ObjectiveTo investigate the effects of different concentrations of ketamine on the differentiation of human T helper (Th) cells.MethodsTwenty patients ASA Ⅰ,20-60 years undergoing elective operation under general anesthesia were enrolled in this study.Peripheral venous blood samples were taken before anesthesia.Peripheral blood mononuclear cells were isolated and assigned to one of 3 groups ( n ＝ 20 each).Peripheral blood mononuclear cells were incubated in the presence of 0.9％ NaCl (group C),2 concentrations of ketamine (2.5,25.0 μg/ml) (groups K1,K2) for 24 h,and were then stimulated with phytohaemagglutinin for another 48 h.The perce.ntage of Thl and Th2 cells were detected by four-color flow cytometry.The Thl/Th2 ratio was calculated.The IL-2,IL-4,IL-6,IL-10,IFN-γ and TNF-α concentrations in the supernatant were determined by cytometric bead array.ResultsThere was no significant difference in the IL-2,IL-4,IL-6,IL-10,IFN-γ and TNF-α concentrations in the supernatant,the percentage of Thl and Th2 cells and Thl/Tb-2 ratio among groups C,K1and K2 ( P ＞ 0.05).ConclusionsThe sedative and anesthetic concentrations of ketamine exert no effect on the differentiation of human Th cells in vitro.