Human caspase-4 mediates noncanonical inflammasome activation against gram-negative bacterial pathogens

Significance The innate immune system provides a first line of defense against invading pathogens. The inflammasome is an innate immune complex that activates inflammatory caspases upon infection, causing cell death and IL-1 cytokine release, which initiate defense against gram-negative bacterial pathogens but also mediate septic shock. Many inflammasome studies have been performed using cells from mice, but mice and humans differ in their complement of inflammatory caspases. Instead of caspase-11, humans encode the putative orthologs caspase-4 and caspase-5. Here, we show that caspase-4 plays a conserved role in inflammasome activation in response to virulent gram-negative pathogens in primary human macrophages. Our findings provide important insight into how inflammasomes are regulated in human cells.