DR3 is a component gene-allele of the AH8.1 haplotype in Northern and Western Europeans.
Nearly half the US population has either DR3 or DR4 (only 1–3% have both), yet only a small percentage (about 0.5%) of these individuals will develop type 1 diabetes.
HLA-DR3 is associated with early-age onset myasthenia gravis, Hashimoto's thyroiditis (along with DR5), primary sclerosing cholangitis,[2] and opportunistic infections in AIDS,[3] but lowered risk for cancers.
[4] It is also associated with membranous glomerulonephritis[5] DRB1*03:01 (see HLA-DR17) DRB1*03:02 (See HLA-DR18) DRB1*03:04 is associated with Graves disease[6] DR3 and/or DQ2 is associated with Moreen's ulceration,[7] "bout onset" multiple sclerosis,[8] Graves' disease[9] and systemic lupus erythematosus[10] DR3-DQ2 linkage is associated with coeliac disease, dermatitis herpetiformis, Diabetes mellitus type 1.
Although it cannot identify the alpha ".5" chain of HLA DQ, DQA1*05:01 gene is almost always found within the DR3-DQ2 haplotype Eurasia (however in older studies DQA1*05:05 is commonly confused with DQA1*05:01)[11] DR3 is genetically linked to HLA-DR52, DRB3*02:02 allele, and HLA-DQ2 (DQ2.5).