Description

Natural killer (NK) cells play a key role in the innate immune system. These lymphocytes react to certain infections and malignancies by direct cytolysis of infected or transformed cells and by secretion of potent immune mediators. NK cells have the ability to recognize foreign or stressed cells that lack antibodies and major histocompatibility complex (MHC) class I proteins on the surface, which would normally go undetected by other immune cells. However, NK cells express an array of inhibitory receptors that recognize self-molecules. If not restrained by inhibitory receptors recognizing MHC class I proteins on the surface of self-cells, NK cells are able to kill normal, healthy cells.