The study investigates the role of cryopyrin (NALP3 or CIAS1) in the activation of the inflammasome, a cytosolic protein complex that activates caspase-1 to process proinflammatory cytokines IL-1β and IL-18. Cryopyrin is essential for caspase-1 activation and IL-1β secretion in response to various stimuli, including ATP, nigericin, maitotoxin, and specific bacterial infections. Cryopyrin-deficient macrophages fail to activate caspase-1 and produce negligible amounts of IL-1β and IL-18. In contrast, cells deficient in the adaptor protein ASC, which also interacts with cryopyrin, exhibit similar defects. The study also shows that cryopyrin is dispensable for NF-κB signaling by TLR2 and TLR4, but essential for ATP-induced caspase-1 activation. Additionally, cryopyrin is crucial for inflammation in vivo, as Cias1−/− mice have enhanced survival and lower serum levels of IL-1β and IL-18 after lethal doses of LPS. The findings suggest that cryopyrin plays a key role in the dynamic assembly of the caspase-1 inflammasome, which is activated by different adaptor proteins in response to various stimuli.The study investigates the role of cryopyrin (NALP3 or CIAS1) in the activation of the inflammasome, a cytosolic protein complex that activates caspase-1 to process proinflammatory cytokines IL-1β and IL-18. Cryopyrin is essential for caspase-1 activation and IL-1β secretion in response to various stimuli, including ATP, nigericin, maitotoxin, and specific bacterial infections. Cryopyrin-deficient macrophages fail to activate caspase-1 and produce negligible amounts of IL-1β and IL-18. In contrast, cells deficient in the adaptor protein ASC, which also interacts with cryopyrin, exhibit similar defects. The study also shows that cryopyrin is dispensable for NF-κB signaling by TLR2 and TLR4, but essential for ATP-induced caspase-1 activation. Additionally, cryopyrin is crucial for inflammation in vivo, as Cias1−/− mice have enhanced survival and lower serum levels of IL-1β and IL-18 after lethal doses of LPS. The findings suggest that cryopyrin plays a key role in the dynamic assembly of the caspase-1 inflammasome, which is activated by different adaptor proteins in response to various stimuli.