Memory and Regulatory T Cells Following T Cell Depletion in Transplantation

描述（由申请人提供）：几十年来，移植界一直在寻求实现对同种异体移植物的免疫耐受，这既是为了患者的健康益处，也是为了节省成本。我们正在与ITN合作，在人体中使用t细胞消耗进行耐受性试验。通过机制试验了解免疫抑制（IS）是否可以完全退出，将大大增强这项研究。我们的目标是使用临床前非人灵长类动物（NHP）肾脏移植模型，作为验证1)耐受性诱导方案和2)临床适用的免疫测定的手段，以帮助确定患者是否可以安全地退出is。在本应用中，我们假设同种异体特异性记忆反应在耗竭后可以被充分阻断，调节性T细胞活性增强，从而实现长期移植

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 This study would be augmented greatly by knowing whether immunosuppression (IS) can be withdrawn completely based on mechanistic assays.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induction regimens and 2) clinically applicable immune assays to assist in determining whether patients can be safely withdrawn from IS.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.