A family of receptors found on NK cells that have specificity for a variety of hla antigens. KIR receptors contain up to three different extracellular immunoglobulin-like domains referred to as D0, D1, and D2 and play an important role in blocking NK cell activation against cells expressing the appropriate hla antigens thus preventing cell lysis. Although they are often referred to as being inhibitory receptors, a subset of KIR receptors may also play an activating role in NK cells.