FIG. 1.

Production of various proinflammatory cytokines by macrophages infected with LLO-producing or LLO-nonproducing L. monocytogenes strains. Adherent macrophages were infected with each L. monocytogenes strain at a MOI of 5 for 1 h. Cells were cultured in the presence of gentamicin, and supernatants were collected at 18 h after infection. The amount of each cytokine was determined by ELISA. Data represent the means and the standard deviations of results from triplicate assays. Similar results were obtained in three independent experiments. (-), no infection.