TABLE 2.

Effects of culture duration on IFN-γ responses by infected reindeer^a

Stimulant	Mean ΔOD ± SEMb with:
	24-h stimulation	48-h stimulation
M. avium PPD	0.118 ± 0.034	0.314 ± 0.056*
M. bovis PPD	0.686 ± 0.111	1.417 ± 0.211*
rESAT-6-CFP-10	1.004 ± 0.223	1.244 ± 0.193
PWM	0.110 ± 0.024‡	0.392 ± 0.092*‡

^aHeparinized blood samples were obtained from M. bovis-infected reindeer 8 months after challenge. Blood was dispensed in 1.5-ml aliquots immediately into individual wells of a 24-well plate. Treatments included no stimulation (PBS), M. avium PPD (40 μg/ml), M. bovis PPD (40 μg/ml), rESAT-6-CFP-10 (10 μg/ml), and PWM (20 μg/ml). Blood cultures were incubated for 24 or 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 means of results for 10 samples.

^b*, response differs from responses to respective antigens/mitogen after a 24-h stimulation (P < 0.01). ‡, effects of culture duration on PWM responses by noninfected reindeer (ΔOD, 0.132 ± 0.037 with a 24-h stimulation versus 0.446 ± 0.159 with a 48-h stimulation [P = 0.07]) were similar to those of infected reindeer.