Stability of OSM transcripts in LPS plus GM-CSF–treated PMN. PMN (5 × 10⁷) were incubated with LPS (100 ng/mL) plus GM-CSF (100 U/mL) for 1 hour and then actinomycin D (5 μg/mL) was added for the indicated times. Total RNA was extracted and Northern blot analysis of OSM and actin mRNAs was performed as indicated in Materials and Methods.