Lymphokine control of type 2 antigen response. IL-10 inhibits IL-5- but not IL-2-induced Ig secretion by T cell-independent antigens.

A supernatant derived from the Th2 clone D10.G4.1 (D10 supernatant) stimulated high numbers of Ig-secreting cells when added to dextran-conjugated anti-delta-antibody (anti-delta-dextran)-activated B cells but stimulated only marginal Ag-specific responses when added to B cells cultured with TNP-Ficoll. When anti-IL-10 antibody was added to cultures containing D10 supernatant, IL-5, and TNP-Ficoll, there was a significant increase in the numbers of anti-TNP-antibody producing cells, suggesting that at least a part of the inhibitory activity of D10 supernatant is mediated by IL-10. Addition of rIL-10 inhibited both TNP-Ficoll- and anti-delta-dextran-mediated Ig secretion that was stimulated in the presence of IL-5 but had no suppressive effect on IL-2-stimulated responses, indicating that its inhibitory effect was selective for a specific mode of B cell activation. Addition of IL-10 did not, however, inhibit anti-delta-dextran-stimulated B cell proliferation. The IL-10-induced-inhibition of Ig secretion was not due to suppression of IFN-gamma production, because the addition of IFN-gamma did not reverse the inhibition, nor did the addition of anti-IFN-gamma mimic the IL-10-mediated inhibition. These data suggest that a composite of lymphokines secreted by Th cells may contain both inhibitory and stimulatory activities. Sorting out the conditions under which stimulation or inhibition is seen may reveal additional diversity in Ag-stimulated pathways of B cell activation.