概要　：　NLR (nucleotide-binding oligomerization domain-leucine rich repeat containing) proteins are diverse innate immune molecules that recognize different but overlapping microbial components. Although the NLR proteins are best known as innate immune receptors, one family member, CIITA (MHC class Ⅱ transactivator), had been shown to activate MHC class Ⅱ genes by coordinating transcription factors at the gene locus. A similar major regulator of MHC class I has been sought for the last 15 years without much success. We recently found another member, NLRC5 as a regulator of MHC class Ⅰ genes. NLRC5 may have a critical role in CD8 T cell-dependent tumor immunity and/or the host response to virus and bacterial infections.