Natural killer cell receptors in the horse: evidence for the existence of multiple transcribed LY49 genes

• Published in: European journal of immunology Vol. 34; no. 3; pp. 773 - 784
• Main Authors: Takahashi, Tomoko, Yawata, Makoto, Raudsepp, Terje, Lear, Teri L., Chowdhary, Bhanu P., Antczak, Douglas F., Kasahara, Masanori
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY‐VCH Verlag 01.03.2004
• Subjects: Amino Acid Sequence; Animals; Antigens, Ly - classification; Antigens, Ly - genetics; Chromosome Mapping; DNA, Complementary - isolation & purification; Evolution; Horse; Horses - immunology; Killer Cells, Natural - immunology; KIR; Lectins, C-Type; LY49; Molecular Sequence Data; NK receptor; Phylogeny; Protein Isoforms - genetics; Protein Isoforms - metabolism; Receptors, Immunologic - classification; Receptors, Immunologic - genetics; Receptors, KIR; Receptors, NK Cell Lectin-Like; Sequence Alignment; Transcription, Genetic
• ISSN: 0014-2980; 1521-4141
• DOI: 10.1002/eji.200324695

In rodents, the Ly49 family encodes natural killer (NK) receptors interacting with classical MHC class I molecules, whereas the corresponding receptors in primates are members of the killer cell immunoglobulin‐like receptor (KIR) family. Recent evidence indicates that the cattle, domestic cat, dog, and pig have a single LY49 and multiple KIR genes, suggesting that predominant NK receptors in most non‐rodent mammals might be KIR. Here, we show that the horse has at least six LY49 genes, five with an immunoreceptor tyrosine‐based inhibition motif (ITIM) and one with arginine in the transmembrane region. Interestingly, none of the horse KIR‐like cDNA clones isolated by library screening encoded molecules likely to function asNK receptors; four types of clones were KIR‐Ig‐like transcript (KIR‐ILT) hybrids and contained premature stop codons and/or frameshift mutations, and two putative allelic sequences predicting KIR3DL molecules had mutated ITIM. To our knowledge, this is the first report suggesting that non‐rodent mammals may use LY49 as NK receptors for classical MHC class I. We also show that horse spleen expresses ILT‐like genes with unique domain organizations. Radiation hybrid mapping and fluorescence in situ hybridization localized horse LY49 and KIR/ILT genes to chromosomes 6q13 and 10p12, respectively.