Natural Killer (NK) cells are a type of innate immune cell that plays a critical role in the early defense against viral infections and tumor cells. NK cells are able to recognize and directly kill virus-infected cells and cancerous cells without prior sensitization or activation, unlike other immune cells that require specific recognition of antigens presented on the surface of the target cells. NK cells can also produce cytokines and chemokines to modulate the immune response and recruit other immune cells to the site of infection or cancer. NK cells are distinguished from other lymphocytes by the expression of specific cell surface receptors, including the activating receptors NKp46, NKp30, and NKp44, and the inhibitory receptors KIR and NKG2A/CD94, which recognize ligands on target cells and regulate NK cell activation and killing.
Facts About Natural Killer Cells
- NK cells are a type of lymphocyte that plays a critical role in innate immunity.
- They were first discovered in the 1970s and were initially thought to be a type of T cell.
- NK cells are distinct from T and B cells because they lack antigen-specific receptors.
- They are present in the blood, lymph nodes, and spleen, and can also be found in some tissues, such as the liver and uterus.
- NK cells can be activated by cytokines, such as interferons, that are released by infected or stressed cells.
- NK cells can also be activated through antibody-dependent cell-mediated cytotoxicity (ADCC), which occurs when antibodies bound to antigens on target cells are recognized by specific receptors on NK cells.
- NK cells have the ability to kill infected or abnormal cells, including virus-infected cells and cancer cells, without prior exposure to those cells.
- NK cells are important for immunosurveillance, which refers to the detection and elimination of abnormal cells before they can develop into tumors or cause other health problems.
- NK cells are also involved in regulating the adaptive immune response by interacting with dendritic cells and other immune cells.
- NK cells can recognize and respond to a wide variety of targets, including tumor cells, virus-infected cells, and even healthy cells that have been stressed or damaged.
- NK cells use several mechanisms to kill target cells, including the release of cytotoxic granules containing perforin and granzymes, the activation of death receptors on target cells, and the secretion of cytokines that induce apoptosis.
- NK cells can also interact with other immune cells, such as macrophages, to help clear dead and senescent cells.
- NK cells are regulated by a complex network of activating and inhibitory receptors that help to prevent them from attacking healthy cells.
- Some viruses, such as HIV, can evade NK cell recognition and killing by downregulating their ligands or receptors.
- Certain genetic disorders, such as familial hemophagocytic lymphohistiocytosis, can impair NK cell function and lead to immune dysregulation and autoimmunity.
- NK cells are also involved in the development of the placenta during pregnancy and help to maintain immune tolerance to the developing fetus.
- There are different subsets of NK cells that have distinct functions and surface markers.
- NK cells can undergo expansion and differentiation in response to certain infections or stimuli, which is one of the reasons they exhibit some adaptive features.
- NK cells are being studied as potential therapies for cancer and viral infections, either alone or in combination with other immune-modulating agents.
- NK cell activity can be enhanced through various lifestyle factors, such as exercise, stress reduction, and a healthy diet, which may help to support immune function and overall health.
