ESAT-6–induced IFN-γ production by PBMCs. (A) Dose-dependent production of IFN-γ induced by ESAT-6 plus anti-CD28. Freshly isolated PBMCs were cultured with different concentrations of ESAT-6 in the presence of anti-CD28 (1μg/mL) for 72 hour. The production of IFN-γ in supernatants was detected by ELISA. (B) ESAT-6–specific IFN-γ secretion was measured by ELISA from PBMCs (n = 22). (C) Representation of ELISPOT results. (D) The frequency of IFN-γ–producing cells was enumerated by ELISPOT assay (n = 22). Cultures were set up in triplicate. Each symbol represents one data point from one donor. *P > .05; **P < .05; ***P < .001. Horizontal bars represent mean values.