IFNG and tuberculosis: Two commercial tests are available: the T-SPOT.TB (Oxford Immunotec, Abingdon, UK), which measures the number of IFN-γ-producing T cells by enzyme-linked immunospot (ELISPOT) assay, and the QuantiFERON-TB Gold In-Tube (QFT-GIT) test and its predecessor the QuantiFERON-TB Gold (QFT-G) test (Cellestis Ltd., Carnegie, Australia), which detect IFN-γ in culture supernatant by enzyme-linked immunosorbent assay (ELISA).