Endogenous memory T cell mediated rejection of high-risk cardiac allografts

摘要 移植是治疗终末期器官疾病最有效的方法。临床上，有两个重要的危险因素 移植结果不佳的原因是移植前受者体内存在供者反应性T细胞，以及 移植前的移植物冷缺血保存(CIS)时间长度。在肾移植患者中， 移植后循环供者反应性记忆T细胞的存在与急性发作的风险增加相关 排斥反应发作，移植物功能延迟和降低，移植物长期存活率较差。在不敏感的情况下 在受体中，记忆T细胞的供体反应性是由于异种(交叉反应)免疫。然而， 同种异体移植物内激活供者反应性内源性记忆T细胞介导急性移植物损伤的机制 人们对此仍然知之甚少。长时间的脑缺血再灌注损伤(IRI)，其特点是 产生的活性氧和促炎细胞因子可直接渗入受体白细胞 进入移植物并导致移植物内这些细胞的激活。IRI还能诱导移植物释放损伤。 损伤和死亡细胞的相关分子模式(湿气)，加剧炎症并促成 导致风险更高的同种异体移植结果更差。我们之前的研究表明，这两个风险因素会导致移植不良 结果是相互关联的。心脏移植后持续的高炎症环境 供者反应性记忆T细胞在长时间顺应性诱导下的同种异体移植 调节共刺激阻断抵抗非致敏受者的急性排斥反应。多个临床移植 研究表明，在同种异体移植损伤期间，循环中有一种潮湿的、无细胞的DNA升高， 为急性排斥反应的早期检测提供了一种有前景的非侵入性生物标志物。此外，最近的工作 从我们的合作者那里发现了新的、药理上有针对性的信号伙伴，需要激活 天然免疫传感器的细胞内游离DNA，如TLR9，可以识别线粒体DNA(MtDNA)。这些 研究结果和我们目前的初步数据让我们假设，延长独联体和随后的 增加IRI促进线粒体DNA的释放，导致TLR9更大的激活和I型干扰素的下游 产生，触发由内源性供体反应性记忆T细胞维持的促炎循环 介导的急性移植物损伤。这一假设将在两个特定的目标上用我们的血管化小鼠进行测试 异位心脏移植模型：首先，我们将在体内测试TLR9信号的调节，以评估对 第二，我们将检测供者反应性记忆T细胞介导的急性移植物损伤的机制(S)。 I型干扰素有助于移植后早期炎症和供者反应性T细胞的激活 调停拒绝。我们预计，这些研究将为改善治疗策略确定新的目标。 抑制先天免疫介导的内源性供者早期激活的实体器官移植结果 反应性记忆T细胞造成急性移植物损伤。

ABSTRACT Transplantation is the most effective treatment for end-stage organ diseases. Clinically, two important risk factors for poor transplant outcomes are the pre-transplant presence of donor-reactive T cells in the recipient and the length of graft cold ischemic storage (CIS) time prior to transplant. In kidney transplant patients, the pre- transplant presence of circulating donor-reactive memory T cells is associated with an increased risk of acute rejection episodes, delayed and decreased graft function and worse long-term graft survival. In unsensitized recipients, donor-reactivity of memory T cells is due to heterologous (cross-reactive) immunity. However, the mechanisms activating donor-reactive endogenous memory T cells within allografts to mediate acute graft injury remain poorly understood. Prolonged CIS increases ischemia-reperfusion injury (IRI), which is characterized by production of reactive oxygen species and proinflammatory cytokines that direct infiltration of recipient leukocytes into the graft and cause activation of these cells within the graft. IRI also induces the graft to release damage associated molecular patterns (DAMPs) from injured and dying cells that exacerbate inflammation and contribute to worse outcomes in higher risk allografts. We previously showed that these two risk factors for poor transplant outcomes are linked. The sustained high-inflammatory environment seen following transplant of cardiac allografts subjected to prolonged CIS is necessary for sufficient activation of donor-reactive memory T cells to mediate costimulatory blockade resistant acute rejection in unsensitized recipients. Multiple clinical transplant studies have shown that one DAMP, cell-free DNA is elevated in the circulation during allograft injury, representing a promising non-invasive biomarker for early detection of acute rejection. Additionally, recent work from our collaborators has found new, pharmacologically targetable signaling partners required for activation of innate immune sensors of cell free DNA, such as TLR9 which can recognize mitochondrial DNA (mtDNA). These findings and our current preliminary data have led us to hypothesize that prolonged CIS and subsequent increased IRI enhance the release of mtDNA, leading to greater TLR9 activation and downstream type I IFN production, triggering a pro-inflammatory cycle that is sustained by endogenous donor-reactive memory T cell mediated acute graft injury. This hypothesis will be tested in two specific aims using our vascularized mouse heterotopic heart transplant model: first, we will test modulation of TLR9 signaling in vivo to assess impact on donor-reactive memory T cell mediated acute graft injury; and second, we will test the mechanism(s) by which type I interferon contributes to early post-transplant inflammation and activation of donor-reactive T cells to mediate rejection. We anticipate that these studies will identify new targets for therapeutic strategies to improve solid organ transplant outcomes by inhibiting innate immune-mediated early activation of endogenous donor- reactive memory T cells to cause acute graft injury.