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

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 unexpec...

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Bibliographic Details
Published in:The Journal of immunology (1950) 2005-03, Vol.174 (6), p.3475-3483
Main Authors: Rogers, Sally L, Gobel, Thomas W, Viertlboeck, Birgit C, Milne, Sarah, Beck, Stephan, Kaufman, Jim
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Base Sequence
Chickens - genetics
Chickens - immunology
DNA, Complementary - genetics
Evolution, Molecular
Humans
Killer Cells, Natural - immunology
Lectins, C-Type - genetics
Lymphoid Tissue - immunology
Major Histocompatibility Complex
Models, Genetic
Models, Immunological
Molecular Sequence Data
Phylogeny
Receptors, Immunologic - genetics
Sequence Homology, Amino Acid
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Summary: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.
ISSN:0022-1767
1550-6606
DOI:10.4049/jimmunol.174.6.3475