Abstract: Objective To study the induction of type I interferon (IFN) by different M. tuberculosis (Mtb) strains and its expression in the peripheral blood of the patients with tuberculosis.  Methods CD14⁺ cells were isolated from the peripheral blood mononuclear cells of 30 healthy people from Feb 2012 to Aug 2012, and were stimulated by the recombinant human macrophage colony stimulating factor (M-CFS) for 7 days, and differentiated into human macrophages. These macrophages were infected with Mtb strains H37Ra and H37Rv, respectively. The expression levels of type Ⅰ IFN genes IFNB and IFNA in the macrophages were detected with real-time PCR assay. We also observed the gene expression of type Ⅰ IFN in different population (15 healthy controls, 15 persons with latent Mtb infection and 15 patients with tuberculosis). Using GraphPad 4.0 software for statistical analysis, P<0.05 was considered statistically significant.  Results After Mtb H37Rv infection, IFNB gene expression in human macrophages was significantly higher than that in the control group (10.38±2.24 vs 6.26±3.42; t=2.47, P=0.026). There were no significant differences in IFNB gene expression between Mtb H37Ra infection group and control group (8.92±0.85 vs 6.26±3.42;t=1.84, P=0.09). There were no significant differences in IFNA gene expression among Mtb H37Rv infection group, H37Ra infection group and control group (5.11±2.31 vs 5.17±3.40 vs 4.41±1.69; F=0.16，P=0.85). The IFNB gene expressions in TB patients (4.32±1.22) were significantly higher than that in healthy controls (2.73±1.23; t=3.55, P=0.0014). There were no significant differences in IFNA gene expression among healthy controls, the persons with latent Mtb infection and the patients with tuberculosis (3.91±0.75 vs 4.25±1.03 vs 4.73±1.44；F=1.93，P=0.064).  Conclusion Virulent Mycobacterium tuberculosis infection can induce type Ⅰ IFN gene expression. Up-regulated expression of IFNB gene can be used as a potential molecular marker in the diagnosis of tuberculosis.

Key words: Tuberculosis, Interferon type Ⅰ, Gene expression