Commercially available assays of IFN-γ target ESAT-6 as well as CFP-10 with and without TB7.7 [4,25], and others have demonstrated detectable IFN-γ responses in HIV-infected subjects with active TB using purified protein derivative (PPD) [8,14] Our assay, which assessed responses to ESAT-6, Ag85 and WCL, may be less likely to generate IFN-γ responses that distinguish between subjects with and without TB. The gene discussed is IFNG; the disease is tuberculosis.