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 "generally recognized as safe" (GRAS). In August 2013, the FDA issued a final ruling, effective August 2014, that defined the term "gluten-free" for voluntary use in the labeling of foods as meaning that the amount of gluten contained in the food is below 20 parts per million. Gluten Gluten (from Latin "gluten", "glue") is a composite of storage proteins termed prolamins and glutelins that is stored together with starch in the endosperm (which nourishes the embryonic plant during germination) of various cereal (grass) grains. It is found in wheat, barley, rye, oats and related species and hybrids (such as spelt,