Objective:,2,To study the immunomodulatory effects of Radix Rehmanniae Recens polysaccharide on cyclophosphamide-induced immunosuppression in mice.,Methods:,2,Sixty male Balb/c mice were randomly divided into the control group, model group, positive control group and Radix Rehmanniae Recens polysaccharide groups with low-, middle-and high-dose, 10 mice in each group.Except the control group, mice in the other groups were intraperitoneally injected with cyclophosphamide(80 mg/kg) once a day for 2 days.From the third day of experiment, mice in the positive control group were treated with 50 mg/kg lentinan by intragastric administration, and mice in the Radix Rehmanniae Recens polysaccharide groups with different doses were treated with 5, 10 and 20 g/kg Radix Rehmanniae Recens polysaccharide solution for 7 days, respectively.After the last administration, the blood was taken, the liver, spleen and thymus were separated.The phagocytosis of monocytes was evaluated by carbon clearance test.The counts of white blood cells, red blood cells, platelets, lymphocytes, neutrophils and monocytes were detected by hematology analyzer.The serum levels of tumor necrosis factor-α(TNF-α), interferon-γ(IFN-γ), interleukin(IL) -4, IL-10 and IL-17 were detected by ELISA.The proportions of CD3,+,CD4,+, and CD3,+,CD8,+, cells in spleen lymphocytes were detected by flow cytometry.,Results:,2,Compared with the control group, the body mass, spleen index and thymus index of the model mice were significantly decreased(,P,<,0.05,P,<,0.01), the clearance coefficient K and phagocytosis index α were significantly decreased(,P,<,0.05) ; the counts of white blood cells, red blood cells, platelets, lymphocytes and neutrophils were significantly decreased(,P,<,0.01), while the count of monocytes was significantly increased(,P,<,0.05) ; the serum levels of TNF-α and IL-17 were significantly increased(,P,<,0.01), while the levels of IFN-γ and IL-4 were significantly decreased(,P,<,0.05,P,<,0.01) ; the expression of CD3,+,CD4,+, cells was significantly decreased(,P,<,0.01), the expression of CD3,+,CD8,+, cells was significantly increased(,P,<,0.05), and the ratio of CD3,+,CD4,+,/CD3,+,CD8,+, was significantly decreased(,P,<,0.01) .Compared with the model group, the spleen index of mice in the Radix Rehmanniae Recens polysaccharide groups with different doses was significantly increased(,P,<,0.01), the clearance coefficient K and phagocytosis index α of mice in the high-dose group were significantly increased(,P,<,0.05,P,<,0.01), and the counts of white blood cells, platelets, lymphocytes and neutrophils were significantly increased(,P,<,0.05,P,<,0.01) .Radix Rehmanniae Recens polysaccharide could significantly reduce the serum levels of TNF-α and IL-17 and promote the expressions of IFN-γ, IL-4 and IL-10 in model mice(,P,<,0.05,P,<,0.01) ; meanwhile, the expression level of CD3,+,CD4,+, cells was up-regulated, the expression level of CD3,+,CD8,+, cells was decreased, and the ratio of CD3,+,CD4,+,/CD3,+,CD8,+, was increased(,P,<,0.05,P,<,0.01) .,Conclusion:,2,Radix Rehmanniae Recens polysaccharide can enhance the immune function of the immunosupression mice induced by cyclophosphamide.