IL1R1 and colitis: Mice with hyper-activation of Nlrp1a, but lacking the IL-1 receptor (Il-1r−/−Nlrp1aQ593P/Q593P), were highly susceptible to DSS-induced colitis compared to littermate controls (Il-1r−/−Nlrp1aQ593P/+), and had to be ethically killed by day 5 (Fig. 4a).