Induction of CD25 in BDCA-1⁺ myeloid DCs. (A) Flow cytometry was performed after 18 hours of culture to assess cell-surface expression of CD1c, CD83, CD25 (x-axis), and HLA-DR (y-axis). At least 3 experiments were performed for each of the conditions; one representative experiment is shown. Percentage of events within the top right quadrant is stated. Greater than 99% of events in controls (cells labeled with isotype control antibodies) were within the bottom left quadrant. (B) Soluble CD25 was assessed by ELISA in cell culture supernatants from BDCA-1⁺ DCs after 18 hours. Black bars represent PGE2-treated DCs; mean ± standard deviation of 2 independent experiments is shown. Background sCD25 level in these experiments was 200 pg/mL.