Natural killer cell

Common card · No. 200599

Natural killer cells, also known as NK cells, are a type of cytotoxic lymphocyte critical to the innate immune system. They are a kind of large granular lymphocyte (LGL), belong to the rapidly expanding family of known innate lymphoid cells (ILC), and represent 5–20% of all circulating lymphocytes in humans. The role of NK cells is analogous to that of cytotoxic T cells in the vertebrate adaptive immune response. NK cells provide rapid responses to virus-infected cells, stressed cells, tumor cells, and other intracellular pathogens based on signals from several activating and inhibitory receptors. While cytotoxic T cells can only activate by detecting the antigen presented on major histocompatibility complex class I (MHC class I) molecules on infected cell surfaces, NK cells recognize and kill stressed cells that are lacking the MHC class I molecules. They were named "natural killers" because of the notion that they do not require activation to kill cells that are missing "self" markers...

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