Anti-GM-CSF auto-Abs cause pulmonary alveolar proteinosis (PAP), a severe lung disease characterized by the accumulation of surfactant in the alveoli, with progressive respiratory failure and an increase in the risk of infection [21], probably due to an impairment of the terminal differentiation of alveolar macrophages affecting their ability to catabolize surfactant, and to protect the host against infectious diseases [21]. This evidence concerns the gene CSF2 and pulmonary alveolar proteinosis.