involved in idiopathic gluten sensitivity (See:Understanding DQ Haplotypes and DQ isoforms on the right). HLA-DQ2 primarily presents gliadins with the HLA-DQ isoform DQ2.5 (DQ α5-β2) isoform. DQA1*0202:DQB1*0201 homozygotes (DQ α2-β2) also appear to be able to present pathogenic gliadin peptides, but a smaller set with lower binding affinity. DQ2.5 and α-gliadin Many of these gliadin motifs are substrates for tissue transglutaminase and therefore can be modified by deamidation in the gut to create more inflammatory peptides. The most important recognition appears to be directed toward the α-/β-gliadins. An example of the repetition of a motif across many proteins, the α-2 gliadin (57-68) and (62-75) are also found on α-4, α-9 gliadin. Many gliadins contain the "α-20 motif", which is found in wheat and other Triticeae genera.(see also: "α-20" gliadin motifs). Alpha-2 secalin, the glutinous protein in rye, is composed of two amino-terminal overlapping T-cell sites at positions (8-19) and (13-23). A2-gliadin Although T-cell responses to many prolamins can be found in coeliac disease, one particular gliadin, α2-gliadin appears to be the focus of T-cells. These responses were dependent on prior treatment with tissue transglutaminase. Α2-gliadin differs from the other α-gliadins, specifically because it contains an insert of 14 amino acids. This particular insertion creates six T-cell sites where, in the most similar gliadins, there are two or fewer sites. The sites belong to three epitope groups "α-I", "α-II", and "α-III" The insertion also creates a larger region of α-gliadin that is resistant to gastrointestinal proteases. The smallest digest of trypsin and chymotrypsin for the region is a 33mer. This particular region has three tissue transglutaminase sites, two sites that lie within the 14 amino acid insertion, a region of maximal stimulation are found with more than 80% reduction in response for native, un-deaminated, sequence at the position. Because of the density of T-cell sites on the "33mer" the affinity for deamidated gliadin is strongly indicates that it may be best treated as a single T-cell site of much higher affinity. This site alone may fulfill all the T-helper cell adaptive immune requirements with HLA-DQ2.5 involvement in some coeliac disease. DQ2.5 and γ-gliadin While gamma gliadin is not as important to DQ2.5 mediated disease as α-2 gliadin there are a number of identified motifs. The gamma epitopes identified are DQ2-"γ-I", -"γ-II" (γ30), -"γ-III", -"γ-IV", -"γ-VI" and -"γ-VII" Some of these epitopes are recognized in children who do not have T-cell reactivities