Abstract: Objective To evaluate the distribution of active T cells and nature killer cells (NK cells),as well as the interferon-γ(γ-IFN) level in tuberculous pleural effusions and malignant ones. Methods The percentages of active T cells (CD3⁺HLA-DR⁺) or NK cells (CD3-CD16⁺/CD56⁺) in tuberculous pleural effusions (23 cases) and malignant ones (22 cases) were detected with flow cytometry. γ-IFN levels were also measured with Elisa method. Results Compared with malignant pleural effusions, tuberculous pleral exudates showed a higher percentage of active T cells and contained more γ-IFN. The percentage of active T cells was positively correlated with γ-IFN in tuberculous pleural effusions. There was a higher percentage of NK cells in malignant pleural exudates. However, The γ-IFN level was not correlated with percentage of NK cells in malignant pleural effusions. The ratio between the percentages of active T cells and NK cells was significantly higher in tuberculous pleural exudates when compared with malignant ones. Conclusion To detectγ-IFN level, also the percentages of active T cells and NK cells in pleural effusions, especially the ratio between the percentages of these two kinds of cells may provide a useful method to distinguish the malignant pleural effusions from tuberculous ones.

Key words: pleural effusion, T cell, nature killer cell, interferon