IL-7 potentiation of IL-4–induced IgE synthesis is at least partly through sCD23 and IL-9. PBMCs were stimulated with IL-4 in the absence (□) or presence of 10 ng/mL IL-7 (▪) with or without neutralizing anti-CD23 MoAb (Mab 25), neutralizing goat anti–IL-9 IgG, control mouse IgG1, or control goat IgG. IgE was quantified in the day-12 supernatants. Results are expressed in percent of decrease as mean ± SD of four experiments.