Regulation of Innate Immune Responses by Alloimmunity in Liver Ischemia-Reperfusion Injury

项目II -项目概要/摘要 缺血-再灌注损伤（IRI）可导致移植物早期功能低下、原发性无功能， 急性和/或慢性排斥反应。在动物模型上研究了肝脏IRI的病理生理学 模型，主要是在原位肝部分热缺血和冷储存/同基因Tx的情况下， 强调先天免疫反应的机制。很明显，这两者之间有很大的差异。 实验模型和临床情况，这可能会导致我们对 发病机制在这方面，是否和如何同种抗原（Ag）/适应性同种免疫的问题， 影响组织炎症反应和损伤对IR具有重要意义。我们比较了肝脏IRI 大鼠和小鼠的同基因和异基因肝移植（奥尔特） 模型结果明确显示，同种异体移植物的组织损伤明显比 在相同保存条件下的同种异体移植物在再灌注早期， 从动力学上来说是排斥反应。淋巴细胞参与移植肝IRI及其作用机制 与同种异体移植物中的明显不同。本项目主要研究CD 4 T细胞在同种异体肝IRI中的作用， vs.长期冷藏后的iso-OLT。我们已经在肝脏部分热缺血模型中发现， 效应记忆（TEM）亚群（CD 44 highCD 62 Llow），但不是幼稚的，CD 4 T细胞能够在Ag非免疫细胞中发挥作用。 通过CD 154依赖性但不依赖于IFN-γ的机制以特异性方式表达。在奥尔特设置中，我们最近 数据明确了IFN-γ在同种异体移植物而非同种异体移植物的肝IRI中的功能。我们假设接受者- 现有的CD 4 TEM细胞在Tx后立即对肝脏IR作出响应。它们通过Ag特异性和 涉及独特效应机制的非特异性途径。我们已经证明，肝脏CD 4 TEM 组成性表达CD 154，并通过CD 40增强先天性炎症免疫激活， 它们的银特异性。在allo-OLT中，我们提出供体allo-Ag可以另外激活受体 浸润同种异体反应性CD 4 TEM细胞以产生IFN-γ，这是增强炎症反应的原因。 免疫激活和肝细胞损伤。因此，CD 4 TEM细胞可以 通过Ag特异性再活化以分泌IFN-γ和Ag通过CD 154与 先天免疫细胞上的CD 40。我们将在两个具体的目标来解决我们的假设，以确定Ag- 在OLT的IRI中的CD 4 T细胞的特异性和效应器机制。这些研究将是第一个 特别是解决了同种异体与同基因肝脏IRI的基本免疫生物学问题， 移植研究结果不仅填补了我们对该病发病机制认识上的差距，而且也是真实的 临床背景下，而且还为我们提供了新的见解，适应性免疫的作用，在调节组织先天 炎症免疫反应。

PROJECT II – PROJECT SUMMARY/ABSTRACT Ischemia-reperfusion injury (lRI) may lead to poor early graft function, primary non-function and predisposes the graft to acute and/or chronic rejection. The pathophysiology of liver IRI has been investigated in animal models, primarily in the setting of hepatic partial warm ischemia in situ, and cold storage/syngeneic Tx, with mechanistic emphasis on innate immune responses. Clearly, there are major discrepancies between these experimental models and the clinical scenario, which may cause deficiencies in our comprehension of the disease mechanism. In this regard, the question of whether and how allo-antigens (Ag)/adaptive allo-immunity impact tissue inflammatory response and injury against IR is of high significance. We have compared liver IRI between syngeneic and allogeneic transplants in both rat and mouse orthotropic liver transplantation (OLT) models. Results showed unequivocally that allografts developed significantly more severe tissue injuries than isografts under the same preservation condition in the early stage of reperfusion, which were distinctive kinetically from rejection. Lymphocytes and their functional mechanisms involved in the liver IRI of allografts are clearly different from those in isografts. This project focuses on the role of CD4 T cells in liver IRI of allo-, vs. iso-OLTs after extended cold storage. We have found in a liver partial warm ischemia model that the effector memory (TEM) subset (CD44highCD62Llow), but not naïve, CD4 T cells were able to function in Ag non- specific manner via a CD154 dependent, but IFN-γ independent mechanism. In the OLT setting, our recent data specified functions of IFN-γ in liver IRI of allo-, but not iso-grafts. We hypothesize that recipient pre- existing CD4 TEM cells are responding to liver IR immediately post Tx. They function via both Ag-specific and non-specific pathways involving distinctive effector mechanisms. We have documented that liver CD4 TEM expressed CD154 constitutively and enhanced innate inflammatory immune activation via CD40, independent of their Ag-specificities. In allo-OLTs, we propose that donor allo-Ags may, additionally, activate recipient infiltrating alloreactive CD4 TEM cells to produce IFN-γ, which is responsible for the enhanced inflammatory immune activation and hepatocellular damage, as compared with those in iso-OLTs. Thus, CD4 TEM cells may promote liver IRI by Ag-specific reactivation to secrete IFN-γ and Ag non-specific interaction via CD154 with CD40 on innate immune cells. We will address our hypothesis in two specific aims to determine Ag- specificities and effector mechanisms of CD4 T cells in IRI of OLTs. These studies will be the first to specifically address the fundamental immunobiology question of liver IRI in allogeneic vs. syngeneic transplantation. Results will not only fulfill the gap in our understanding of the disease pathogenesis in real clinical setting, but also provide us novel insight into the role of adaptive immunity in regulating tissue innate inflammatory immune responses.