RA enhances the secretion of IL-10 from CD27⁺ B cells. (A) CD27⁺ B cells (0.5 × 10⁶/mL) were cultured with CpG (1 μg/mL) in the presence or absence of RA (100 nM). At indicated days, cell supernatants were harvested and subjected to ELISA for determination of IL-10. The results represent mean ± SEM. (*P < .05, paired sample t test; n = 7). (B) CD27⁺ B cells were cultured with CpG (1 μg/mL) with or without RA (100 nM) in the presence or absence of anti–IL-10 antibody (0.5 μg/mL, α–IL-10) or control Ig antibody (0.5 μg/mL, Ig). Supernatants were harvested at day 3 and subjected to ELISA specific for IgG. The results represent mean ± SEM of 4 independent experiments.