In the QuantiFERON-TB Gold In-Tube (QFT-GIT) assay the concentration of interferon-γ (IFN-γ) is measured in plasma after incubation with Mtb antigen peptides (early secretory antigenic target 6-kD protein [ESAT-6], culture filtrate protein 10 [CFP-10] and tuberculosis-7.7 [TB7.7]). The gene discussed is IFNG; the disease is tuberculosis.