Dose-dependent suppression of p40 and p35 mRNA expression by LPS pretreatment. Human monocytes were preincubated with varying concentrations of LPS before stimulation with IFN-γ/LPS for 5 hours. Amplified cDNA fragments for β-actin, p40, and p35 were resolved on a 2% agarose gel and visualized by ethidium bromide. The amplified cDNA fragments had the expected lengths of 290 bp for p40, 414 bp for p35, and 225 bp for β-actin.