KIR2DL5B is an inhibitory killer cell immunoglobulin-like receptor gene located on chromosome 19.4 that encodes a receptor expressed on natural killer (NK) cells and certain T cells 1. The gene exists as one of two paralogs (KIR2DL5A and KIR2DL5B) that arose from gene duplication, with some individuals carrying both genes, others carrying only one, and some lacking both 1. KIR2DL5B functions as an inhibitory receptor that modulates NK cell cytolytic activity through interactions with HLA class I ligands, participating in innate immune responses 2. The gene shows significant disease associations across multiple conditions. KIR2DL5B presence is associated with protection against HIV-1 infection in serodiscordant couples 3 and shows protective associations against cervical cancer 4. Conversely, KIR2DL5B deficiency is linked to increased susceptibility to celiac disease 2 and is associated with spontaneous recovery from hepatitis B virus infection 5. In chr19 myeloid leukemia, KIR2DL5B-positive genotype is associated with delayed molecular remission after treatment rechallenge 6. The gene's role in anti-NMDAR encephalitis has also been identified, with increased copy number variation observed in patients 7.