FIG. 2.

In vitro recognition of protein antigens. The in vitro capacity of antigens to induce IFN-γ in blood from cattle naturally exposed to M. bovis (n = 37) was determined for ESAT-6, CFP-10, MPB70, and MPB83 either individually (5 μg/ml) or as a combined protein cocktail (5 μg/ml per constituent). Responses induced by PPD-B (10 μg/ml), staphylococcal enterotoxin B (SEB) (1 μg/ml), or the no-antigen control were also determined. The antigen-induced IFN-γ response for each animal is represented by open circles, and the horizontal line provides the mean (±SEM), with results expressed as the background-corrected OD₄₅₀.