IFN-γ release is determined in response to stimulation with two highly immunogenic and specific MTB antigens, i.e. early secretory antigenic target 6 (ESAT-6) and culture filtrate protein 10 (CFP-10), either in peripheral blood mononuclear cells (T-SPOT.TB) or in whole blood (QFT-Plus) (Andersen et al. 2000; Fox et al. 2007). Here, IFNG is linked to tuberculosis.