Bronchiolitis obliterans organizing pneumonia (BOOP): the cytological and immunocytological profile of bronchoalveolar lavage.

The cytological and immunocytological profile of bronchoalveolar lavage (BAL) was studied in 10 patients with idiopathic bronchiolitis obliterans organizing pneumonia (BOOP) and compared with the data in idiopathic pulmonary fibrosis (IPF) (n = 22), chronic eosinophilic pneumonia (CEP) (n = 9), and extrinsic allergic alveolitis (EAA) (n = 24). Lymphocyte subsets were enumerated using an immunoperoxidase slide assay. The BAL pattern in BOOP patients was characterized by several features: 1) colorful cell differentials with an increase in all cell types, most markedly in lymphocytes, and more moderately in neutrophils, eosinophils and mast cells, as well as the presence of foamy macrophages and, occasionally, of plasma cells; 2) decreased CD4/CD8 ratio; 3) normal percentage of CD57+ cells; and 4) increase in activated T-cells in terms of human leucocyte antigen-DR (HLA-DR) expression, and occasionally also interleukin-2 receptor (CD25) expression. The findings were most similar to those in EAA except for the CD25 expression, which was always normal, and the CD57+ cells, which were increased in EAA. The increase in lymphocytes discriminated best between BOOP and IPF. The eosinophils were significantly higher in CEP than in BOOP with little overlap. In conclusion, BAL may be of value to distinguish between BOOP and other interstitial lung disease.