HLA-DR3
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 associated with HLA-DR3 or HLA-DR4. Nearly half the US population has either DR3 or DR4, yet only a small percentage of these individuals will develop type 1 diabetes.
Serology
Some DR3 also react with HLA-DR17 and/or HLA-DR18. The DRB1*03:04 primarily reacts with DR3. The serotypes of *03:05, *03:06, *03:08 to *03:31 are unknown.Disease associations
By serotype
HLA-DR3 is associated with early-age onset myasthenia gravis, Hashimoto's thyroiditis, primary sclerosing cholangitis, and opportunistic infections in AIDS, but lowered risk for cancers. It is also associated with membranous glomerulonephritisBy allele
DRB1*03:01DRB1*03:02
DRB1*03:04 is associated with Graves disease
By haplotypes
DR3 and/or DQ2 is associated with Moreen's ulceration, "bout onset" multiple sclerosis, Graves' disease and systemic lupus erythematosusDR3-DQ2 linkage is associated with coeliac disease, dermatitis herpetiformis, Diabetes mellitus type 1. DR3-DQ2 is the serological marker for HLA-DQ2.5cis isoform. 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