HLA DQ typing consists of two subunits of the DQ molecule, an alpha and beta subunit. So, both DQ types that indicate a risk of celiac disease, DQ2 and DQ8, are made up of two protein subunits designated alpha and beta. They determine the complex letter and number combinations reported. For example, the full DQ2 molecule is typically HLA DQA1*05xx DQB1*02xx. The A1 is the alpha unit and the B1 is the beta subunit.
The beta subunit is the most important component of the DQ molecule, but the alpha subunit has also been shown to carry an increased risk for celiac disease. Unfortunately, since testing for both is more complicated and expensive it is not always done.
Also, some think that since the beta subunit carries most of the risk and the alpha unit only minor risk, testing for only the beta subunit is adequate. Several clinical laboratories have chosen this approach. They only test for, and report on, DQ2 and DQ8 based on beta subunit types, so their results typically look like this: HLA DQB1*02 detected, DQ2 positive, etc. However, the alpha subunit of DQ2 also carries some risk for celiac disease.
Gluten sensitivity is found in all DQ types except DQ4. Other DQ types, particularly DQ1, DQ5, are associated with a risk of gluten related neurological and skin problems. Microscopic colitis, food allergies and oral allergy syndrome reactions are also found in association with other DQ types.
DQ2 and DQ8 also seem to carry a risk of mastocytic enterocolitis.
According to data accumulated, but as of February 2008, not yet published by Dr. Ken Fine, unless you are DQ4/DQ4 you are still at risk for being sensitive to or intolerant of gluten. According to Fine’s fecal gliadin antibody data all DQ types except for DQ4 carry a risk of gluten sensitivity.
The presence of one copy of DQ1, DQ3, DQ5, DQ6, DQ7, or DQ9, even with one DQ4, is associated with a risk for elevated stool gliadin antibody and symptoms of gluten sensitivity that responds to a gluten free diet.