Ongoing IgE Synthesis by Atopic B Cells Is Enhanced by Interleukin-3 and Suppressed Directly by Interferon-Gamma in vitro

Human recombinant interleukin-3 (rIL-3; 10 U/ml) consistently augmented spontaneous IgE synthesis by isolated atopic B cells in vitro, whereas rIL-4 (1-1,000 U/ml) failed to induce IgE synthesis by these cells. Recombinant interferon-gamma (rIFN-gamma) suppressed ongoing IgE production by atopic B cells in a dose-dependent manner. IFN-gamma also inhibited IgE synthesis by a human myeloma cell line (U-266), demonstrating the direct effect of IFN-gamma on the terminal differentiation of IgE-secreting plasma cells. IL-3 and IFN-gamma from different sources displayed the same effects on IgE synthesis. Neutralizing antibodies toward IL-3 or IFN-gamma abolished their activities toward IgE synthesis, supporting the specificity of the effect of these cytokines. The quantity of endogenous IFN-gamma produced by stimulated T cells was significantly decreased in atopic patients compared to nonatopic controls, which might be responsible for the propensity of a high blood IgE level in atopic patients.