IL-18R expression in DC2 lineage. (A-H) FACS surface analysis. IL-18Rα surface expression on pre-DC2s (eg, plasmacytoid DCs) (panel A). Identity and purity of pre-DC2s as determined by IL-3Rα (CD123) (panel B) and HLA-DR (panel C) expression. Pre-DC2s were negative for lineage markers (not shown). IL-12Rβ1 (panel D) and IL-12Rβ2 (panel E) expression on pre-DC2s. IL-18Rα surface expression on DC2s (panel F), pre-DC1s (panel G), and DC1s (panel H). Solid lines indicate the specific antibodies, and dotted lines indicate isotype-matched immunoglobulin controls. (I) PCR analysis of IL-18Rα and IL-18Rβ chain on DC1 and DC2 lineage, and Th1-polarized cells (positive control). An IL-18Rα fragment spanning nucleotides 833 to 1523 was amplified in DC2 lineage as a 690-bp band. Please note that in pre-DC2s, in addition to the expected band, another smaller band was reproducibly coamplified. Nucleotides 940 to 1589 of IL-18Rβ chain were amplified in DC2 lineage and in pre-DC1s, resulting in a band at 649 bp. As a positive control for IL-18Rα and IL-18Rβ, mRNA was obtained on day 6 of coculture of naive Th cells with DC1s, at which time Th cells abundantly express surface IL-18Rα as determined by FACS analysis (data not shown). Control amplification was performed for β-actin.