Bronchoalveolar lavage and lung histology. Comparative analysis of inflammatory and immunocompetent cells in patients with sarcoidosis and hypersensitivity pneumonitis

To determine whether bronchoalveolar lavage reflects the histologic aspects of the lung histology in patients with sarcoidosis and hypersensitivity pneumonitis, cells recovered from lavage fluid were compared with tissue sections from transbronchial lung biopsies in 33 patients. The evaluation of cellular types and their topographic distribution in situ was determined by using monoclonal antibodies in combination with immunohistochemical techniques. Cell counts in bronchoalveolar lavage and lung biopsies were significantly correlated both in sarcoidosis and hypersensitivity pneumonitis. In fact, the relative proportions of inflammatory and immunocompetent cells recovered from lavage fluid accurately overlapped those observed in lung tissue sections. However, in patients with more pronounced alveolitis, the frequency of macrophages in tissue sections was higher than that observed in the bronchoalveolar lavage, and the degree of lymphocytes in the lavage was higher than that observed in the corresponding biopsy. Specifically, in these patients the lavage underestimated the amount of macrophages in the lung biopsies and overestimated the number of lymphocytes that were present in the lung parenchyma. This was more evident in patients with hypersensitivity pneumonitis, where the intensity of alveolitis was higher than in sarcoidosis. Our data support the idea that, at least in patients with sarcoidosis and hypersensitivity pneumonitis, bronchoalveolar lavage correctly samples the alveolitis. Discrepancies in patients with very high intensity alveolitis could be due to a more pronounced recirculation of lymphocytes from the parenchyma to the alveolar spaces.