Background: Gliadins, a family of wheat proteins, are central to the pathogenesis of celiac disease (CD). In addition to 'immunogenic' effects, gliadin directly affects cultured cells and intestine preparations, and produces damage in vivo, via a separate 'toxic' peptide, such as A-gliadin p31-43 (P31-43). Aims: Understanding the molecular mechanisms underlying direct non T-cell mediated effects of gliadin peptides, and assessing their potential role in promoting CD.Method: Gliadin effects were tested on a number of cell lines and on cultured mucosa samples by evaluating cytoskeleton rearrangements, endocytosis, proliferation and apoptosis. Standard biochemical methods were used to assess prolonged epidermal growth factor receptor (EGFR) activation. Results: Crude gliadin peptic-tryptic peptides (PTG], or P31-43 alone, fully reproduce the effects of epidermal growth factor (EGF] on actin cytosketon, cell cycle and cell proliferation of various cell lines. Inhibitor studies demonstrate the role of EGFR in the early response to gliadin exposure, pointing to activation of the EGFR pathway. Peptide P31-43 is not similar to any EGFR ligand, but can delay inactivation of the EGFR interfering with its endocytosis. Gliadin-induced delay of EGFR endocytosis in cultured intestinal biopsies, together with S-phase entry of epithelial intestinal cells, confirm a role for EGFR activation in CD. Conclusion: The ability of gliadin peptides to delay EGFR inactivation through interference with the endocytic pathway suggests a model where gliadin fragments amplify the effects of trace amounts of EGF, and possibly of other growth factors, by prolonging receptor activation. The results, using cultures of coeliac intestinal biopsies, highlight the role of the EGF pathway in establishing and maintaining the typical atrophic and proliferative alterations of the small intestine in CD.

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A sizeable proportion of asymptomatic potential celiac patients showed fluctuation or negativization of antibody production, and many of these, with persistently positive anti-TG2, did not develop mucosal damage after 9 years of follow-up. Celiac population is a multivariate aggregate of individuals with different genetic and phenotypic profiles. Caution is required before prescribing a gluten-free diet for life to asymptomatic individuals with potential CD.

Dietary gluten has been associated with an increased risk of type 1 diabetes. We have evaluated inflammation and the mucosal immune response to gliadin in the jejunum of patients with type 1 diabetes. Small intestinal biopsies from 17 children with type 1 diabetes without serological markers of celiac disease and from 50 age-matched control subjects were examined by immunohistochemistry. In addition, biopsies from 12 type 1 diabetic patients and 8 control subjects were cultured with gliadin or ovalbumin peptic-tryptic digest and examined for epithelial infiltration and lamina propria T-cell activation. The density of intraepithelial CD3 ؉ and ␥␦ ؉ cells and of lamina propria CD25 ؉ mononuclear cells was higher in jejunal biopsies from type 1 diabetic patients versus control subjects. In the patients' biopsies cultured with peptic-tryptic gliadin, there was epithelial infiltration by CD3 ؉ cells, a significant increase in lamina propria CD25 ؉ and CD80 ؉ cells and enhanced expression of lamina propria CD54 and crypt HLA-DR. No such phenomena were observed in control subjects, even those with celiac disease-associated HLA haplotypes. In conclusion, signs of mucosal inflammation were present in jejunal biopsies from type 1 diabetic patients, and organ culture studies indicate a deranged mucosal immune response to gliadin.

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Under the umbrella of coeliac disease (CD), or gluten‐sensitive enteropathy, the concepts of silent, latent and potential CD have recently been introduced. While silent CD is marked by severe damage to the jejunal mucosa in the absence of clinical symptoms, both latent and potential CD are characterized by a jejunal mucosa that would be reported as normal by most clinical pathologists in an individual on a gluten‐containing diet. As opposed to potential coeliac patients, latent subjects sometime in their life have had a flat jejunal biopsy which recovered on a gluten‐free diet. Latent coeliac patients are often symptomatic; neither high titres of gliadin antibodies nor mucosal changes (including raised intraepithelial lymphocyte counts) are obligate features of latent CD, although the presence of elevated endomysial antibodies is probably the best predictor of progression towards villous atrophy. The term potential CD has been proposed for those subjects who do not have, and have never had, a jejunal biopsy consistent with overt CD, and yet have immunological abnormalities similar to those found in coeliac patients. Good markers of potential CD include the presence of serum endomysial antibodies, a high count of intraepithelial lymphocytes and subtle pathological alterations such as increased density of intraepithelial lymphocytes expressing γδ T cell receptor, signs of activated mucosal cell‐mediated immunity, coeliac‐like intestinal antibody pattern, and positive rectal gluten challenge.

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Most of the patients with serum antiendomysium antibodies and normal jejunal histology showed immunohistochemical signs of immune activation in the epithelium, lamina propria, and crypts. We recommend that such patients be monitored to assess their progress and to determine whether they need a gluten-free diet.