What role do natural killer (NK) cells play in the immune response?

Natural killer (NK) cells are a crucial component of the innate immune system, primarily recognized for their role in identifying and eliminating infected cells or tumor cells. This unique function is vital in maintaining the body’s defense mechanisms, particularly in the early stages of infection and cancer.

NK cells are equipped with the ability to recognize stressed cells in the absence of antibodies and major histocompatibility complex (MHC) molecules. They distinguish between healthy cells and those that are infected or malignant, allowing them to target and destroy these harmful cells effectively. This action occurs through the release of cytotoxic granules that contain perforin and granzymes, which induce apoptosis in the target cells.

While NK cells can produce certain cytokines, their primary function revolves around direct cytotoxicity rather than the production of these signaling molecules. They are not primarily known for enhancing antibody production or being directly involved in B cell activation, as those roles are typically fulfilled by other immune cells, like helper T cells.

Thus, the role of NK cells in recognizing and killing infected or cancerous cells stands out as a fundamental aspect of their contribution to immune responses, underlining their significance in immunological defense strategies.