IFNG and tuberculosis: The WHO endorsed (10) IGRA tests use Mtb antigens ESAT-6 and CFP-10 to stimulate T cells in whole blood (QTF-Plus and WANTAI TB IGRA) or isolated peripheral blood mononuclear cells (PBMCs) (T-SPOT.TB), followed by interferon-γ (IFNγ) detection after 24 hours of incubation by ELISA or ELISpot, respectively.