Induction of IL-18BP by IFN-γ is at the transcriptional level and depends on de novo protein synthesis. (A) Semiquantitative RT-PCR of IL-18BP mRNA from Hep G2 cells that were preincubated with actinomycin D (Act. D, 1 μg/ml, 30 min), washed, and incubated with IFN-γ (100 units/ml) for the indicated times. RT-PCR of β-actin mRNA is shown as a control. (B) Semiquantitative RT-PCR of IL-18BP mRNA from Hep G2 cells that were preincubated with cycloheximide (CHX, 20 μg/ml) and IFN-γ (100 units/ml) for the indicated times.