KIR3DL2

Killer cell immunoglobulin-like receptors (KIRs) are transmembrane glycoproteins expressed on natural killer (NK) cells and subsets of T cells. KIR proteins are classified based on the number of extracellular immunoglobulin (Ig) domains—either two (2D) or three (3D)—and the length of their cytoplasmic tails: long (L) or short (S). KIR3DL2 is a member of the 3DL family, containing three Ig-like domains and a long cytoplasmic tail. The long tail includes one or more immune tyrosine-based inhibitory motifs (ITIMs), which mediate inhibitory signaling upon ligand engagement. In contrast, KIRs with short cytoplasmic tails lack ITIMs and instead signal through association with TYRO protein tyrosine kinase binding protein, resulting in activating signals. The KIR genes are polymorphic and highly homologous, clustered on chromosome 19q13.4 within the 1 Mb leukocyte receptor complex (LRC). The gene content of this cluster varies among haplotypes, but several "framework" genes—including KIR3DL2—are found in all haplotypes. == Function ==

KIR3DL2 is involved in the regulation of innate immune responses, primarily through its expression on NK cells and γδ T cells, a subset of non-MHC-I-restricted T cells. The ligand for KIR3DL2 includes subsets of HLA class I molecules, and interaction with these ligands typically transduces inhibitory signals that suppress NK cell-mediated cytotoxicity. In addition, the protein IGSF8 (Immunoglobulin superfamily member 8) has been identified as a binding partner of KIR3DL2. Engagement of KIR3DL2 by IGSF8 functions as an immune checkpoint that inhibits NK cell cytotoxic activity, highlighting its role in immune evasion mechanisms in cancer. == See also ==