Abstract: The concept that rheumatoid arthritis (RA) is an autoimmune disease is supported by variety of autoantibodies in patient's serum. The most important of these are rheumatoid factors (RFs), antibodies that react with the patient's own Ig. It has been suggested that IgM-RF plays a role in disease pathogenesis. The main source of IgM-RF are B cells that express the pan T-cell marker, CDS: We conducted this study to test the ...