CD4 and pulmonary tuberculosis: When we used the radiographic score to represent the extent or severity of pulmonary TB, we found that it was positively correlated with the percentage of PD-1 on CD4 lymphocytes (Pearson correlation: 0.458, p = 0.021) or Th1 cells (CD4+ and IFN-γ+) (Pearson correlation: 0.446, p = 0.025) (Fig. 4), although the percentage of PD-1 on lymphocytes was not significantly different between the TB and control groups.