HB-EGF mRNA levels in GM-CSF–treated PMN. (A) Time-course. PMN were incubated with 25 ng/mL GM-CSF. At the time-points indicated, total mRNA was extracted and analyzed for HB-EGF, IL-1ra, and actin mRNA expression. The experiment depicted is representative of 2. (B) Dose-dependence. PMN were stimulated with increasing doses of GM-CSF for 2 hours and then total RNA was extracted and analyzed for HB-EGF, IL-1ra, and actin mRNA expression. The experiment depicted is representative of 2.