Abstract
Many receptors on natural killer (NK) cells recognize major histocompatibility complex class I molecules in order to monitor unhealthy tissues, such as cells infected with viruses, and some tumors. Genes encoding families of NK receptors and related sequences are organized into two main clusters in humans: the natural killer complex on Chromosome 12p13.1, which encodes C-type lectin molecules, and the leukocyte receptor complex on Chromosome 19q13.4, which encodes immunoglobulin superfamily molecules. The composition of these gene clusters differs markedly between closely related species, providing evidence for rapid, lineage-specific expansions or contractions of sets of loci. The choice of NK receptor genes is polarized in the two species most studied, mouse and human. In mouse, the C-type lectin-related Ly49 gene family predominates. Conversely, the single Ly49 sequence is a pseudogene in humans, and the immunoglobulin superfamily KIR gene family is extensive. These different gene sets encode proteins that are comparable in function and genetic diversity, even though they have undergone species-specific expansions. Understanding the biological significance of this curious situation may be aided by studying which NK receptor genes are used in other vertebrates, especially in relation to species-specific differences in genes for major histocompatibility complex class I molecules.
Highlights
Natural killer (NK) cells destroy cells infected with certain viruses and other intracellular pathogens
Features of NK receptor genes both within and between species are consistent with rapid evolutionary change
Studies focus on human killer cell immunoglobulin-like receptor (KIR) and mouse Ly49 genes, but there are indications from the few studies of other vertebrates that variable C-type lectin and immunoglobulin superfamily (IgSF) receptors for major histocompatibility complex (MHC) class I molecules may co-exist in a species, such as horse [96], or may be functionally replaced by another divergent family of genes, as may be the case in chicken [100,101]
Summary
Natural killer (NK) cells destroy cells infected with certain viruses and other intracellular pathogens. These proteins are structurally similar to KIR genes but differ from other loci in the LRC by interacting with ligands other than MHC class I molecules [15].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
