HLA--Dw4 and rheumatoid arthritis.

Forty-seven patients with a "definite" or "classical" rheumatoid arthritis according to the ARA criteria were typed for the serologically detectable HLA--A, --B, and --C antigens and 36 of these patients were typed for the HLA--D antigens, Dw1, 2, 3, 4, 6, 7, and 8 by the MLC technique. The frequency of Dw4 was increased to 44.4% in the patients compared to 17.2% in normal controls (P = 8 X 10(-4)). The frequency of Dw1 and Dw7 was also increased although this was only of borderline significance. The frequency of Dw2 was remarkably low, especially in females, which is of interest, as the same antigen has a low frequency in some other autoimmune diseases. No significant deviations of the frequencies of HLA--A, --B, and --C antigens were found in rheumatoid arthritis patients.