The proportion of NKT-like (CD56+CD3+) cells that expressed only perforin and no granzyme B was significantly higher in both smokers (14.0; p < 0.001) and HNS (13.8; p < 0.01) than in COPD subjects (5.4) (data not shown). This evidence concerns the gene NCAM1 and chronic obstructive pulmonary disease.