Cpb1–C3–C3aR pathway is required for caspase-11–dependent cell death in response to Gram-negative bacterial pathogens. Indicated RAW macrophage cell lines were infected with (A) Salmonella Typhimurium (SL1344; MOI 100:1) or (B) S. flexneri (M90T; MOI 50:1) for 18 h and cytotoxicity was measured. (C) BMDMs were infected with S. Typhimurium (SL1344 ΔorgA/fliC; MOI, 100:1) for 18 h and cytotoxicity was measured. All cytotoxicity was measured by release of LDH. Statistics analyzed via the unpaired Student’s t test. *, P < 0.05; **, P < 0.01; ***, P < 0.001. Data are representative of at least three independent experiments (A–C), with three technical replicates each time.