The covalent interaction of C3 with IgG immune complexes

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dc.contributor.authorVivanco Martínez, Fernando
dc.contributor.authorMuñoz, Esther
dc.contributor.authorVidarte, Luis
dc.contributor.authorPastor Vargas, Carlos
dc.date.accessioned2024-01-29T14:23:06Z
dc.date.available2024-01-29T14:23:06Z
dc.date.issued1999
dc.description.abstractAntigens (Ags) are converted into immune complexes (antigen-antibody complexes, IC) as soon as they encounter their specific antibodies (Abs). In fluids containing complement, the process of IC formation and fixation of complement components occur simultaneously. Hence, the formation of Ag-Ab-complement complexes is the normal way of eliminating Ags from a host. C3b-C3b-IgG covalent complexes are immediately formed on interaction of serum C3 with IgG-IC. These C3b-C3b dimers constitute the core for the assembly of C3/C5-convertase on the IC, which are subsequently converted into iC3b-iC3b-IgG by the complement regulators. These complexes are detected on SDS-PAGE by two bands of molecular composition, C3alpha65-C3alpha43 (band A) and C3alpha65-heavy chain of the Ab (band B), which correspond to C3b-C3b and C3b-IgG covalent interaction respectively, and that identify opsonized IC (C3b-IC). C3b can attach to Fab and Fc regions of the Ab molecule with similar efficiency. The presence of multiple C3b binding regions on IgG is considered an advantageous characteristic that facilitates the elimination of Ags in the form of C3b(n)-IC. Ab molecules on the IC recognize the Ag, and also serve as a very good acceptor for C3b binding. In this way, Ags, even if they have no acceptor sites for C3b, can be efficiently processed and removed. When C3 is activated in serum by IC or other activators, secondary C3b-IgG covalent complexes are generated, with bystander monomeric circulating IgG, and thus constitute, physiological products of complement activation. These complexes gain importance when IgG concentration is extremely high as in cases of infusion of intravenous IgG (IVIG) in several pathologies. The covalent attachment of activated complement C3 (C3b, iC3b, C3 d,g) to Ags or IC links innate and adaptative immunity by targeting Ags to different cells of the immune system (follicular dendritic cells, phagocytes, B cells). Hence C3b marks Ags definitively, from the earliest contact with the innate immune system until their complete elimination from the host.
dc.description.departmentDepto. de Bioquímica y Biología Molecular
dc.description.facultyFac. de Ciencias Químicas
dc.description.refereedTRUE
dc.description.sponsorshipMinisterio de Educación (España)
dc.description.sponsorshipComunidad de Madrid
dc.description.statuspub
dc.identifier.citationVivanco F, Muñoz E, Vidarte L, Pastor C. The covalent interaction of C3 with IgG immune complexes. Mol Immunol. 1999 Sep-Oct;36(13-14):843-52. doi: 10.1016/s0161-5890(99)00105-4. PMID: 10698338.
dc.identifier.doi10.1016/s0161-5890(99)00105-4
dc.identifier.issn0161-5890
dc.identifier.officialurlhttps://doi.org/10.1016/s0161-5890(99)00105-4
dc.identifier.pmid10698338
dc.identifier.urihttps://hdl.handle.net/20.500.14352/96144
dc.issue.number13-14
dc.journal.titleMolecular Immunology
dc.language.isoeng
dc.page.final852
dc.page.initial843
dc.publisherElsevier
dc.rightsAttribution-NonCommercial-NoDerivatives 4.0 Internationalen
dc.rights.accessRightsrestricted access
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subject.cdu577.1
dc.subject.keywordImmunecomplexes
dc.subject.keywordC3
dc.subject.keywordIgG
dc.subject.keywordFab
dc.subject.keywordFc
dc.subject.keywordComplement
dc.subject.ucmCiencias Biomédicas
dc.subject.unesco2412 Inmunología
dc.titleThe covalent interaction of C3 with IgG immune complexes
dc.typejournal article
dc.type.hasVersionVoR
dc.volume.number36
dspace.entity.typePublication
relation.isAuthorOfPublication6f3e7679-cbc7-4f23-8355-2de0876d46ad
relation.isAuthorOfPublication25af78c7-0077-4891-a14e-bcd8e51fe408
relation.isAuthorOfPublication.latestForDiscovery6f3e7679-cbc7-4f23-8355-2de0876d46ad
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