Memory and Regulatory T Cells Following T Cell Depletion in Transplantation

描述(由申请人提供)：几十年来，移植团体一直在寻求实现对同种异体移植的免疫耐受，这既是为了患者的健康利益，也是作为一种节省成本的措施。与ITN合作，我们正在进行一项人类T细胞耗竭的耐受性试验。通过了解免疫抑制(IS)是否可以基于机械检测完全撤销，这项研究将得到极大的加强。我们的目标是使用临床前的非人类灵长类(NHP)肾移植模型作为一种手段来验证1)耐受诱导方案和2)临床适用的免疫分析，以帮助确定患者是否可以安全地退出IS。在这个应用中，我们假设同种异体特异性记忆反应在耗尽后可以被充分阻断，调节性T细胞的活性增强，从而使长期移植 将实现NHP肾移植受者的耐受性。此外，我们假设耐受性的获得和丧失是可测量的，并可通过拟议的分析进行预测。我们将这些假设建立在以下观察基础上。首先，在NHP或人类中，单独的淋巴细胞耗尽通常不会导致耐受诱导，但会增加具有效应型(TEFF)或记忆型(TMEM)表型的T细胞的相对频率。其次，随着短期IS的加入，NHP中T细胞的耗尽已被证明可以延长同种异体移植物的存活时间，并造成供者特异性的无反应。第三，通过在啮齿动物模型中使用常见的IS药物，可以允许甚至增强体内调节性T细胞(Treg)的活性。最后，我们开发了一种在人类身上的体外测试，当在啮齿动物身上测试时，它准确地反映了对移植物的免疫状态。具体目的1是研究T细胞耗竭的NHP肾移植受者的TMEM细胞增殖，以及他克莫司(TAC)对控制TMEM数量的影响。我们将a)检测TAC加或不加西罗莫司(SRL)对接受同种异体肾移植的恒河猴抗CD3免疫毒素(IT)介导的T细胞耗竭后TMEM细胞恢复的影响；b)检测T细胞恢复过程中TMEM细胞的体外活性；c)监测影响T细胞耗竭和恢复的因素。对于特定的目标2，我们将移植第二组猴子，并用IT/类固醇/TAC/SRL治疗，以测试一套新的免疫耐受测试。我们将a)在受者NHP接受SRL单一疗法时确定同种异体移植的耐受性状态，b)将猴子分配到耐受组或非耐受组并随后撤销SRL，c)对供者皮肤移植物进行耐受性测试，以及d)监测Treg细胞的频率和活性。在特定的目标3中，我们将确定Treg细胞的活性是否与慢性移植物肾病(CAN)的进展呈负相关。我们将a)监测在CAN耐受性丧失/进展的情况下Treg活性的变化，b)确定是否恢复SRL治疗阻断或延迟由于CAN导致的肾功能的进一步丧失。

DESCRIPTION (provided by applicant): The transplant community has sought to achieve immune tolerance to allografts for decades, both for the health benefit of the patient and as a cost saving measure. In collaboration with ITN, we are conducting a tolerance trial using T-cell depletion in humans. This study would be augmented greatly by knowing whether immunosuppression (IS) can be withdrawn completely based on mechanistic assays. Our goal here is to use a preclinical non-human primate (NHP) renal transplant model as a means of validating 1) tolerance induction regimens and 2) clinically applicable immune assays to assist in determining whether patients can be safely withdrawn from IS. In this application, we hypothesize that the allo-specific memory response can be blocked sufficiently after depletion, and regulatory T cell activity enhanced, such that long term transplant tolerance in NHP renal transplant recipients will be achieved. Further, we hypothesize that the acquisition and loss of tolerance is measurable and predictable by the proposed assays. We base these hypotheses on the following observations. First, lymphocyte depletion alone in NHP or in humans does not generally result in tolerance induction but does increase the relative frequency of T cells with an effector (TEFF) or memory (TMEM) phenotype. Second, with the addition of short-term IS, T-cell depletion in NHPs has been shown to prolong allograft survival and to create donor-specific unresponsiveness. Third, regulatory T-cell (TREG) activity can be permitted, even enhanced, in vivo through the use of common IS drugs in rodent models. Lastly, we have developed an in vitro assay in humans, which when tested in rodents accurately reflects the immune status toward the graft. Specific Aim 1 is to characterize TMEM cell expansion in T-cell depleted NHP renal transplant recipients and the impact tacrolimus (TAC) on controlling the TMEM population. We will a) examine the effects of TAC with or without sirolimus (SRL) on TMEM cell recovery following anti-CD3 immunotoxin (IT)-mediated T-cell depletion in rhesus macaques receiving a life sustaining renal allograft, b) examine TMEM cell activity in vitro during T cell recovery, c) monitor factors that influence T cell depletion and recovery. For Specific Aim 2, we will transplant a second set of monkeys and treat with IT/steroid/TAC/SRL to test a novel set of immune tolerance assays. We will a) determine allograft tolerance status while recipient NHPs are on SRL monotherapy, b) assign monkeys to either tolerant or non-tolerant groups and subsequently withdraw SRL, c) test for tolerance with a donor skin graft, and d) monitor TREG cell frequency and activity. In Specific Aim 3 we will determine whether TREG cell activity inversely correlates with the progression of chronic allograft nephropathy (CAN). We will a) monitor changes in TREG activity with the loss of tolerance/progression of CAN, b) determine whether resumption of SRL treatment blocks or delays further loss of kidney function due to CAN.