Tuberculosis patients display a high proportion of CD8(+) T cells with a high cytotoxic potential

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (Mtb) and remains a major cause of morbidity and mortality worldwide. In the host's immune response system, T cells play a critical role in mediating protection against Mtb infection, but the role of CD8(+) T cells is still controversial. We evaluated the phenotypical characterization and cytotoxic ability of CD8(+) T cells by flow cytometry‐based assay. Cytokine levels in serum were measured by multiplex cytokine assay. Our data show that cells from TB patients have an increased percentage of peripheral blood CD8(+)αβ(+) T (p = 0.02) and CD56(+)CD8(+) T (p = 0.02) and a decreased frequency of NKG2D(+)CD8(+) T (p = 0.02) compared with healthy donors. Unlike CD8(+) T cells from healthy donors, CD8(+) T cells from TB patients exhibit greater cytotoxicity, mediated by HLA class I molecules, on autologous monocytes in the presence of mycobacterial antigens (p = 0.005). Finally, TB patients have a proinflammatory profile characterized by serum high level of TNF‐α (p = 0.02) and IL‐8 (p = 0.0001), but, interestingly, IL‐4 (p = 0.002) was also increased compared with healthy donors. Our data show evidence regarding the highly cytotoxic status of CD8(+) T cells in Mtb infection. These cytotoxic cells restricted to HLA‐A, B, and C could be used to optimize strategies for designing new TB vaccines or for identifying markers of disease progression.