Acid alpha-naphthyl acetate esterase staining of lymphocytes in pleural effusions

Cytocentrifuged preparations of mononuclear cells in blood and pleural fluid were stained for acid alpha-naphthyl acetate esterase (ANAE) in order to characterize the lymphocytes of pleural effusions histochemically. The cellular samples were obtained from 42 patients with pleural effusions caused by tuberculosis, pneumonia, cancer, malignant lymphoma, sarcoidosis, congestive heart failure, hepatic cirrhosis or nonspecific causes. The mean percentage of ANAE-positive lymphocytes from patients with tuberculous pleural effusion was significantly greater (P less than 0.001) in pleural fluid (85.6%) than in peripheral blood (70.0%). Tuberculous pleural fluid also contained a higher mean percentage of ANAE-positive lymphocytes than did pleural fluid from patients with cancer (75.0%), malignant lymphoma (50.0%), pneumonia, nonspecific disease (74.9%) or transudates (59.3%). The findings show that ANAE staining is useful for demonstrating T lymphocytes in pleural effusions. The pathogenetic role of these T lymphocytes and the diagnostic significance of demonstrating ANAE-positive cells in pleural effusions are discussed.