What causes celiac disease?

Celiac disease is caused by an abnormal immune reaction to gluten. Consuming gluten triggers destruction of villi, tiny finger-like projections lining the small intestine that absorb nutrients from food. People who are genetically susceptible have particular variants of the genes encoding major histocompatibility complex (MHC) class II molecules, which play a role in the sensing of foreign proteins by the immune system. The MHC class II genes HLA-DQ2 or HLA-DQ8 bind to gluten-derived peptides, triggering the immune response that causes intestinal damage. Although HLA-DQ2 or HLA-DQ8 seem to be required to develop the disease, they are not sufficient, since only 1% of the population has celiac disease, in spite of 40% having HLA-DQ2 or HLA-DQ8.^[1]