The NLR family is a group of recently identified cytoplasmic PRRs that contain more than 23 members in humans (15) . The major role of NLRs is to recognize cytoplasmic microbial PAMPs and/or endogenous danger signals and initiate immunological responses, although the physiological function of most NLRs is poorly understood at present (31) . Members of the NLR family are categorized into at least five subfamilies according to their N-terminal structure, including NODs (nucleotidebinding oligomerization domain-1), NALPs (NACHT-, LRR-and pyrindomain-containing proteins), IPAF (ICE-protease activating factor), NAIPs (neuronal apoptosis inhibitor factors) and class II transactivator (CIITA) (32) .