EBNA2 induces IL-18Rα expression in BL cells. (A) RT-PCR for IL-18Rα and the housekeeping gene, HPRT, in BL2, BL2-B95, BL2-P3, BL41, BL41-B95, BL41-P3, and KG-1 cells. (B) Flow cytometric analysis of IL-18Rα expression in BL2, BL2-B95, BL41, BL41-B95, and KG-1 cells. Cells were reacted with a mouse monoclonal antibody to IL-18Rα (filled histogram) or an isotype-matched control antibody (open histogram), followed by an FITC-labeled secondary antibody. (C) RT-PCR for IL-18Rα and HPRT in BL41 and BL41-P3 cells transfected with expression plasmids for EBNA2, LMP1, or the EBNA2-mutant WW323SR, as indicated. (D) BL2 cells, transiently transfected with an expression plasmid for EBNA2, were reacted 48 hours after transfection with a phycoerythrin-labeled mouse monoclonal antibody to IL-18Rα. Micrograph shows phase contrast and red fluorescence.