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Encyclopedia > Cytotoxic T cell

A cytotoxic T cell (also known as TC, CTL or killer T cell) belongs to a sub-group of T lymphocytes (a type of white blood cell) which are capable of inducing the death of infected somatic or tumor cells; they kill cells that are infected with viruses (or other pathogens), or are otherwise damaged or dysfunctional. Most cytotoxic T cells express T-cell receptors (TcRs) that can recognise a specific antigenic peptide bound to Class I MHC molecules, present on all nucleated cells, and a glycoprotein called CD8, which is attracted to non-variable portions of the Class I MHC molecule. The affinity between CD8 and the MHC molecule keeps the TC cell and the target cell bound closely together during antigen-specific activation. CD8+ T cells are recognized as TC cells once they become activated and are generally classified as having a pre-defined cytotoxic role within the immune system. T cells are a subset of lymphocytes that play a large role in the immune response. ... White blood cells or leucocytes are cells which form a component of the blood. ... An infection is the detrimental colonization of a host organism by a foreign species. ... The term somatic refers to the body, as distinct from some other entity, such as the mind. ... Tumor or tumour literally means swelling, and is sometimes still used with that meaning. ... Groups I: dsDNA viruses II: ssDNA viruses III: dsRNA viruses IV: (+)ssRNA viruses V: (-)ssRNA viruses VI: ssRNA-RT viruses VII: dsDNA-RT viruses A virus is a microscopic particle (ranging in size from 20 - 300 nm) that can infect the cells of a biological organism. ... A pathogen (literally birth of pain from the Greek παθογένεια) is a biological agent that can cause disease to its host. ... The T cell receptor or TCR is responsible for recognizing antigen bound to Major histocompatibility complex (MHC). ... An antigen is a substance that stimulates an immune response, especially the production of antibodies. ... Peptides (from the Greek πεπτος, digestible), are the family of short molecules formed from the linking, in a defined order, of various α-amino acids. ... MHC I (1hsa) vs MHC II (1dlh) (more details. ... A glycoprotein is a macromolecule composed of a protein and a carbohydrate (an oligosaccharide). ... CD8 (cluster of differentiation 8) is a molecule that is expressed on the surface of cytotoxic T cells. ... Look up affinity in Wiktionary, the free dictionary. ...

Contents

Cytotoxic T cell development

Development of single positive T cells in the thymus
Development of single positive T cells in the thymus

Hematopoetic stem cells in the bone marrow migrate into the thymus, where they undergo VDJ recombination of their beta-chain TcR DNA to form a developmental form of the TcR protein, known as pre-TcR. If that rearrangement is successful, the cells then rearrange their alpha-chain TcR DNA to create a functional alpha-beta TcR complex. This highly-variable genetic rearrangement product in the TcR genes helps create millions of different T cells with different TcRs, helping the body's immune system respond to virtually any protein of an invader. The vast majority of T cells express alpha-beta TcRs (αβ T cells), but some T cells in epithelial tissues (like the gut) express gamma-delta TcRs (γδ T cells), which recognize non-protein antigens. Image File history File links Download high-resolution version (3117x4230, 1190 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Thymus Cytotoxic T cell ... Image File history File links Download high-resolution version (3117x4230, 1190 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Thymus Cytotoxic T cell ... Note that some complexity is omitted from the diagram. ... Grays Anatomy illustration of cells in bone marrow. ... In human anatomy, the thymus is an organ located in the upper anterior portion of the chest cavity. ... // VDJ recombination VDJ recombination is a mechanism of DNA recombination used by humans and other vertebrates for protection against attacks by bacterial, viral, and parasitic invaders. ... The T cell receptor or TCR is responsible for recognizing antigen bound to Major histocompatibility complex (MHC). ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... T cells are a subset of lymphocytes that play a large role in the immune response. ... γδ T cells represent a small subset of T cells that possess a distinct T cell receptor (TCR) on their surface. ...


T cells with functionally stable TcRs express both the CD4 and CD8 co-receptors and are therefore termed "double-positive" (DP) T cells (CD4+CD8+). The double-positive T cells are exposed to a wide variety of self-antigens in the thymus and undergo two selection criteria : (1) negative selection, in which those double-positive T cells that bind too strongly to MHC-presented self antigens undergo apoptosis because their propensity to become autoreactive could lead to autoimmunity; and (2) positive selection, in which those double-positive T cells that bind too weakly to MHC-presented self antigens undergo apoptosis because of their inability to recognize MHC-protein complexes. Only those T cells that bind to the MHC-self-antigen complexes weakly are positively selected. Those cells that survive positive and negative selection differentiate into single-positive T cells (either CD4+ or CD8+) dependent on whether their TcR recognizes an MHC class I presented antigen (CD8) or an MHC class II presented antigen (CD4). It is the CD8+ T-cells that will mature and go on to become cytotoxic T cells following their activation with a class I restricted antigen. This is the gayest shit ive ever read it my life and i have no idea what it means or what it means or what it means or what it means, thankyou for nothing.... eck eck..... hpnotiQ` CD4 (cluster of differentiation 4) is a molecule that is expressed on the surface of T helper cells (as well as regulatory T cells and dendritic cells). ... CD8 (cluster of differentiation 8) is a molecule that is expressed on the surface of cytotoxic T cells. ... This page is a candidate to be copied to Wiktionary. ... MHC may be: an abbreviation for Mount Holyoke College an abbreviation for Mars Hill College an abbreviation for Managed health care an abbreviation for major histocompatibility complex the US Navy hull classification symbol for Coastal Minehunter the Mile High Club This page concerning a three-letter acronym or abbreviation is... An antigen is a substance that stimulates an immune response, especially the production of antibodies. ... A cell undergoing apoptosis. ... Autoimmunity is the failure of an organism to recognize its own constituent parts (down to the sub-molecular levels) as self, which results in an immune response against its own cells and tissues. ... A cell undergoing apoptosis. ...


Cytotoxic T cell activation

With the exception of some cell types such as non-nucleated cells (including erythrocytes), Class I MHC is expressed by all host cells. When these cells are infected with a virus (or another intracellular pathogen), the cells "break down" foreign proteins via antigen processing. These result in peptide fragments, some of which are presented by MHC Class I to the T cell antigen receptor (TcR) on CD8+ T cells. The eukaryotic cell nucleus. ... Human red blood cells Red blood cells are the most common type of blood cell and are the vertebrate bodys principal means of delivering oxygen to body tissues via the blood. ... Groups I: dsDNA viruses II: ssDNA viruses III: dsRNA viruses IV: (+)ssRNA viruses V: (-)ssRNA viruses VI: ssRNA-RT viruses VII: dsDNA-RT viruses A virus is a microscopic particle (ranging in size from 20 - 300 nm) that can infect the cells of a biological organism. ... In cell biology, molecular biology and related fields, the word intracellular means inside the cell. It is used in contrast to extracellular (outside the cell). ... A pathogen or infectious agent is a biological agent that causes disease or illness to its host. ... Two methods exist for an antigen to be processed and presented on the cell surface. ... The T cell receptor or TCR is responsible for recognizing antigen bound to Major histocompatibility complex (MHC). ...


The activation of cytotoxic T cells is dependent on several simulanteous interactions between molecules expressed on the surface of the T cell and molecules on the surface of the antigen presenting cell (APC). For instance, consider the two signal model for TC cell activation. The first signal occurs when the TcR of the TC cell strongly interacts with a peptide-bound MHC class I molecule on the APC. There is a second interaction between the CD8 coreceptor and the class I MHC molecule to stablize this signal. The second signal comes from an interaction between the CD28 molecule on the T cell and either CD80 or CD86 (also called B7-1 and B7-2) on the surface of the APC. CD80 and CD86 are known as costimulators for T cell activation. This second signal can be assisted (or replaced) by stimulating the TC cell with cytokines released from helper T cells. Once activated, the TC cell undergoes clonal expansion with the help of a cytokine called Interleukin-2 (IL-2) that is a growth and differentiation factor for T cells. This increases the number of cells specific for the target antigen that can then travel throughout the body in search of antigen-positive somatic cells. An antigen presenting cell (APC) is a cell that displays foreign antigen complexed with MHC on its surface. ... CD8 (cluster of differentiation 8) is a molecule that is expressed on the surface of cytotoxic T cells. ... Structure of human CD28. ... The protein CD80 is a molecule which provides a costimulatory signal necessary for T cell activation and survival. ... The protein CD86 is a molecule which provides a costimulatory signal necessary for T cell activation and survival. ... During the activation of T cells, co-stimulation of molecules is often crucial to the development of an effective immune response. ... A helper (or TH) T cell is a T cell (a type of white blood cell) which has on its surface antigen receptors that can bind to fragments of antigens displayed by the Class II MHC molecules found on professional antigen-presenting cells (APCs). ... Interleukin-2 (IL2) is an interleukin, a type of biological response modifier that can improve the bodys natural response to disease. ... Differentiation can mean the following: In biology: cellular differentiation; evolutionary differentiation; In mathematics: see: derivative In cosmogony: planetary differentiation Differentiation (geology); Differentiation (logic); Differentiation (marketing). ... A somatic cell is generally taken to mean any cell forming the body of an organism: the word somatic is derived from the Greek word sōma, meaning body. Somatic cells, by definition, are not germline cells. ...


When exposed to infected/dysfunctional somatic cells, TC cells release the cytotoxins perforin and granulysin. These form pores in the target cell's plasma membrane causing ions and water to flow into the target cell that make the cell expand and eventually lyse. TC also release granzyme, a serine protease, that can enter target cells via the perforin-formed pore and induce apoptosis (cell death) by activation of cellular enzymes called caspases. A second way to induce apoptosis is via cell-surface interactions between the TC and the infected cell. When a TC is activated it starts to express the surface protein FAS ligand (FasL), which can bind to Fas molecules expressed on the target cell. However, this Fas-Fas ligand interaction is thought to be more important to the disposal of unwanted T lymphocytes during their development or to the lytic activity of certain TH cells than it is to the cytolytic activity of TC effector cells. Perforin is a cytolytic protein found in the granules of CD8 T-cells and NK cells. ... Granulysin is a substance released by T-cells (CD 8) when they are attached to infected body cells. ... Drawing of a cell membrane A component of every biological cell, the cell membrane (or plasma membrane) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... Lysis (Greek lusis from luein = to separate) is the reduction of symptoms of a disease the dissolving of cells osmotic lysis chemical lysis viral lysis a dialogue of Plato about friendship (philia) This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the... Granzymes are exogenous serine proteases that are released by cytoplasmic granules within cytotoxic T cells and natural killer cells. ... Crystal structure of Trypsin, a typical serine protease. ... A cell undergoing apoptosis. ... Caspases are a group of cysteine proteases, enzymes with a crucial cysteine residue that can cleave other proteins, after an aspartic acid residue, a specificity which is unusual among proteases. ... The FAS ligand or FasL is a type II transmembrane protein that belongs to the tumor necrosis factor (TNF) family. ... FAS can stand for: The Femmes Africa Solidarité The Federation of American Scientists The Federation of Astronomical Societies The Fetal alcohol syndrome FAS ligand or Fas ligand, in cell and molecular biology, is an important cell surface receptor protein. ... T cells are a subset of lymphocytes that play a large role in the immune response. ...


Cytotoxic T cell role in disease pathogenesis

  • Hepatitis B virus (HBV) infection

During HBV infection cytotoxic T cells play an important pathogenetic role. They contribute to nearly all of the liver injury associated with HBV infection and, by killing infected cells and by producing antiviral cytokines capable of purging HBV from viable hepatocytes, cytotoxic T cells also eliminate the virus.[1] Recently platelets have been shown to facilitate the accumulation of virus-specific cytotoxic T cells into the infected liver.[2] Hepatitis B is a disease of the liver and is caused by the Hepatitis B virus (HBV), a member of the Hepadnavirus family[1] and one of several unrelated viral species which cause viral hepatitis. ... A 250 ml bag of newly collected platelets. ...


External links

  • Flash animation at McGraw-Hill immunology-Cytotoxic%20T%20Cell

The McGraw-Hill Companies logo. ...

References

  1. ^ Iannacone M. et al (2006). "Pathogenetic and antiviral immune responses against hepatitis B virus". Future Virology 1 (2): 189-196. 
  2. ^ Iannacone M. et al (2005). "Platelets mediate cytotoxic T lymphocyte-induced liver damage". Nat Med 11: 1167-1169. 

  Results from FactBites:
 
Cytotoxic T cell - Wikipedia, the free encyclopedia (419 words)
Cytotoxic T cells are activated when their TCR binds to an MHC class I molecule presenting viral antigen, which can occur on any nucleated or neoplastic cell.
cells release the cytoxins perforin and granulysin, which forms pores in the target cell's plasma membrane; this causes ions and water to flow into the target cell, making it expand and eventually lyse.
cells have the protein CD8 present on the cell surface, which is attracted to portions of the Class I MHC molecule.
BioCarta - Charting Pathways of Life (323 words)
Cytotoxic T cells are a key part of the cellular immune response, killing cells that display foreign antigen on their surface, primarily virus-infected cells.
Cytotoxic T cells also express Fas ligand to bind to Fas on target cells and induce apoptosis.
Cytotoxic T cell activation also requires additional signals provided by helper T cells in addition to signals provided by antigen-presenting cells.
  More results at FactBites »

 
 

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