Abstract: Objective To analyze the differences of T lymphocytes, interleukin-2 (IL-2), soluble interleukin-2 receptor (sIL-2R) between in the sera and pleural effusions of patients with tuberculous pleurisy, and to explore the immune mechanism of tuberculous pleurisy. Methods Sandwich enzyme-linked immunosorbent assay (ELISA) were used to detect the IL-2, sIL-2R in peripheral bloods and pleural effusions of 150 patients, who were hospitalized in Shanghai Pulmonary Hospital from June 2010 to December 2011, and diagnosed as tuberculous pleurisy of initial treatment, meeting the inclusion criteria. The ratios of T lymphocytes of peripheral blood and pleural effusion were detected in these 150 tuberculous pleurisy patients with the flow cytometers. Statistical analysis was performed with SPSS 16.0 statistical software. Using paired samples statistics (t test) to compare the test results of peripheral blood and pleural fluid.  Results (1) Of the patients with tuberculous pleurisy, the ratios of CD3⁺ and CD4⁺ T cells in pleural effusions（（85.11±7.70）%,（55.67±12.94）%） significantly higher than those in peripheral bloods （（70.91±10.33）%,（42.87±11.12）%）（t=－9.846, P=0.03; t=－7.455, P=0.001）. While the ratio of CD8⁺ T cells in pleural fluid（（17.92±7.63）%） significantly lessthan that in peripheral blood （（22.74±6.78）%）（t=4.372, P=0.012）. The ratio of CD4⁺/CD8⁺ in pleural effusion（3.77±2.07）significantly higher than that in peripheral blood（2.13±1.16）（t=－6.542, P=0.001）. (2) The concentrations of IL-2, sIL-2R in pleurisy fluids（（68.55±41.40）pg/ml，（1672.25±713.75）pmol/L）were significantly higher than those in the peripheral bloods from the patients with tuberculous pleurisy（（32.97±32.30）pg/ml，(193.89±87.30）pmol/L)（t=－7.282, P=0.000; t=－15.783, P=0.000）. (3) The level of IL-2 in pleural effusions（（68.55±41.40）pg/ml） was 2.079 times higher than that in the peripheral bloods（（32.97±32.30）pg/ml）. The level of sIL-2R in pleural effusion（（1672.25±713.75）pmol/L） was 8.625 times higher than that in the peripheral bloods（（193.89±87.30）pmol/L）. Conclusion (1)CD3⁺ T cell, CD4⁺T cell, IL-2, and sIL-2R played an important role in the occurrence and development of tuberculous pleurisy. (2)The immune response was stronger in the pleura. It was more difficult to the control of the infection in the pleura because of significantly higher concentration of sIL-2R in pleural effusion.

Key words: Tuberculosis, pleural/immunology, Pleural effusion, T-lymphocytes, Interleukin-2