[The role of CD8+CD28- regulatory T lymphocytes in pulmonary tuberculosis].

OBJECTIVE: To study the role of CD(8)(+)CD(28)(-) regulatory T cells in tuberculosis. METHODS: The positive rates of CD(3)(+)CD(8)(+)CD(28)(-) T cells, CD(3)(+) T cells, CD(3)(+)CD(8)(+) T cells and CD(8)(+)CD(28)(+) T cells, and the content of IL-6 in CD(8)(+)CD(28)(-) T cells in leukocytes of peripheral blood from 15 patients with pulmonary tuberculosis, 15 patients with chronic bronchitis and 15 healthy controls were detected by flow cytometry. RESULTS: The positive expression rates of CD(3)(+) T cells of tuberculosis group [(41 +/- 16)%] and bronchitis controls [(40 +/- 10)%] were significantly lower than those from healthy controls [(44 +/- 6)%] respectively, but no differences were found between tuberculosis group and bronchitis controls. The CD(3)(+)CD(8)(+) T cells in CD(3)(+) T cells from the tuberculosis group [(47 +/- 16)%] and bronchitis controls [(44 +/- 10)%] were significantly higher than those from the healthy controls [(41 +/- 12)%] respectively, but no differences were found between the tuberculosis group and bronchitis controls. The CD(8)(+)CD(28)(+) T cells in CD(3)(+) T cells from tuberculosis group [(15 +/- 8)%] and bronchitis controls (20 +/- 7%) were significantly lower than those from healthy controls [(32 +/- 9)%] respectively, and those of the tuberculosis group were significantly lower than those from the bronchitis controls. CD(8)(+)CD(28)(-) T cells in CD(3)(+) T cells from tuberculosis group [(27 +/- 9)%] and bronchitis controls [(22 +/- 9)%] were significantly higher than those from healthy controls [(10 +/- 4)%] respectively, and those of the tuberculosis group were significantly higher than those of the bronchitis controls. The level of IL-6 secreted by CD(8)(+)CD(28)(-) T cells from tuberculosis group [(32.4 +/- 2.4)%] was significantly higher than bronchitis controls [(19.7 +/- 3.2)%] and healthy controls [(15.2 +/- 2.7)%] and no differences were found between bronchitis controls and healthy controls. CONCLUSIONS: The number of CD(8)(+)CD(28)(-) T cells and their production of IL-6 in the peripheral blood of tuberculosis patients are significantly increased as compared with the control groups, while the number of CD(8)(+)CD(28)(+) T cells (cytotoxic T cell) is significantly decreased. The results suggest that these cells and IL-6 may be involved in the pathogenesis of pulmonary tuberculosis.