The Effects of Low-Dose Dexamethasone on Cell Kinetics, Cytokine Productivity and Natural Killer Cell Cytotoxicity in Murine Lymphoid Organs In Vivo.

Low-dose dexamethasone is widely used in perioperative settings for its antiemetic and analgesic effects. The present study aimed to investigate the impacts of low-dose dexamethasone on cell kinetics, cytokine productions and cytotoxic activity of natural killer (NK) cells in lymphoid organs. Female Balb/c mice were intraperitoneally administered normal saline (Group N), low-dose dexamethasone (0.1 mg/kg) (Group L), or high-dose dexamethasone (20 mg/kg) (Group H). Measurement of cell counts of thymocytes and splenocytes, and phenotypic analyses of the lymphocytes and the cytotoxicity of NK cells in the splenocytes using flow cytometry were performed. The production of cytokines in the splenocytes ex vivo was measured by ELISA. There was a marked decrease in the number of lymphocytes in Group H, while the number of splenocytes was significantly increased in Group L compared to Group N at 24 hours after administration (p = 0.019). The production of IFN-γ was dose-dependently decreased by dexamethasone. The proportions of double-positive thymocytes and CD4+ splenocytes were reduced in Group H, but there were no significant changes in lymphocyte subsets between Groups N and L until 48 hours after administration. The cytotoxicity of NK cells in Group L was increased compared to that in Group N at 24 and 48 hours (p = 0.008 and p = 0.018, respectively). Low-dose dexamethasone augmented immune cell mobilization and upregulated cytotoxicity of NK cells while suppressing cytokine production. These results suggested that low-dose dexamethasone have conflicting immunological effects and transiently enhances innate immunity such as NK cell function.