Abstract: Abstract: Objective To explore changes of the myeloid derived suppressor cell (MDSC), regulatory T cell (Treg), traditional T cell, and their mechanisms in lung tumor mice. Methods Twenty C57BL/6 mice were randomly divided into the experimental and the normal control groups. The experimental group was injected with Lewis lung cancer cells (LLC, 100 μL 1×106 ) subcutaneously to prepare the lung tumor model mice, the normal control group was given the same amount of saline (NC). Spleen cells were obtained from LLC and NC groups. Flow cytometry was used to detect the ratio and number changes of MDSC, Treg, CD4+ and CD8+ T cells in the lung tumor of mice. CD4+ and CD8+ T cell apoptosis were detected by Annexin-Ⅴstaining, and their proliferation were detected by 5-bromine deoxidization uracil nucleoside (BrdU) incorporation. Results Compared with normal control mice, the ratio and number of MDSC in spleen increased significantly in LLC group (P < 0.01), in addition, the ratio of CD4+ Foxp3+ Treg in CD4+ T cells and their number in spleen increased significantly in LLC group. However, the ratio and number of CD4+ and CD8+ T cells in spleen decreased significantly in LLC group (P < 0.05). The proliferation of CD4+ and CD8+ T cells decreased significantly in LLC group compared with that of NC group (P < 0.05), while the apoptosis of CD8+ T cells increased significantly (P < 0.05). Conclusion MDSC and Treg cells increase in lung tumor model mice, which inhibit proliferation of CD4+ and CD8+ T cells and promote apoptosis of CD8+ T cells.

Key words:  lung neoplasms, carcinoma, Lewis lung, T-lymphocytes, regulatory, CD4-positive T-lymphocytes, CD8- positive T-lymphocytes, cell proliferation, apoptosis, myeloid derived suppressor cell