NOS2 and chronic obstructive pulmonary disease: The number of iNOS positive cells (Figure 4a) was higher in smokers than in non-smokers (p = 0.08, p = 0.004, respectively), the differences between the subgroups were: never smokers vs ex smokers p = 0.181 (%), p = 0.04 (total), non-symptomatic smokers vs stage 0 COPD p = 0.279 (%), p = 1.00 (total).