[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"doc-seo-453154-105":3,"detail-sidebar-cat-0-en-105":81,"doc-detail-453154-en":130},{"code":4,"msg":5,"data":6},0,"ok",{"site_id":7,"language":8,"slug":9,"title":10,"keywords":11,"description":12,"schema_data":13,"social_meta":74,"head_meta":76,"extra_data":78,"updated_unix":80},105,"en","complement-measurement-introduction","Complement: Measurement - Introduction","","Complement system proteins and cell-membrane receptors coordinate innate defense by activating three initiation pathways and a common terminal process that deposits C3b, drives phagocytosis, forms the membrane attack complex to lyse bacteria, and promotes inflammation. The text explains why measuring complement pathway activity and individual component levels supports clinical assessment in immunodeficiency and inflammatory diseases such as systemic lupus erythematosus, and summarizes available immunochemical methods for protein level and functional activity testing.",{"@graph":14,"@context":73},[15,34,56],{"@type":16,"itemListElement":17},"BreadcrumbList",[18,23,27,31],{"item":19,"name":20,"@type":21,"position":22},"https://docshare.wps.com","Home","ListItem",1,{"item":24,"name":25,"@type":21,"position":26},"https://docshare.wps.com/document/","Document",2,{"item":28,"name":29,"@type":21,"position":30},"https://docshare.wps.com/document/healthcare/","Healthcare",3,{"item":32,"name":10,"@type":21,"position":33},"https://docshare.wps.com/document/complement-measurement-introduction/453154/",4,{"url":32,"name":10,"@type":35,"image":36,"author":41,"headline":10,"publisher":44,"fileFormat":47,"inLanguage":8,"description":12,"dateModified":48,"datePublished":49,"encodingFormat":47,"isAccessibleForFree":50,"interactionStatistic":51},"DigitalDocument",{"url":37,"@type":38,"width":39,"height":40},"https://docshare.wps.com/thumbnails/complement-measurement-introduction/453154.png","ImageObject",300,407,{"name":42,"@type":43},"Aria","Person",{"url":19,"name":45,"@type":46},"DocShare","Organization","application/pdf","2026-11-05","2026-09-30",true,{"@type":52,"interactionType":53,"userInteractionCount":55},"InteractionCounter",{"@type":54},"ViewAction",8,{"@type":57,"mainEntity":58},"FAQPage",[59,65,69],{"name":60,"@type":61,"acceptedAnswer":62},"What is the clinical purpose of measuring complement activity and components?","Question",{"text":63,"@type":64},"Measurement of complement pathway activity and individual component levels helps in immunodeficiency and inflammatory conditions involving complement activation, such as systemic lupus erythematosus (SLE).","Answer",{"name":66,"@type":61,"acceptedAnswer":67},"Which laboratory methods are used to measure complement protein levels?",{"text":68,"@type":64},"Standard immunochemical methods are used. Nephelometry and turbidimetry assay components present in relatively high concentrations, while ELISA and radioimmunoassay measure components present in relatively low concentrations.",{"name":70,"@type":61,"acceptedAnswer":71},"How does the classical complement pathway become activated?",{"text":72,"@type":64},"Immune complexes containing IgG or IgM activate the classical pathway by binding C1q, which leads to sequential activation of C1r and C1s, followed by cleavage steps that form the classical pathway C3 convertase and generate C3b.","https://schema.org",{"og:url":32,"og:type":75,"og:title":10,"og:site_name":45,"og:description":12},"article",{"robots":77,"canonical":32},"index,follow",{"doc_id":79,"site_id":7},453154,1790906865,{"code":4,"msg":82,"data":83},"success",[84,88,92,96,101,106,110,114,119,122,126],{"id":22,"doc_module":4,"doc_module_name":25,"category_name":85,"show_sort_weight":86,"slug":87},"Story & Novel",90,"story-novel",{"id":26,"doc_module":4,"doc_module_name":25,"category_name":89,"show_sort_weight":90,"slug":91},"Literature",80,"literature",{"id":33,"doc_module":4,"doc_module_name":25,"category_name":93,"show_sort_weight":94,"slug":95},"Exam",70,"exam",{"id":97,"doc_module":4,"doc_module_name":25,"category_name":98,"show_sort_weight":99,"slug":100},5,"Comic",60,"comic",{"id":102,"doc_module":4,"doc_module_name":25,"category_name":103,"show_sort_weight":104,"slug":105},6,"Technology",50,"technology",{"id":107,"doc_module":4,"doc_module_name":25,"category_name":29,"show_sort_weight":108,"slug":109},7,40,"healthcare",{"id":55,"doc_module":4,"doc_module_name":25,"category_name":111,"show_sort_weight":112,"slug":113},"Research & Report",30,"research-report",{"id":115,"doc_module":4,"doc_module_name":25,"category_name":116,"show_sort_weight":117,"slug":118},9,"Religion & Spirituality",20,"religion-spirituality",{"id":117,"doc_module":4,"doc_module_name":25,"category_name":120,"show_sort_weight":117,"slug":121},"World Cup","world-cup",{"id":123,"doc_module":4,"doc_module_name":25,"category_name":124,"show_sort_weight":123,"slug":125},10,"Lifestyle","lifestyle",{"id":127,"doc_module":4,"doc_module_name":25,"category_name":128,"show_sort_weight":97,"slug":129},19,"General","general",{"code":4,"msg":82,"data":131},{"doc_id":79,"user_id":132,"nickname":42,"user_avatar":133,"doc_module":4,"category_id":107,"category_name":29,"doc_title":10,"doc_description":12,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":55,"is_deleted":4,"is_public":22,"is_downloadable":22,"audit_status":22,"page_count":107,"language":139,"language_code":8,"site_id":7,"html_lang":8,"table_of_contents":140,"faqs":141,"seo_title":142,"seo_description":12,"update_tm":143,"read_time":144,"preview_page_count":4},2336464648322,"https://ap-avatar.wpscdn.com/avatar/2200025388227c56fec?_k=1778556882303663488","Complement: Measurement  \nJonathan North, City Hospital NHS Trust, Birmingham, UK K Whaley, University of Kuwait, Safat, Kuwait  \nThe complement system comprises a group of serum proteins and cell membrane receptors that function primarily to fight infection. Clinically, measurement of complement pathway activity and individual component levels is of value in cases of immunodeficiency and inflammatory conditions that involve complement activation.  \nIntroduction  \nThe complement system comprises a group of serum proteins and cell membrane receptors that function primarily to fight infection. These components interact in three activation pathways and one final pathway. The central results of activation of these pathways are to deposit the opsonin C3b on bacteria to promote phagocytosis, to lyse bacteria by the assembly of the terminal membrane attack complex and to promote inflammation. Clinically, measurement of pathway activity and individual component levels is, therefore, of value in cases of immunodeficiency and inflammatory conditions that involve complement activation, the prime example of the latter being systemic lupus erythematosus (SLE) .  \nThe measurement of complement protein levels is readily achieved using standard immunochemical methods. Nephelometry and turbidimetry can be used to assay levels of serum complement components that are present in relatively high concentrations (e.g. C3, C4, C1-inhibitor (C1-inh)) . Enzyme-linked immunosorbent assay (ELISA) or radioimmunoassay (RIA) are used to measure components present in relatively low concentrations, but serum/ plasma concentrations of all components have been successfully measured by ELISA. It is also possible to determine the functional activity of the majority of the complement components. To fully appreciate the conditions required for the functional assays, it is important to understand the process that is occurring. Accordingly a summary of the complement pathways, stressing certain conditions necessary for activation, is given in the following section, with more detailed descriptions to be found in the individual assay sections. Full methodologies for the assays described in this chapter are given in the literature listed for further reading.  \nThe classical pathway  \nImmune complexes that contain immunoglobulin G (IgG) or IgM can activate the classical pathway by the binding of the first component of complement (C1) via the C1qsubcomponent. Once bound, the subcomponent C1r is activated and this, in turn, activates C1s. The integrity of  \nthe C1q–C1r–C1s complex is calcium-dependent. Activated C1s is a serine protease that activates C4 by limited proteolysis. Cleaved C4 (C4b) will bind to the activating complex. C2 binds to C4b when magnesium ions are present and C1s will then activate C2 to form the C4b2a complex (classical pathway C3 convertase) that activates C3 by limited proteolysis. Activated C3 (C3b) will bind covalently to certain surfaces (see below) and act as a highaffinity ligand for C3b receptors on phagocytes.  \nIn addition to the inherent instability of C4b2a, spontaneous activation of the classical pathway is controlled in the initial stages by the serine protease inhibitor C1-inhibitor (C1-inh), which binds to C1r and C1s and prevents C4 activation. C4-binding protein (C4bp) dissociates the C4b2a complex and acts as a cofactor for the cleavage of C4b by factor I.  \nMannan-binding lectin activation of complement  \nIn addition to immune complexes, several molecules can bind the collagenous region of C1q and cause classical pathway activation. Such molecules include C-reactive protein and fibronectin, and molecules that have an anionic nature such as DNA, lipopolysaccharide and mucopolysaccharides.  \nIn contrast, mannan-binding lectin (MBL) is a protein that structurally resembles C1q itself and can activate C4 in the absence of antibody and C1q when bound to specific carbohydrates (e.g. those of many bacteria) . MBL circulates as a macromolecular co","cbCaior5Rx54IHzg","https://ap.wps.com/l/cbCaior5Rx54IHzg","pdf",119438,"English","# Complement: Measurement\n## Introduction\n## The classical pathway\n## Mannan-binding lectin activation of complement\n## The alternative pathway","[{\"question\":\"What is the clinical purpose of measuring complement activity and components?\",\"answer\":\"Measurement of complement pathway activity and individual component levels helps in immunodeficiency and inflammatory conditions involving complement activation, such as systemic lupus erythematosus (SLE).\"},{\"question\":\"Which laboratory methods are used to measure complement protein levels?\",\"answer\":\"Standard immunochemical methods are used. Nephelometry and turbidimetry assay components present in relatively high concentrations, while ELISA and radioimmunoassay measure components present in relatively low concentrations.\"},{\"question\":\"How does the classical complement pathway become activated?\",\"answer\":\"Immune complexes containing IgG or IgM activate the classical pathway by binding C1q, which leads to sequential activation of C1r and C1s, followed by cleavage steps that form the classical pathway C3 convertase and generate C3b.\"}]","Complement: Measurement - Introduction | PDF",1790738358,18]