Effect of IL-18 on DC2 phenotype. (A-E) FACS surface analysis of DC2s and IL-18–DC2s. DC2s were obtained by culture of pre-DC2s with IL-3 (DC2) or IL-3 plus IL-18 (IL-18–DC2) for 3 days, and stained with indicated antibodies. Surface expression on DC2s is compared with IL-18–DC2s. (F) IL-27, IL-23, and IL-12 mRNA expression in DC1s and DC2s. DC1s were obtained by culture of monocytes for 6 days in the presence of IL-4 and GM-CSF (DC1) and further stimulated with LPS (1 μg/mL) and CD40L-expressing irradiated P3 × TBA7 cells (+CD40L) as indicated. DC2s were derived from plasmacytoid DCs by culture with IL-3 (DC2), or IL-3 plus IL-18 (IL-18–DC2) for 3 days, and further matured as indicated by addition of CD40L-expressing irradiated P3 × TBA7 cells (+ CD40L). Messenger RNA expression of IL-27 (consisting of p28 and EBI3 chains), IL-23 (p19 and IL-12 p40), and IL-12 (p35 and p40) was analyzed by PCR as outlined in “Materials and methods.” Control amplification was performed for β-actin. This figure is representative of 4 independent experiments.