Killer activation receptor

Killer Activation Receptors (KARs) are activating receptors expressed on the plasma membrane (cell membrane) of Natural Killer cells (NK cells). These KARs are essential in order for NK cells to regulate and induce human immune responses through activating signals. Our immune system works with our NK cells to target pathogens and invaders like bacteria, cancer cells, and infectious cells. Killer Inhibitory Receptors (abbreviated as KIRs in this text) are responsible for sending the inhibitory signals to NK cells. These KIRs counterbalance activating signals from KARs by sending competitive inhibitory signals. This occurs so that there is regulation of the NK cells functions on host cells or transformed cells. These receptors have a broad binding specificity that are able to send different signals. It is the balance between these competing signals that determines if the cytotoxic activity of the NK cell and apoptosis of the distressed cell occurs. Natural Cytotoxicity Receptors (NCRs) and NKG2D are the two important KARs that are expressed on NK cells that recognize stress-induced ligands and aid in marking them for destruction.