ESAT-6-specific transgenic CD4+ T cells, when monitored in vivo, reveal that T cell priming for ESAT-6 begins only after 10 days of infection and is initially restricted to the mediastinal lymph nodes, with subsequent differentiation into proliferative effector cells capable of producing IFN-γ and TNF-α in vitro [7]. The gene discussed is IFNG; the disease is infection.