Natural Killer (NK) cells are an essential component of the innate immune system. They are a specialized type of lymphocyte, a class of white blood cells, responsible for recognizing and eliminating infected cells and tumor cells, without requiring prior exposure or recognition of specific antigens. NK cells are named so due to their effectiveness at killing abnormal cells without the need for activation or targeting by other immune responses.
NK cells are characterized by the presence of specific cell surface receptors that allow them to recognize and differentiate between normal healthy cells and abnormal or infected cells. These receptors include killer cell immunoglobulin-like receptors (KIRs), natural cytotoxicity receptors (NCRs), and other activating and inhibitory receptors.
Once activated, NK cells secrete cytotoxic granules containing perforin and granzymes, which initiate a process called apoptosis in the target cells. This leads to the destruction of the target cell membrane and subsequent cell death. Additionally, NK cells can also produce cytokines, such as interferon-gamma (IFN-γ), which play a critical role in activating other components of the immune system.
Apart from their role in eliminating virally infected cells and tumor cells, NK cells also regulate the adaptive immune response by interacting with dendritic cells and influencing the activation and function of T cells and B cells.
Overall, natural killer cells are a crucial component of the immune system, serving as the body's first line of defense against infected or abnormal cells. Their ability to eliminate threats without prior antigen recognition makes them an important immune cell for quick responses to emerging threats.
