Killer cell immunoglobulin-like receptors (KIRs) are transmembrane glycoproteins expressed by natural killer cells and subsets of T cells. 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. KIR3DL1 is a receptor on natural killer (NK) cells for HLA Bw4 allele. It inhibits the activity of NK cells thus preventing cell lysis. KIR3DL1 and KIR3DS1 are highly homologous. This antibody is raised against human KIR3DL1and has a molecular weight of 49 kDa.