IL-21-induced IgE secretion by human B cells is STAT3-dependent. (A) PB B cells from 5 healthy donors (●) and 5 HIES patients with heterozygous STAT3 mutations (○) were cultured (∼ 20 × 103 cells/200 μL per well) in quadruplicate with CD40L, CD40L/IL-4 (100 U/mL), CD40L/IL-21 (50 ng/mL), or CD40L/IL-4/IL-21 for 10 to 12 days. Each point represents IgE secretion by an individual normal donor or HIES patient; the gray column represents the mean. ***P = .001 (unpaired Student t test). (B,C) B cells from 2 donors (◇,○) and 2 HIES patients (■,▴) were cultured with CD40L and increasing concentrations of IL-21 (0-100 ng/mL) in the absence (B) or presence (C) of IL-4 (100 U/mL). IgE secretion was determined after 12 days. Note the different scales of the y-axes in panels B and C.
