It is important to note that Mtb-specific CD4 T cells from patients with smear+ TB disease had higher PD-1 expression ex vivo and reduced proliferative capacity in vitro, compared with individuals with LTBI, yet Mtb-specific CD4 T cells from smear+ TB that had proliferated also expressed PD-1 (Figure 8). The gene discussed is PDCD1; the disease is tuberculosis.