Elevated concentrations of CCR7 ligands in patients with eosinophilic pneumonia

Previous studies suggest that dendritic cells and macrophages play an important role in inflammation of eosinophilic pneumonia. The mechanism of dendritic cell and macrophage accumulation into the lung, however, is unknown. Here, we hypothesized that CCR7 ligands, CCL19 and CCL21, contribute to the accumulation of dendritic cells and alveolar macrophages in the inflamed lung of patients with eosinophilic pneumonia.

Concentrations of the CCR7 ligands as well as CCL16, CCL17 and CCL22 in the bronchoalveolar lavage fluid of 53 patients with eosinophilic pneumonia, 29 patients with sarcoidosis, 18 patients with idiopathic pulmonary fibrosis and 12 healthy volunteers were measured by enzyme-linked immunosorbent assay. Cell sources of CCR7 ligands and CCR7-expressing cells in the bronchoalveolar lavage fluid were evaluated by immunocytochemistry.

CCL19 and CCL21 levels in the bronchoalveolar lavage fluid were significantly higher in patients with eosinophilic pneumonia than in controls. Levels of CCL19, but not CCL21, were statistically correlated with the levels of CCL16, CCL17 and CCL22 in patients with eosinophilic pneumonia. Immunocytochemistry revealed CCL19 expression in dendritic cells, macrophages and T-lymphocytes harvested from patients with eosinophilic pneumonia, and CCR7 expression in dendritic cells and macrophages. Levels of CCL19, but not CCL21, were significantly decreased after remission in patients with eosinophilic pneumonia. After provocation tests, CCL19 levels were elevated in all patients with eosinophilic pneumonia.

These findings indicate that CCL19 rather than CCL21 may contribute to the accumulation of dendritic cells and macrophages in the inflamed lungs of patients with eosinophilic pneumonia.