Figure 1: The inflammasomes in IL-1β and IL-18 activation. Certain danger signals and pathogens trigger the assembly of a multiprotein complex called the inflammasome. Inflammasomes consist of a scaffolding protein, in particular NLRP1, NLRP3, NLRC4, AIM2, and recently discovered RIG-I and IFI16, of ASC and of procaspase-1. NLRP1 and NLRC 4 can also bind procaspase-1 directly. The assembly is responsible for autoproteolysis and thereby activation of caspase-1 which subsequently can cleave the non-active inflammatory cytokines pro-IL-1β and pro-IL-18 into their mature and biologically active variants.

ASC, apoptosis-associated speck-like protein containing a caspase recruitment domain; CARD, caspase activation and recruitment domain; Casp1, enzymatically active caspase-1; dsDNA, double stranded deoxyribonucleic acid; IFI16, interferon gamma-inducible protein 16; IL-18, interleukin-18; IL-1β, interleukin-1β; MDP, muramyl dipeptide; NLRC4, NLR family CARD domain-containing protein 4; NLRP1, NOD-like receptor family, pyrin domain containing 1; NLRP3, NOD-like receptor family, pyrin domain containing 3; pro-Casp1, procaspase-1; PYD, pyrin domain; RIG-I, retinoic acid inducible gene-I; ROS, reactive oxygen species; ssRNA, single stranded ribonucleic acid.