FIG. 1.

Caspase-1 is required for pore formation in response to Legionella infection. BMMs adherent to glass coverslips were infected with L. pneumophila at different MOIs for 1 h in the presence of anti-L. pneumophila antibody, and the cultures were processed for pore formation assays by double staining with EtBr and acridine orange. (A) Caspase-1^−/− and C57BL/6 BMMs were infected for 1 h with L. pneumophila at an MOI of 2, 10, or 100. (B) Representative images of pore formation in caspase-1^−/− or C57BL/6 BMMs at 1 h after infection with L. pneumophila at an MOI of 10 per cell. Acridine orange-stained BMMs (green) show total cells in each field, and EtBr (red) indicates permeabilized BMMs (middle panels). Right panels show merged images. Data are representative of those found in four independent experiments. *, P < 0.05 in comparison to C57BL/6 BMMs. WT, wild type.