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). Here, CD4 is linked to disease arising from reactivation of latent virus.