Killer activation receptor

Killer Activation Receptors (KARs) are receptors expressed on the plasma membrane (cell membrane) of Natural Killer cells (NK cells). KARs work together with Killer Inhibitory Receptors (abbreviated as KIRs in the text), which inactivate KARs in order to regulate the NK cells functions on hosted or transformed cells. These receptors have a broad binding specificity and are able to broadcast opposite signals. It is the balance between these competing signals that determines if the cytotoxic activity of the NK cell and apoptosis of distressed cell occurs.