FIG. 7.

Pore formation and cell lysis induced by L. pneumophila requires caspase-1, Ipaf, and bacterial flagellin but not Asc. BMMs from wild-type (WT), Asc^−/−, Ipaf^−/−, or Casp1^−/− mice were either noninfected or infected with the indicated L. pneumophila variants at an MOI of 50. (A and D) Macrophages were assayed for PI uptake at 2 h postinfection by flow cytometry. Noninfected controls are represented in gray with a dashed outline, and the overlaid samples are represented by a solid black line. (B, C, and E) LDH release assays were performed at the indicated times for wild-type BMMs infected with indicated L. pneumophila variants (B and E) or wild-type, Asc^−/−, Ipaf^−/−, or Casp1^−/− BMMs infected with wild-type L. pneumophila (C). Values represent the percentage of LDH released compared to that for cells lysed with Triton X-100. Data points are averages ± standard deviations. Data for wild-type macrophages infected with wild-type L. pneumophila are the same in panels B and C. Macrophages were incubated in the presence of an additional 50 mM KCl or 50 mM NaCl where indicated (D and E). Data are representative of five (A), four (B and C), or three (D and E) experiments.