WT, NAIP-/- (A–C) and NLRC4-/- (D–F) THP-1 monocyte-derived macrophages were treated with siRNA targeting a control scrambled siRNA, siRNA targeting CASP4 (A, D) or CASP5 (B, E), or siRNA targeting both CASP4 and CASP5 (C, F) for 48 hours. Cells were primed with 100 ng/mL Pam3CSK4 for 16 hours. Cells were then infected with PBS (Mock) or WT S. Typhimurium at an MOI = 20 for 6 hours. Release of IL-1β into the supernatant was measured by ELISA. As a control, cells were transfected with LPS. ns–not significant, *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001 by Tukey’s multiple comparisons test. Error bars represent the standard deviation of triplicate wells from one experiment. Data shown are representative of at least three independent experiments.