移植物功能的重要障碍。由慢性排斥反应、感染、药物毒性和恶性肿瘤引起的晚期同种异体移植失败，强调了在肾和胰岛移植中长期给予免疫抑制的局限性。因此，移植的最终目标是实现长期植入，而不需要维持免疫抑制。临床试验耐受性方案目前正在人体中进行测试，但在人体中实现真正的耐受性仍然存在实质性障碍。这项多项目资助的主要目标是通过确定诱导肾脏和胰岛异体移植物持久耐受的必要条件，以及确定炎症和记忆T细胞在耐受的主要障碍中的作用，来改善肾脏和胰岛移植后的结果。我们的中心假设是，早期的促炎反应在很大程度上是由于供体组织的缺血再灌注和缺氧损伤引起的，从而激发了不良形式的抗供体免疫，从而引发急性临床或亚临床排斥反应，并夸大了随后存在的供体反应记忆的扩张，以及移植后新获得的供体反应记忆T细胞的发展。因此，我们假设促抗炎细胞因子和抗供体记忆反应的不利平衡是诱导和维持耐受性的主要障碍。我们提出了新的和相互关联的策略来改变同种免疫反应的平衡，以促进调节和长期耐受性，同时考虑到胰岛和肾脏移植中炎症和记忆相关的耐受性障碍。将这两个相互关联的体内项目的具体目标与机制研究联系起来的基本原理是，我们现在有了测试炎症反应与攻击性和记忆反应平衡、T细胞调节和耐受性诱导的相关性和相互关系的工具。因此，应该有可能定义和系统地应用导致灵长类同种异体移植受体耐受的先天和适应性免疫反应的扰动。此外，该计划将导致项目1和项目2开发的最佳耐受性诱导方案的交叉受精和共享方面。

DESCRIPTION (provided by applicant): Despite improvements in early post-transplant survival rates over the last two decades, a relentless annual attrition rate of 3-5 % in recipients of previously successful renal allografts continues to limit longer term outcomes. Long term outcomes with islet transplantation are simply unacceptable with only 10% of recipients remaining insulin free at five years. In islets metabolic exhaustion due to an inadequate islet cell mass may be an important impediment to long term graft function. Late allograft failure, resulting from chronic rejection, infection, drug toxicity, and malignancies emphasizes the limitations of chronically administered immunosuppression in kidney and islet transplantations. Therefore the ultimate goal of transplantation is to achieve long-term engraftment without maintenance immunosuppression. Pilot clinical tolerance protocols are currently being tested in humans, but there remain substantial barriers to achieving true tolerance in humans. The major objective of this Multi-Project grant is to improve the outcome following kidney and islet transplantation by defining the essential conditions for induction of durable tolerance to kidney and islet allografts, and defining the roles of inflammation and memory T cells in being major barriers to tolerance. Our central hypothesis is that the early pro-inflammatory responses due in large measure to ischemia-reperfusion and anoxic injury to the donor tissues incites adverse forms of anti-donor immunity, thereby provoking acute clinical or subclinical rejection and exaggerating the subsequent expansion of pre-existing donor reactive memory, and post transplant development of newly acquired donor reactive memory T cells. Thus, we hypothesize that an adverse balance of pro- to anti-inflammatory cytokines and anti-donor memory responses represent major obstacles to the induction and maintenance of tolerance. We propose novel and inter-related strategies to alter the balance of the alloimmune response to favor regulation and long-term tolerance taking into consideration the inflammatory- and memory-related barriers to tolerance in the context of islet and kidney transplantation. The rationale linking the specific aims of the two interrelated in vivo projects and the mechanistic studies is that we now have the tools to test the relevance and inter-relationship of inflammatory responses to the balance of aggressive and memory responses, T cell regulatory and tolerance induction. It, therefore, should be possible to define and systematically apply the perturbations of the innate and adaptive immune response that lead to tolerance in primate allograft recipients. Moreover, the Program will lead to cross-fertilization and sharing of facets of the best tolerance inducing regimens developing from Project 1 with those of Project 2. PROJECT 1: Novel Tolerance Strategy in Renal Allograft Recipients (Cosimi, A. Benedict) PROJECT 1 DESCRIPTION (provided by applicant): Despite improvement in short-term results through the use of new immunosuppressive agents, long-term allograft survival has not improved significantly over the past decade, due predominantly to chronic rejection but also to infection and post-transplant malignancies, all attributable to chronic immunosuppression. Therefore, induction of specific transplantation tolerance, which might eliminate most limitations of conventional immunosuppressive therapy remains a major goal. Based upon the mixed chimerism approach, which was first demonstrated to be an effective means of inducing allograft tolerance in mice, we first developed a clinically relevant non-myeloablative preparative regimen that permitted the induction of mixed chimerism and renal allograft tolerance following donor bone marrow transplantation (DBMT) in MHC fully mismatched cynomolgus monkeys. More recently, this was applied clinically to recipients of HLA-identical and haplo-type identical kidneys. A disadvantage of the current preparative regimen is the requirement for conditioning beginning 6 days prior to organ transplantation, making it applicable only for recipients of living donor allografts and only prospectively with respect to the organ transplant. The major goal of this project is to develop a novel regimen, the "Delayed Tolerance" protocol to extend the clinical applicability of the mixed chimerism approach. In this protocol, recipients would initially undergo kidney transplantation (KTx) with conventional immunosuppression and then receive non-myeloablative conditioning and DBMT sometime later. This protocol could potentially extend the applicability to all recipients of previously transplanted allografts, including recipients of organs from deceased donors, if DBM is cryopreserved at the time of initial organ procurement from the deceased donor. This approach could prove to be even more effective than our current approach, since the tolerance conditioning regimen is instituted in the absence of pro-inflammatory cytokines that may impair tolerance induction in the peritransplant period. On the other hand, if tolerance induction is delayed, it might be predicted that the presence of the renal allograft could result in sensitization to donor antigen with memory T cell activation increasing. Therefore, to establish the "Delayed Tolerance" protocol, we will specifically: 1) identify the optimal timing for tolerance induction with minimal inflammatory responses, yet least likelihood of memory T cell activation, 2) evaluate methods to overcome memory T cell responses and 3) evaluate the addition of anti-inflammatory agents to the mixed chimerism protocol. Detailed mechanistic studies will be performed and the analyses planned should provide clinically relevant information for rationally developing new tolerance strategies for not only kidney but also all allograft recipients.