Designing induction therapies to target memory T cells in high risk recipients

摘要 抗体介导的淋巴细胞耗尽是消除移植中供者反应性T细胞的常用策略 收件人。然而，记忆T细胞对耗竭更有抵抗力，并与急性 多克隆兔抗胸腺细胞球蛋白或抗胸腺细胞球蛋白治疗移植受者的排斥反应 CD52单抗。了解淋巴细胞减少性移植中重组T细胞的机制和组成 因此，受者对于合理使用淋巴清除性治疗和改善移植物延长是至关重要的。 功效。我们研究的最终目标是开发出最大限度地减少体内平衡扩张和 将平衡转向胸腺生成，从而避免过度免疫抑制。在之前的资助期间 周期中，我们在小鼠心脏移植模型中使用了小鼠ATG类似物(MATG)来建立内稳态 整个T细胞室的重建是由抗耗竭的记忆CD4+T细胞通过B细胞驱动的 CD40/CD154途径。而B细胞和T细胞之间的同源TCR-pMHC相互作用 可有可无，我们确定移植后炎症和B细胞衍生细胞因子IL-1β、IL-6和IL-27是关键 促进体内平衡T细胞恢复的因素。我们的初步数据表明，通过模式传递信号 识别受体TLR4、TLR9和巨噬细胞诱导的C型凝集素(Mincle或Clec4e)需要 启动B细胞产生促炎细胞因子。我们进一步鉴定了先天类边缘带(MZ)B 淋巴细胞减少受者作为移植后炎症初始感受器的细胞。遗传缺陷或 MZ B细胞的特异性耗竭显著延迟了mATG治疗的同种心脏移植受者的T细胞重建。 我们假设，淋巴切除时移植引起的炎症促进快速T细胞 重建。移植物释放的湿气激活B细胞，分泌促炎细胞因子，进一步 放大B细胞活化，直接促进T细胞增殖。特别是，通过C型激活的MZ B细胞 凝集素受体Mincle和TLRs作为移植后炎症促进促炎的初始感受器 滤泡B细胞的功能。因此，记忆T细胞的动态平衡恢复和随后的同种异体移植 通过最小化DAMPS信号或靶向MZ B细胞的激活和功能，可以减少排斥反应。 我们将在两个特定的目标中检验这一假设：目的1.测试MZ B细胞作为移植物主要感受器的作用 淋巴细胞减少受者的组织损伤。目的2.探讨C型凝集素受体的作用机制 Mincle促进mATG淋巴切除后B细胞的促炎功能。 拟议的研究将从机械上剖析同种异体移植引发的炎症途径。 缺血/再灌流损伤促使耐耗竭的记忆T细胞快速重建。基于这些 洞察，我们将测试几种临床相关方法的有效性，以抑制病原体的恢复 ATG治疗受者中供者反应性记忆T细胞和延长同种异体心脏移植存活时间。

ABSTRACT Antibody-mediated lymphocyte depletion is a common strategy to eliminate donor-reactive T cells in transplant recipients. However, memory T cells are more resistant to depletion and have been associated with acute rejection episodes in transplant recipients treated with polyclonal rabbit anti-thymocyte globulin (ATG) or anti- CD52 mAb. Understanding the mechanisms and composition of T cells reconstituted in lymphopenic transplant recipients is thus critical for the rational use of lymphoablative therapies and for improving their graft-prolonging efficacy. The ultimate goal of our studies is to develop approaches that minimize homeostatic expansion and shift the balance towards thymopoiesis, thus avoiding over-immunosuppression. During the previous funding cycle, we used a murine ATG analog (mATG) in a mouse heart allograft model to establish that homeostatic reconstitution of the entire T cell compartment is driven by depletion-resistant memory CD4+ T cells via B cells and CD40/CD154 pathway. While cognate TCR-pMHC interactions between B cells and T cells were dispensable, we identified posttransplant inflammation and B cell-derived cytokines IL-1β, IL-6 and IL-27 as key factors facilitating homeostatic T cell recovery. Our preliminary data indicate that signaling through pattern recognition receptors TLR4, TLR9 and a Macrophage-inducible C-type lectin (Mincle, or Clec4e) is required to initiate B cell production of proinflammatory cytokines. We further identified innate-like marginal zone (MZ) B cells acting as initial sensors of posttransplant inflammation in lymphopenic recipients. Genetic deficiency or specific depletion of MZ B cells markedly delays T cell reconstitution in mATG treated heart allograft recipients. We hypothesize that inflammation induced by transplantation at the time of lymphoablation promotes rapid T cell reconstitution. DAMPs released by the graft activate B cells to secrete proinflammatory cytokines that further amplify B cell activation and directly enhance T cell proliferation. In particular, MZ B cells activated via C-type lectin receptor Mincle and TLRs act as initial sensors of posttransplant inflammation facilitating proinflammatory functions of follicular B cells. Therefore, the homeostatic recovery of memory T cells and ensuing allograft rejection may be decreased by minimizing DAMPs signaling or by targeting MZ B cell activation and functions. We will test this hypothesis in two Specific Aims: Aim 1. To test the role of MZ B cells as primary sensors of graft tissue injury in lymphopenic recipients. Aim 2. To investigate the mechanisms by which C-type lectin receptor Mincle facilitates B cell proinflammatory functions after mATG lymphoablation. The proposed studies will mechanistically dissect how inflammatory pathways triggered by allograft ischemia/reperfusion injury drive rapid reconstitution of depletion-resistant memory T cells. Based on these insights, we will test the efficacy of several clinically relevant approaches for inhibiting recovery of pathogenic donor-reactive memory T cells and prolonging heart allograft survival in ATG treated recipients.