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

摘要 抗体介导的淋巴细胞清除是移植中清除供者反应性T细胞的常用策略 受惠人士然而，记忆性T细胞对耗尽更有抵抗力，并且与急性炎症相关。 用多克隆兔抗胸腺细胞球蛋白（ATG）或抗- mAb.了解淋巴细胞减少移植中T细胞重建的机制和组成 因此，接受者对于合理使用淋巴清除疗法和改善其移植物延长至关重要 功效我们研究的最终目标是开发最小化稳态扩张的方法， 将平衡向胸腺生成转移，从而避免过度免疫抑制。在过去的融资中 循环中，我们在小鼠心脏同种异体移植物模型中使用鼠ATG类似物（mATG）来建立 整个T细胞区室的重建由抗耗竭记忆性CD 4 + T细胞通过B细胞驱动 和CD 40/CD 154通路。虽然B细胞和T细胞之间的同源TCR-pMHC相互作用是 因此，我们确定了移植后炎症和B细胞衍生的细胞因子IL-1β、IL-6和IL-27是 促进稳态T细胞恢复的因素。我们的初步数据表明，信号通过模式 需要识别受体TLR 4、TLR 9和巨噬细胞诱导的C型凝集素（Mincle或Clec 4 e）， 启动B细胞产生促炎细胞因子。我们进一步确定了先天样边缘区（MZ）B 淋巴细胞减少的受者作为移植后炎症的初始传感器。遗传缺陷或 MZ B细胞的特异性消耗显著延迟mATG处理的心脏同种异体移植物受体中的T细胞重建。 我们假设，在淋巴消融时，移植诱导的炎症促进了快速T细胞增殖， 重组由移植物释放的DAMP激活B细胞以分泌促炎细胞因子， 放大B细胞活化并直接增强T细胞增殖。特别是，MZ B细胞通过C-型 凝集素受体Mincle和TLR作为移植后炎症的初始感受器，促进促炎性反应 滤泡B细胞的功能。因此，记忆T细胞的稳态恢复和随后的同种异体移植 通过使DAMP信号传导最小化或通过靶向MZ B细胞活化和功能可以降低排斥。 我们将在两个具体目标中检验这一假设：目标1。检测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。目标2.探讨C型凝集素受体 Mincle促进mATG淋巴消融后的B细胞促炎功能。 拟议的研究将从机制上剖析同种异体移植物如何触发炎症通路 缺血/再灌注损伤驱动抗耗竭记忆T细胞快速重建。基于这些 我们将测试几种临床相关方法抑制致病性细胞恢复的有效性， 供体反应性记忆T细胞和延长ATG治疗的受者的心脏移植物存活。

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.