Gluten immunochemistry in foods that have added gluten, such as wheat bread, food pastes. The major gluten proteins that are involved in coeliac disease are the α-gliadin isoforms. Alpha gliadin is composed of repeated motifs that, when digested, can be presented by HLA-DQ molecules. DQ2.5 recognizes several motifs in gluten proteins, and therefore HLA-DQ can recognize many motifs on each gliadin (see Understanding DQ haplotypes and DQ isoforms on the right) However, numbers of different proteins from the grass tribe Triticeae have been found to carry motifs presented by HLA DQ2.5 and DQ8. Wheat has a large number of these proteins because
Gluten immunochemistry include: LTP (albumin/globulin), thioredoxin-hB, and wheat flour peroxidase. A particular 5 residue peptide, Gln-Gln-Gln-Pro-Pro motif, has been found to be a major wheat allergen. New immunogenic motifs appear in the literature almost monthly and new gliadin and "Triticeae" protein sequences appear that contain these motifs. The HLA DQ2.5 restricted peptide "I I Q P Q Q P A Q" produced approximately 50 hits of identical sequences in NCBI-Blast search is one of a several dozen known motifs whereas only a small fraction of Triticeae gluten variants have been examined. For this reason the immunochemistry is best discussed at the level