Anti-transglutaminase antibodies antigen, presented by MHC molecules (HLA in humans) on antigen-reactive B-cells. These T-helper cells then stimulate B-cells to multiply and mature into plasma cells that make IgA and IgG to that protein. In the case of celiac disease, the current understanding is that tTG autoimmunity arises when T-cells are generated against wheat gliadin and similar gluten proteins made by a class of grasses called "Triticeae", which includes wheat (See Wheat taxonomy), barley, and rye. The T-cells are defined by the ability to react to HLA-DQ8 and DQ2.5 restricted antigens and gliadin is one of the antigens. Gliadin is a favored
Anti-gliadin antibodies in food products. Some of these antibodies can recognize only wheat prolamins or very closely related grass seeds; others can detect antigens over broad taxa. The G12 antibody is the newest example which detects the most immunotoxic fragment, a 33-mer peptide from �-2 gliadin; available from Romer Laboratories and the Spanish company Biomedal. It recognizes the toxic fraction of wheat, barley, rye and also of oat. The R5 sandwich assay is another such assay. This assay can recognize wheat, barley and rye, which makes it ideal for evaluating the presence of contaminants in gluten-free foods that do not contain oat.