HLA-DR4 antigen and IgM rheumatoid factors.

To investigate the possible relation between the DR4 antigen and IgM rheumatoid factors (RF). 80 patients with rheumatoid arthritis were tested for 7 HLA-DR antigens and 38 HLA-A, B, C antigens, and compared with 66 normal controls. The DR4 antigen prevalence was 48.7% in the patients and 12.1% in the controls (p less than 0.001). Studying the relationship between the HLA-DR4 antigen and IgM, the genetic marker was present in 89.7% of 51 seropositive patients and in 39% of 29 seronegatives (p less than 0.00001). On the other hand we discovered a positive association between HLA-DR3 and antinuclear antibodies (p less than 0.01). These results suggest the existence of immune response genes in the major histocompatibility complex of humans.