TCF3 mutations affect in vitro plasmablast differentiation and immunoglobulin production. (A and B) PBMCs were stimulated with CD40L (100 ng/ml) and IL-21(100 ng/ml) for 5 days. (A) Plasmablast frequency in healthy controls (HC), haploinsufficient (HI, monoallelic LOF), Null (biallelic LOF), and dominant negative (DN, monoallelic DN) individuals was determined by the percentage of CD27+CD38+ cells from total CD19+ B cells. (B) Concentration (ng/ml) of immunoglobulin production in the cell culture supernatant post CD40L and IL-21 stimulation determined by ELISA. (A and B) Bars show mean ± SEM of the average of two independent experiments with individuals represented by unique symbols as indicated.