HLA DQ2 DQ8

About HLA DQ2 DQ8

HLA DQ2 and HLA DQ8 are MHC class II molecules, encoded by combinations of the DQA1 and DQB1 genes in the HLA region on chromosome 6p21.32, that present peptides to CD4 T cells. They are central to the development of celiac disease because their peptide binding grooves bind gluten derived peptides especially well after these peptides have been modified by the enzyme tissue transglutaminase, which converts glutamine residues to glutamate. Presentation of these peptides activates gluten specific T cells in the lining of the small intestine, leading to inflammation, villous atrophy, and production of antibodies against tissue transglutaminase. About 95 percent of people with celiac disease carry HLA DQ2, mostly the DQ2.5 form encoded by DQA1 05 and DQB1 02, and most of the rest carry HLA DQ8, encoded by DQA1 03 and DQB1 0302. These HLA types are common in the general population, but only a small fraction of carriers develop celiac disease, showing that they are necessary but not sufficient. As a result, HLA DQ typing is mainly useful for excluding celiac disease, since its absence makes the disease very unlikely, which can help when antibody testing is unreliable. The DQ2 and DQ8 haplotypes are also strongly associated with type 1 diabetes, especially in people carrying both, and with other autoimmune conditions.