The identification of gluten peptides eliciting intestinal T cell responses is crucial for the design of a peptide-based immunotherapy in celiac disease (CD). To date, several gluten peptides have been identified to be active in CD. In the present study, we investigated the recognition profile of gluten immunogenic peptides in adult HLA-DQ2⁺ celiac patients. Polyclonal, gliadin-reactive T cell lines were generated from jejunal mucosa and assayed for both proliferation and IFN-γ production in response to 21 peptides from wheat glutenins and α-, γ-, and ω-gliadins. A magnitude analysis of the IFN-γ responses was performed to assess the hierarchy of peptide potency. Remarkably, 12 of the 14 patients recognized a different array of peptides. All α-gliadin stimulatory peptides mapped the 57–89 N-terminal region, thus confirming the relevance of the known polyepitope 33-mer, although it was recognized by only 50% of the patients. By contrast, γ-gliadin peptides were collectively recognized by the great majority (11 of 14, 78%) of CD volunteers. A 17-mer variant of 33-mer, QLQPFPQPQLPYPQPQP, containing only one copy of DQ2-α-I and DQ2-α-II epitopes, was as potent as 33-mer in stimulating intestinal T cell responses. A peptide from ω-gliadin, QPQQPFPQPQQPFPWQP, although structurally related to the α-gliadin 17-mer, is a distinct epitope and was active in 5 out of 14 patients. In conclusion, these results showed that there is a substantial heterogeneity in intestinal T cell responses to gluten and highlighted the relevance of γ- and ω-gliadin peptides for CD pathogenesis. Our findings indicated that α-gliadin (57–73), γ-gliadin (139–153), and ω-gliadin (102–118) are the most active gluten peptides in DQ2⁺ celiac patients.

Celiac disease (CD) results from a permanent intolerance to dietary gluten and is due to a massive T cell-mediated immune response to gliadin, the main component of gluten. In this disease, the regulation of immune responses to dietary gliadin is altered. Herein, we investigated whether IL-10 could modulate anti-gliadin immune responses and whether gliadin-specific type 1 regulatory T (Tr1) cells could be isolated from the intestinal mucosa of CD patients in remission. Short-term T cell lines were generated from jejunal biopsies, either freshly processed or cultured ex vivo with gliadin in the presence or absence of IL-10. Ex vivo stimulation of CD biopsies with gliadin in the presence of IL-10 resulted in suppression of Ag-specific proliferation and cytokine production, indicating that pathogenic T cells are susceptible to IL-10-mediated immune regulation. T cell clones generated from intestinal T cell lines were tested for gliadin specificity by cytokine production and proliferative responses. The majority of gliadin-specific T cell clones had a Th0 cytokine production profile with secretion of IL-2, IL-4, IFN-γ, and IL-10 and proliferated in response to gliadin. Tr1 cell clones were also isolated. These Tr1 cells were anergic, restricted by DQ2 (a CD-associated HLA), and produced IL-10 and IFN-γ, but little or no IL-2 or IL-4 upon activation with gliadin or polyclonal stimuli. Importantly, gliadin-specific Tr1 cell clones suppressed proliferation of pathogenic Th0 cells. In conclusion, dietary Ag-specific Tr1 cells are present in the human intestinal mucosa, and strategies to boost their numbers and/or function may offer new therapeutic opportunities to restore gut homeostasis.

The gluten-free diet is, to date, the only efficacious treatment for patients with Celiac Disease. In recent years, the impressive rise of Celiac Disease incidence, dramatically prompted changes in the dietary habit of an increasingly large population, with a rise in demand of gluten-free products. The formulation of gluten-free bakery products presents a formidable challenge to cereal technologists. As wheat gluten contributes to the formation of a strong protein network, that confers visco-elasticity to the dough and allows the wheat flour to be processed into a wide range of products, the preparation of cereal-based gluten-free products is a somehow difficult process. This review focuses on nutritional and technological quality of products made with gluten-free cereals available on the market. The possibility of using flour from naturally low toxic ancient wheat species or detoxified wheat for the diet of celiacs is also discussed.

Background & Aims: The extensive infiltration of CD8⁺ T cells in the intestinal mucosa of celiac disease (CD) patients is a hallmark of the disease. We identified a gliadin peptide (pA2) that is selectively recognized by CD8⁺ T cells infiltrating intestinal mucosa of HLA-A2⁺ CD patients. Herein, we investigated the phenotype, the tissue localization, and the effector mechanism of cells responsive to pA2 by using the organ culture of CD intestinal mucosa. The target of pA2-mediated cytotoxicity was also investigated by using the intestinal epithelial cell lines Caco2 and HT29, A2⁺ and A2⁻, respectively, as target cells. Methods: Jejunal biopsy specimens from CD patients were cultured in vitro with pA2, and cellular activation was evaluated by immunohistochemistry and cytofluorimetric analysis. Cytotoxicity of pA2-specific, intestinal CD8⁺ T cells was assayed by granzyme-B and interferon-γ release and by apoptosis of target cells. Results: pA2 challenge of A2⁺ CD mucosa increased the percentage of CD8⁺CD25⁺ and of CD80⁺ cells in the lamina propria, the former mainly localized beneath the epithelium, as well as the number of terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling-positive cells (TUNEL⁺) in the epithelium. Intraepithelial CD3⁺ cells and enterocyte expression of Fas were also increased. CD8⁺CD25⁺ and CD8⁺FASL⁺ T cells were significantly increased in cell preparations from biopsy specimens cultured with pA2. CD8⁺ T-cell lines released both granzyme-B and interferon-γ following recognition of pA2 when presented by Caco2 and not by HT29. Conclusions: These data indicate that gliadins contain peptides able to activate, through a TCR/HLA class I interaction, CD8-mediated response in intestinal CD mucosa and to induce the enterocyte apoptosis.

It has been reported that interferon (IFN)-γ-secreting T cells reactive to gluten can be detected in the peripheral blood of individuals with treated coeliac disease (CD) after a short consumption of wheat-containing food. By contrast, very little is known about the reproducibility of this in-vivo procedure in the same patient cohort which underwent two, or more, gluten consumptions. Fourteen coeliac patients in remission consumed wheat bread for 3 days; 13 underwent a second gluten challenge after a wash-out of 3–10 months on a strict gluten-free diet. Immune reactivity to gluten was analysed in peripheral blood by detecting IFN-γ before and 6 days after commencing a gluten diet. Gliadin-specific IFN-γ-secreting CD4⁺ T cells increased significantly on day 6 of the first challenge. These cells resulted as prevalently human leucocyte antigen (HLA)-DQ restricted and with a phenotype of gut homing, as suggested by the expression of β7-integrin. Similarly, reactiveness to gliadin was observed after the second wheat consumption, although with an individual variability of responses at each challenge. Our findings confirmed that the short wheat challenge is a non-invasive approach to investigate the gluten-related immune response in peripheral blood of subjects intolerant to gluten. Furthermore, we demonstrated that the in-vivo procedure can be reproduced in the same subject cohort after a gluten wash-out of at least 3 months. Our study has important implications for the application of this procedure to clinical practice.

Abstract: In celiac disease (CD), abnormal immune-mediated responses follow ingestion of gluten. Although the triggering agent is a dietary protein, the disease has autoimmune components because of the presence of autoantibodies and its association with autoimmune conditions. We review the most recent studies on CD pathogenesis and the possibilities to modulate immune dysfunction in CD.