CSF2 and chronic obstructive pulmonary disease: In contrast to COPD, in asthma there are several reports of increased GM-CSF expression in airway secretions and tissue.12–17 In particular, increased sputum GM-CSF expression is associated with more severe disease.12, 13 We have confirmed these earlier reports and found that sputum GM-CSF concentration was increased in moderate to severe asthma, but not in mild disease.