Although ESAT-6 suppresses mouse and human T-cell secretion of IFN-γ, it elicits strong T-cell responses in animal models and humans, and is therefore, a candidate vaccine antigen and indeed has been cloned into BCG.39 On the other hand, CFP-10 elicits robust T-cell responses in mice, reactive with T cells from humans with tuberculosis and does not have immune-suppressive activity.40,41 To explain the ambiguity in immunogenicity of these proteins, we proposed that their intracellular processing generated immunogenic moieties within APCs. The gene discussed is IFNG; the disease is tuberculosis.