T cell mechanisms that distinguish robust tolerance from metastable allograft acceptance and failed tolerance (Project 2)

项目总结 引导一种强大的容忍状态，这种状态在不利的干扰下仍能稳定地保持，对于 耐受机制在人的一生中维持对移植器官的接受的能力 收件人。临床中成功诱导的耐受状态可以是持久的，然而在患者的子集中， 长期存活的同种异体移植物可能会丢失。这种损失与移植前特定的供者有关。 抗体，在某些情况下，发生在感染发作之后。这些观察结果强调了有必要 从那些不那么健壮/亚稳定的个体中找出那些已经达到健壮耐受性的个体 耐受性，感染可能引发同种异体反应性和同种异体排斥反应，干预或更密切 监控可能是必要的。虽然许多因素可能有助于完全稳健的容忍状态，但在 在目前的资助期，我们的研究重点是促进供者反应性T细胞的机制 抗CD154抗体联合供者脾细胞诱导完全不相合同种异体心脏移植耐受 在老鼠身上。我们确定多种冗余的诱导T细胞耐受机制维持了移植 该模型中的耐受性，即受限制的供者反应性T细胞数量和T细胞受体亲和力 水平接近幼稚小鼠；诱导细胞固有低反应性和表达 持续存在的供体特异性T常规细胞产生的负共抑制分子； 供者特异性CD4+T细胞中FoxP3+细胞的百分比。我们还展示了亲- 感染过程中产生的炎性细胞因子覆盖了一些T细胞耐受机制，导致 在同种异体移植排斥反应中，但当感染被清除后，这种耐受性自发地恢复。最后，我们 结果表明，感染后恢复的耐受性在质量上受到侵蚀，更容易逆转。那 已建立的容忍机制仍然对环境线索作出反应，突出了容忍的必要性 在成长过程中既要坚韧，又要有弹性，这样才能成功地在一生中保持移植物的接受性。 收件人的身份。 受体致敏和随之而来的免疫记忆目前被认为是最重要的 在临床上达到耐受性的障碍。临床研究已经确认了先前的移植排斥反应和 怀孕是重要的致敏事件。这项建议建立在我们目前的发现基础上，并侧重于 移植排斥反应(目标1)或怀孕(目标2)后的预先致敏可防止特异性T细胞的建立 细胞耐受机制。从这些研究中获得的见解将为T细胞如何 耐受机制协同调节强大的移植耐受，指导生物标记物的识别 对于强大的耐受性，并最终导致合理设计的疗法，以实现强大的 致敏受体的耐受性或在感染侵蚀后恢复强大耐受性。

PROJECT SUMMARY Inducing a robust state of tolerance that is stably maintained despite adverse perturbations is essential for the ability of tolerance mechanisms to maintain the acceptance of the transplanted organ for the life of a recipient. Successfully induced tolerant states in the clinic can be persistent, however in a subset of patients, long-term surviving allografts can be lost. This loss has been correlated with pre-transplant donor-specific antibodies, and in some cases, occurred after episodes of infection. These observations underscore the need to identify individuals who have achieved robust tolerance from those who achieved a less robust/metastable tolerance, where infections may trigger alloreactivity and allograft rejection, and where interventions or closer monitoring may be necessary. While many factors are likely to contribute to a fully robust state of tolerance, in the current funding period, we focused our investigations on the mechanisms that enforce donor-reactive T cell tolerance induced to fully mismatched heart allografts with anti-CD154 in combination with donor spleen cells in mice. We determined that multiple redundant induced T cell tolerance mechanisms maintained transplant tolerance in this model, namely constrained donor-reactive T cell numbers and T cell receptor avidities to levels approximating those in naïve mice; induced cell-intrinsic hypo-responsiveness and expression of negative co-inhibitory molecules by the persisting donor-specific T conventional cells; and increased percentages of FoxP3+ cells within the donor-specific CD4+ T cells. We also demonstrated that pro- inflammatory cytokines produced during infection overrode some of the T cell tolerance mechanisms, resulting in allograft rejection, but that tolerance returned spontaneously when the infection was cleared. Finally, we showed that the restored tolerance after infection was eroded in quality and more susceptible to reversal. That established tolerance mechanisms remain responsive to environmental cues highlights the need for tolerance to be robust at initiation as well as resilient, in order for it to successfully maintain graft acceptance for the life of the recipient. Recipient sensitization and the ensuing immunological memory is currently considered the most important barrier to achieving tolerance in the clinic. Clinical studies have identified previous transplant rejection and pregnancy as important sensitizing events. This proposal builds on our current findings and focuses on how prior sensitization after graft rejection (Aim 1) or pregnancy (Aim 2) prevents the establishment of specific T cell tolerance mechanisms. The insights gained from these studies will provide granularity into how T cell tolerance mechanisms cooperate to mediate robust transplant tolerance, guide the identification of biomarkers for robust tolerance, and ultimately, lead to rationally designed therapies that are tailored to achieving robust tolerance in sensitized recipients or for restoring robust tolerance after erosion by infection.