FIG. 2.

IFN-γ responses to M. avium PPD stimulation (A) and M. bovis PPD stimulation (B) by M. bovis-infected (n = 13) (open squares) and noninfected (n = 4) (solid squares) reindeer. Heparinized blood samples were obtained at the indicated time points and dispensed immediately in 1.5-ml aliquots into individual wells of a 24-well plate. Treatment was no stimulation (PBS), M. avium PPD (40 μg/ml), or M. bovis PPD (40 μg/ml). 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 PPD stimulation minus the response to no stimulation (ΔIFN-γ, OD) and are means ± standard errors of the means. Asterisks indicate responses by M. bovis-infected reindeer that differ (P < 0.05) from the respective responses by noninfected reindeer.