CD177+ 中性粒细胞在炎症性肠病发生发展过程中的免疫调节机制

Early and persistent infiltration of neutrophils or polymorphonuclear leukocytes (PMN) into the inflamed mucosa is present in patients with inflammatory bowel disease (IBD), and PMN have been considered to play an important role in the immunopathology through innate and adaptive immune responses. CD177 is a specific antigen expressed in PMN and involved in PMN maturation and migration. In our preliminary experiments, we have found that CD177+ PMN are markedly increased in peripheral blood and inflamed mucosa of IBD patients, have an increase of migration capacity, release high levels of anti-microbial peptides, reactive oxygen species and neutrophil extracellular traps (NET), and secret high levels of anti-inflammatory cytokines (eg, TGF-b), but produce low levels of pro-inflammatory cytokines (eg, IL-17A, IFN-g, IL-6). Importantly, CD177-/- mice develop severer colitis compared with wild-type mice in response to insult of dextran sulfate sodium (DSS) in the drinking water. These data indicate a protective role of CD177+ PMN in the development of intestinal inflammation, particularly in human IBD. In this study, we will investigate the potential role of PMN in intestinal homeostasis and regulation of intestinal inflammation. Moreover, we will also study the role of CD177+ PMN in regulating intestinal inflammation in IBD patients and its role in regulating intestinal epithelial cell, CD4+ T cell, Treg cell and macrophage activation and immune responses. Acute and chronic experimental colitis models in CD177-/- mice will be established to examine how CD177+ PMN regulate intestinal inflammation. This work will determine the potential role of CD177+ PMN in the pathogenesis of IBD, and provide an important therapeutic target for human IBD.

中性粒细胞（PMN）早期浸润于炎症性肠病（IBD）肠黏膜组织内，通过固有性和获得性免疫应答效应参与肠黏膜炎症修复和病理损伤。CD177特异表达在PMN，参与其成熟和诱导向血管外迁移。我们前期研究发现IBD患者外周血和肠黏膜组织内CD177+ PMN显著增多，趋化迁移能力增强，分泌抗菌肽、活性氧和释放胞外诱捕网增多，表达TGF-b明显升高；DSS诱导CD177-/- 小鼠发生严重结肠炎，提示CD177+ PMN对黏膜炎症发生有免疫保护作用。因此，本课题重点研究PMN对肠黏膜内环境免疫调节和IBD发生时免疫效应应答作用，利用IBD患者外周血、肠黏膜组织和CD177-/- 小鼠模型，探讨CD177+ PMN在肠黏膜炎症发生过程中作用，以及对肠黏膜上皮细胞、CD4+ T、Treg细胞、巨噬细胞的免疫调节，阐明其在IBD发生过程中的免疫效应效应，为揭示IBD发病机制和临床靶向生物治疗提供新的依据。

中性粒细胞（PMN）早期浸润于炎症性肠病（IBD）肠黏膜组织内，通过固有性和获得性免疫应答效应参与肠黏膜炎症修复和病理损伤。CD177特异表达在PMN，参与其成熟和诱导向血管外迁移。我们研究发现IBD患者外周血和肠黏膜组织内CD177+ PMN显著增多，趋化迁移能力增强，分泌抗菌肽、活性氧和释放胞外诱捕网（NET）增多，表达TGF-b明显升高。RNA基因测序分析发现IBD患者CD177+和CD177- PMN表达的差异基因主要包括细菌防御能力、过氧化氢、活性氧产物；CD177+ PMN细胞表达促炎症细胞因子水平（IFN-g、IL-6、IL-17A）显著降低，而产生IL-22和TGF-b明显升高，抗菌活性（如表达活性氧产物、抗菌肽、NET形成）比CD177- PMN明显升高。构建CD177基因敲除小鼠，发现DSS诱导CD177-/-小鼠发生严重结肠炎，肠上皮细胞屏障功能和抗菌免疫活性显著下降，主要机制是由于CD177-/- PMN产生IL-22水平明显下降，提示CD177+ PMN对肠黏膜炎症发生中起着免疫保护作用。进一步，我们发现CD177+ PMN功能受损后，引起肠上皮层内TCRgd+CD8aa+ IEL细胞增殖分化，表达细胞焦亡基因升高，DSS诱导急性肠炎模型或鼠柠檬酸菌感染肠炎模型显示肠道炎症加重。CD177-/-小鼠发生结肠炎后，发现粪便中富马酸水平显著降低；而在IBD患者粪便中也呈此类趋势。使用富马酸二甲酯治疗后发现CD177-/-小鼠肠道炎症明显缓解，主要是通过抑制Gasdermin D裂解，从而有效抑制TCRgd+CD8aa+ IEL的激活和效应应答。本研究阐明了CD177+ PMN在肠黏膜炎症发生过程中的免疫调节作用，为临床靶向PMN的功能治疗肠道炎症性疾病（如IBD）提供重要的理论依据。