Natural killer (NK) cells are the integral component of innate immunity, and kill infected cells, tumors and stressed cells without prior sensitization. Further, they secrete inflammatory cytokines, which drive the antigen specific adaptive immunity, NK cells distinguish these abnormal cells from healthy cells through variable inhibitory and activating Killer Cell Ig-Like Receptors (KIRs). The inhibitory KIRs recognize determinants expressed on the surface of abnormal cells and subvert these unhealthy cells. Genes encoding KIRs and HLA ligands belong to polymorphic gene families located on different chromosomes, feature variation in the number and type of genes. Since the integration of signals transduced from inhibitory and activating receptors help to balance the NK cell response between tolerance of healthy cells and killing of unhealthy cells, the combinations of KIR and HLA class I molecules play an important role in human immunity and disease. The KIR genotyping test identifies the presence and absence of 15 distinct KIR genes.

** Du Z, Gjertson DW, Reed EF, Rajalingam R. Receptor-ligand analyses define minimal killer cell Ig-like receptor (KIR) in humans. Immunogenetics 2008; 59:1-15.