In bronchial epithelial cells collected by bronchoscopic brush biopsy, the expression of hemoglobin genes (HBA1, HBA2, HBB and HBD) was strongly correlated with Pre-bronchodilator FEV1 PP in patients with asthma enrolled in SARP I&II but not in controls (Fig. 3A, B; Supplementary Fig. 1). Here, HBD is linked to asthma.