In a previous study, the gp91phox-/- mouse had a spontaneous pro-inflammatory phenotype and then a more exaggerated emphysematous phenotype in a cigarette smoke-induced mouse model, while a double knockout (DKO) mouse lacking in both gp91phox and MMP12 failed to develop emphysema, even after chronic cigarette smoke exposure for over a month. Here, CYBB is linked to pulmonary emphysema.