Tuberculous pleural effusions: Lymphocyte phenotypes in comparison with other lymphocyte-rich effusions

This study investigated whether the analysis of T cell subsets and of activation markers on T cells in pleural fluids can be helpful for diagnostic purposes in tuberculous pleurisy and other lymphocyte-rich pleural effusions. Pleural effusion fluids were obtained from 18 patients with tuberculous pleurisy (TB), 21 with effusions following radiotherapy (RT) for a malignant disease, and 11 with congestive heart failure (CHF). Lymphocyte subsets were analyzed by a battery of monoclonal antibodies using an immunoperoxidase method. The majority of the lymphocytes were CD3-positive T cells (TB, 86 ± 7% of lymphocytes; RT, 81 ± 8%; CHF, 84 ± 12%). The ratios of CD4-positive helper-inducer to CD8-positive suppressor-cytotoxic T cells were higher than those reported for the peripheral blood but not significantly different between the study groups (TB, 3.3 ± 1.9; RT, 2.8 ± 1.1). The activation marker studies revealed that only a few pleural T cells were positive for CD38, CD25 (interleukin-2 receptor), HLA-DR antigen, and OKT9 (transferrin receptor), the proportion of CD25-positive T cells being higher in TB and in RT than in CHF and the proportion of HLA-DR-positive T cells being higher in TB than in CHF (P < 0.05). Significant differences were not observed relative to the natural killer-cytotoxic phenotypes staining positive for Leu-7 or for CD16. Thus, we concluded that phenotypic analysis of lymphocytes is of limited diagnostic usefulness to differentiate tuberculous from other nonmalignant effusions.