natural killer cell(Noun)
Any cell that expresses cell surface receptors that deliver signals to either activate or inhibit a response as part of the immune system
Natural killer cell
Natural killer cells are a type of cytotoxic lymphocyte critical to the innate immune system. The role NK cells play is analogous to that of cytotoxic T cells in the vertebrate adaptive immune response. NK cells provide rapid responses to virally infected cells and respond to tumor formation, acting at around 3 days after infection. Typically immune cells detect MHC presented on infected cell surfaces, triggering cytokine release causing lysis or apoptosis. NK cells are unique, however, as they have the ability to recognize stressed cells in the absence of antibodies and MHC, allowing for a much faster immune reaction. They were named “natural killers” because of the initial notion that they do not require activation in order to kill cells that are missing “self” markers of major histocompatibility complex class 1. NK cells are defined as large granular lymphocytes and constitute the third kind of cells differentiated from the common lymphoid progenitor generating B and T lymphocytes. NK cells are known to differentiate and mature in the bone marrow, lymph node, spleen, tonsils and thymus where they then enter into the circulation. NK cells differ from Natural Killer T cells phenotypically, by origin and by respective effector functions; often NKT cell activity promotes NK cell activity by secreting IFNγ. In contrast to NKT cells, NK cells do not express T-cell antigen receptors or Pan T marker CD3 or surface immunoglobulins B cell receptors, but they usually express the surface markers CD16 and CD56 in humans, NK1.1 or NK1.2 in C57BL/6 mice. Up to 80% of human NK cells also express CD8.
The numerical value of natural killer cell in Chaldean Numerology is: 7
The numerical value of natural killer cell in Pythagorean Numerology is: 6
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"natural killer cell." Definitions.net. STANDS4 LLC, 2017. Web. 19 Sep. 2017. <http://www.definitions.net/definition/natural killer cell>.