FIG. 4.

The IDO-specific inhibitor 1-MT antagonizes the IFN-γ-induced inhibition of N. caninum growth in bovine endothelial cells. Bovine endothelial cells (BAOEC cells; 3 × 10⁴ cells per well) were stimulated with bovine IFN-γ (100 U/ml) in the presence or absence of 1-MT (1.5 mM). (A) After 72 h of stimulation supernatants were harvested, and the kynurenine content was determined by use of the Ehrlich reagent. The data are means and standard errors of the means of three independent experiments performed in triplicate. Significant inhibition of IDO by 1-MT is indicated by an asterisk. OD₍₄₉₂₎, optical density at 492 nm. (B) After 72 h cultures were infected with T. gondii tachyzoites (2 × 10⁴ tachyzoites per well), and T. gondii growth was monitored using [³H]uracil. The data are means and standard errors of the means of three independent experiments performed in triplicate. Significant inhibitory effects of 1-MT (P < 0.05) or supplemental tryptophan (0.6 mM) are indicated by asterisks. (C) After 72 h cultures were infected with N. caninum tachyzoites (2 × 10⁴ tachyzoites per well), and N. caninum growth was monitored using [³H]uracil. The data are means and standard errors of the means of three independent experiments performed in triplicate. Significant inhibitory effects of 1-MT (P < 0.05) or supplemental tryptophan (0.6 mM) are indicated by asterisks. (D) BAOEC cells (2 × 10⁵ cells) were cultured in medium in the absence or in the presence of IFN-γ (100 U/ml) or l-kynurenine (20 μg/ml). After 3 days cells were harvested, and the number of cells was determined. The data are means and standard errors of the means of three independent experiments.