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.

Effects of Estrogen on Mucosal Structure and Numbers and Distribution of Intraepithelial Lymphocytes and Goblet Cells in Small Intestine of Rats

To study the effects of estrogen on the structure of the intestinal mucosal barrier, 18 healthy female Wistar Rats underwent estrus synchronization. In diestrus, they were divided into three groups： one sham operated control group （SHAM） ; one ovariec- tomized group （OVX） ; and one ovariectomized plus estradiol benzoate group （ OVX ＋ E2 ）. Intestinal mu- cosal epithelial cells, intraepithelial lymphocytes （[EL）, and goblet cells （GCs） were observed by light microscope. The results showed that in the OVX group, the intestinal mucosa damaged obviously, the villus atrophied, the ratio of villus height to crypt depth reduced, and the number of IELs and GCs re- duced. The indicators of OVX ＋ Ez group were signif- icantly higher than OVX group, but some indicators were lower than SHAM. These indicated that the function of intestinal mucosal barrier was greatly dam- aged in ovariectomied rat, and proper dosage of estra- diol benzoate Would improve the function of small in- testinal mucosal barrier in ovariectomied rat to some degree.

Duodenal intraepithelial T lymphocytes in patients with functional dyspepsia

AIM： To quantify the intraepithelial lymphocytes （IELs） and to document the membrane expression of CD4, CD8, TCRγδ and adhesion and/or activation-associated molecules （CD103, CD28, CD44, CD69, HLA-DR, CD95/ Fas） in the duodenal mucosa of patients with functional dyspepsia （FD） in order to provide arguments for an immunological process in FD. METHODS： Twenty-six FD patients according to Rome Ⅱ criteria （20 were H pylori negative） were studied and compared to 12 healthy adults. IELs were isolated from five duodenal biopsy samples, then quantified by microscopy and flow cytometry while the membrane phenotypes were determined by cytofluorometry. RESULTS： Duodenal histological examination was normal. In H pylori negative patients, the number of IELs was not different from that in healthy controls. Median percentage expression of CD4, CD8, or TCRy8 and CD103, CD44, CD28, CD69 on CD3＋ IELs, among the adhesion/activation associated molecules tested, was not different from that in healthy controls. In contrast, the median percentage expression of CD95/ Fas [22 （9-65） vs 45 （19-88）, P = 0.03] and HLADR expressing CD3＋ IELs [4 （0-30） vs 13 （4-42）, P = 0.04] was significantly lower in the H pylori negative FD group than in healthy controls, respectively. The number of IELs was significantly greater in H pylori positive FD patients than in healthy controls [median ratio for 100 enterocytes 27.5 （6.7-62.5） vs 10.8 （3-33.3）, P = 0.02] due to a higher number of CD8＋ CD3＋ IELs. CONCLUSION： In H pylori negative FD patients, the phenotypic characterization of IELs suggests that we cannot exclude a role of IELs in FD.

Lymphocytic esophagitis: Still an enigma a decade later

Lymphocytic esophagitis (LE) is a clinicopathologic entity first described by Rubio et al in 2006. It is defined as peripapillary intraepithelial lymphocytosis with spongiosis and few or no granulocytes on esophageal biopsy. This definition is not widely accepted and the number of lymphocytes needed to make the diagnosis varied in different studies. Multiple studies have described potential clinical associations and risk factors for LE, such as old age, female gender and smoking history. This entity was reported in inflammatory bowel disease in the pediatric population but not in adults. Other associations include gastroesophageal reflux disease and primary esophageal motility disorders. The most common symptom is dysphagia, with a normal appearing esophagus on endoscopy, though esophageal rings, webs, nodularities, furrows and strictures have been described. Multiple treatment modalities have been used such as proton pump inhibitors and topical steroids. Esophageal dilation seems to be therapeutic when dysphagia is present along with esophageal narrowing secondary to webs, rings or strictures. The natural history of the disease remains unclear and needs to be better delineated. Overall, lymphocytic esophagitis seems to have a chronic and benign course, except for two cases of esophageal perforation in the literature, thought to be secondary to this entity.

Microscopic colitis as a missed cause of chronic diarrhea

AIM: To determine the prevalence of increased intraepithelial lymphocytes, using immunohistochemistry in patients with normal colonoscopy and near normal biopsy. METHODS: We retrospectively reviewed all non-malignant colon mucosal biopsies between 2005 and 2007, reported as normal, chronic inflammation or melanosis coli in patients who were undergoing routine colonoscopy. Immunohistochemistry using CD3 was performed on all mucosal biopsies and an intraepithelial lymphocyte count (IEL) was determined. Cases with an IEL count of ≥ 20 IELs per 100 surface epithelial cells were correlated with demographic, clinical and follow-up data. A further subgroup was evaluated for lymphocytic colitis.RESULTS: Twenty (8.3%) of 241 cases revealed an IEL count ≥ 20. Six (2.5%) patients were identified as having lymphocytic colitis (P < 0.001), of whom, five were missed on initial evaluation (P = 0.01). Four of these five patients were labeled with diarrhea-predominant irritable bowel syndrome (IBS). On follow-up, three of the remaining 20 cases were diagnosed with malignancy (renal cell carcinoma and myelodysplastic syndrome) and one had an unknown primary tumor with multiple liver metastases. Two cases of collagenous colitis with an IEL count < 10 were included in this study. Increased IELs were not confined to patients with diarrhea as a primary presenting symptom, but were also present in patients with abdominal pain (n = 7), constipation (n = 3) and loss of weight (n = 1). CONCLUSION: Immunohistochemistry using CD3 is of value in identifying and quantifying IELs for the presence of microscopic colitis in patients with diarrheapredominant IBS.

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.