Eosinophilic pneumonia is characterized by the prominent accumulation of eosinophils and lymphocytes in the lung parenchyma. Liver-expressed chemokine (LEC)/CC chemokine ligand 16 (CCL16) is a novel functional ligand for H4 which is expressed on eosinophils and also an affinity ligand for CCR1, CCR2, CCR5 and CCR8 which are expressed on T lymphocytes and monocytes. The purpose of this study is to clarify the role of LEC/CCL16 in eosinophilic pneumonia.
The LEC/CCL16 level was measured using an enzyme-linked immunosorbent assay in the bronchoalveolar lavage fluid (BALF) of 33 patients with eosinophilic pneumonia, 26 patients with sarcoidosis and 10 healthy volunteers. The cell sources of LEC/CCL16 in BALF were evaluated by immunocytochemistry.
The LEC/CCL16 levels in BALF from patients with eosinophilic pneumonia were significantly higher than those from patients with sarcoidosis and healthy volunteers. The BALF LEC/CCL16 levels correlated with the numbers of BALF eosinophils and lymphocytes, respectively. The BALF LEC/CCL16 levels were significantly decreased after remission in eosinophilic pneumonia. In immunocytochemistry, the LEC/CCL16 expression was clearly observed in CD1a-positive dendritic cells as well as in CD68-positive macrophages harvested from patients with eosinophilic pneumonia, but not from the controls.
These results suggest that LEC/CCL16 produced by dendritic cells as well as by alveolar macrophages contributes to the accumulation of eosinophils and lymphocytes into the inflamed lungs of patients with eosinophilic pneumonia.