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Topic: Complement system


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  1.4.3 Products of the complement system
Complement is a complex system containing more than 30 various glycoproteins present in serum in the form of components, factors, or other regulators and/or on the surface of different cells in the form of receptors.
The main functions of the complement cascade and its role in the acute inflammatory reaction are summarized in Table 1.8.
This new lectin pathway of complement activation is important not only for the killing of microorganisms through the interaction of carbohydrates on their surfaces and MBP or other collectins (humoral lectins found in humans and other mammals) but also for the opsonizing activity.
nic.sav.sk /logos/books/scientific/node28.html   (1634 words)

  
  Complement system - Wikipedia, the free encyclopedia
The complement proteins are synthesized mainly by hepatocytes; however, significant amounts are also produced by monocytes, macrophages, and epithelial cells in the gastrointestinal and genitourinary tracts.
Three biochemical pathways activate the complement system: the classical complement pathway, the alternate complement pathway, and the mannose-binding lectin pathway.
The classical pathway is triggered by activation of the C1-complex (which consists of one molecule C1q and two molecules C1r and C1s), either by C1q's binding to antibodies from classes M and G, complexed with antigens, or by its binding C1q to the surface of the pathogen.
en.wikipedia.org /wiki/Complement_system   (1038 words)

  
 BioCarta - Charting Pathways of Life   (Site not responding. Last check: 2007-09-19)
Most complement proteins exist in plasma as inactive precursors that cleave and activate each other in a proteolytic cascade in response to three different mechanisms by which the complement system is activated, the classical pathway, the alternative pathway and the lectin-induced pathway (see Pathways for each of these individually).
These three systems are distinct in the initiation of the proteolytic cascade but share most of their components and all three converge in the creation of a C3 convertase that cleaves the C3 complement protein, leading ultimately to the formation of the membrane attack complex, MAC, a pore causing lysis of cells.
Proteolysis is triggered in the alternative pathway by the spontaneous activation of C3 convertase from C3 and is triggered in the lectin-induced pathway by the recognition of carbohydrates on the bacterial cell surface by mannan-binding protein, Mbp.
www.biocarta.com /pathfiles/h_compPathway.asp   (373 words)

  
 Complement System
Be sure at the outset to get your mind around the idea that the complement system is a set of over 20 different protein molecules always found in the blood.
With an infection, this system of molecules is activated, leading to a sequence of events on the surface of the pathogen that helps destroy the pathogen and eliminate the infection.
C3b remains bound to the complex at the surface of the microorganism.
courses.washington.edu /conj/inflammation/complement.htm   (482 words)

  
 Introduction   (Site not responding. Last check: 2007-09-19)
In addition to these plasma proteins, the complement system includes multiple distinct cell-surface receptors that exhibit specificity for the physiological fragments of complement proteins and that occur on inflammatory cells and cells of the immune system.
The role of complement in inflammation and tissue injury has become apparent through clinical investigations and discoveries that the pathogenesis of certain experimental inflammatory diseases is complement-dependent.
Complement mediated lysis occurs in many kinds of cells: erythrocytes, platelets, bacteria, viruses possessing a lipoprotein envelope, and lymphocytes.
www-micro.msb.le.ac.uk /MBChB/Merralls/Intro.html   (501 words)

  
 The Immune System   (Site not responding. Last check: 2007-09-19)
The major components of the innate defense system are the natural defense system, the complement system, the phagocytic cells, and the interferon system.
The complement system consists of at least 20 serum proteins which, when stimulated, respond with a series of chain reactions similar to the "domino effect," i.e., something happens to activate the first component which in turn activates the next component which in turn activates the next component, etc., until the reaction is complete.
This complement system reaction, which at times appears to be detrimental, hastens the accumulation of disease fighting cells (phagocytes) to the area by providing a fluid "pathway" and by producing chemotactic substances which attract phagocytes.
edis.ifas.ufl.edu /BODY_VM027   (3705 words)

  
 1.4.3 Products of the complement system   (Site not responding. Last check: 2007-09-19)
Complement is a complex system containing more than 30 various glycoproteins present in serum in the form of components, factors, or other regulators and/or on the surface of different cells in the form of receptors.
The main functions of the complement cascade and its role in the acute inflammatory reaction are summarized in Table 1.8.
This new lectin pathway of complement activation is important not only for the killing of microorganisms through the interaction of carbohydrates on their surfaces and MBP or other collectins (humoral lectins found in humans and other mammals) but also for the opsonizing activity.
www.fmed.uniba.sk /patfyz/ZapalWEB/node28.html   (1641 words)

  
 Complement Levels: The Test Sample
The complement system is a set of circulating blood proteins that act as mediators of inflammatory response — especially in the destruction of foreign substances like bacteria and viruses.
The complement system has evolved to recognize antigen antibody complexes (immune complexes) as well as certain structures and polysaccharides (complex carbohydrates) found on the outside membranes of microorganisms and other foreign cells.
Complement and the regulation of its activity is an important part of the immune system.
www.labtestsonline.org /understanding/analytes/complement_levels/sample.html   (541 words)

  
 BioCarta - Charting Pathways of Life   (Site not responding. Last check: 2007-09-19)
The complement system is part of the defense against invading cells and is composed of about twenty different proteins found in the plasma.
There are two different complement systems, the classical complement pathway initiated by antibody complexes on the cell surface, and an alternative complement pathway that is initiated without antibodies.
The proteolytic complement cascade is then amplified on the cell membrane through sequential cleavage of complement factors and recruitment of new factors until a cell surface complex containing C5b, C6, C7, and C8 is formed.
www.biocarta.com /pathfiles/classicPathway.asp   (287 words)

  
 Complement deficiencies
Complement deficiencies are a group of disorders in which there is a reduced level of specific proteins, complement, involved in proper immune functioning.
A complement deficiency syndrome characterized by recurrent infections of the skin, mucous membranes, and gastrointestinal tract and the absence of pus formation.
A rare complement disorder characterized by episodes of red blood cell destruction (hemolysis) and blood in the urine (hemoglobinuria) that is worse at night.
www.healthatoz.com /healthatoz/Atoz/ency/complement_deficiencies.jsp   (674 words)

  
 Complement
Historically, the term complement (C) was used to refer to a heat-labile serum component that was able to lyse bacteria (activity is destroyed (inactivated) by heating serum at 56 degrees C for 30 minutes).
Complement can opsonize bacteria for enhanced phagocytosis; it can recruit and activate various cells including polymorphonuclear cells (PMNs) and macrophages; it can participate in regulation of antibody responses and it can aid in the clearance of immune complexes and apoptotic cells.
Complement activation can be divided into four pathways (figure 1): the classical pathway, the lectin pathway, the alternative pathway and the membrane attack (or lytic) pathway.
pathmicro.med.sc.edu /ghaffar/complement.htm   (2312 words)

  
 Understanding the Immune System - The Body
The immune system is a bodywide network of cells and organs that has evolved to defend the body against attacks by "foreign" invaders.
The organs of the immune system are connected with one another and with other organs of the body by a network of lymphatic vessels similar to blood vessels.
The complement system consists of a series of proteins that work to "complement" the work of antibodies in destroying bacteria.
www.thebody.com /nih/immune_system.html   (2947 words)

  
 Complement Molecules   (Site not responding. Last check: 2007-09-19)
The complement is activated by the presence of bacteria and also indirectly by other immune cells and by antibodies.
Complement is part of the innate immune system which means it is non-selective and will attack any invading bacteria.
This starts a "cascade" where additional complement proteins are enabled to bind, and so on, until a large complement complex is bound to the surface of the invading cell.
www.newton.dep.anl.gov /askasci/mole00/mole00193.htm   (512 words)

  
 The Complement System
C3 is the most abundant protein of the complement system (~1.3 mg/ml).
The explosive potential of the complement system requires that it be kept under tight control.
This emphasizes the important role of the complement system in clearing away antigen-antibody complexes.
users.rcn.com /jkimball.ma.ultranet/BiologyPages/C/Complement.html   (1282 words)

  
 The Individualist: Complement System
Three biochemical pathways activate the complement system: the classical complement pathway, the alternate complement pathway, and the Mannan-binding lectin (MBL) pathway.
The main functions of the complement cascade and its role in the acute inflammatory reaction are summarized in Table 1.
It is thought that the complement system might play a role in many diseases with an immune component, such as Alzheimer's disease, asthma, lupus erythematosus, various forms of arthritis, autoimmune heart disease and multiple sclerosis.
www.dadamo.com /wiki/wiki.pl/Complement_System   (2254 words)

  
 eMedicine - Complement Deficiency : Article by Ruchir Agrawal, MD   (Site not responding. Last check: 2007-09-19)
The complement system currently is known to contain at least 30 different proteins, which are primarily formed in the liver and circulate in their inactive form.
Hemolytic activity of the complement system is measured as hemolysis of sheep erythrocytes sensitized by specific antibodies.
Ratnoff WD: Inherited deficiencies of complement in rheumatic diseases.
www.emedicine.com /ped/topic447.htm   (3850 words)

  
 The COMPLEMENT SYSTEM   (Site not responding. Last check: 2007-09-19)
Complement proteins are synthesized by the liver and circulate within the plasma in inactive forms.
IgM or IgG antibody Molecules, bound to the surface of micro-organisms, activate the complement System.
In this scenario the complement system could be considered as specific, but the antibody brings about the specificity so it merely complements the specific function of antibody.
sprojects.mmi.mcgill.ca /immunology/complement.htm   (255 words)

  
 eMedicine - Complement Deficiencies : Article by R Krishna Chaganti
Although the complement system is part of the body's innate, relatively nonspecific defense against pathogens, its role is hardly primitive or easily understood.
The 3 major sequelae of complement deficiencies, based on the pathophysiology of each defect, are (1) defects that result in inadequate opsonization, (2) defects in cell lysis, and (3) the association of complement deficiencies with immune complex diseases.
The reason complement deficiency increases the risk of developing SLE is that complement helps in the prevention of immune complex disease by decreasing the number of circulating immune complexes; the greater the concentration of these precipitating immune complexes, the higher the likelihood that they will deposit in nearby tissues and cause an inflammatory response.
www.emedicine.com /med/topic419.htm   (4484 words)

  
 Lecture 11: Complement   (Site not responding. Last check: 2007-09-19)
The complement system is a complex system of serum proteins which interact in a cascade, many of the early components are serine proteases which activate each other sequentially.
The central component of the complement system is C3.
The phenotype of these deficiencies tell us a good deal about the role of the complement system, though in the case of C1 INH it is complicated by the activity if C1 INH in inhibiting the serum proteases kallikrein and plasmin as well as C1s so that it's loss also dysregulates coagulation.
immserv1.path.cam.ac.uk /~immuno/part1/lec10/lec10_97.html   (1461 words)

  
 Lund Virtual Medical Journal
The complement system represents the first line of defense against invading microorganisms, and pathogens have developed numerous strategies to minimize activation of the complement components.
The complement system is a powerful part of the innate immune response that can recognize and eliminate pathogens without previous activation of the adaptive immune system.
The complement proteins circulate in the blood and extracellular fluid, and they are activated by pathogens through a series of coordinated events that lead to formation of membrane attack complex on the surface of the bacteria, which eventually results in phagocytosis of the microbes.
www.medfak.lu.se /search_medfak/html/monthly.php   (438 words)

  
 Is the Complement System Irreducibly Complex?
Activated complement proteins initiate a cascade of enzymatic reactions that ultimately results in a large hole literally punctured through the membrane of the invading microorganism, or in the hemolytic transfusion reaction, in red blood cells.
Below is a schematic of the major players in all three complement activation pathways of vertebrates* (please note: unfortunately, many of the proteins were numbered in the order they were discovered, not in their respective order in the pathways).
The occurrence of simpler systems in phylogenetically older organisms suggests an evolutionary pathway and the occurrence of numerous homologies between the genes suggests a mechanism for its evolution.
www.talkorigins.org /faqs/behe/icsic.html   (2897 words)

  
 Complement   (Site not responding. Last check: 2007-09-19)
The complement system found in the blood of mammals is composed of heat labile substances (proteins) that combine with antibodies or cell surfaces.
The complement system can be activated via two distinct pathways; the classical pathway and the alternate pathway.
Because both the classical and alternate pathways depend upon C3b, regulation of the complement cascade is mediated via 3 proteins that affect the levels and activities of this component.
www.cehs.siu.edu /fix/medmicro/cment.htm   (678 words)

  
 MichaelPangburn   (Site not responding. Last check: 2007-09-19)
One of the major systems for killing microorganisms such as bacteria, yeasts, viruses and parasites is referred to as the "complement system." This system got its name from the discovery over 80 years ago that antibodies alone could not kill bacteria.
To investigate these reactions many of the proteins of the complement system are purified and used to analyze protein-protein interactions, to study mechanisms of activation and to understand how each of these reactions contributes to the overall process leading to killing of infectious organisms.
C5 convertase of the alternative pathway of complement Kinetic analysis of the free and surface-bound forms of the enzyme.
www.uthct.edu /BIRE/Faculty/MichaelPangburn.htm   (1011 words)

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