WT, NAIP-/- clone #12, and two independent clones of NLRC4-/- THP-1 monocyte-derived macrophages were primed with 100 ng/mL Pam3CSK4 for 16 hours. Cells were then treated with PBS (Mock), PA alone, LFnFlaA310–475 alone (LFnFlaA), LFnPrgJ alone, LFnYscF alone, PA+LFnFlaA310–475 (FlaTox), PA+LFnPrgJ (PrgJTox), or PA+LFnYscF (YscFTox) for 6 hours (A, C). As a control, cells were primed with 500 ng/mL LPS for 4 hours and treated with 10 μM nigericin for 6 hours (B, D). Release of IL-1β into the supernatant was measured by ELISA. ns–not significant, *p < 0.05, **p < 0.01, ****p < 0.0001 by Šídák’s multiple comparisons test (A), or by unpaired t-test (B), or by Dunnett’s multiple comparisons test (C, D). Error bars represent the standard deviation of triplicate wells from one experiment. Data shown are representative of at least three independent experiments.