ABCG1 and pulmonary alveolar proteinosis: Because ATP-binding cassette transporter family members A1 and G1 (ABCA1 and ABCG1, respectively) mediate cholesterol efflux from macrophages and their expression is abnormal in PAP25,26, we evaluated the effects of ex vivo statin exposure on ABCG1/ABCA1 mRNA levels in PAP patient-derived alveolar macrophages.