| Objective Inflammatory bowel disease（IBDs）,including ulcerative colitis（UC）and Crohn’s disease（CD）,is a chronic,recurrent inflammation of the gastrointestinal tract.It is generally believed that the pathogenesis of IBDs is related to host genetic susceptibility.Recent studies have confirmed that T cells play an important role in maintaining intestinal immune system homeostasis of IBDs.Mucosal associated invariant T（MAIT）cells are a unique subgroup of newly discovered non-traditional T lymphocytes,and their role in IBDs is unclear.The main purpose of this study is to explore the role and related mechanism of MAIT cells in acute colitis in mice.Methods Acute colitis were induced in wild type（WT）C56BL/6 mice.The proportion,typing,apoptosis,proliferation,activation and cytokine secretion of MAIT cells in mice were detected by flow cytometry.Then,acute colitis were induced in both WT and MR1knockout(MR1-/-)mice.The mice were divided into four groups:WT control,MR1-/-control,WT DSS group and MR1-/-DSS.During the modeling period,the body weight and disease activity of mice were measured.At the end of the model,the length and weight of colon in mice were recorded and the histological differences of colon in the four groups were compared.The expression of intestinal barrier associated protein ZO-1 and apoptosis of intestinal epithelial cells were detected by immunofluorescence.The content of IL-6 and IL-1βprotein in colon was detected by ELISA,the expression of ZO-1 and Claudin1 in colon was detected by Western Blot,the intestinal permeability of mice was detected by FITC-dextran,and the translocation of intestinal bacteria were detected by liver blood plate coating.The infiltration of colonic toxic T cells and the apoptosis of intestinal epithelial cells were detected by flow cytometry,and the expression of Ki-67 in colon was detected by immunohistochemistry.Mouse colonic MAIT cells were separated and purified by magnetic beads,and MAIT cells and CT26 were co-cultured for 48 hours.The proliferation and apoptosis of CT26 were analyzed by flow cytometry.Finally,the content of intestinal goblet cells in the four groups was detected by AB-PAS staining,and the changes of intestinal flora were detected by 16Sr DNA sequencing.Results（1）The proportion and absolute number of MAIT cells decreased significantly in peripheral blood and spleen,but aggregated in colon and showed apoptosis and activation phenotype.In addition,the expression of IL-17A,IFN-γ,granzyme B and CD107A in colonic MAIT cells of colitis mice increased.（2）MAIT deficiency resulted in weight loss,colon shortening,histopathological score and disease activity increased in colitis mice.At the same time,the expression of intestinal barrier-related proteins ZO-1 and Claudin1 decreased and inflammatory molecules IL-1βand IL-6 increased in acute colitis mice with MAIT cell deletion.The absence of MAIT cells also increased the apoptosis and decreased the proliferation of intestinal epithelial cells in acute mice.（3）In the co-culture system of MAIT cells and intestinal epithelial cells,the apoptosis and proliferation of intestinal epithelial cells were significantly enhanced.The proliferation and apoptosis of intestinal epithelial cells were significantly decreased after the application of TGF-βneutralizing antibody to co-culture system.The loss of goblet cells was more severe in the mice with MAIT cell deficiency.The 16Sr DNA microflora sequencing also demonstrated that the altered microflora composition with MAIT cell deficiency mice led to the imbalance of intestinal microflora,and the abundance of Lactobacillus.johnsonii in was significantly reduced.Conclusion MAIT cells can reduce the severity of colitis in mice,promote the self-renewal of intestinal epithelial cells,inhibit intestinal inflammation,protect intestinal epithelium and mucus barrier,and prevent intestinal flora disorder.In a word,MAIT cells play an important role in maintaining intestinal integrity.An in-depth understanding of the regulatory mechanism of MAIT cells on colitis will provide new ideas and strategies for biological immunotherapy of colitis. |
