Rheumatoid factors and HLA-DR4 in RA.

The levels of serum rheumatoid factors (RF) and the in vitro production of immunoglobulin were studied in 21 patients with rheumatoid arthritis (RA) and compared to the in vitro responses of 20 controls. In RA patients the levels of serum IgM RF and IgG RF were not significantly increased in patients possessing HLA-DR4 or any other DR antigen. Lymphocytes from seropositive RA patients released measurable quantities of IgM RF spontaneously, greatest in those possessing HLA-DR4. When lymphocytes were treated with either pokeweed mitogen or the T cell mitogen derived from Mycoplasma arthritidis the increased production of IgM RF was not related to HLA-DR4 status, either for RA patients or controls. Seronegative RA lymphocytes, while having similar IgM RF responses to controls, differed in having IgG RF in their serum.