CSF2 and pulmonary alveolar proteinosis: On the other hand, patients suffering from an auto-immune driven deficiency in GM-CSF, develop a severe lung condition called pulmonary alveolar proteinosis, characterized by an accumulation of surfactant and cell debris in the alveolar lumen due to an ineffective macrophage maturation, demonstrating the major role of GM-CSF in AM physiology [15].