New tests based on the expression of interferon-gamma (IFN-γ) by sensitized lymphocytes in response to specific M. tuberculosis antigens (e.g., early secretory protein 6 [ESAT-6] and culture filtrate protein 10 [CFP-10]) appear to be more specific (8) and sensitive (9) than the TST in identifying latent and active TB. This evidence concerns the gene IFNG and tuberculosis.