CSF2 and asthma: Granulocyte–macrophage colony-stimulating factor (GM-CSF) is a major regulator of inflammatory cells of the myeloid lineage and has been implicated in asthma and COPD.7 It is released by a range of structural and inflammatory cells, including airway epithelium, airway smooth muscle (ASM), fibroblasts, T lymphocytes, mast cells, eosinophils and macrophages.