Abstract: Objective To study the immunotherapeutic effects and its mechanism of IFN-γ combined with M.vaccae vaccine on mice model with tuberculosis.Methods Sixty BALB/c mice were randomly divided into 5 groups: normal group,tuberculosis model group,IFN-γ group,M.vaccae vaccine group,the IFN-γ+ M.vaccae vaccine group.Each group included 12 mice.Forty-eight mice was infected by the tail vein with 1×10⁶CFU of M.tuberculosis H₃₇Rv strain,and treated intraperitoneally with the saline,IFN-γ,IFN-γ combined with M.vaccae vaccine at 10 days after infection.Six mice each group were sacrificed at 6 weeks after infection.The body weights of the mice and the weights of lungs and spleens from the mice were measured.The lungs and spleens of the mice were taken,determined the CFU,and observed histopathologic changes.The level of IFN-γ and IL-4 in the blood were detected with ELISA method.The expression of IFN-γ mRNA and IL-4 mRNA in lungs were detected by RT-PCR method.The survival times in the other 30 mice were evaluated in 60 days.Results The pathological changes of lungs in the three treatment groups were localized,while those in tuberculosis model group were extensive.All of mice died in tuberculosis model group,none of mice died in the normal group and the IFN-γ+ M.vaccae vaccine group,only one mice died in IFN-γ group and M.vaccae vaccine group.At 6 weeks after infection,compared with tuberculosis model group,the CFUs in lungs and spleens were significantly decreased in IFN-γ groups(7.12±0.51) and(6.42±0.48) and in M.vaccae vaccine groups(6.31±0.47) and(6.07±0.39),particularly in the IFN-γ+ M.vaccae vaccine group(2.67±0.36) and(2.12±0.33)(P<0.05).The level of IFN-γ in the blood and the expression of IFN-γ mRNA in lung tissue of mice in tuberculosis model group(162±46) pg/ml and(0.18±0.06) were lower than that in normal group((521±198) pg/ml and(0.98±0.13))(P<0.01),and IFN-γ groups(402±134) pg/ml and(0.66±0.08),M.vaccae vaccine groups(416±153) pg/ml and(0.68±0.09) and IFN-γ+ M.vaccae vaccine group(493±145) pg/ml,(0.81±0.11) were higher than that in tuberculosis model group(P<0.05).The level of IL-4 in the blood and the expression of IL-4 mRNA in lung tissue in tuberculosis model group((102±24.8) pg/ml and(1.46±0.25))were higher than that in normal group((56.2±14.5) pg/ml and(0.04±0.01))(P<0.01),and IFN-γ groups((73.5±15.3) pg/ml and(0.63±0.12)),M.vaccae vaccine groups(71.3±14.6) pg/ml and(0.59±0.13) and IFN-γ+ M.vaccae vaccine group(60.8±12.7) pg/ml and(0.28±0.03) were lower than that in tuberculosis model group(P<0.05).Conclusions IFN-γ combined with M.vaccae vaccine could improve host defence against the infection of Mycobacterium tuberculosis,and reduce mycobacterial growth during tuberculosis,and might be associated with a decrease in inflammation in lung and spleen tissue by activating the Th1 response,and inhibiting the Th2 response,and they have cooperative effect.

Key words: interferon-&gamma, M.vaccae, mycobacterium, tuberculosis, cytokines