We studied T-cell quantitative enumeration after stimulation with ESAT-6, CFP-10 and also the sum of both antigens together (ESAT6/CFP10) with T-SPOT.TB; and the amount of IFN-γ release in QFT-G-IT, in the contacts included, according to the different degrees of exposure to the index case. The gene discussed is IFNG; the disease is tuberculosis.