HLA-DR antigens and HLA-DQ beta chain polymorphism in susceptibility to rheumatoid arthritis.

Forty four patients with rheumatoid arthritis (RA) were studied for HLA-DR antigens and for HLA-DQ beta chain gene restriction fragment length polymorphism using DNA hybridisation. A significant increase in the prevalence of the DR4 antigen and a tendency towards an increase of DR1 was found in patients with RA. No allelic form of HLA-DQ restriction fragment length polymorphism patterns was increased, but the prevalence of an allele characterised by a combination of 7.5 and 3 kb fragments was decreased among patients with RA. The DQw8 subtype represented by a 12 kb fragment was the most common DR4 associated allele, and a 3.7 kb fragment related to DQw7 was found in only 5/25 (20%) DR4 positive patients and 2/12 (17%) controls. The results support the hypothesis that RA susceptibility factors are primarily located within HLA-DR genes but HLA-DQ genes may have a role in protection from the disease.