IL-21 inhibits IL-4–induced IgE but not IgG1 production from splenic B cells.

Purified splenic B cells from BALB/c mice were stimulated with LPS (10 μg/mL) in the presence of IL-4 (50 ng/mL) or indicated amounts of IL-21 (0-20 ng/mL) or both for 7 days. IgE (A), IgG1 (B), and IgG2a (C) levels in the supernatant of the culture were determined by ELISA. Data are mean ± SD from 5 independent experiments. Single and double asterisks indicate significantly different from the mean value of the corresponding response in the absence of IL-21,P < .01 and P < .001, respectively.