What is the significance of "natural killer" cells in the immune response?

Natural killer (NK) cells are a critical component of the innate immune system, and their primary role is to identify and eliminate infected or tumor cells. They are unique lymphocytes that function without the need for prior sensitization to a specific antigen, which differentiates them from B and T lymphocytes that require recognition of specific pathogens.

The significance of NK cells lies in their ability to detect stressed cells, including those infected by viruses or undergoing transformation into cancer cells. They accomplish this by recognizing certain markers on the surfaces of these cells. Once identified, NK cells can induce apoptosis (programmed cell death) in the target cells through the release of cytotoxic granules, which contain proteins that disrupt the integrity of the target cell's membrane.

Additionally, NK cells contribute to the immune response by producing cytokines that help to shape the adaptive immune response, particularly by influencing T cells. Their swift action helps to control infections and limit tumor progression before a more specific immune response can take over, highlighting their role as a first line of defense in the immune system.

In summary, the role of natural killer cells is fundamental in targeting and destroying infected or tumor cells, making them an essential player in maintaining the body's immune health.