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de Boer ECW, Thielen AJF, Langereis JD, Kamp A, Brouwer MC, Oskam N, Jongsma ML, Baral AJ, Spaapen RM, Zeerleder S, Vidarsson G, Rispens T, Wouters D, Pouw RB, Jongerius I. The contribution of the alternative pathway in complement activation on cell surfaces depends on the strength of classical pathway initiation. Clin Transl Immunology 2023; 12:e1436. [PMID: 36721662 PMCID: PMC9881211 DOI: 10.1002/cti2.1436] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 10/31/2022] [Accepted: 12/23/2022] [Indexed: 01/28/2023] Open
Abstract
Objectives The complement system is an important component of innate immunity. The alternative pathway (AP) amplification loop is considered an essential feed forward mechanism for complement activation. However, the role of the AP in classical pathway (CP) activation has only been studied in ELISA settings. Here, we investigated its contribution on physiologically relevant surfaces of human cells and bacterial pathogens and in antibody-mediated complement activation, including in autoimmune haemolytic anaemia (AIHA) setting with autoantibodies against red blood cells (RBCs). Methods We evaluated the contribution of the AP to complement responses initiated through the CP on human RBCs by serum of AIHA patients and recombinant antibodies. Moreover, we studied complement activation on Neisseria meningitidis and Escherichia coli. The effect of the AP was examined using either AP-depleted sera or antibodies against factor B and factor D. Results We show that the amplification loop is redundant when efficient CP activation takes place. This is independent of the presence of membrane-bound complement regulators. The role of the AP may become significant when insufficient CP complement activation occurs, but this depends on antibody levels and (sub)class. Our data indicate that therapeutic intervention in the amplification loop will most likely not be effective to treat antibody-mediated diseases. Conclusion The AP can be bypassed through efficient CP activation. The AP amplification loop has a role in complement activation during conditions of modest activation via the CP, when it can allow for efficient complement-mediated killing.
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Affiliation(s)
- Esther CW de Boer
- Department of Immunopathology, Sanquin Research and Landsteiner LaboratoryAmsterdam Infection and Immunity Institute, Amsterdam University Medical CentreAmsterdamThe Netherlands,Department of Pediatric Immunology, Rheumatology, and Infectious Diseases, Emma Children's HospitalAmsterdam University Medical CentreAmsterdamThe Netherlands
| | - Astrid JF Thielen
- Department of Immunopathology, Sanquin Research and Landsteiner LaboratoryAmsterdam Infection and Immunity Institute, Amsterdam University Medical CentreAmsterdamThe Netherlands
| | - Jeroen D Langereis
- Laboratory of Medical Immunology, Radboud Institute for Molecular Life SciencesRadboudumcNijmegenThe Netherlands,Radboud Center for Infectious Diseases, RadboudumcNijmegenThe Netherlands
| | - Angela Kamp
- Department of Immunopathology, Sanquin Research and Landsteiner LaboratoryAmsterdam Infection and Immunity Institute, Amsterdam University Medical CentreAmsterdamThe Netherlands
| | - Mieke C Brouwer
- Department of Immunopathology, Sanquin Research and Landsteiner LaboratoryAmsterdam Infection and Immunity Institute, Amsterdam University Medical CentreAmsterdamThe Netherlands
| | - Nienke Oskam
- Department of Immunopathology, Sanquin Research and Landsteiner LaboratoryAmsterdam Infection and Immunity Institute, Amsterdam University Medical CentreAmsterdamThe Netherlands
| | - Marlieke L Jongsma
- Department of Immunopathology, Sanquin Research and Landsteiner LaboratoryAmsterdam Infection and Immunity Institute, Amsterdam University Medical CentreAmsterdamThe Netherlands
| | - April J Baral
- Translational and Clinical Research InstituteNewcastle upon TyneUK
| | - Robbert M Spaapen
- Department of Immunopathology, Sanquin Research and Landsteiner LaboratoryAmsterdam Infection and Immunity Institute, Amsterdam University Medical CentreAmsterdamThe Netherlands
| | - Sacha Zeerleder
- Department of Immunopathology, Sanquin Research and Landsteiner LaboratoryAmsterdam Infection and Immunity Institute, Amsterdam University Medical CentreAmsterdamThe Netherlands,Department of Hematology, Luzerner KantonsspitalLuzern and University of BernBernSwitzerland,Department for BioMedical ResearchUniversity of BernBernSwitzerland
| | - Gestur Vidarsson
- Department of Experimental Immunohematology, Sanquin Research, and Landsteiner LaboratoryAmsterdam University Medical CenterAmsterdamThe Netherlands
| | - Theo Rispens
- Department of Immunopathology, Sanquin Research and Landsteiner LaboratoryAmsterdam Infection and Immunity Institute, Amsterdam University Medical CentreAmsterdamThe Netherlands
| | - Diana Wouters
- Department of Immunopathology, Sanquin Research and Landsteiner LaboratoryAmsterdam Infection and Immunity Institute, Amsterdam University Medical CentreAmsterdamThe Netherlands,Centre for Infectious Disease ControlNational Institute for Public Health and the Environment (RIVM)BilthovenThe Netherlands
| | - Richard B Pouw
- Department of Immunopathology, Sanquin Research and Landsteiner LaboratoryAmsterdam Infection and Immunity Institute, Amsterdam University Medical CentreAmsterdamThe Netherlands,Sanquin Health SolutionsAmsterdamThe Netherlands
| | - Ilse Jongerius
- Department of Immunopathology, Sanquin Research and Landsteiner LaboratoryAmsterdam Infection and Immunity Institute, Amsterdam University Medical CentreAmsterdamThe Netherlands,Department of Pediatric Immunology, Rheumatology, and Infectious Diseases, Emma Children's HospitalAmsterdam University Medical CentreAmsterdamThe Netherlands
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Evaluating the clinical utility of measuring levels of factor H and the related proteins. Mol Immunol 2022; 151:166-182. [PMID: 36162225 DOI: 10.1016/j.molimm.2022.08.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 08/04/2022] [Accepted: 08/15/2022] [Indexed: 11/21/2022]
Abstract
After years of disappointing clinical results, the tide has finally changed and complement targeted-therapies have become a validated and accepted treatment option for several diseases. These accomplishments have revitalized the field and brought renewed attention to the prospects that complement therapeutics can offer. Streamlining diagnostics and therapeutics is imperative in this new era of clinical use of complement therapeutics. However, the incredible success in therapeutics has not been accompanied by the development of novel standardized tools for complement testing. Complement biomarkers can assist in the risk assessment and diagnosis of diseases as well as the prediction of disease progression and treatment response. Recently, a group of complement proteins has been suggested to be highly relevant in various complement-associated disorders, namely the human factor H (FH) protein family. This family of closely related proteins consists of FH, FH-like protein 1, and five factor H-related proteins, and they have been linked to eye, kidney, infectious, vascular, and autoimmune diseases as well as cancer. The goal of this review is to provide a comprehensive overview of the available data on circulating levels of FH and its related proteins in different pathologies. In addition, we examined the current literature to determine the clinical utility of measuring levels of the FH protein family in health and disease. Finally, we discuss future steps that are needed to make their clinical translation a reality.
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Halting targeted and collateral damage to red blood cells by the complement system. Semin Immunopathol 2021; 43:799-816. [PMID: 34191092 PMCID: PMC8243056 DOI: 10.1007/s00281-021-00859-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 04/18/2021] [Indexed: 12/12/2022]
Abstract
The complement system is an important defense mechanism against pathogens; however, in certain pathologies, the system also attacks human cells, such as red blood cells (RBCs). In paroxysmal nocturnal hemoglobinuria (PNH), RBCs lack certain complement regulators which sensitize them to complement-mediated lysis, while in autoimmune hemolytic anemia (AIHA), antibodies against RBCs may initiate complement-mediated hemolysis. In recent years, complement inhibition has improved treatment prospects for these patients, with eculizumab now the standard of care for PNH patients. Current complement inhibitors are however not sufficient for all patients, and they come with high costs, patient burden, and increased infection risk. This review gives an overview of the underlying pathophysiology of complement-mediated hemolysis in PNH and AIHA, the role of therapeutic complement inhibition nowadays, and the high number of complement inhibitors currently under investigation, as for almost every complement protein, an inhibitor is being developed. The focus lies with novel therapeutics that inhibit complement activity specifically in the pathway that causes pathology or those that reduce costs or patient burden through novel administration routes.
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Poppelaars F, Goicoechea de Jorge E, Jongerius I, Baeumner AJ, Steiner MS, Józsi M, Toonen EJM, Pauly D. A Family Affair: Addressing the Challenges of Factor H and the Related Proteins. Front Immunol 2021; 12:660194. [PMID: 33868311 PMCID: PMC8044877 DOI: 10.3389/fimmu.2021.660194] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 03/08/2021] [Indexed: 12/19/2022] Open
Abstract
Inflammation is a common denominator of diseases. The complement system, an intrinsic part of the innate immune system, is a key driver of inflammation in numerous disorders. Recently, a family of proteins has been suggested to be of vital importance in conditions characterized by complement dysregulation: the human Factor H (FH) family. This group of proteins consists of FH, Factor H-like protein 1 and five Factor H-related proteins. The FH family has been linked to infectious, vascular, eye, kidney and autoimmune diseases. In contrast to FH, the functions of the other highly homologous proteins are largely unknown and, hence, their role in the different disease-specific pathogenic mechanisms remains elusive. In this perspective review, we address the major challenges ahead in this emerging area, including 1) the controversies about the functional roles of the FH protein family, 2) the discrepancies in quantification of the FH protein family, 3) the unmet needs for validated tools and 4) limitations of animal models. Next, we also discuss the opportunities that exist for the immunology community. A strong multidisciplinary approach is required to solve these obstacles and is only possible through interdisciplinary collaboration between biologists, chemists, geneticists and physicians. We position this review in light of our own perspective, as principal investigators of the SciFiMed Consortium, a consortium aiming to create a comprehensive analytical system for the quantitative and functional assessment of the entire FH protein family.
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Affiliation(s)
- Felix Poppelaars
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Elena Goicoechea de Jorge
- Department of Immunology, Faculty of Medicine, Complutense University and Research Institute Hospital 12 de Octubre (imas12), Madrid, Spain
| | - Ilse Jongerius
- Department of Immunopathology, Sanquin Research and Landsteiner Laboratory of the Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands
- Department of Pediatric Immunology, Rheumatology, and Infectious Diseases, Emma Children’s Hospital, Amsterdam University Medical Centre, Amsterdam, Netherlands
| | - Antje J. Baeumner
- Institute of Analytical Chemistry, Chemo-and Biosensors, Faculty of Chemistry and Pharmacy, University of Regensburg, Regensburg, Germany
| | | | - Mihály Józsi
- Department of Immunology, ELTE Eötvös Loránd University, Budapest, Hungary
- MTA-ELTE Complement Research Group, Eötvös Loránd Research Network (ELKH), Department of Immunology, ELTE Eötvös Loránd University, Budapest, Hungary
| | | | - Diana Pauly
- Department of Ophthalmology, University Hospital Regensburg, Regensburg, Germany
- Experimental Ophthalmology, University Marburg, Marburg, Germany
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de Boer ECW, van Mourik AG, Jongerius I. Therapeutic Lessons to be Learned From the Role of Complement Regulators as Double-Edged Sword in Health and Disease. Front Immunol 2020; 11:578069. [PMID: 33362763 PMCID: PMC7758290 DOI: 10.3389/fimmu.2020.578069] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 10/12/2020] [Indexed: 12/22/2022] Open
Abstract
The complement system is an important part of the innate immune system, providing a strong defense against pathogens and removing apoptotic cells and immune complexes. Due to its strength, it is important that healthy human cells are protected against damage induced by the complement system. To be protected from complement, each cell type relies on a specific combination of both soluble and membrane-bound regulators. Their importance is indicated by the amount of pathologies associated with abnormalities in these complement regulators. Here, we will discuss the current knowledge on complement regulatory protein polymorphisms and expression levels together with their link to disease. These diseases often result in red blood cell destruction or occur in the eye, kidney or brain, which are tissues known for aberrant complement activity or regulation. In addition, complement regulators have also been associated with different types of cancer, although their mechanisms here have not been elucidated yet. In most of these pathologies, treatments are limited and do not prevent the complement system from attacking host cells, but rather fight the consequences of the complement-mediated damage, using for example blood transfusions in anemic patients. Currently only few drugs targeting the complement system are used in the clinic. With further demand for therapeutics rising linked to the wide range of complement-mediated disease we should broaden our horizon towards treatments that can actually protect the host cells against complement. Here, we will discuss the latest insights on how complement regulators can benefit therapeutics. Such therapeutics are currently being developed extensively, and can be categorized into full-length complement regulators, engineered complement system regulators and antibodies targeting complement regulators. In conclusion, this review provides an overview of the complement regulatory proteins and their links to disease, together with their potential in the development of novel therapeutics.
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Affiliation(s)
- Esther C W de Boer
- Sanquin Research, Department of Immunopathology, and Landsteiner Laboratory, Amsterdam University Medical Centre, Amsterdam Infection and Immunity Institute, Amsterdam, Netherlands.,Department of Pediatric Immunology, Rheumatology, and Infectious Diseases, Emma Children's Hospital, Amsterdam University Medical Centre, Amsterdam, Netherlands
| | - Anouk G van Mourik
- Sanquin Research, Department of Immunopathology, and Landsteiner Laboratory, Amsterdam University Medical Centre, Amsterdam Infection and Immunity Institute, Amsterdam, Netherlands
| | - Ilse Jongerius
- Sanquin Research, Department of Immunopathology, and Landsteiner Laboratory, Amsterdam University Medical Centre, Amsterdam Infection and Immunity Institute, Amsterdam, Netherlands.,Department of Pediatric Immunology, Rheumatology, and Infectious Diseases, Emma Children's Hospital, Amsterdam University Medical Centre, Amsterdam, Netherlands
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