title: Characterization of the chicken C-type lectin-like receptors B-NK and B-lec suggests that the NK complex and the MHC share a common ancestral region.
abstract: The sequencing of the chicken MHC led to the identification of two open reading frames, designated B-NK and B-lec, that were predicted to encode C-type lectin domains. C-type lectin domains are not encoded in the MHC of any animal described to date; therefore, this observation was completely unexpected, particularly given that the chicken has a "minimal essential MHC." In this study, we describe the initial characterization of the B-NK and B-lec genes, and show that they share greatest homology with C-type lectin-like receptors encoded in the human NK complex (NKC), in particular NKR-P1 and lectin-like transcript 1 (LLT1), respectively. In common with NKR-P1 and LLT1, B-NK and B-lec are located next to each other and transcribed in opposite orientation. Like human NKR-P1, B-NK has a functional inhibitory signaling motif in the cytoplasmic tail and is expressed in NK cells. In contrast, B-lec contains an endocytosis motif in the cytoplasmic tail, and like LLT1, is an early activation Ag. Further analysis leads us to propose that there are four subgroups of C-type lectin-like receptors in the NKC, which arose as a result of duplication events. Moreover, this analysis suggests that the NKC may be considered a fifth paralogous region, and therefore shares an ancient common origin with the MHC. This provides evidence that C-type lectin-like receptors were present in the preduplication, primordial MHC region, and suggests that an original function of MHC molecules was for recognition by NK cell receptors encoded nearby.
authors.affiliation: Institute for Animal Health, Compton, Berkshire, United Kingdom.
authors.forename: Sally L
authors.initials: SL
authors.lastname: Rogers
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Göbel
authors.forename: Birgit C
authors.initials: BC
authors.lastname: Viertlboeck
authors.forename: Sarah
authors.initials: S
authors.lastname: Milne
authors.forename: Stephan
authors.initials: S
authors.lastname: Beck
authors.forename: Jim
authors.initials: J
authors.lastname: Kaufman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002645:Chickens / Q000235:genetics* / Q000276:immunology*; D018076:DNA, Complementary / Q000235:genetics; D019143:Evolution, Molecular; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology*; D037181:Lectins, C-Type / Q000235:genetics*; D008221:Lymphoid Tissue / Q000276:immunology; D008285:Major Histocompatibility Complex; D008957:Models, Genetic; D018448:Models, Immunological; D008969:Molecular Sequence Data; D010802:Phylogeny; D011971:Receptors, Immunologic / Q000235:genetics*; D017386:Sequence Homology, Amino Acid
chemical_list: D018076:DNA, Complementary; D037181:Lectins, C-Type; D011971:Receptors, Immunologic