FIG. 3.

IFN-γ responses to recombinant ESAT-6, CFP-10, and ESAT-6-CFP-10. Heparinized blood samples were obtained from reindeer and dispensed immediately in 1.5-ml aliquots into individual wells of a 24-well plate. Treatment was either no stimulation (PBS), rESAT-6 (10 μg/ml), rCFP-10 (10 μg/ml), or rESAT-6-CFP-10 (10 μg/ml). Whole-blood cultures were incubated for 48 h, plasma was harvested, and IFN-γ concentrations were determined using an ELISA-based kit (Cervigam; Pfizer Animal Health). Absorbencies of standards and test samples were read at 450 nm using an ELISA plate reader. Duplicate samples for individual treatments were analyzed. Data are presented as the response to antigen stimulation minus the response to no stimulation (ΔIFN-γ, OD) and are means ± standard errors of the means. Responses at 90, 103, 120, and 160 days after challenge were averaged (n = 4). Open bars, responses by M. bovis-infected reindeer (n = 10); solid bars, responses by noninfected reindeer (n = 4). Asterisks indicate responses by M. bovis-infected reindeer that differ (P < 0.05) from the respective responses by noninfected reindeer.