Cross immune reaction between Mycobacteria smegmatis and Mycobacteria tuberculosis
Objective 
To identify the cross-reactive antigens shared by Mycobacteria smegmatis(MS) and Mycobacteria tuberculosis(MTB) and to analyze their antigenicity. 
 
 
Methods 
Bacterial antigens were extracted from strains of MS and MTB by ultrasonication. Western blot assay was performed to analyze common antigens that reacted with both of the antiserum samples against MS and MTB. The extracted bacterial antigens were mixed with incomplete Freund′s adjuvant and then were injected into muscles of mice. Cytokines secreted by murine spleen lymphocytes following stimulation with various antigens of MS and MTB were determined by ELISPOT and flow cytometry on the 7th day. IgG levels in serum samples were detected by ELISA 7 days after injection. 
 
 
Results 
There were cross-reactive antigens shared by MS and MTB. Potent humoral immune responses and cellular immunity against both MS and MTB could be induced by those cross-reactive antigens after sensitization the mice by either MS or MTB antigens. Cytokines of IL-2 and IFN-γ in CD4+ and CD8+ T cells of mice stimulated with MS or MTB antigens were significantly increased as compared with those of non-sensitization group and those of Brucella antigens stimulation group. 
 
 
Conclusion 
Cross-reactive antigens shared by MS and MTS can effectively promote specific immune reactions to the infection of MTB, which provides a scientific basis for the development of tuberculosis vaccines. 
 
 
Key words: 
Mycobacteria tuberculosis; Mycobacteria smegmatis; Cross-reactive antigen; Immune response