Differences in baseline TGF-α levels are not related to differences in ADAM17 expression between groups. PBECs were cultured and seeded in duplicates. Cultures were growth factor-deprived overnight and directly harvested for total cell lysates or incubated for 24 hrs with and without 5% CSE. A) ADAM17 and actin were detected by western blotting in PBECs from non-smokers (n = 4), healthy smokers (n = 3) and COPD patients (n = 4) as indicated by arrows. B) Densitometry was performed and levels were related to actin levels. The ADAM17/actin ratios and medians are depicted. Significance is indicated (* = p < 0.05). C) TIMP-3 levels are not different between groups. Absolute values and medians are shown.