Celiac disease, HLA and evolution
Juan-Ignacio Serrano Vela
Coeliac disease is a lifelong intolerance to gluten affecting genetically predisposed individuals. HLA genes are the main genetic factors, and the risk variants coding for the proteins HLA-DQ2 and HLA-DQ8 are necessary for the development of the disease. Although these variants are present in 30% of the general population, the prevalence of the disease is around 1%. Thus, other genetic as well as environmental factors are involved. Gluten is the storage protein found in wheat, barley, rye and oats. Undigested gluten peptides are the triggers of an abnormal immune response in the small intestine, characterized by a chronic inflammation and autoimmunity. Villous atrophy in the duodenum, or even milder intestinal lesions, are key features of the disease, but other associated conditions can also occur. Gluten consumption has extended worldwide since mankind started wheat cultivation around 10,000 years ago. The prevalence of coeliac disease has also increased over time, especially during the 20th century, in parallel with the gluten enrichment of wheat as a result of crossbreeding programs and the use of gluten in the food industry. The evolutionary role of HLA risk variants is yet to be solved.