[Lymphocyte and lymphocyte subsets in pleural fluid--comparison of malignant and non-malignant disorders]

The role of lymphocytes in host defence in neoplastic disorders is known. Accumulation of lymphocytes in pleural cavity frequently occurs in different diseases. The aim of the study was to evaluate: 1) the frequency of lymphocyte predominance in different malignant and non-malignant pleural effusions; 2) lymphocyte phenotype and the ratio between helper (CD4+) and cytotoxic/suppressor (CD8+) lymphocytes in malignant and non-malignant effusions. Patients with mesothelioma, lung cancer, lymphoma and metastatic neoplasms were analysed. Analysis was performed on fluids with or without malignant cells. Non-malignant fluids were obtained from patients with: congestive heart failure, liver cirrhosis, pneumonia and tuberculosis. Lymphocytes were the predominant cell type in neoplastic effusions. For further analysis effusions with more than 10% of lymphocytes were included: 12 malignant and 9 non-malignant. For lymphocyte subpopulations analysis, the monoclonal antibodies anti-CD4 and anti-CD8 and APAAP method was used. We observed lower percentage of CD4+ lymphocytes (47%) and higher percentage of CD8+ (39%) lymphocytes in malignant when compared to non-malignant fluids (58% vs 31% respectively). The CD4+/CD8+ ratio was significantly lower in pleural fluid in cases with neoplastic disease when compared to benign cause of pleural involvement (1.03 vs 1.85). Our observations suggest the potential role of lymphocytes, especially CD8+ cells in local response in malignancy in pleural disease.