Modulation of Dendritic Cell Phenotype and its Function by Probiotics in Experimental Colitis in Rats

Background:Distortion of intestinal flora is one of the major mechanisms involved in the development of inflammatory bowel disease(IBD),probiotics have therapeutic effect on IBD,yet its immune response modulating mechanism is not well known.Aims:To assess the effect of probiotics on intestinal tract inflammation,modulation of intestinal microbial flora and activation and function of dendritic cells(DCs).Methods:Thirty Wistar rats were randomly divided into normal control group,colitis control group and probiotics-treated group.Histological inflammatory score of colonic mucosa was studied and intestinal microbial flora was analyzed.Expressions of major histocompatibility complex(MHC)-Ⅱand costimulatory molecule CD86 on DCs were analyzed by flow cytometry.The capacity of DCs to stimulate T cell proliferation was determined by mixed lymphocyte reaction(MLR).Results:The colonic mucosal inflammatory score differed significantly between normal control group,colitis control group and probiotics-treated group(4.35±0.88,10.25±1.36 and 7.94±0.85,respectively,P0.05).The amount of lactobacillus and Bacillus bifidus in feces was lower in colitis control group than that in normal control group,while the amount of enterobacillus and fungus was higher(P0.01).The microbial flora imbalance in cecum was ameliorated in probiotics-treated group and the amount of lactobacillus and Bacillus bifidus was significantly higher than that of colitis control group and close to that of normal control group.Expressions of MHC-Ⅱ molecule on DCs in normal control group,colitis control group and probiotics-treated group were(26.2±7.2)%,(84.6±9.4)% and(66.5±8.4)%,respectively(P0.05),while that of CD86 were(20.5±7.7)%,(80.6±8.8)% and(59.8±10.0)%,respectively(P0.05).Conclusions:Probiotics may attenuate the distortion of intestinal microbial flora imbalance,significantly down-regulate the activation of DCs in mesenteric lymph nodes,decrease its capacity of stimulating T cell proliferation,thereby decrease the intestinal inflammatory response in rats colitis.