NCAM1 and chronic obstructive pulmonary disease: Using the same number of effector cells (effector to target ratio of 5:1), both NK (CD56+CD3-) cells and NKT-like (CD56+CD3+) cells from COPD subjects were significantly less cytotoxic (16.8% and 16.7% specific lysis, respectively) than those from smokers (51.9%; p < 0.001 and 52.5%; p < 0.001) and HNS (66.0%; p < 0.001 and 69.6%; p < 0.001) (Figure 4A and 4B).