The role of TIGIT in Treg-mediated suppression of C8+ T cells in Transplantation

总结/摘要 移植是终末期器官衰竭的治疗策略。为了避免免疫介导的排斥反应 移植组织的受体接受终身免疫抑制。钙调磷酸酶和mTOR抑制剂， 免疫抑制在预防移植物排斥方面是成功， 目标毒性。为了更好地保护移植物和移植受体的健康， 一直在寻求免疫抑制疗法。Belatacept是一种CTLA-4 Ig融合蛋白， 免疫系统通过结合抗原呈递细胞（APC）上的CD 80和CD 86来阻断CD 28 （共刺激）和CTLA-4（共抑制）信号传导。通过阻止特定于 在免疫细胞中，使用CTLA-4 Ig减轻了与钙调磷酸酶抑制剂相关的脱靶毒性， 增加了移植物的寿命和患者的健康。然而，CTLA-4 Ig与增加的 与钙调磷酸酶抑制剂相比，急性排斥反应发作的风险，这已经阻止了其广泛的临床应用。 尽管长期结果有所改善，但仍然没有通过。调节性T细胞对维持免疫至关重要 体内平衡和促进移植耐受，但通过CD 28和CTLA-4的信号传导的阻断， 不利于其生存和功能。因此，CTLA-4 Ig治疗抑制了Tcl 3对CD 8 + T细胞的控制， 当它们执行急性排斥反应时。识别可以靶向的共刺激和共抑制途径 在CTLA-4 Ig治疗的情况下，增强TGFAP的抑制能力对于改善 靶向免疫抑制疗法。TIGIT是具有IG和ITIM结构域的T细胞抑制性受体 表达在T细胞上，可以用抗体靶向以微调Treg功能。激动性抗TIGIT 已经显示抗体诱导Treg-1中共刺激阻断抗性记忆T细胞的凋亡。 依赖的方式。该提案中概述的实验研究了TIGIT信号转导的机制。 在面对CTLA-4 Ig治疗以减少对同种异体移植物的CD 8 + T细胞应答时，TCR 4增强Treg功能 挑战.在目标1中，我们将确定细胞自主TIGIT信号传导是否增加TIGIT的丰度。 在移植的组织内，并增加抑制性分子的分泌以增强Treg功能。在目标2中 我们将确定Treg特异性TIGIT信号传导对效应CD 8 + T细胞对同种异体移植物应答的影响。 这些研究将使用新型Treg特异性TIGIT敲除动物（Foxp 3-Cre X TIGITfl/fl）进行。 总之，这些数据将阐明TIGIT激动剂与TIGIT激动剂组合的治疗潜力。 共刺激阻断疗法以减轻急性同种异体移植物排斥。

Summary/Abstract Transplantation is a curative strategy for end stage organ failure. In order to avoid immune-mediated rejection of the grafted tissue, recipients receive life-long immunosuppression. Calcineurin and mTOR inhibitors for immunosuppression are successful in preventing graft rejection but are associated with significant adverse off- target toxicities. In order to better preserve the health of both the graft and the transplant recipient, alternative immunosuppressive therapies have been sought. Belatacept, a CTLA-4Ig fusion protein, suppresses the immune system by binding to CD80 and CD86 on antigen presenting cells (APCs) to block CD28 (costimulatory) and CTLA-4 (coinhibitory) signaling on T cells. By blocking interactions that are specific for immune cells, the use of CTLA-4Ig mitigates off-target toxicities associated with calcineurin inhibitors and increases the longevity of the graft and health of the patient. However, CTLA-4Ig is associated with increased risk of acute rejection episodes compared to calcineurin inhibitors, which has prohibited its widespread clinical adoption despite the improved long-term outcomes. Regulatory T cells are essential to maintaining immune homeostasis and promoting tolerance in transplant, but the blockade of signaling through CD28 and CTLA-4 is detrimental to their survival and function. Therefore, CTLA-4Ig therapy inhibits Tregs from controlling CD8+ T cells as they execute acute rejection. Identifying costimulatory and coinhibitory pathways that can be targeted to enhance the suppressive capacity of Tregs in the setting of CTLA-4Ig therapy is essential to improving targeted immunosuppressive therapies. TIGIT is a T-cell inhibitory receptor with Ig and ITIM domains expressed on Tregs that can be targeted with antibodies to fine-tune Treg function. Agonistic anti-TIGIT antibodies have been shown to induce apoptosis of costimulation blockade-resistant memory T cells in a Treg- dependent manner. The experiments outlined in this proposal study the mechanisms by which TIGIT signaling on Tregs enhances Treg function in the face of CTLA-4Ig therapy to reduce CD8 + T cell responses to allograft challenge. In Aim 1 we will determine if cell-autonomous TIGIT signaling increases the abundance of Tregs within grafted tissue and increases the secretion of suppressive molecules to enhance Treg function. In Aim 2 we will determine the impact of Treg-specific TIGIT signaling on effector CD8+ T cell responses to allograft. These studies will be performed using novel Treg-specific TIGIT knockout animals (Foxp3-Cre x TIGITfl/fl). Together, these data will illuminate the therapeutic potential of TIGIT agonism in combination with costimulation blockade therapeutics to mitigate acute allograft rejection.