Bronchoalveolar lavage, histological and immunohistochemical features in cryptogenic organizing pneumonia.

This study describes bronchoalveolar lavage (BAL), histological and immunohistochemical features in a series of 10 patients with cryptogenic organizing pneumonia (COP). The histological diagnosis was performed by transbronchial biopsy in seven cases and by open lung biopsy in three cases. All patients showed a marked increase in lymphocytes and a mild increase in neutrophils and eosinophils in BAL fluid. The number of T-lymphocytes expressing human leucocyte antigen-DR (HLA-DR) surface antigen was increased (p < 0.002). The majority of lymphocytes expressed the CD8 phenotype, so that the CD4/CD8 ratio was markedly decreased. Masson bodies were present in the lung specimens of all patients. Most of the epithelial cells surrounding the Masson bodies were immunoreactive with an anti-granulocyte/macrophage colony-stimulating factor (GM-CSF) monoclonal antibody. The great majority of mononuclear cells in the lung specimens showed immunoreactivity with anti-CD3, anti-CD8 and anti-CD45R0 monoclonal antibodies. In the Masson bodies, spindle cells were immunoreactive with anti-alpha smooth muscle (alpha-sm) actin monoclonal antibody. Glucocorticoid treatment (the therapy of choice in COP) downregulated GM-CSF messenger ribonucleic acid (mRNA) expression in lung epithelial cell lines. These findings indicate that the combination of bronchoalveolar lavage cell profile with histological evidence is a valuable means of corroborating a clinical diagnosis of cryptogenic organizing pneumonia, and that granulocyte/macrophage colony-stimulating factor may be one of the cytokines involved in the pathogenesis.