Killer cell immunoglobulin-like receptors (KIRs) are transmembrane glycoproteins expressed bynatural killer cells and subsets ofCD8+ T cells.[5] The KIR genes are polymorphic and highly homologous and they are found in a cluster on chromosome 19q13.4 within the 1 Mbleukocyte receptor complex (LRC). The gene content of the KIR gene cluster varies among haplotypes, although several "framework" genes are found in all haplotypes (KIR3DL3, KIR3DP1, KIR2DL4, KIR3DL2). The KIR proteins are classified by the number of extracellular immunoglobulin domains (2D or 3D) and by whether they have a long (L) or short (S) cytoplasmic domain. KIR proteins with the long cytoplasmic domain transduce inhibitory signals upon ligand binding via an immune tyrosine-based inhibitory motif (ITIM), while KIR proteins with the short cytoplasmic domain lack the ITIM motif and instead associate with the TYRO protein tyrosine kinase binding protein to transduce activating signals. The ligands for several KIR proteins are subsets of HLA class I molecules; thus, KIR proteins are thought to play an important role in regulation of the immune response. This gene is one of the "framework" loci that is present on all haplotypes. Alternative splicing results in multiple transcript variants.[4]
The only so far reported ligand of KIR2DL4 is the non-classical HLA class 1 geneHLA-G, leading to the inhibition of the cytolytic NK cell function.[5]
^"Human PubMed Reference:".National Center for Biotechnology Information, U.S. National Library of Medicine.
^Selvakumar A, Steffens U, Dupont B (October 1996). "NK cell receptor gene of the KIR family with two IG domains but highest homology to KIR receptors with three IG domains".Tissue Antigens.48 (4 Pt 1):285–94.doi:10.1111/j.1399-0039.1996.tb02647.x.PMID8946682.
Selvakumar A, Steffens U, Palanisamy N, Chaganti RS, Dupont B (1997). "Genomic organization and allelic polymorphism of the human killer cell inhibitory receptor gene KIR103".Tissue Antigens.49 (6):564–73.doi:10.1111/j.1399-0039.1997.tb02803.x.PMID9234477.
Becker S, Tonn T, Füssel T, Uhrberg M, Bogdanow M, Seifried E, Seidl C (2003). "Assessment of killer cell immunoglobulinlike receptor expression and corresponding HLA class I phenotypes demonstrates heterogenous KIR expression independent of anticipated HLA class I ligands".Hum. Immunol.64 (2):183–93.doi:10.1016/S0198-8859(02)00802-9.PMID12559621.
Williams F, Maxwell LD, Halfpenny IA, Meenagh A, Sleator C, Curran MD, Middleton D (2003). "Multiple copies of KIR 3DL/S1 and KIR 2DL4 genes identified in a number of individuals".Hum. Immunol.64 (7):729–32.doi:10.1016/S0198-8859(03)00089-2.PMID12826375.
