替代激活的巨噬细胞在炎症性肠病发病中免疫调节作用机制研究

Inflammatory bowel diseases (IBD) comprise two types of chronic intestinal disorders including Crohn's disease and ulcerative colitis. Abnormal immune responses in intestinal mucosa toward commensal bacterial flora together with persistent mucosal infection, intestinal mucosal barrier defects, genetic and environmental factors may be associated with the etiology and pathogenesis of human IBD. Alternatively activated macrophages (AAM) express high levels of IL-10 and low levels of IL-12, and inhibit T cell activation and proliferation through cell contact or secretion of inhibitory cytokines. Thus, they play an important role in the Th2-mediated immune responses. In our previous study, we have found that the levels of AAM and Bcl-6+ macrophages were markedly decreased in inflamed mucosa of huamn IBD, and that Bcl-6-transfected macrophages could inhibit CD4+ T cell activation and proliferation. Thus, AAM are supposed to be involved in the immunopathological damage in intestinal mucosa. In this study, we will study peripheral blood-derived and intestinal mucosal AAM from IBD patients, particularly from those patients treated with anti-TNF monoclonal antibody, and investigate the potential roles in the development of IBD. Moreover, acute and chronic colitis models in mice will be established to study the immigration, homing, and proliferation of AAM in intestinal mucosa-associated lymphoid tissues, and explore the immunoregulatory role in intestinal lamina propria under inflammatory conditions. Experimental therapy with different subsets of AAM will also be performed to determine whether they could prevent intestinal mucosal inflammation. This work will clarify the potential role of AAM in the pathogenesis of IBD and provide an important theoretical basis for IBD immune therapy.

炎症性肠病(IBD)包括克罗恩病和溃疡性结肠炎，其病因和发病机制可能与肠黏膜免疫应答异常有密切关系。替代激活的巨噬细胞（AAM）表达高水平IL-10、低水平IL-12，抑制T细胞增殖分化，参与Th2免疫应答效应。我们前期的研究发现IBD患者肠黏膜组织内AAM和Bcl-6+巨噬细胞表达下降，Bcl-6转染的巨噬细胞对CD4+ T细胞有免疫抑制效应。据此提出AAM可能参与了肠黏膜免疫病理损伤过程。本课题重点研究IBD患者，尤其是接受抗TNF抗体治疗前后外周血单核细胞来源和肠黏膜组织内AAM水平变化，分析AAM在IBD发生过程中的免疫病理调节作用。建立急性、慢性结肠炎小鼠动物模型，研究AAM在肠黏膜相关淋巴组织内迁移、着陆、增殖分化，以及在肠黏膜固有层组织内免疫调节效应；使用不同亚型AAM体内治疗，观察肠黏膜炎症发展变化，阐明其在肠黏膜炎症发生过程中效应应答，为临床上治疗IBD提供重要理论依据。

炎症性肠病(IBD)包括克罗恩病和溃疡性结肠炎，其病因和发病机制可能与肠黏膜免疫应答异常有密切关系。替代激活的巨噬细胞（AAM或M2型巨噬细胞）表达高水平IL-10、低水平IL-12，抑制T细胞增殖分化，参与Th2免疫应答效应。本课题首先重点研究了在肠黏膜炎症发生时，肠上皮细胞（IEC）表达胰岛素样生长因子（IGF-1），并诱导肠黏膜组织内的IGF-1受体（IGF-1R）阳性的单核巨噬细胞表达高水平IL-10，提示IGF-1可以诱导肠黏膜组织内单核细胞向具有免疫抑制功能的M2型巨噬细胞转化，并具有免疫抑制功能。建立TNBS诱导小鼠结肠炎模型，使用IGF1致敏的单核细胞治疗，发现可显著抑制小鼠结肠炎发生，降低肠黏膜炎症程度，表现为小鼠体重增加，无腹泻和脱肛现象发生。进一步研究发现，肠道微生物抗原刺激可诱导IEC分泌凝血酶致敏蛋白1（thrombospondin-1, TSP1），TSP1可以通过结合CD36+单核细胞，诱导表达高水平TGF-β。使用TNBS建立小鼠实验性结肠炎模型，体内使用TSP1致敏的单核细胞治疗，发现可有效降低结肠炎发生，降低肠黏膜炎症损伤程度。建立了小鼠肠道食物过敏损伤的动物模型，通过灌胃方法使用酪酸梭菌治疗，发现可有效抑制肠黏膜过敏性炎症。研究发现产生丁酸的酪酸梭菌可显著诱导肠黏膜组织内B细胞激活，产生高水平IL-10。提示产生丁酸的酪酸梭菌可提高对食物过敏反应引起的肠黏膜炎症保护作用，为临床上对食物过敏反应治疗提供了重要的理论依据。研究发现在IBD患者炎症肠黏膜组织内miR-10a表达显著下降，其主要表达在肠黏膜组织CD4+ T细胞和树突状细胞。miR-10a体外可抑制IBD患者CD4+ T细胞向Th1和Th17细胞分化，提示IBD患者肠黏膜组织内miR-10a表达下降，不能有效应Th1和Th17细胞效应应答，促使肠黏膜炎症发生。另外，研究发现在IBD发生时，炎症肠黏膜组织内miR-301a表达明显升高，其主要表达在肠黏膜组织内CD4+ T细胞。体外培养CD4+ T细胞，使用慢病毒包装的miR-301a进行转染，发现使用miR-301a慢病毒转染的CD4+ T细胞可促使向Th17细胞增殖分化（表达IL-17A、RORC升高）和TNF-a表达，进而促使肠黏膜炎症发生。这些研究提示靶向这些miRs治疗可能用于临床上治疗IBD。