HLADQ2

HLADQ2, often written HLA-DQ2, refers to a human leukocyte antigen (HLA) class II serotype and genetic risk factor most commonly discussed in relation to celiac disease. It is a cell-surface protein formed as a heterodimer from the DQA1 and DQB1 gene products. HLA-DQ2 participates in the immune system’s presentation of extracellular peptides to CD4+ T cells, enabling the adaptive immune response. The DQ2 heterodimer is encoded within the highly variable HLA region on chromosome 6 and shows extensive genetic diversity across individuals.

There are several functional variants of HLA-DQ2, with HLA-DQ2.5 (comprising DQA1*05:01 and DQB1*02:01) representing the best-known and strongest genetic risk factor for celiac disease. In the general population, HLA-DQ2 is carried by a substantial minority, estimates ranging from about 30 to 40 percent depending on ethnicity. However, carriage of HLA-DQ2 alone does not determine disease; most carriers do not develop celiac disease, highlighting the influence of additional genetic and environmental factors, such as gluten exposure.

Clinical significance and use in testing: HLA typing for DQ2 is often employed in the diagnostic workup of suspected celiac disease to help rule out the condition. If HLA-DQ2 is absent, celiac disease is highly unlikely, making the diagnosis less probable. Conversely, the presence of HLA-DQ2 (especially DQ2.5) indicates genetic susceptibility but is not diagnostic by itself and must be interpreted alongside serological tests and, if indicated, intestinal biopsy. HLA-DQ2 is also of interest in population genetics and immunogenetics research and is considered alongside related haplotypes such as HLA-DQ8.