HLA-DR3 is a set of serotypes that recognize the gene products of four HLA-DRB1 alleles: DRB1*0301, *0302, *0303 and *0304.
According to Wikipedia's HLA-DR3 page, (edited 2017), HLA-DR3 is composed of the HLA-DR17 and HLA-DR18 split 'antigens' serotypes. (The immune system is capable of discerning a cell as being 'self' or 'non-self' according to that cell's serotype. In humans, that serotype is largely determined by human leukocyte antigen HLA system, the human version of the major histocompatibility complex.)
- According to Wikipedia's HLA-DR17 page, (edited 2016), HLA-DR17 (DR17) is an HLA-DR serotype that recognizes the DRB1*0301 and *0304 gene products. DR17 is found at high frequency in Western Europe (such as Western Ireland, N. Spain, Sardinia).
- According to Wikipedia's HLA-DR18 page, (edited 2016), HLA-DR18 (DR18) is a HLA-DR serotype that recognizes the DRB1*0302 and *0303 gene products. Compared to DR17 which is found at high frequency in Western Europe, DR18 is found more in SE Europe and Central Asia.
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. DRB1*0304 is associated with Graves' disease. 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. It is also associated with Membranous glomerularnephritis.
DR3 is genetically linked to HLA-DR52, DRB3*0202 allele, and HLA-DQ2 (DQ2.5).
For a list of SNPs, see the HLA-DRB1 page.