Clinical features, autoantibodies and HLA-DR antigens in rheumatoid arthritis.

HLA-DR4 was associated with seropositive but not seronegative disease in 105 Caucasians with rheumatoid arthritis (RA). There were no clinical or radiological differences between DR4 positive and negative RA groups, although 7 of 8 patients with early disease onset (less than 30 yr) were DR4 positive. High rheumatoid factor (RF) titers were more frequent in DR4 negative RA. A plot of the frequency distribution of RF titers in DR4 negative disease showed a bimodal distribution with seronegative and high titer groups. HLA-DR3 was not associated with high RF titers but was associated with high titers of antinuclear antibodies.