In most parameters analyzed, non-COPD smokers presented an intermediate phenotype between non-smoker controls and COPD subjects (FEV1, % predicted; FEV1/FVC, %; DLCO, % predicted; PaO2, mmHg; CD45+CD34+CD133+ cells; mean wall thickness (um); lumen area, % total area and muscular area, % total area) (Additional file 2: Table S1). This evidence concerns the gene CD34 and chronic obstructive pulmonary disease.