GSDMD and infection: Notably, Δ6 Yptb infection led to robust GSDMD cleavage in WT Caco-2 cells, which was completely absent in CASP4−/− Caco-2 cells, indicating that caspase-4 is required for GSDMD cleavage in human IECs in response to Yersinia lacking its secreted effectors (Fig. 3A).