T cell regulation of in vitro IgM-rheumatoid factor production by normal human B cells. Differential effects of stimulation with immobilized monoclonal antibodies to CD3 and Staphylococcus aureus.

The roles of T cells in in vitro IgM-RF production were examined utilizing two different polyclonal B cell stimulators, Staphylococcus aureus Cowan I (SA) and immobilized mAb to the CD3 molecular complexes (64.1). In cultures stimulated with SA, T4 cells alone but not T8 cells alone could support IgM-RF production. This function of T4 cells could be replaced by IL2 alone or factors generated from mitogen activated T cells (TF). Moreover, when IL2 was supplemented to the cultures, T8 cells as well as T4 cells enhanced the IgM-RF production. Treatment of the T cell subsets with mitomycin C decreased or abrogated the helper function along with a decrease in IL2 production by the T cell subsets in SA stimulated cultures. By contrast, in cultures stimulated with immobilized anti-CD3, T4 cells that had been treated with mitomycin C could induce production of large amounts of IgM-RF, whereas control T4 cells as well as control T8 cells suppressed IgM-RF production. These results indicate that the regulatory functions of T cells in IgM-RF production might be different depending upon the nature of stimulation signals.