In this figure, datasets on human samples from one cohort (BALO cohort) are presented and all the IL-26 protein concentrations were quantitated in cell-free IS fluid samples using ELISA. (A) Concentrations of IL-26 in IS fluid during stable clinical conditions compared with exacerbations (n=13), (B) concentrations of IL-26 in IS fluid over time; during stable clinical conditions, prior to exacerbation and during exacerbation (n=9). (C) Concentrations of IL-26 in IS fluid from COPD-current smokers (n=10) and COPD-former smokers (n=21) during stable clinical conditions and for COPD-current smokers (n=5) and COPD-former smokers (n=11) during exacerbations. (D) Concentrations of IL-26 in IS fluid from healthy nonsmokers without COPD (n=8) and smokers with COPD (n=31) and COPD exacerbations, as assessed during stable clinical conditions (n=16). (E) Concentrations of IL-26 in IS fluid samples from smokers with COPD in relation to age during stable clinical conditions (n=31). (F) Concentrations of IL-26 in IS fluid samples from smokers with COPD, in relation to age during exacerbations (n=16). The P-values are according to Wilcoxon signed ranked test for (Figure 3A), Friedman test (Figure 3B), Mann–Whitney test (Figure 3C,D), and Spearman’s rank correlation (Figure 3E,F). The P-values <0.05 are considered significant. Concentrations of IL-26 on the y-axis are represented in log scale. Notably, the term “stable” in the figure panels signifies “stable clinical conditions” in the legend.