Autoimmune pulmonary alveolar proteinosis (aPAP) is characterized by the accumulation of phospholipids and surfactant proteins in the peripheral air spaces due to alveolar macrophage dysfunction caused by anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies (GMAb). Here, CSF2 is linked to autoimmune pulmonary alveolar proteinosis.