CASP4 and infection: Importantly, the processed form was detected only upon infection with WT F. novicida but not upon infection with the ΔFPI mutant strongly suggesting that caspase-4 processing is associated with cytosolic detection of F. novicida. Altogether, our data demonstrate that in human macrophages, cytosolic F. novicida sensing primarily depends on caspase-4 and on the non-canonical inflammasome.