FIGURE 3.

IFN-β pretreatment of M. tuberculosis–infected macrophages enhances IL-12 and TNF-α production. WT macrophages were infected with M. tuberculosis alone or in the presence of IFN-β (2 ng/ml), added at the indicated times prior to infection. Cytokine levels in culture supernatants were determined by ELISA at 24 h postinfection. Uninfected control samples were below the detection limit (20 pg/ml) for the cytokines measured (data not shown). Graphs show means ± SEM of triplicate samples. Data are representative of two independent experiments. Significance was determined using a two-way ANOVA with a Bonferroni post hoc test. *p < 0.05, **p < 0.01, ***p < 0.001.