When age, gender, and oral corticosteroid use were controlled for, a significant increase in furin expression was observed in sputum samples from those with severe asthma who didn't smoke versus those who had mild-to-moderate asthma and the healthy volunteer controls. A significant increase in furin expression was observed in those with severe asthma who smoke versus the healthy control volunteers. Expression level in the bronchial biopsies were similar regardless of the severity of asthma.

Abbreviations used in the figure:

• SA: severe asthma
• ns: nonsmoker
• s: smoker
• MMA: mild-to-moderate asthma
• HV: healthy volunteer