In light of the absence of an emphysema phenotype in the lungs of Mal−/− mice, unlike the emphysema observed in Tlr4−/− mice, we next assessed whether the levels of oxidative stress and apoptosis (both elevated in Tlr4−/− lungs) were also unaltered in Mal−/− lungs. Here, TLR4 is linked to pulmonary emphysema.