The above data indicating increased PD-1 expression on Mtb-specific CD4 T cells in smear+ TB patients, compared with healthy, asymptomatic individuals with LTBI, were based on analysis of Mtb-specific CD4 T cells circulating in peripheral blood, and thus may not reflect the phenotype of Mtb-specific T cells at the site of infection in the lung. Here, CD4 is linked to tuberculosis.