Flow Cytometry Analysis of Whole-Blood NK Cells Expressing Single Killer Cell Immunoglobulin–Like Receptors

Human natural killer (NK) cells are regulated by a sophisticated system of inhibitory and stimulatory receptors as well as comodulating receptors. Killer cell immunoglobulin–like receptors (KIRs) are type 1 transmembrane receptors expressed on NK cells and a subset of T cells. Depending on their structure, KIRs have either inhibitory or activating properties. Inhibitory KIRs are characterized by a long cytoplasmic tail encompassing one or two immunoreceptor tyrosine-based inhibitory motif(s) (ITIM). Expression of both activating and inhibitory KIRs on NK cells occurs randomly. However, the host’s genetic environment can influence their expression pattern significantly.