NK (CD56+CD3−) cells from healthy smokers (25.6%, 14.1–50.1; p<0.001), current smokers with COPD (35.1%, 13.2–72.8; p<0.001) and ex-smokers with COPD (18.4%, 11.9–58.8; p<0.005) were significantly more activated ex vivo than those from healthy non-smokers (8.9%, 3.6–22.8) (Figure 2C). This evidence concerns the gene NCAM1 and chronic obstructive pulmonary disease.