MPO and chronic obstructive pulmonary disease: The number of myeloperoxidase (MPO) positive neutrophils was significantly higher in the lamina propria of severe/very severe (242 [129–387]) COPD patients than in the other three groups (p = 0.0009, p = 0.0016 and p = 0.047, in comparison with control non smokers, control healthy smokers and mild/moderate COPD, respectively).