Serum effects of mitogenic reactivity in subjects with systemic lupus erythematosus, rheumatoid arthritis and scleroderma. Technical considerations and lack of correlation with anti-lymphocyte antibodies.

Methodological problems which affect the assessment of humoral effects on mitogenic reactivity include: (1) the source and concentration of serum used to support cell cultures; (2) the day to-day variability of inhibitory effects and (3) the specific activity of [3H]thymidine added to the culture. These problems were alleviated by addition of half concentration (7-5%) of pooled normal human serum to all cultures, the intoruction of anti-lymphocyte serum as a suitable internal control for monitoring the suppressability of lymphocytes and a reduction of specific activity of the [3H]thymidine to 1-3 C2/mM. Inhibitory factors were loosely bound to the lymphocyte surface and eluted off after incubation at 37 degrees C for 1 hr. Cells from twenty-five subjects and paired controls were cultured simultaneously in medium containing either 15% normal human serum (NHS) or 7-5% patient and 7-5% NHS. The cells were stimulated with various dilutions of phytohaemagglutinin, Con A or pokeweed mitogen. Lupus serums suppressed the reactivity of autologous lymphocytes to PHA and pokeweed mitogen. Serums from subjects with RA and scleroderma did not significantly inhibit blastogenesis of autologous lymphocytes. One-half of the lupus serums significantly inhibited the reactivity of homologous lymphocytes to two of three mitogens. Only one of eight scleroderma serums and none of twelve RA serums and none of twelve RA serums had this effect. All patients serums were examined for antilymphocyte antibodies by microcytotoxicity and immunofluorescent techniques. These antibodies were usually found in SLE, and were often observed in subjects with rheumatoid arthritis but not scleroderma. A firm relationship between serum suppressors of lymphocyte blastogenesis and anti-lymphocyte antibodies was not found.