Interleukin 5 and granulocyte-macrophage colony-stimulating factor levels in bronchoalveolar lavage fluid in interstitial lung disease

The purpose of this study was to evaluate the role of several eosinophil growth factors including interleukin (IL)-5, interleukin (IL)-3 and granulocyte-macrophage colony-stimulating factor (GM-CSF) in the pathogenesis of interstitial lung disease with eosinophilia. IL-5, IL-3 and GM-CSF in bronchoalveolar lavage fluid (BALF) were measured by enzyme-linked immunosorbent assay (ELISA) in patients with eosinophilic pneumonia (EP), bronchiolitis obliterans organizing pneumonia (BOOP), idiopathic pulmonary fibrosis (IPF), sarcoidosis and healthy volunteers. IL-5 in BALF was high only in patients with EP. IL-3 in BALF was undetectable in the majority of patients with these diseases. GM-CSF in BALF was detectable in 30-67% of each group of patients. In patients with BOOP and IPF, the number of eosinophils of BALF was higher in patients with detectable GM-CSF than in patients in whom GM-CSF was below the detection limit. Eosinophil cationic protein (ECP) was detected in all patients with EP and some with BOOP and IPF. There was a significant correlation between ECP levels and percentage or number of eosinophils in BALF. The results suggest the possibility that interleukin 5 in eosinophilic pneumonia, and granulocyte-macrophage colony-stimulating factor in bronchiolitis obliterans organizing pneumonia and idiopathic pulmonary fibrosis may play important roles in eosinophil recruitment in the lung. Activation of eosinophils in the lung is likely to be induced by both interleukin 5 and granulocyte-macrophage colony-stimulating factor.