Increased PPD-induced IFN-γ production was observed in both LTBI and smear+ TB groups, suggesting that the capacity of PD-1/PD-L1 blockade to augment Mtb-specific IFN-γ production is not unique to Mtb infection status and is not directly correlated with ex vivo expression of PD-1, which was significantly lower on PPD-specific CD4 T cells in individuals with LTBI, compared with smear+ TB. Here, CD4 is linked to tuberculosis.