We also quantitated extracellular concentrations of IL-26 in IS from healthy nonsmokers and found that the average IL-26 concentration was much higher in samples harvested during stable clinical conditions in the smokers (current plus former smokers) with COPD than in the healthy nonsmokers, and this was even more true for the samples harvested during exacerbations (Figure 4D). This evidence concerns the gene IL26 and chronic obstructive pulmonary disease.