HLA-DR3 is composed of the HLA-DR17 and HLA-DR18 split 'antigens' serotypes. DR3 is a component gene-allele of the AH8.1 haplotype in Northern and Western Europeans. Genes between B8 and DR3 on this haplotype are frequently associated with autoimmune disease. Type 1 diabetes mellitus is strongly associated with HLA-DR3 or HLA-DR4.
Some DR3 also react with HLA-DR17 and/or HLA-DR18. The DRB1*0304 primarily reacts with DR3. The serotypes of *0305, *0306, *0308 to *0331 are unknown.
HLA-DR3 is associated with early-age onset myasthenia gravis, Hashimoto's thyroiditis (along with DR5), primary sclerosing cholangitis, and opportunistic infections in AIDS, but lowered risk for cancers.
DRB1*0301 (see HLA-DR17)
DRB1*0302 (See HLA-DR18)
DRB1*0304 is associated with graves disease
DR3 and/or DQ2 is associated with Moreen's ulceration, "bout onset" multiple sclerosis, Grave's disease and systemic lupus erythematosus
DR3-DQ2 linkage is associated with coeliac disease, dermatitis herpetiformis, Diabetes mellitus type 1. DR3-DR2 is the serological marker for HLA-DQ2.5cis isoform. Although it cannot identify the alpha ".5" chain of HLA DQ, DQA1*0501 gene is almost always found within the DR3-DQ2 haplotype Eurasia (however is older studies DQA1*0505 is commonly confused with DQA1*0501)
DR3 is genetically linked to HLA-DR52, DRB3*0202 allele, and HLA-DQ2 (DQ2.5).