Abstract: Objective To explore the protective effect of mycobacterium vaccae to pulmonary tuberculosis of the experimental aged mice. Methods 30 aged C57BL/6J mice were randomly divided into three groups: the non-immunity protective group(group C);the mycobacterium vaccine preventative group(group M),and the Bacillus Calmette-Guerin(BCG)protective group(group B).All the subjects were injected subcutaneously 0.1 ml Physiological saline,22.5 μg mycobacterium vaccine,and 0.1 mg BCG respectively at the 0 week. Four weeks later,0.2 ml standard vaccine of H37Rv with concentration of 5×10⁵/ml was injected through the lateral tail vein to attack the toxin.Six weeks later after the infection,the mice were killed.The Flow Cytometer was used to test the Peripheral blood T lymphocyte sub-groups of the mice and to count the numbers of mycobacterium tuberculosis in the alveolus macrophages,quantitative culture of mycobacterium tuberculosis of lung tissue and the histopathological changes were analyzed. Results the ratio of CD4T lymphocyte and CD4/CD8 were(48.81±3.10、3.84±0.37) and(48.08±3.72、4.16±0.24) respectively and significantly higher than that in group C which is(38.97±3.03、3.25±0.26)(P<0.01).However,the ratio of CD4/CD8 of group M was lower than that in group B(P<0.05).The numbers of mycobacterium tuberculosis in the alveolus macrophages,quantitative culture of mycobacterium tuberculosis of lung tissue were(2.3±0.5、(1.06±0.25)×10⁵cfu) and(2.7±0.6、(1.21±0.37)×10⁵cfu)respectively and decreased significantly than that in group C(5.4±0.9、(4.07±0.97)×10⁵cfu)(P<0.01).The histopathological changes show that the tuberculosis in group M and group B was mainly proliferation without necrosis;the tuberculosis in group C was mainly lymphocyte tuberosity and necrosis. Conclusion Mycobacterium vaccine can enhance the activity of CD4T lymphocyte and can prevent preferably the pulmonary tuberculosis of aged mice.

Key words: Mycobacterium vaccae, Vaccines, Pulmonary tuberculosis