Indeed, in accordance with this concept, Freeman et al. (42) showed that CD56+ cells (in fact a mixture of NK cells and CD56+ T lymphocytes) isolated from lung parenchymal samples of non-COPD smokers and COPD patients with a smoking history, although similar in terms of frequencies between the cohorts, had a different cytotoxic activity toward autologous lung epithelial cells. The gene discussed is NCAM1; the disease is chronic obstructive pulmonary disease.