FIG. 6.
Heat-killed L. pneumophila induces IL-10 production in Legionella-infected BM macrophages. (A) BM macrophages (105 cells) were infected with L. pneumophila on day 0. Heat-killed bacteria (HKB) and IL-12 plus IL-18 (10 ng/ml) were added to the wells at 2 h and 24 h after infection, respectively. Seven days after infection, IL-10 production in supernatants was determined. The results are expressed as means ± standard deviations for five wells. Similar results were obtained in at least two independent experiments. An asterisk indicates a P value of <0.05 in a comparison with the group receiving IL-12 plus IL-18 but not heat-killed bacteria. (B) BM macrophages (105 cells) were infected with L. pneumophila on day 0. Heat-killed bacteria (HKB) were added to the wells at 2 h after infection. Anti-IL-10 antibodies (Ab) and IL-12 plus IL-18 (10 ng/ml) were added to the wells at 24 h after infection. Seven days after infection, IFN-γ production in the wells was determined. The results are expressed as means ± standard deviations for five wells. Similar results were obtained in at least two independent experiments. An asterisk indicates a P value of <0.05 in a comparison with the group receiving IL-12 plus IL-18 and heat-killed bacteria but not antibodies.