Pulmonary sarcoidosis: flow cytometry measurement of lung T cell activation

Lung T cell activation is considered a major factor in the pathogenesis of pulmonary sarcoidosis. Our study was designed to investigate several parameters of T cell activation among blood and alveolar cell populations, including expression of HLA-DR or MLR antigens, increased cell size, and presence of dividing cells. Blood sampling and bronchoalveolar lavages were performed in 20 patients with pulmonary sarcoidosis. Cell populations were analyzed by flow cytometry using immunofluorescence labeling with monoclonal antibodies to lymphocyte differentiation or activation antigens. Cell types were identified by their light-scattering properties. Cell cycle analysis was done after staining with acridine orange. Bronchoalveolar lavage contained a higher proportion of small T4-positive lymphocytes, and large cells of the same phenotype were detected in three patients. T cells bearing HLA-DR antigens were detected in six of 14 bronchoalveolar lavage samples. A marked increased of MLR-positive cells was found in the peripheral blood of eight of eight patients and in the bronchoalveolar lavage of five of seven patients. Increased percentages of cells in the S + G2 + M phases were found in blood lymphocytes from three patients and in half the bronchoalveolar lavage samples. Therefore, a variety of activation markers may be expressed by alveolar T cells. Their qualitative and quantitative assessment may provide additional criteria for staging the intensity of the alveolitis, and the possible relationship between these markers and disease progression or activity deserves long-term clinical investigation.