PD-1 on IFN-γ+ CD4 T cells responding to HCMV pp65 (Supplementary Figure 1C) and SEB (Supplementary Figure 1D) was similar between individuals with LTBI and smear+ TB patients, thus suggesting upregulation of PD-1 on Mtb-specific CD4 T cells may be driven by exposure to high levels of mycobacterial antigens in vivo. Here, CD4 is linked to tuberculosis.