Effects of LPS or PTXL pretreatment on the mRNA expression for IL-12p40 and p35 in human monocytes. Human monocytes were preincubated with LPS (50 ng/mL) or PTXL (10 μmol/L) for 24 hours before stimulation with IFN-γ/LPS. Five hours after the stimulation procedure, mRNA was isolated and expression of p40, p35, and β-actin was determined by RT-PCR. The resulting cDNA fragments 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. One representative of 5 independent experiments is shown.