Oat Sensitivity - Avenin-sensitive Enteropathy - Immunological Evidence - Cellular Immunity

Cellular Immunity

In gluten-sensitive enteropathy, prolamins mediate between T-cells and antigen presenting cells, whereas anti-transglutaminase antibodies confer autoimmunity via covalent attachment to gliadin. In 16 examined coeliacs, none produced a significant Th1 response. Th1 responses are needed to stimulate T-helper cells that mediate disease. This could indicate that coeliac disease does not directly involve avenin or that the sample size was too small to detect the occasional responder.

Evidence that there are exceptional cases came in a 2004 study on oats. The patients drafted for this study were those who had symptoms of celiac disease when on a 'pure-oat' challenge, therefore not representative of a celiac sample. This study found that 4 patients had symptoms after oat ingestion, 3 had elevated Marsh scores for histology, and avenin responsive T-cells, indicating avenin-sensitive enteropathy(ASE). All three patients were DQ2.5/DQ2 (HLA DR3-DQ2/DR7-DQ2) phenotype. Patients with DQ2.5/DQ2.2 tend to be the most prone toward gluten sensitive enteropathy (GSE), have the highest risk for GS-EATL, and shows signs of more severe disease at diagnosis. While DQ2.5/DQ2 phenotype represents only 25% of celiac patients, it accounts for all of the ASE celiacs, and 60-70% of patients with GS-EATL. Synthetic avenin peptides were synthesized either in native or deamidated form, the deamidated peptides showed higher response.

DQ2.5/T-cell receptor recognition from 2 Oat-sensitive coeliacs TCR-Site1 Y Q P Y P E Q E~E~P F V TCR-Site2 Q Y Q P Y P E Q Q Q P F V Q Q Q Q Antibody recognition site(see above) CIP2 (γ-avenin) T T T V Q Y D P S E Q Y Q P Y P E Q Q Q P F V Q Q Q P P F

The overlap of the antibody and T-cell sites, given trypsin digestion of avenin, suggest this region is dominant in immunity. The TCR-site1 was synthetically made as deamidated ("~E~") and native peptide requires transglutaminase to reach full activation. Two studies to date have looked at the ability for different oat-strains to promote various immunochemical aspects of celiac disease. While preliminary these studies indicate different strains may have different risk for avenin-sensitivity

Read more about this topic:  Oat Sensitivity, Avenin-sensitive Enteropathy, Immunological Evidence

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