IL-10 does not enhance mRNA degradation. (A) Monocytes were stimulated for 24 hours with IFN-γ (100 U/mL) in the presence or absence of IL-10 (100 U/mL). Actinomycin D (5 μg/mL) was added to the cells, and RNA was extracted at 0, 1, 2, and 3 hours. Northern blot analysis was performed. (B) Induced levels of ICAM-1 mRNA at time zero were determined by densitometry for IFN-γ and IFN-γ plus IL-10. The values were set at 100% and plotted against the percent reduction in the amount of mRNA. The RNA half-life measured the time at which mRNA declined by 50%. Data are representative of 3 experiments.