Analysis of bronchoalveolar lavage cells in chronic eosinophilic pneumonia before and during corticosteroid therapy.

Bronchoalveolar lavage was performed in patients with chronic eosinophilic pneumonia of unknown origin diagnosed histopathologically, and the alveolar fluid cells were investigated before and during corticosteroid therapy. The counts of eosinophils in bronchoalveolar lavage fluid decreased markedly during steroid therapy compared with before therapy, and the ratios of interleukin 2 receptor-positive T cells and HLA DR-positive T cells to all T lymphocytes in the lavage fluid also decreased. Both before and during steroid therapy, many macrophages in bronchoalveolar lavage fluid phagocytosed EG2-positive granules and stained immunohistochemically as CD71-positive 'responsive macrophages'. The decrease of activated T lymphocytes and the active phagocytosis of eosinophil granules by macrophages might play an important role in the mechanism of healing in chronic eosinophilic pneumonia.