A cytotoxic (or TC) 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 I MHC molecules of virus infected somatic cells and tumor cells. T cells are a subset of lymphocytes that play a large role in the immune response. ... White blood cells (also called leukocytes or immune cells) are a component of blood. ... An antigen is a molecule that stimulates the production of antibodies. ... The major histocompatibility complex (MHC) is a large genomic region or gene family found in most vertebrates containing many genes with important immune system roles. ... Somatic means to refer to the body. ...
Once activated by a MHC-antigen complex, TC cells release the protein perforin, 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. TC also release granzyme, a serine protease, that can enter target cells via the perforin-formed pore and induce apoptosis (cell death). Perforin is a cytolytic protein found in the granules of CD8 T-cells and NK cells. ... A pore, in general, is some form of opening, usually very small. ... 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 same... Granzymes are exogenous serine proteases that are released by cytoplasmic granules within cytotoxic T cells and natural killer cells. ... In biochemistry, a serine proteases or serine endopeptidases (newer name) are a class of peptidases which are characterised by the presence of a serine residue in the active center of the enzyme. ... In biology, apoptosis (from the Greek words apo = from and ptosis = falling, pronounced ap-a-tow-sis[1]) is one of the main types of programmed cell death (PCD). ...
Most TC cells have present on the cell surface the protein CD8, which is attracted to portions of the Class I MHC molecule. This affinity keeps the TC cell and the target cell bound closely together during antigen-specific activation. TC cells with CD8 surface protein are called CD8+ T cells.
CytotoxicTlymphocytes are lymphocytes that kill other ("target") cells.
T cells is to monitor all the cells of the body, ready to destroy any that express foreign antigen fragments in their class I molecules.
Unlike CTL, which are mediators of adaptive immunity; that is, learn to respond to a particular antigen, NK cells are part of the innate immune system.
Most cytotoxicT cells express T-cell receptors (TcRs) that can recognise a specific antigenic peptide bound to Class I MHC molecules on an antigen presenting cell, and a glycoprotein called CD8, which is attracted to non-variable portions of the Class I MHC molecule.
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 activation of cytotoxicT 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).
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