Killer cell immunoglobulin-like receptor 2DL5(KIR2DL5), which belongs to the immunoglobulin superfamily, is an inhibitory receptor of NK cells.KIR2DL5 (CD158f) is the most recently identified inhibitory member of human killer-cell Ig-like receptors (KIRs), which enable NK cells to sense self-HLA.KIR2DL5 is encoded by two paralogous genes displaying copy number variation and allelic polymorphism-KIR2DL5A and KIR2DL5B. Functional polymorphisms in both its promoter and its coding regions are critical for understanding the KIR2DL5 role in immunity and its importance for human health.