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A New Tool for Complement Research: In vitro Reconstituted Human Classical Complement Pathway

The complement, as part of the innate immune system, represents the first line of defense against Gram-negative bacteria invading the bloodstream. The complement system is a zymogen cascade that ultimately assemble into the so-called membrane attack complex (MAC), which lyses Gram-negative bacteria...

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Autores principales: Mutti, Michele, Ramoni, Katharina, Nagy, Gábor, Nagy, Eszter, Szijártó, Valéria
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6288441/
https://www.ncbi.nlm.nih.gov/pubmed/30564230
http://dx.doi.org/10.3389/fimmu.2018.02770
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author Mutti, Michele
Ramoni, Katharina
Nagy, Gábor
Nagy, Eszter
Szijártó, Valéria
author_facet Mutti, Michele
Ramoni, Katharina
Nagy, Gábor
Nagy, Eszter
Szijártó, Valéria
author_sort Mutti, Michele
collection PubMed
description The complement, as part of the innate immune system, represents the first line of defense against Gram-negative bacteria invading the bloodstream. The complement system is a zymogen cascade that ultimately assemble into the so-called membrane attack complex (MAC), which lyses Gram-negative bacteria upon insertion into the outer membrane. Traditionally, serum has been used as complement source, for example to study the bactericidal activity of monoclonal antibodies or antibodies raised upon vaccination. Due to the significant donor to donor variability, as well as susceptibility of complement factors to handling and storage conditions, assay reproducibility using human serum is low. Moreover, the presence of pre-existing antibodies and antimicrobial compounds are confounding factors. To remove antibodies from human serum, we applied κ/λ-light chain specific affinity chromatography, however the method severely reduced the complement activity due to the depletion of complement components. Therefore, we attempted to reconstitute human complement—namely the alternative (rAP) and the classical (rCP) pathways—from purified complement factors. We found that adding C1-inhibitor to the mixture was essential to maintain a stable and functional C1 and thus to generate an active rCP. We further confirmed the functionality of the rCP by testing the complement-dependent bactericidal activity of a human monoclonal antibody, A1124 against an E. coli clinical isolate belonging to the ST131 clonal complex, and that of a polyclonal IVIg against a laboratory E. coli strain (MG1655) not expressing LPS O-antigen and capsule. Although the alternative pathway did not have any bactericidal activity by itself, it enhanced MAC deposition induced by rCP and increased the overall bactericidal activity against the ST131 E. coli strain. In conclusion, we report for the first time the successful in vitro reconstitution of the classical pathway of the human complement to establish a serum-free, complement dependent bactericidal assay. This system offers high level of standardization and could support the study of the complement in different research fields.
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spelling pubmed-62884412018-12-18 A New Tool for Complement Research: In vitro Reconstituted Human Classical Complement Pathway Mutti, Michele Ramoni, Katharina Nagy, Gábor Nagy, Eszter Szijártó, Valéria Front Immunol Immunology The complement, as part of the innate immune system, represents the first line of defense against Gram-negative bacteria invading the bloodstream. The complement system is a zymogen cascade that ultimately assemble into the so-called membrane attack complex (MAC), which lyses Gram-negative bacteria upon insertion into the outer membrane. Traditionally, serum has been used as complement source, for example to study the bactericidal activity of monoclonal antibodies or antibodies raised upon vaccination. Due to the significant donor to donor variability, as well as susceptibility of complement factors to handling and storage conditions, assay reproducibility using human serum is low. Moreover, the presence of pre-existing antibodies and antimicrobial compounds are confounding factors. To remove antibodies from human serum, we applied κ/λ-light chain specific affinity chromatography, however the method severely reduced the complement activity due to the depletion of complement components. Therefore, we attempted to reconstitute human complement—namely the alternative (rAP) and the classical (rCP) pathways—from purified complement factors. We found that adding C1-inhibitor to the mixture was essential to maintain a stable and functional C1 and thus to generate an active rCP. We further confirmed the functionality of the rCP by testing the complement-dependent bactericidal activity of a human monoclonal antibody, A1124 against an E. coli clinical isolate belonging to the ST131 clonal complex, and that of a polyclonal IVIg against a laboratory E. coli strain (MG1655) not expressing LPS O-antigen and capsule. Although the alternative pathway did not have any bactericidal activity by itself, it enhanced MAC deposition induced by rCP and increased the overall bactericidal activity against the ST131 E. coli strain. In conclusion, we report for the first time the successful in vitro reconstitution of the classical pathway of the human complement to establish a serum-free, complement dependent bactericidal assay. This system offers high level of standardization and could support the study of the complement in different research fields. Frontiers Media S.A. 2018-12-04 /pmc/articles/PMC6288441/ /pubmed/30564230 http://dx.doi.org/10.3389/fimmu.2018.02770 Text en Copyright © 2018 Mutti, Ramoni, Nagy, Nagy and Szijártó. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Immunology
Mutti, Michele
Ramoni, Katharina
Nagy, Gábor
Nagy, Eszter
Szijártó, Valéria
A New Tool for Complement Research: In vitro Reconstituted Human Classical Complement Pathway
title A New Tool for Complement Research: In vitro Reconstituted Human Classical Complement Pathway
title_full A New Tool for Complement Research: In vitro Reconstituted Human Classical Complement Pathway
title_fullStr A New Tool for Complement Research: In vitro Reconstituted Human Classical Complement Pathway
title_full_unstemmed A New Tool for Complement Research: In vitro Reconstituted Human Classical Complement Pathway
title_short A New Tool for Complement Research: In vitro Reconstituted Human Classical Complement Pathway
title_sort new tool for complement research: in vitro reconstituted human classical complement pathway
topic Immunology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6288441/
https://www.ncbi.nlm.nih.gov/pubmed/30564230
http://dx.doi.org/10.3389/fimmu.2018.02770
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