Objective:To investigate the cellular immune responses induced by Mycobacterium tuberculosis H37Ra and examine its protective efficacy against MTB in mice.Methods:Balb/c mice were divided into H37Ra

BCG and NS groups randomly

and intracutaneously injected at caudal region with H37Ra

BCG and NS respectively.At 8 weeks after immunization

some mice were sacrificed

and the percentages of CD3

+

T

CD4

+

T and CD8

+

T-lymphocyte in spleen were detected by flow cytometry.The spleen lymphocytes of mice were cultured with PPD in vitro;the proliferation of splenocytes was detected by MTT assay.The productions of IFN-γin the supematant of culture were determined by ELISA.After 8 weeks of immunization

Balb/c mice were challenged via intraperitoneal route with MTB H37Rv strain.Four weeks later

mice were sacrificed

then the bacteria load in the lung were determined.Results:After 8 weeks of immunization

the percentages of CD3

+

T and CD4

+

T-lymphocyte in mice of H37Ra vaccination were significantly higher than those of the NS control subjects（41.63±1.68）%

（27.08±0.58）% vs （38.34±0.74）%

（24.37±1.60）%（P

<

0.05）.Compared with the BCG group

the percentages of CD3

+

T

CD4

+

T and CD8

+

T- lymphocyte in mice of H37Ra vaccination were slightly higher

the percentages of CD4

+

T and CD8

+

T-lymphocyte were not significantly different among 3 groups（P

>

0.05）.The proliferation of antigen-specific lymphocytes

the productions of IFN-γin the H37Ra group were significantly higher than those of the NS group（P

<

0.05）

while proliferation and IFN-γwere not significantly different between the H37Ra and BCG groups（P

>

0.05）.At 4 weeks after challenge

compared with the NS group

the mean numbers of viable bacteria in the lung of the H37Ra group reduced 0.954log

10

CFU（P

<

0.05）.Between the H37Ra and BCG groups

there were no difference（P

>

0.05）.Conclusion:Mycobacterium tuberculosis H37Ra could induce specific cellular immune responses in mice.The immunity effect of H37Ra is similar to BCG.