ABCA1 and autoimmune pulmonary alveolar proteinosis: Because statin therapy reduced cholesterol levels in foamy alveolar macrophages from autoimmune PAP patients ex vivo and Csf2rb−/− mice in vivo (Figs. 2e, 3c), and cholesterol efflux is reduced in macrophages from apoE−/−GM-CSF−/− mice27, we measured the effects of statin on efflux of radiolabelled cholesterol from alveolar macrophages or bone marrow-derived macrophages in the presence of cholesterol acceptors—high-density lipoprotein (HDL) or apolipoprotein-A1 (Apo-A1), which preferentially accept cholesterol from macrophages via ABCG1 and ABCA1, respectively28.