The NLR family shares a domain organization consisting of a C-terminal LRR domain, a central nucleotide-binding NACHT domain, and an N-terminal protein-protein interaction domain composed of a CARD, pyrin domain (PYD) or baculovirus inhibitor of apoptosis repeat (BIR) domain (33) . NODs and IPAF contain CARD effector domains, whereas NALPs have PYD domains, and NAIPs possess BIR domains.