B cell sIgG1 expression induced by BCR and CD38 ligation is increased by RA. B cells were cultured for 5 days as described in Fig. 4. At the end of culture, cells were stained with a PerCP-labeled anti-IgG1 antibody and subjected to flow cytometric analysis. (A) Graphs showing the percentage of sIgG1-positive cells after BCR and CD38 ligation (1 μg/ml), with and without RA (10 nM). (B) Graphs showing that the majority of IgG1-positive cells were located in sectors III, IV, and V, and RA increased the percentage of IgG1-positive cells in each sector. Anti-μ was used as stimulus in the experiment shown. The dashed line illustrates the isotype control. (C and D) Charts summarizing the data for each sector and treatment. *, P < 0.05.