OSM mRNA expression in human PMN. PMN (5 × 10⁷) were cultured for up to 18 hours in the presence of LPS (100 ng/mL) plus GM-CSF (100 U/mL) (right panel). In other experiments, PMN were cultured for 1 hour in the presence of LPS and/or GM-CSF, PMA (100 ng/mL), or in medium alone (control) (left panel). Total RNA was extracted and Northern blots of OSM and GAPDH were run as specified in Materials and Methods.