CHARACTERIZATION AND QUANTIFICATION OF ALVEOLAR MONOCYTE-LIKE CELLS IN HUMAN CHRONIC INFLAMMATORY LUNG-DISEASE

This flow cytometric study was designed to identify, characterize and quantify alveolar monocyte-like cells in healthy volunteers and in pat ients with chronic inflammatory lung disease. Cells were obtained by b ronchoalveolar lavage (BAL) from 19 patients with sarcoidosis, 29 with idiopathic pulmonary fibrosis, 10 with extrinsic allergic alveolitis, 19 with collagen vascular disease, and from 10 healthy volunteers. By taking advantage of the distinct electro-optical features of alveolar macrophages (AMs) and monocyte-like cells, the numbers of alveolar mo nocyte-like cells were counted, the cell dimensions calculated, and th e densities of antigens on the surface of alveolar monocyte-like cells and AMs were compared. By using a panel of monoclonal antibodies dete cting CD11b, CD14, CD16, and human leucocyte antigen-DR (HLA-DR), the immunophenotypes of these cells were selectively characterized. In the BAL fluid of patients with chronic inflammatory lung disease, signifi cantly increased numbers of alveolar monocyte-like cells were detected that exhibited an immunophenotype intermediate between blood monocyte s and mature AMs. Positive correlations were found between numbers of monocyte-like cells and expression of the monocyte-associated surface antigens CD11b and CD14 on total AMs; in contrast, an inverse relation ship existed between monocyte numbers and expression of the macrophage -associated surface antigens CD16 and HLA-DR. When the patients were a ssigned to two groups according to the percentage of BAL monocyte-like cells being lower or higher than 13% (=mean value of the controls +2S D), it could be demonstrated that a high percentage of BAL monocyte-li ke cells was associated with significantly reduced lung function param eters. In summary, our flow cytometric data strongly support the view that considerable numbers of blood monocytes are recruited to the bron choalveolar space in patients with chronic inflammatory lung disease.