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Encyclopedia > Natural killer cell

Natural NK cells are cytotoxic; small granules in their cytoplasm contain special proteins such as perforin and proteases known as granzymes. Upon release in close proximity of a cell to be killed, perforin forms pores in the cell membrane of the target cell through which the granzymes and associated molecules can enter, where they induce apoptosis. The distinction between apoptosis and cell lysis is important in immunology: lysing a virally infected cell would only release the parasites, whereas apoptosis leads to destruction of the virus inside. Cytotoxicity is the quality of being poisonous to cells. ... Granulocytes are a category of white blood cells, characterised by the fact that all types have differently staining granules in their cytoplasm on light microscopy. ... Cytoplasm is like jelly-like material that fills cells. ... Perforin is a cytolytic protein found in the granules of CD8 T-cells and NK cells. ... Granzymes are exogenous serine proteases that are released by cytoplasmic granules within cytotoxic T cells and natural killer cells. ... Drawing of a cell membrane A component of every biological cell, the selectively permeable cell membrane (or plasma membrane or plasmalemma) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... A cell undergoing apoptosis. ... Lysis (Greek lusis from luein = to separate) refers to the death of a cell by bursting, often by viral or osmotic mechanisms that compromise the integrity of the cellular membrane. ...


NK cells are characterised immunohistochemically by the presence of CD56 and/or CD16 and the absence of CD3 on the cell membrane in humans. The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...


NK cells are activated in response to interferons or macrophage-derived cytokines. They serve to contain viral infections while the adaptive immune response is generating antigen specific cytotoxic T cells that can clear the infection. Patients deficient in NK cells prove to be highly susceptible to early phases of herpes virus infection. Interferons (IFNs) are natural proteins produced by the cells of the immune systems of most animals in response to challenges by foreign agents such as viruses, bacteria, parasites and tumor cells. ... A macrophage of a mouse stretching its arms to engulf two particles, possibly pathogens Macrophages (Greek: big eaters, makros = long, phagein = eat) are white blood cells, more specifically phagocytes, acting in the nonspecific defense as well as the specific defense system of vertebrate animals. ... Cytokines are small protein molecules that regulate communication among immune system cells and between immune cells and those of other tissue types. ... The human immunodeficiency virus (HIV) A bacteriophage virus A virus is a submicroscopic parasitic particle that infects cells in biological organisms. ... An antigen is a substance that stimulates an immune response, especially the production of antibodies. ... A cytotoxic (or TC) T cell is a T cell (a type of white blood cell) which has on its surface antigen receptors called T-cell receptors (TCRs) that can bind to fragments of antigens displayed by the Class I MHC molecules of virus (or other intracellular pathogen) infected somatic... Genera Subfamily Alphaherpesvirinae    Simplexvirus    Varicellovirus    Mardivirus    Iltovirus Subfamily Betaherpesvirinae    Cytomegalovirus    Muromegalovirus    Roseolovirus Subfamily Gammaherpesvirinae    Lymphocryptovirus    Rhadinovirus Unassigned    Ictalurivirus The Herpesviridae are a family of DNA viruses that cause diseases in humans and animals. ...


If NK cells defend the body against viruses and other pathogens, they must possess mechanisms to decide if a cell is infected or not. The exact mechanisms are as yet unknown, but recognition of 'altered self' is thought to be involved. To control their cytotoxic activity, they possess two types of surface receptors: 'activating receptors' and 'inhibitory receptors'. In biochemistry, a receptor is a protein on the cell membrane or within the cytoplasm that binds to a specific factor (a ligand), such as a neurotransmitter, hormone, or other substance, and initiates the cellular response to the ligand. ...


These 'inhibitory receptors' recognize MHC (major histocompatibility complex) class I alleles, which could explain why NK cells kill cells with low levels of MHC class I molecules - a concept that is known as "missing-self" recognition. It has been suggested that Class I MHC be merged into this article or section. ... An allele is any one of a number of viable DNA codings of the same gene (sometimes the term refers to a non-gene sequence) occupying a given locus (position) on a chromosome. ...


Different families of NK receptors exist and many of these receptors seem to have evolved recently. A speculative phylogenetic tree of all living things, based on rRNA gene data, showing the separation of the three domains, bacteria, archaea and eukaryotes. ...


Natural NK cells attack cells that have been infected by microbes, but not microbes themselves.


See also

The immune system is the system of specialized cells and organs that protect an organism from outside biological influences. ... Granzymes are exogenous serine proteases that are released by cytoplasmic granules within cytotoxic T cells and natural killer cells. ... It has been suggested that Class I MHC be merged into this article or section. ...

Literature

  • Immunobiology The Immune System In Health And Disease by Janeway, Travers, Walport & Shlomchik Churchchill Livingstone Copyright 2005
  • Cellular and Molecular Immunology by Abbul K. Abbas & Andrew Lichtman Saunders Copyright 2003
  • How the Immune System Works, 2nd edition, by Lauren Sompayrac, PhD Blackwell Publishing 2003

External links

  • http://www.nkcells.info - MediaWiki based information platform specializing on natural killer cells
Blood - Blood plasma - edit
Pluripotential hemopoietic stem cell | Red blood cells (ReticulocyteNormoblast) | White blood cells
Lymphocytes (Lymphoblast)
T cells (CytotoxicHelperRegulatory T cell) | B cells (Plasma cells & Memory B cells) | Natural killer cell
Myelocytes (Myeloblast)
Granulocytes (NeutrophilEosinophilBasophil) | Mast cell precursors | Monocytes (HistiocyteMacrophagesDendritic cellsLangerhans cells, MicrogliaKupffer cellsOsteoclasts) | Megakaryoblast | Megakaryocyte | Platelets

  Results from FactBites:
 
Natural killer cell - Wikipedia, the free encyclopedia (386 words)
Natural NK cells are cytotoxic; small granules in their cytoplasm contain special proteins such as perforin and proteases known as granzymes.
NK cells are activated in response to interferons or macrophage-derived cytokines.
Patients deficient in NK cells prove to be highly susceptible to early phases of herpes virus infection.
  More results at FactBites »

 
 

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