AIM2 is one of the human IFN-inducible proteins, encoding a 39 kD protein. It contains a 200 amino acid repeat, which is a signature of the HIN-200 family (hematopoietic IFN-inducible nuclear proteins). Expression of AIM2 can inhibit cell growth and tumor formation, possibly through inducing apoptosis and suppressing nuclear factor-kappa B transcriptional activity and desensitizing tumor necrosis factor-alpha-mediated nuclear factor-kappa B activation. Furthermore, the gene for AIM2 shows a high frequency of mutations associated with microsatellite unstable colorectal cancers. AIM2 plays a critical role in the activation of caspase-1, the protease responsible for the processing of pro-inflammatory cytokines IL-1beta and IL-18. AIM2 is also essential for mediating inflammatory reactions triggered by cytoplasmic DNA. AIM2 is an important sensor for different pathogens through the binding of cytoplasmic double-stranded DNA through HIN-200 domain and formation of inflammatsomes including ASC/AIM2. This complex then triggers caspase-1 activation. Recent studies also show that AIM2/ASC complex acts as a novel caspase-8 activation platform.