SFTPD and chronic obstructive pulmonary disease: Thus, the appearance of foamy macrophages in the Sftpd−/− lung may not be specific to COPD-related processes, although induction of MMP-12-synthesizing foamy macrophages results after exposure of mice to cigarette smoke (276), and foamy macrophages provide a source of ROS and inflammatory signaling in mouse models as a result of Sftpd deficiency (125).