ACE2 and chronic obstructive pulmonary disease: In contrast, ACE2 expression was lower in peripheral airways in COPD patients (mean + SEM: 1.5% ± 0.7) versus both smokers without COPD and NS controls (6.1% ± 1.7; 6.6% ± 2, P < 0.05 and P = 0.01, respectively, Fig. 1B and Additional file 1: Fig. S1B).