What is a "natural killer cell"?

A natural killer cell is a specialized type of lymphocyte that contributes to the innate immune response in the human body. These cells are known for their ability to recognize and eliminate virus-infected cells, as well as tumor cells. Unlike other immune cells, NK cells do not require prior activation to initiate their killing mechanisms. They identify abnormal cells by detecting changes in their surface proteins and release cytotoxic granules that induce cell death. NK cells also secrete cytokines that help regulate immune responses and coordinate the activities of other immune cells. Overall, NK cells play a crucial role in immune surveillance and defense against various pathogens and abnormal cells.