A third receptor activates inflammasome following L. monocytogenes infection. Macrophages were infected with L. monocytogenes strains (MOI 6) and IL-1β secretion determined after four hours. A) WT, Nalp3−/−, and ASC−/− macrophages infected with WT or ΔLLO mutant L. monocytogenes. B) WT, Nalp3−/−, and ASC−/− macrophages were infected with either flaA or ΔLLO mutant L. monocytogenes. Error bars, s.d. Representative of three experiments. *p = 0.05.