CSF2 and pulmonary alveolar proteinosis: Immune checkpoint blockades, a Nobel prize-winning discovery, were first observed in the immune system of mice and then translated for therapeutic use in humans (Alt-mann, 2018); and the development of granulocyte-macrophage colony-stimulating factor (GM-CSF) therapy for pulmonary alveolar proteinosis (PAP) was influenced by observations in mice, in which the deficiency of GM-CSF results in PAP (Trapnell et al., 2009).