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

摘要 器官移植是治疗终末期器官疾病最有效的方法。临床上，两个重要的风险因素 移植结果不佳的原因是受者中移植前存在供体反应性T细胞， 移植前移植物冷缺血储存（CIS）时间长度。在肾移植患者中， 循环供者反应性记忆T细胞的移植存在与急性淋巴细胞白血病的风险增加有关。 排斥反应、移植物功能延迟和降低以及移植物长期存活率更差。未致敏 在接受者中，记忆T细胞的供体反应性是由于异源（交叉反应性）免疫。但 激活同种异体移植物内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 仍然知之甚少。延长的CIS增加缺血再灌注损伤（IRI），其特征在于 产生活性氧和促炎细胞因子，直接浸润受体白细胞 并引起移植物内这些细胞的活化。IRI还诱导移植物释放损伤 相关的分子模式（DAMP）从受伤和垂死的细胞，加剧炎症，并有助于 高风险同种异体移植的预后更差。我们以前的研究表明，这两个导致移植效果不佳的风险因素 结果是相互关联的。心脏移植后持续的高炎症环境 接受长时间CIS的同种异体移植物对于供体反应性记忆T细胞的充分活化是必要的， 介导共刺激阻断抵抗性急性排斥反应。多次临床移植 研究表明，一种DAMP，即游离DNA在同种异体移植物损伤期间在循环中升高， 代表用于早期检测急性排斥的有前景的非侵入性生物标志物。此外，最近的工作 来自我们的合作者已经发现了新的，可靶向的信号合作伙伴所需的激活 细胞游离DNA的先天免疫传感器，例如TLR 9，其可以识别线粒体DNA（mtDNA）。这些 研究结果和我们目前的初步数据使我们假设，长期的CIS和随后的 增加的IRI增强mtDNA的释放，导致更大的TLR 9活化和下游I型IFN 产生，触发由内源性供体反应性记忆T细胞维持的促炎周期 介导的急性移植物损伤。这一假设将在两个特定的目标进行测试，使用我们的血管化小鼠 异位心脏移植模型：首先，我们将在体内测试TLR 9信号传导的调节，以评估对心脏移植的影响。 供者反应性记忆T细胞介导的急性移植物损伤;其次，我们将测试其机制， I型干扰素有助于移植后早期炎症和供体反应性T细胞的活化， 调解拒绝。我们预计，这些研究将确定治疗策略的新靶点， 通过抑制先天免疫介导的内源性供体的早期激活的实体器官移植结果- 反应性记忆T细胞导致急性移植物损伤。

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.