Background: Granulocyte macrophage colony stimulating factor (GMCSF) has been implicated as an important mediator in the pathogenesis of asthma and chronic obstructive pulmonary disease (COPD). However, the expression of GMCSF and its receptor in airway samples in asthma and COPD across disease severity needs to be further defined.
Methods: We measured sputum GM-CSF in 18 control subjects, 45 subjects with asthma, and 47 subjects with COPD. Enumeration of GM-CSF+ cells in the bronchial submucosa and airway smooth muscle bundle was performed in 29 control subjects, 36 subjects with asthma, and 10 subjects with COPD.
Results: The proportion of subjects with measurable GM-CSF in the sputum was raised in the moderate (7/14) and severe (11/18) asthmatics, and in those with COPD GOLD stage II (7/16), III (8/17) and IV (7/14) compared to controls (1/18) and mild asthmatics (0/13); p=0.001). The sputum GM-CSF concentration was correlated with the sputum eosinophilia in subjects with moderate-severe asthma (rs=0.41; p=0.018). The median (interquartile range) GM-CSF and GM-CSFR+ cells/mm2 submucosa was increased in severe asthma (1.4 [3.0]) and (2.1 [8.4]) compared to mild-moderate asthmatics (0 [2.5]) and (1.1 ), and healthy controls (0[0.5]) and (0 [1.6]), (p=0.004, and p=0.02 respectively).
Conclusions: Our findings support a potential role for GM-CSF in asthma and COPD and suggest that over-expression of GM-CSF in sputum and the bronchial mucosa is a particular feature of severe asthma.