Elevated expression of T-bet in mycobacterial antigen-specific CD4+ T cells from patients with tuberculosis

T-bet is a T-box transcriptional factor that controls the differentiation and effector functions of CD4 T cells. In this study, we studied the role of T-bet in regulating CD4+ T cell immunity against tuberculosis (TB). T-bet expression in Mycobacterium tuberculosis antigen-specific CD4+ T cells was significantly higher in patients with active TB than in individuals with latent TB infection (p < 0.0001). Comparison of T-bet expression in TCM and TEM subsets showed that CD4+T-bet+M. tuberculosis antigen-specific CD4+ T cells had significantly lower frequency of TCM (p = 0.003) and higher frequency of TEM (p = 0.003) than CD4+T-bet− cells. The expression of PD-1 in antigen-specific CD4+ T cells was significantly higher in patients with TB than in individuals with latent TB infection (p = 0.006). CD4+CD154+T-bet+ T cells had significantly higher expression of PD-1 than CD4+CD154+T-bet− T cells (p = 0.0028). It is concluded that T-bet expression might be associated with differentiation into effector memory cells and PD-1 expression in mycobacterial antigen-specific CD4+ T cells.