IL-4 down-regulates protease-activated receptor mRNA expression in monocyte-derived human macrophages. (A) RT-PCR analysis shows PAR mRNA expression in macrophages treated with 25 ng/mL IL-4 for 1, 2, or 4 days. (B) Semiquantitative analysis of the mRNA expression. PAR mRNA was normalized to GAPDH mRNA. PAR1 expression was set to 100% in each experiment. Results are mean ± SEM of 3 independent experiments. (C) Flow cytometric analysis of PARs on macrophages treated with 25 ng/mL of IL-4 for 1, 2, or 4 days. CD68 was used as macrophage-specific marker. Nonshaded peaks represent cells stained with isotype-matched control antibodies. Results of 1 of 3 independent experiments are shown.