Comparative ability of PMN and PBMC to express HB-EGF mRNA when stimulated with GM-CSF. GM-CSF induced HB-EGF transcripts in PMN and, more dramatically, in PBMC, while LPS, which upregulated IL-1ra in PMN and IL-6 in PBMC, was ineffective on HB-EGF mRNA production. PBMC presented also a costitutive, low production of HB-EGF mRNA. Purified populations of PMN and PBMC from the same donor were cultured with or without 25 ng/mL GM-CSF and 100 ng/mL LPS for 2 hours and then total RNA was extracted and Northern blot analysis for HB-EGF, IL-1ra, IL-6, and actin mRNA was performed. Ten micrograms of total RNA was loaded on each gel lane. The experiment depicted is representative of 4.