RA stimulates memory B cells via RARs. (A) CD27+ B cells (0.5 × 106/mL) were stimulated with CpG (1 μg/mL) in the presence or absence of RA, Am580 (AM), TTNPB (TT), or SR-11217 (SR) (all 100 nM) for 72 hours, and thymidine incorporation was determined. The data represent mean cpm ± SD of triplicates from 1 representative experiment of 3. (B) CD27+ B cells (0.5 × 106/mL) were stimulated with CpG (1 μg/mL) in the presence or absence of RA (1 nM). Where indicated, cells were pretreated with Ro 41-5253 (500 nM) for 30 minutes prior to stimulation, and thymidine incorporation was determined after 3 days. The data represent mean cpm ± SD of triplicates from 1 representative experiment of 3. (C) CD27+ B cells (1 × 106/mL) were stimulated with CpG (1 μg/mL) in the presence or absence of RA (1 nM or 100 nM) for 24 hours. Where indicated, cells were pretreated with Ro 41-5253 (500 nM) for 30 minutes prior to stimulation. Total-cell extracts were subjected to Western blot analysis and examined for cyclin D3 expression. One representative experiment is shown. (D) Cells were cultured as in panel B with or without RA (1 or 100 nM). At day 3, cell supernatants were harvested and subjected to ELISA for determination of IgG. The results represent mean IgG ± SD of duplicates of 1 representative experiment. Ro indicates Ro 41-5253.
