抗原特异性骨髓来源抑制细胞的免疫学特性及在原发性胆汁性肝硬化中的作用

Primary biliary cirrhosis (PBC) is a prototypical autoimmune liver disease characterized by serum antimitochondrial autoantibodies (AMA), the hallmark of disease, and the small interlobular bile ducts cholangitis. AMA is directed against pyruvate dehydrogenase E-2 subunit (PDC-E2). Our published study identified myeloid-derived suppressor cells (MDSCs) played a critical immunoregulatory role in mice immune-mediated liver injury models. In our present studies, we investigated the monocytic MDSCs were significantly enriched in peripheral blood of PBC patients compared to healthy controls. Therapy responders showed significantly higher levels of circulating MDSCs than those corresponding nonrespenders. Moreover, in our 2-octynoic acid (2OA) coupled to bovine serum albumin (BSA) immunized autoimmune cholangitis mice model, 2OA-BSA stimulated specific bone marrow MDSCs had more power to inhibit hepatic inflammation response than naïve bone marrow MDSCs. This study tries to answer the following scientific questions: a) Does immune regulation of MDSCs depend on specific antigen; b) Does specific antoantigen (eg. 2OA or PDC-E2) promote the expansion of functional specific MDSCs population in vitro? We will utilize a series of in vivo and in vitro mice/human experiments, such as adoptive MDSCs transfer, the expansion of antoantigen stimulated MDSCs and so on, in order to identify the role of antigen-specific MDSCs in liver-specific autoimmunity by limiting T cell mediated inflammation and harmful pathology. These researches may provide support for the potential use of immuno-regulatory cells to regulate excessive T cell responses in PBC patients.

原发性胆汁性肝硬化(PBC)是以血清抗线粒体抗体(AMA)阳性、肝内小叶间胆管炎为特点的自身免疫性肝病。AMA针对的自身抗原是丙酮酸脱氢酸复合体-E2亚基(PDC-E2)。我们前期发现，骨髓来源抑制细胞(MDSCs)在小鼠肝脏免疫调控中发挥关键作用。PBC患者外周血单核细胞型MDSCs明显扩增并与治疗应答相关。2OA-BSA免疫诱导的自身免疫性胆管炎小鼠预实验中，来自2OA致敏小鼠骨髓的MDSCs免疫调控作用更强。因此，我们的关键科学问题是：①MDSCs的免疫调控作用是否依赖于抗原特异性；②特异性抗原(如：2OA和PDC-E2)能否更好地体外扩增MDSCs并保持免疫学活性？本课题将通过系列MDSCs过继性回输、特异性抗原刺激MDSCs扩增等体内外实验，阐述抗原特异性MDSCs的免疫学特性，及其对T细胞介导的自身免疫性胆管炎的免疫调控作用，为将抗原特异性MDSCs过渡到临床生物治疗提供依据。

机体骨髓造血系统对炎症病灶存在着负反馈应答，髓系抑制细胞（MDSC）可在诸多肝脏炎症性疾病中发挥着重要调控作用。本课题聚焦MDSC在原发性胆汁性胆管炎（PBC）发病过程中发挥的作用及机制。我们纳入了148例慢性肝病（PBC、AIH、CHB、NAFLD）患者和45例匹配的对照者，比较各组人群MDSC的数量、表型和功能特性。结果发现PBC患者外周血可出现单核细胞型MDSCs-的明显积聚。此外，PBC患者外周MDSC的水平与疾病相关生化指标（ALP、Tbil）具有明显的相关性。值得注意的是，PBC患者对 UDCA 标准化治疗的生化反应同样也与外周MDSC的水平密切相关。高表达MDSC患者，UDCA治疗反应更佳。更重要是，我们验证了 PBC患者外周 MDSC具有 强大的免疫负调控功能。同时，我们还特别关注MDSC在患者肝内的表达和分布情况。与外周情况一致，PBC患者肝内出现同样出现MDSC明显积聚，且主要集中在发生炎症的汇管区。MDSC的数量与肝脏组织病理学炎症程度和纤维化分级呈正相关。我们进一步对肝内MDSC谱系调控因素进行探讨，发现PBC患者肝内小胆管和肝细胞高表达CCN1蛋白，CCN1通过与MDSC表面的整合素受体integrinαMβ2结合，可诱导STAT3的磷酸化，从而促进MDSC扩增；并可诱导MDSCs高表达iNOS,发挥对T细胞增殖的免疫抑制作用。上述结果提示，功能性MDSC是维持慢性患者肝内免疫稳态的重要负性调控细胞，并具有潜在的免疫治疗价值。