阻断Kupffer细胞中IRE1-XBP1通路诱导肝移植免疫耐受形成

Kupffer cells (KCs)，the most important resident macrophages of the liver, comprise one of the major population of the hepatic non nonparenchymal cell fraction, and the tolerogenic properties of the liver are generally accepted. Therefore increased attention has focused on the possible role and mechanism of KCs from liver allograft in tolerance induction. Over a decade of research, our group found that KCs played a dual role in the pathological changes after liver transplantation, and its mechanism is closely associated with modulating Th1/Th2 and/or Th17/Treg balance. Recently, a few studies reported that inositol requiring enzyme 1-X-box binding protein 1 (IRE1-XBP1) pathway, one branch of the unfolded protein response, plays a pivotal role in regulation of immune function, including regulation of MHC II gene, survival and development of APC and sustained Th1/Th17 associated cytokines secretion, but so far there is no related research in solid organ transplantation, especially in liver. We hereby put forward a hypothesis that blockage of IRE1-XBP1 pathway in KCs may induce liver transplant tolerance via cytokine-driven immune deviation and active suppression.To clarify the role of the pathway in liver tolerance induction, we will separate KCs and establish rat's liver transplantation model, using AdV-XBP1 and XBP1-shRNAs plasmids to enhance or inhibit XBP1 expression in vitro and in vivo. Once the hypothesis of blockage of IRE1-XBP1 pathway in KCs mediating the self-tolerance induction in liver transplantation is corroborated, this pathway can become a novel target for treatment of acute rejection.

移植肝脏具有免疫耐受性的重要原因是肝内存在Kupffer细胞（KCs）等特异性免疫细胞。项目组前期研究发现：KCs在肝移植急性排斥反应（AcR）过程中起着即促进AcR，又诱导免疫耐受的双重角色，其原因与调控Th1/Th2及Th17/Treg免疫平衡相关。新近发现IRE1-XBP1通路参与了机体免疫调控的诸多环节，阻断该通路可削弱Th1、Th17型反应及APC抗原呈递功能，但目前相关研究尚未涉及器官移植领域，更无与KCs及肝移植免疫耐受相关研究报道，我们认为该通路在肝移植免疫中也起重要作用。因此，本项目选择肝KCs为靶细胞，以XBP1为切入点，分离KCs并建立肝移植AcR模型，采用过表达XBP1、XBP1-shRNAs质粒及转基因等手段，增强或抑制该基因在体内外表达，探讨IRE1-XBP1通路对KCs功能和T细胞增殖、功能的影响及其分子机制，阐明该通路在诱导移植肝脏免疫耐受形成中的作用机制。

Kupffer细胞（KCs）在术后诱导移植肝脏免疫耐受中起着双重效应，但其确切机制目前尚不清楚。本课题通过抑制或过表达KCs中IRE1-XBP1通路活性，探讨这一通路诱导活化KCs极性变化及诱导肝移植术后免疫耐受的分子机制。研究发现：(1) 抑制KCs 中IRE1-XBP1通路可改变其表型为M2型，削弱其抗原呈递功能；并通过抑制JAK-STAT通路的表达，使KCs分泌M2型细胞因子谱，有利于Th1/Th17向Th2/Treg免疫偏移并抑制T淋巴细胞增殖及凋亡水平。增强KCs 中IRE1-XBP1活性则使KCs呈M1型表现，促进炎症反应的发生发展。(2) 通过转染携带XBP1-shRNA的PFCN阻断受体肝脏KCs中IRE1-XBP1通路，可以改善急性排斥模型受体的生存时间以及肝脏功能，并能减轻AcR对肝脏组织的破坏程度；以上结果提示：抑制KCs中IRE1-XBP1通路活性，通过诱导活化KCs极性转化，诱导Th1/Th17向Th2/Treg免疫偏倚，有利于免疫耐受微环境的诱导。