Immunocompetent cells in bronchoalveolar lavage reflect the cell populations in transbronchial biopsies in pulmonary sarcoidosis

Abstract

The purpose of this study was to examine the relationship between the inflammatory cells seen in transbronchial lung biopsy samples (TBB) and the bronchoalveolar lavage fluid (BAL) taken from patients with pulmonary sarcoidosis. Monoclonal antibodies and histochemical methods were used to identify mononuclear inflammatory cells in cryostat tissue sections and to compare these with cell populations in BAL-derived cytospin preparations. The subsets of lymphocytes identified in BAL accurately reflected the type and proportion of subsets present in the TBB. Although the ratio of T4+:T8+ lymphocytes was variable from patient to patient, concordance between BAL and TBB specimens was found in each subject. In the BAL, a high proportion of T lymphocytes expressed class II MHC antigen (HLADR+). Monoclonal antibodies were also used to identify subpopulations of macrophages and dendritic cells in the BAL and tissue samples. Macrophage subsets defined by phenotypic differences were found in both cases. Although no clear quantitative correlation could be established, a qualitative concordance was revealed. These results suggest that analysis of BAL samples accurately reflects the heterogeneity of the mononuclear inflammatory cell infiltrate in tissue biopsy samples in sarcoidosis. However, the spatial relationships between subpopulations of cells identified by immunohistologic analysis in tissue sections offers insights into the pathogenetic mechanisms involved that are not revealed by analysis of cytospin preparations from BAL.