PDCD1 and tuberculosis: Although, in this study, we did not measure PD-1 expression on antigen-specific cells, recent studies have shown that PD-1 expression is increased on TB-specific CD4 T cells from patients with active TB [47] and that blockade of the PD-1/PD-L pathway can recover cytokine and proliferative responses of these cells in vitro [42, 48].