OBJECTlVE To investigate the effect of α-glycan isolated from Isatis indigotica on humoral immunity and cellular immunity functions in mice immunized with H1N1 influenza vaccine. METHODS BALB/c mice were immunized intramuscularly once with H1N1 influenza vaccine ( 3 μg) plusα-glycan ( 100μg) each mouse. The serum total antibody titer and its isotype antibody titer of immu-nized mice were analyzed by ELlSA at 5, 8, 10, 12 and 14 d after injection at vaccine. The proliferation activities of spleen T and B lymphocytes were determined with MTT method. The levels of cytokines interferon-γ( lFN-γ) , tumor necrosis factorα( TNF-α) , interleukin-4( lL-4) and lL-12 were measured by ELlSA kits. The populations of CD4+, CD8+, CD3+ and CD19+ lymphocytes were determined by flow cytometry. Furthermore, the proliferation rate of macrophages was studied with MTT method in vitro. RESULTS The α-glycan from I.indigotica could gradually induce high specific-antibody production 5-14 d after immunization with H1N1 influenza antigen plus theα-glycan in mice compared to immunization with antigen alone ( P<0.01) . After injection of antigen withα-glycan for 5 d, the main lgG isotype was lgM, and the titer levels of total lgG, lgG1 , lgG2a and lgG2b were also significantly raised following 5-14 d after immunization. The α-glycan significantly promoted the spleen T and B lymphocytes proliferation ( growth rate 44.2%and 37.8%) , stimulated the secretion of lFN-γand lL-12 of splenocytes ( P<0.01, P<0.05) , and also promoted lL-4 secretion of thymocytes (P<0.01). The polysaccharide significantly raised the percent age of CD3+T cells ( P<0.01) , CD3+/CD19+ T lymphocytes ( P<0.01) , and CD8+ T cells ( P<0.01) but decreased the percentage of CD4+/CD8+ T lymphocytes compared with antigen alone group ( P<0.01) . Furthermore, the α-glycan exhibited significant effects on the proliferation and TNF-α secre-tion of MH-S macrophages. CONCLUSlON Theα-glycan isolated from I.indigotica can improve humoral and cellular immunity response in mice immunized with H1N1 influenza vaccine.