肠道微生物和iNKT细胞在炎症性肠病的发病过程中发挥关键作用，但其潜在调控机制尚不清楚。我们前期工作发现在恶唑酮诱导的肠炎小鼠中CCL25/CCR9相互作用可促进 iNKT细胞的诱导和功能，同时单位点CpG甲基化水平可影响启动子活性，还发现肠道微生物种类改变可引起甲基化转移酶差异。据此我们提出假设肠道微生物通过改变CCL25启动子甲基化水平影响CCL25表达，从而调节iNKT细胞的数量和功能，对肠道炎症反应发挥保护性或致病性作用。本研究首先利用恶唑酮诱导的小鼠肠炎模型，探索肠道微生物种类改变对CCL25/CCR9相互作用的影响；其次利用体内和体外实验，初步揭示肠道微生物调节CCL25/CCR9相互作用的靶位点；最后利用结肠活检标本初步阐明CCL25甲基化与CCL25启动子密切相关。本研究为寻找炎症性肠病的治疗新策略提供理论研究基础。

Intestinal microbiota and invariant natural killer T (iNKT) cells play the critical role in the pathogenesis of inflammatory bowel disease (IBD) . However, the regulation mechanism of intestinal microbiota and iNKT cells remain poorly defined. Our previous work showed that chemokine ligand 25 (CCL25)/chemokine receptor 9 (CCR9) interaction may promote the induction and function of iNKT cells during oxazolone-induced colitis in mice, and the methylation level of CpG affected the activity of the promoter, as well as the change of intestinal microbiota species affected the CCL25 expression by regulating the methylation level of CCL25 promoter. Therefore, we hypothesized that intestinal microbiota mediates iNKT cells by regulating the methylation level of CCL25 promoter, and plays the critical protective or pathogenic role in the intestinal inflammation of IBD. This study firstly used a mice model of oxazolone-induced colitis to explore the affection of CCL25/CCR9 interaction after the change of intestinal microbiota species; secondly, we applied the vivo and vitro experiment to explore the target sites of intestinal microbiota regulating CCL25/CCR9 interaction; finally, we clarified the methylation level of CCL25 was closely related to the CCL25 promoter using the colon biopsy specimens. The study findings will help to provide new ideas for the treatment of IBD.