FIG. 1.
Effects of Th1 cytokines on the growth of L. pneumophila in BM macrophages. BM macrophages (105 cells) were infected with L. pneumophila (105 CFU; infectivity ratio, 1:1) on day 0. Cytokines (20 ng/ml) were added to the wells of macrophage cultures at 24 h after infection (day 1). At the indicated times, supernatants and macrophages were collected and viable bacterial numbers were compared in the control group (open circle) and in groups treated with IL-12 (closed circle), IL-18 (open square), IL-12 plus IL-18 (closed square), and IFN-γ (open triangle). The results are expressed as means ± standard deviations for five wells per group. Similar results were obtained in three independent experiments. An asterisk indicates a P value of <0.05 in a comparison with the control group.