PRF1 and chronic obstructive pulmonary disease: The proportions of both CD56dimCD16+ and CD56brightCD16- NK cells expressing both perforin and granzyme B were also significantly higher in COPD subjects (74.6 and 44.8, respectively) compared to both HNS (46.2; p < 0.001 and 18.5; p < 0.01) and smokers (55.9; p < 0.01 and 24.9; p < 0.05)(Figure 3B).