Intestinal epithelium, intraepithelial lymphocytes and the gut microbiota-Key players in the pathogenesis of celiac disease

Celiac disease(CD) is a chronic immune-mediated disorder triggered by the ingestion of gluten in genetically predisposed individuals. Before activating the immune system, gluten peptides are transferred by the epithelial barrier to the mucosal lamina propria, where they are deamidated by intestinal tissue transglutaminase 2. As a result, they strongly bind to human leucocyte antigens(HLAs), especially HLA-DQ2 and HLA-DQ8, expressed on antigen-presenting cells. This induces an inflammatory response, which results in small bowel enteropathy. Although gluten is the main external trigger activating both innate and adaptive(specific) immunity, its presence in the intestinal lumen does not fully explain CD pathogenesis. It has been hypothesized that an early disruption of the gut barrier in genetically susceptible individuals, which would result in an increased intestinal permeability, could precede the onset of gluten-induced immune events. The intestinal barrier is a complex functional structure, whose functioning is dependent on intestinal microbiotahomeostasis, epithelial layer integrity, and the gutassociated lymphoid tissue with its intraepithelial lymphocytes(IELs). The aim of this paper was to review the current literature and summarize the role of the gut microbiota, epithelial cells and their intercellular junctions, and IELs in CD development.

Effect of Polysaccharides from Hedyotis diffusa on Immune Cells of Small Intestinal Mucosa of Chicks

[Objectives]This study aimed to investigate the effect of polysaccharides from Hedyotis diffusa on the immune cells of the intestinal mucosa of chicks.[Methods]Total 200 seven-day-old AA chicks were evenly and randomly divided into four groups:control group and three treatment groups.The chicks in the control group(group I)were fed basal diet,and those in the treatment groups were fed with basal diet supplemented with 0.4(group II),0.8(group III)and 1.2(group IV)g/kg H.diffusa polysaccharides(OPS),respectively.At the age of 14,28 and 42 d,10 chicks from each of the groups were sacrificed,respectively for counting of intraepithelial lymphocytes(IELs)and lamina propria secretory IgA(SIgA)positive cells in small intestinal mucosa.[Results]At the age of 14 d,the duodenal and jejunal IEL and SIgA positive cell counts in groups II,III and IV were significantly greater than those in group I(P<0.05).At the age of 28 d,the jejunal IEL count of group IV was significantly lower than those of groups I,II and III(P<0.05);and there was no significant difference in IEL or SIgA positive cell count between group I and the other groups(P>0.05).At the age of 42 d,the duodenal and jejunal IEL counts in group II were significantly greater than those in groups I,III and IV(P<0.05),while the differences in duodenal and jejunal IEL count between groups III,IV and I were insignificant(P>0.05).The duodenal SIgA positive cell counts in the treatment groups were insignificantly different from that in group I(P>0.05).The jejunal SIgA positive cell count in group II was significantly greater than those in groups I,III and IV(P<0.05).There was no significant difference in jejunal SIgA positive cell count between groups III and IV and group I(P>0.05).[Conclusions]OPS at 0.4 g/kg can promote the proliferation of immune cells in the small intestine mucosa of 14-42-day-old AA chicks,and it is recommended to be added to the feed.