A T cell activity that enhances polyclonal IgE production and its inhibition by interferon-gamma.

The addition of concanavalin A-stimulated supernatants of the helper T cell clone, D9.1, to cultures of lipopolysaccharide (LPS)-stimulated T-depleted mouse spleen cells caused more than a 100-fold increase in immunoglobulin (Ig) E production. These supernatants cause a 10-fold to 15-fold increase in IgG1, a fivefold to 10-fold increase in IgA, and a fivefold to 10-fold decrease in IgG3. These effects are optimal when the supernatants are added 1 to 2 days after stimulation with LPS. Cells from mouse strains that normally give little or no IgE response in vivo give normal IgE levels in response to LPS plus the supernatant of Concanavalin A-stimulated D9.1 cells in vitro. The enhancement of both IgE and IgG1 can be completely inhibited by relatively low concentrations of interferon-gamma (IFN-gamma). Both the IgE-enhancing activity and IFN-gamma act directly upon purified B cells.