When analyzing the data from bacterial cultures of IS samples from smokers with COPD in the BALO cohort, we found that the subjects with COPD that had growth of pathogenic bacteria in IS samples at any time point during stable clinical conditions did consistently display a clearly increased average extracellular concentration of IL-26 in the very same IS samples, in comparison with the subjects who did not display this growth at any time point (Figure 7A). Here, IL26 is linked to chronic obstructive pulmonary disease.