Analysis of NK cells showed the proportion of these cells expressing surface CD158e1 was also significantly lower in healthy smokers (7.7%, 3.1–13.2; p<0.01) and current smokers with COPD (4.8%, 2.1–16.3; p<0.001) compared to healthy non-smokers (24.2%, 18.1–29.3) (Figure 4iiC). This evidence concerns the gene KIR3DL1 and chronic obstructive pulmonary disease.