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Perforin
Perforin-1 is a protein that in humans is encoded by the ''PRF1'' gene and the ''Prf1'' gene in mice. Function Perforin is a pore forming cytolytic protein found in the granules of cytotoxic T lymphocytes (CTLs) and natural killer cells (NK cells). Upon degranulation, perforin molecules translocate to the target cell with the help of calreticulin, which works as a chaperone protein to prevent perforin from degrading. Perforin then binds to the target cell's plasma membrane via membrane phospholipids while phosphatidylcholine binds calcium ions to increase perforin's affinity to the membrane. Perforin oligomerises in a Ca2+ dependent manner to form pores on the target cell. The pore formed allows for the passive diffusion of a family of pro-apoptotic proteases, known as the granzymes, into the target cell. The lytic membrane-inserting part of perforin is the MACPF domain. This region shares homology with cholesterol-dependent cytolysins from Gram-positive bacteria. Perforin has ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MACPF
The Membrane Attack Complex/Perforin (MACPF) superfamily, sometimes referred to as the MACPF/CDC superfamily, is named after a domain that is common to the membrane attack complex (MAC) proteins of the complement system (C6, C7, C8α, C8β and C9) and perforin (PF). Members of this protein family are pore-forming toxins (PFTs). In eukaryotes, MACPF proteins play a role in immunity and development. Archetypal members of the family are complement C9 and perforin, both of which function in human immunity. C9 functions by punching holes in the membranes of Gram-negative bacteria. Perforin is released by cytotoxic T cells and lyses virally infected and transformed cells. In addition, perforin permits delivery of cytotoxic proteases called granzymes that cause cell death. Deficiency of either protein can result in human disease. Structural studies reveal that MACPF domains are related to cholesterol-dependent cytolysins (CDCs), a family of pore forming toxins previously thought ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Granzyme
Granzymes are serine proteases released by cytoplasmic granules within cytotoxic T cells and natural killer (NK) cells. They induce programmed cell death (apoptosis) in the target cell, thus eliminating cells that have become cancerous or are infected with viruses or bacteria. Granzymes also kill bacteria and inhibit viral replication. In NK cells and T cells, granzymes are packaged in cytotoxic granules along with perforin. Granzymes can also be detected in the rough endoplasmic reticulum, golgi complex, and the trans-golgi reticulum. The contents of the cytotoxic granules function to permit entry of the granzymes into the target cell cytosol. The granules are released into an immune synapse formed with a target cell, where perforin mediates the delivery of the granzymes into endosomes in the target cell, and finally into the target cell cytosol. Granzymes are part of the serine esterase family. They are closely related to other immune serine proteases expressed by innate immune cel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Granzyme
Granzymes are serine proteases released by cytoplasmic granules within cytotoxic T cells and natural killer (NK) cells. They induce programmed cell death (apoptosis) in the target cell, thus eliminating cells that have become cancerous or are infected with viruses or bacteria. Granzymes also kill bacteria and inhibit viral replication. In NK cells and T cells, granzymes are packaged in cytotoxic granules along with perforin. Granzymes can also be detected in the rough endoplasmic reticulum, golgi complex, and the trans-golgi reticulum. The contents of the cytotoxic granules function to permit entry of the granzymes into the target cell cytosol. The granules are released into an immune synapse formed with a target cell, where perforin mediates the delivery of the granzymes into endosomes in the target cell, and finally into the target cell cytosol. Granzymes are part of the serine esterase family. They are closely related to other immune serine proteases expressed by innate immune cel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytotoxic T Cell
A cytotoxic T cell (also known as TC, cytotoxic T lymphocyte, CTL, T-killer cell, cytolytic T cell, CD8+ T-cell or killer T cell) is a T lymphocyte (a type of white blood cell) that kills cancer cells, cells that are infected by intracellular pathogens (such as viruses or bacteria), or cells that are damaged in other ways. Most cytotoxic T cells express T-cell receptors (TCRs) that can recognize a specific antigen. An antigen is a molecule capable of stimulating an immune response and is often produced by cancer cells, viruses, bacteria or intracellular signals. Antigens inside a cell are bound to class I MHC molecules, and brought to the surface of the cell by the class I MHC molecule, where they can be recognized by the T cell. If the TCR is specific for that antigen, it binds to the complex of the class I MHC molecule and the antigen, and the T cell destroys the cell. In order for the TCR to bind to the class I MHC molecule, the former must be accompanied by a glycoprotein ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Killer Cell
Natural killer cells, also known as NK cells or large granular lymphocytes (LGL), are a type of cytotoxic lymphocyte critical to the innate immune system that 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 cell and other intracellular pathogens acting at around 3 days after infection, and respond to tumor formation. Typically, immune cells detect the major histocompatibility complex (MHC) presented on infected cell surfaces, triggering cytokine release, causing the death of the infected cell by lysis or apoptosis. NK cells are unique, however, as they have the ability to recognize and kill stressed cells in the absence of antibodies and MHC, allowing for a much faster immune reaction. They were named "natural killers" because ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Familial Hemophagocytic Lymphohistiocytosis
Hemophagocytic lymphohistiocytosis (HLH), also known as haemophagocytic lymphohistiocytosis (British spelling), and hemophagocytic or haemophagocytic syndrome, is an uncommon hematologic disorder seen more often in children than in adults. It is a life-threatening disease of severe hyperinflammation caused by uncontrolled proliferation of activated lymphocytes and macrophages, characterised by proliferation of morphologically benign lymphocytes and macrophages that secrete high amounts of inflammatory cytokines. It is classified as one of the cytokine storm syndromes. There are inherited and non-inherited (acquired) causes of hemophagocytic lymphohistiocytosis (HLH). Signs and symptoms The onset of HLH occurs before the age of one year in approximately 70 percent of cases. Familial HLH should be suspected if siblings are diagnosed with HLH or if symptoms recur when therapy has been stopped. Familial HLH is an autosomal recessive disease, hence each sibling of a child with familial ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Degranulation
Degranulation is a cellular process that releases antimicrobial cytotoxic or other molecules from secretory vesicles called granules found inside some cells. It is used by several different cells involved in the immune system, including granulocytes (neutrophils, basophils, and eosinophils) and mast cells. It is also used by certain lymphocytes such as natural killer cell, natural killer (NK) cells and cytotoxic T cells, whose main purpose is to destroy invading microorganisms. Mast cells Antigens interact with IgE molecules already bound to high affinity Fc receptors on the surface of mast cell A mast cell (also known as a mastocyte or a labrocyte) is a resident cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a par ...s to induce degranulation, via the activation of tyrosine kinases within the cell. The mast cell releases a mixture of compounds, includi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calreticulin
Calreticulin also known as calregulin, CRP55, CaBP3, calsequestrin-like protein, and endoplasmic reticulum resident protein 60 (ERp60) is a protein that in humans is encoded by the ''CALR'' gene. Calreticulin is a multifunctional soluble protein that binds Ca2+ ions (a second messenger in signal transduction), rendering it inactive. The Ca2+ is bound with low affinity, but high capacity, and can be released on a signal (see inositol trisphosphate Inositol trisphosphate or inositol 1,4,5-trisphosphate abbreviated InsP3 or Ins3P or IP3 is an inositol phosphate signaling molecule. It is made by hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2), a phospholipid that is located in the p ...). Calreticulin is located in storage compartments associated with the endoplasmic reticulum and is considered an ER resident protein. The term "Mobilferrin" is considered to be the same as calreticulin by some sources. Function Calreticulin binds to misfolded proteins and prevents ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytolysin
Cytolysin refers to the substance secreted by microorganisms, plants or animals that is specifically toxic to individual cells, in many cases causing their dissolution through lysis. Cytolysins that have a specific action for certain cells are named accordingly. For instance, the cytolysins responsible for the destruction of red blood cells, thereby liberating hemoglobins, are named ''hemolysins'', and so on. Cytolysins may be involved in immunity as well as in venoms. Hemolysin is also used by certain bacteria, such as ''Listeria monocytogenes'', to disrupt the phagosome membrane of macrophages and escape into the cytoplasm of the cell. History and background The term "Cytolysin" or "Cytolytic toxin" was first introduced by Alan Bernheimer to describe membrane damaging toxins ( MDTs) that have cytolytic effects to cells. The first kind of cytolytic toxin discovered have hemolytic effects on erythrocytes of certain sensitive species, such as Human. For this reason "Hemolysin" wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Complement Component 9
Complement component 9 (C9) is a MACPF protein involved in the complement system, which is part of the innate immune system. Once activated, about 12-18 molecules of C9 polymerize to form pores in target cell membranes, causing lysis and cell death. C9 is one member of the complement membrane attack complex (MAC), which also includes complement components C5b, C6, C7 and C8. The formation of the MAC occurs through three distinct pathways: the classical, alternative, and lectin pathways. Pore formation by C9 is an important way that bacterial cells are killed during an infection, and the target cell is often covered in multiple MACs. The clinical impact of a deficiency in C9 is an infection with the gram-negative bacterium ''Neisseria meningitidis.'' Structure C9 genes include 11 exons and 10 introns An intron is any nucleotide sequence within a gene that is not expressed or operative in the final RNA product. The word ''intron'' is derived from the term ''intragenic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Complement Membrane Attack Complex
The membrane attack complex (MAC) or terminal complement complex (TCC) is a complex of proteins typically formed on the surface of pathogen cell membranes as a result of the activation of the host's complement system, and as such is an effector of the immune system. Antibody-mediated complement activation leads to MAC deposition on the surface of infected cells. Assembly of the MAC leads to pores that disrupt the cell membrane of target cells, leading to cell lysis and death. The MAC is composed of the complement components C5b, C6, C7, C8 and several C9 molecules. A number of proteins participate in the assembly of the MAC. Freshly activated C5b binds to C6 to form a C5b-6 complex, then to C7 forming the C5b-6-7 complex. The C5b-6-7 complex binds to C8, which is composed of three chains (alpha, beta, and gamma), thus forming the C5b-6-7-8 complex. C5b-6-7-8 subsequently binds to C9 and acts as a catalyst in the polymerization of C9. Structure and function MAC is composed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Defensin
Defensins are small cysteine-rich cationic proteins across cellular life, including vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ... and invertebrate animals, plants, and fungi. They are host defense peptides, with members displaying either direct Antimicrobial peptides, antimicrobial activity, Immune system, immune signalling activities, or both. They are variously active against bacteria, fungus, fungi and many enveloped and nonenveloped viruses. They are typically 18-45 amino acids in length, with three or four highly conserved disulphide bonds. In animals, they are produced by cells of the innate immune system and epithelial cells, whereas in plants and fungi they are produced by a wide variety of tissues. An organism usually produces many different defensins, some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
