Immunohistochemistry was performed to examine Nrf2 and Keap-1 protein expression in alveolar macrophages and bronchial epithelium of NS (n = 12), S (n = 12) and COPD patients (n = 12) (Supplement Figs. 4 and 5). This evidence concerns the gene NFE2L2 and chronic obstructive pulmonary disease.