CD4 and tuberculosis: The frequencies of CD244/2B4-expressing antigen-responsive CD4+ T cells increased significantly in retreatment active TB patients as compared with latent infection individuals (p = 0.0051) and new active TB patients (p = 0.0004) (Fig. 1F and 2C), while the difference between new active TB patients and latent infection individuals was not significant (Fig. 2C).