NCAM1 and chronic obstructive pulmonary disease: As well as a reduction in the overall proportion of NK (CD56+CD3-) cells in the peripheral blood of COPD subjects, the proportion of NK cells in the cytotoxic CD56dimCD16+ subset was decreased (79.9%) compared to smokers (88.7%; p < 0.001) and HNS (88.6%; p < 0.01; Figure 2A), with a corresponding rise in the proportion of immunoregulatory CD56brightCD16- cells in COPD subjects.