Murine caspase-11 is an upstream protease of caspase-1 and interacts with the proform of caspase-1 which in turn activates IL-1 beta. Caspase-11 is not constitutively expressed in most cell types. Its expression can be upregulated by LPS, IFN-gamma, and other pro-inflammatory stimuli. NF-kappaB and STAT1 were reported to be involved in the activation. Caspase-11 knock -out mice were resistant to endotoxin shock and do not produce IL-1 after stimulation with LPS. Their production of IFN-gamma was also deficient.