Abstract: Objective To investigate the different influence of BCG vaccination to the antituberculosis treatment and to the peripheral blood T lymphocyte subset at different period. Methods 80 SD rats with PPD skin-test negative were randomly divided into 4 groups: group 1 started BCG at the same time that the treatment started,group 2 started BCG after the treatment started for 1 month,group 3 was the control group,group 4 was to judge the effect of the model.Every rat was injected a dose of 108 CFU mycobacterium tuberculosis(Mtb) at beginning of the observation.At the end of the(1st) month,the rats of the group 4 were killed to conduct pathological and tuberculosis bacterial examinations,while the rats of group 1,2 and 3 were given anti-tuberculosis chemotherapy.Group 1 was given BCG vaccination at the beginning of anti-tuberculosis chemotherapy,group 2 was given BCG vaccination after anti-tuberculosis chemotherapy stared for one month Mortality of each group was measured.CD3⁺,CD4⁺,CD8⁺ and DP T lymphocytes in peripheral blood of rats were measured at the beginning and the end of(1st)、(2nd)、(3rd) and(5th) month of experiment.Absolute value of peripheral blood lymphocyte of the rats in group 1,2 and 3 were examined at the(2nd) month and the(5th) month of experiment. Results (1) Within 1 month of the injection of Mtb,2 rats died in group 1,3 and 4 and 1 rat died in group 2.Mortality after 4-month of antituberculosis chemotherapy: group 1 was 22.2%(4/18) which was higher than that of group 2(0/19,P<0.05).Mortality of group 3 was 5.6%(1/18).(2) The value of CD4/CD8 decreased and the level of CD8⁺ cell increased(P<0.05 or(P<0.05 or p<0.01)..(3)In group1,the percentage of T cell(CD3⁺) and CD4⁺ decreased,while the lymphocyte absolute value and the percentage of CD8⁺,DP T cell increased((P<0.05 or P<0.01);after the treatment for 2 months,the level of CD3⁺,CD4⁺ T lymphocytes was at normal level while CD8⁺ and DP T cell were still maintained at high level.(4) In group 2,the level of CD8⁺ and DP T cell went up statistically significant,but the change of CD3⁺,CD4⁺ T lymphocytes was not statistically significant,P>0.05. Conclusion The sum of lymphocyte increased significantly while the percentage of T cell among the sum of lymphocyte decreased significantly is an important immunity character in the group that started BCG at the same time of antituberculosis chemotherapy and the mortality increased after the(1st) month.DP T cell is the protective immune relation cell against tuberculosis.Immunotherapy with BCG should start after q month of anti-tuberculosis chemotherapy.

Key words: Tuberculosis, Cellular immunology, T-lymphocytes subset, BCG, Immunotherapy