IFNG and infection: [34] Macrophage activation byTh1 cells and their cytokines, IFN-γ andTNF-α, improves M. tb control but thisactivation was shown to be insufficient tocompletely clear the infection.[36] ActiveTB emerges either as progressive primaryTB infection or as a consequence ofimmune suppression after long stages ofpathogen persistence (Fig. 3).