Effect of LPS pretreatment on IL-12p40 mRNA expression. RT-PCR analysis of IL-12p40 in monocytes stimulated with and without prior exposure to LPS for 24 hours. Cells were harvested 5 hours after the stimulation procedure. Relative quantities of RT-PCR signal for p40 as determined by PCR-ELISA followed by normalization to β-actin are shown. Results are given as box plots with vertical lines displaying the 10th and 90th percentile. Horizontal lines show the median of the results of 10 independent experiments. For statistical analysis, the Mann-Whitney Rank Sum Test was performed. A representative kinetic experiment shows IL-12p40 mRNA, which was harvested at different time points between 2 hours to 48 hours after the stimulation procedure.