scholarly journals Different Aspects of Classical Pathway Overactivation in Patients With C3 Glomerulopathy and Immune Complex-Mediated Membranoproliferative Glomerulonephritis

2021 ◽  
Vol 12 ◽  
Author(s):  
Marloes A. H. M. Michels ◽  
Nicole C. A. J. van de Kar ◽  
Sanne A. W. van Kraaij ◽  
Sebastian A. Sarlea ◽  
Valentina Gracchi ◽  
...  
Keyword(s):  
Immune Complex ◽  
Membranoproliferative Glomerulonephritis ◽  
Alternative Pathway ◽  
Classical Pathway ◽  
Healthy Controls ◽  
C3 Glomerulopathy ◽  
Hemolytic Assay ◽  
The Stability ◽  
The Complement System

The rare and heterogeneous kidney disorder C3 glomerulopathy (C3G) is characterized by dysregulation of the alternative pathway (AP) of the complement system. C3G is often associated with autoantibodies stabilizing the AP C3 convertase named C3 nephritic factors (C3NeF). The role of classical pathway (CP) convertase stabilization in C3G and related diseases such as immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) remains largely unknown. Here, we investigated the CP convertase activity in patients with C3G and IC-MPGN. Using a refined two-step hemolytic assay, we measured the stability of CP convertases directly in the serum of 52 patients and 17 healthy controls. In four patients, CP convertase activity was prolonged compared to healthy controls, i.e. the enzymatic complex was stabilized. In three patients (2 C3G, 1 IC-MPGN) the convertase stabilization was caused by immunoglobulins, indicating the presence of autoantibodies named C4 nephritic factors (C4NeFs). Importantly, the assay also enabled detection of non-immunoglobulin-mediated stabilization of the CP convertase in one patient with C3G. Prolonged CP convertase activity coincided with C3NeF activity in all patients and for up to 70 months of observation. Crucially, experiments with C3-depleted serum showed that C4NeFs stabilized the CP C3 convertase (C4bC2a), that does not contain C3NeF epitopes. All patients with prolonged CP convertase activity showed clear signs of complement activation, i.e. lowered C3 and C5 levels and elevated levels of C3d, C3bc, C3bBbP, and C5b-9. In conclusion, this work provides new insights into the diverse aspects and (non-)immunoglobulin nature of factors causing CP convertase overactivity in C3G/IC-MPGN.

scholarly journals C4 nephritic factor in patients with immune-complex-mediated membranoproliferative glomerulonephritis and C3-glomerulopathy

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Nóra Garam ◽  
Zoltán Prohászka ◽  
Ágnes Szilágyi ◽  
Christof Aigner ◽  
Alice Schmidt ◽  
...  
Keyword(s):  
Immune Complex ◽  
Membranoproliferative Glomerulonephritis ◽  
Alternative Pathway ◽  
Classical Pathway ◽  
Complement Alternative Pathway ◽  
Nephritic Factor ◽  
C3 Nephritic Factor ◽  
Hemolytic Assay ◽  
Stage Renal Disease ◽  
End Stage

Abstract Background Acquired or genetic abnormalities of the complement alternative pathway are the primary cause of C3glomerulopathy(C3G) but may occur in immune-complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) as well. Less is known about the presence and role of C4nephritic factor(C4NeF) which may stabilize the classical pathway C3-convertase. Our aim was to examine the presence of C4NeF and its connection with clinical features and with other pathogenic factors. Results One hunfe IC-MPGN/C3G patients were enrolled in the study. C4NeF activity was determined by hemolytic assay utilizing sensitized sheep erythrocytes. Seventeen patients were positive for C4NeF with lower prevalence of renal impairment and lower C4d level, and higher C3 nephritic factor (C3NeF) prevalence at time of diagnosis compared to C4NeF negative patients. Patients positive for both C3NeF and C4NeF had the lowest C3 levels and highest terminal pathway activation. End-stage renal disease did not develop in any of the C4NeF positive patients during follow-up period. Positivity to other complement autoantibodies (anti-C1q, anti-C3) was also linked to the presence of nephritic factors. Unsupervised, data-driven cluster analysis identified a group of patients with high prevalence of multiple complement autoantibodies, including C4NeF. Conclusions In conclusion, C4NeF may be a possible cause of complement dysregulation in approximately 10–15% of IC-MPGN/C3G patients.

Inherited complement deficiencies

1984 ◽  
Vol 306 (1129) ◽  
pp. 419-430 ◽  
Keyword(s):  
Immune Complex ◽  
Complement System ◽  
Lupus Erythematosus ◽  
Alternative Pathway ◽  
Strong Association ◽  
Factor H ◽  
Complement Deficiency ◽  
Classical Pathway ◽  
The Complement System

Isolated genetic deficiencies of individual components of the complement system have been described in man for all the components of the classical pathway and the membrane attack complex as well as for Factor I, Factor H and properdin. It is only for Factor B and Factor D of the alternative pathway that homozygous deficiency states are not so far known. Complement deficiency states provide the most direct way of looking at the role of the complement system in vivo and emphasize the importance of complement in resistance to bacterial infection and in particular to infection with Neisseria . This association is not unexpected since in vitro studies have shown complement to be an efficient enhancer of phagocytosis and inflammation. The particularly frequent occurrence of neisserial infection may be ascribed to the ability of these organisms to survive in phagocytic cells so that the plasma cytolytic activity provided by complement is needed to kill them. On the other hand the strong association between complement deficiencies and immune-complex diseases - especially systemic lupus erythematosus — was unexpected and seems paradoxical in view of the large part played by complement in the pathogenesis of immune complex mediated tissue damage. The paradox can be explained in part by the necessity for an intact complement system in the solubilization and the proper handling of immune complexes. It is also likely that complement deficiency can allow the persistence of low virulence organisms that produce disease solely by an immune complex mechanism. Recently described deficiencies of complement receptors and their effects in vivo are described.

scholarly journals CFHR5 Genetic Variations and Serum Levels in Patients with Immune-Complex-Mediated Membranoproliferative Glomerulonephritis and C3-Glomerulopathy

2020 ◽  
Author(s):  
Nóra Garam ◽  
Marcell Cserhalmi ◽  
Zoltán Prohászka ◽  
Ágnes Szilágyi ◽  
Nóra Veszeli ◽  
...  
Keyword(s):  
Immune Complex ◽  
Membranoproliferative Glomerulonephritis ◽  
Kidney Diseases ◽  
Alternative Pathway ◽  
Serum Levels ◽  
Genetic Alterations ◽  
Factor H ◽  
Complement Factor ◽  
C3 Glomerulopathy

Abstract Background: Factor H-related-5 (FHR-5) is a member of the complement Factor H protein family. Due to the homology to Factor H, the main complement regulator of the alternative pathway, it may also be implicated in pathomechanism of kidney diseases where Factor H and alternative pathway dysregulation play a role. Here, we report the first observational study on CFHR5 variations along with serum FHR-5 levels in immune-complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) and C3 glomerulopathy (C3G) patients together with the clinical, genetic, complement and follow-up data.Results: 120 patients with a histologically-proven diagnosis of IC-MPGN/C3G were enrolled in the study. FHR-5 serum levels were measured in ELISA, the CFHR5 gene was analyzed by Sanger-sequencing, and selected mutants were studied as recombinant proteins in ELISA and SPR.Eight relevant CFHR5 variations in 14 patients (11.7%) were observed, 5 of them identified as pathogenic for C3G. The FHR-5G278S and FHR-5R356H mutations altered the interaction of FHR-5 with C3b, when compared to the FHR-5WT. Serum FHR-5 levels were lower in patients compared to controls. Low serum FHR-5 concentration at presentation associated with better renal survival during the follow-up period, furthermore, it showed clear association with signs of hypocomplementemia and clinically meaningful clusters.Conclusions: Our observations support the hypothesis that FHR-5 protein and its genetic alterations play a role in the pathogenesis of IC-MPGN/C3G.

scholarly journals FHR-5 Serum Levels and CFHR5 Genetic Variations in Patients With Immune Complex-Mediated Membranoproliferative Glomerulonephritis and C3-Glomerulopathy

2021 ◽  
Vol 12 ◽  
Author(s):  
Nóra Garam ◽  
Marcell Cserhalmi ◽  
Zoltán Prohászka ◽  
Ágnes Szilágyi ◽  
Nóra Veszeli ◽  
...  
Keyword(s):  
Immune Complex ◽  
Membranoproliferative Glomerulonephritis ◽  
Kidney Diseases ◽  
Alternative Pathway ◽  
Serum Levels ◽  
Factor H ◽  
Fine Tuning ◽  
Complement Factor ◽  
C3 Glomerulopathy

BackgroundFactor H-related protein 5 (FHR-5) is a member of the complement Factor H protein family. Due to the homology to Factor H, the main complement regulator of the alternative pathway, it may also be implicated in the pathomechanism of kidney diseases where Factor H and alternative pathway dysregulation play a role. Here, we report the first observational study on CFHR5 variations along with serum FHR-5 levels in immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) and C3 glomerulopathy (C3G) patients together with the clinical, genetic, complement, and follow-up data.MethodsA total of 120 patients with a histologically proven diagnosis of IC-MPGN/C3G were enrolled in the study. FHR-5 serum levels were measured in ELISA, the CFHR5 gene was analyzed by Sanger sequencing, and selected variants were studied as recombinant proteins in ELISA and surface plasmon resonance (SPR).ResultsEight exonic CFHR5 variations in 14 patients (12.6%) were observed. Serum FHR-5 levels were lower in patients compared to controls. Low serum FHR-5 concentration at presentation associated with better renal survival during the follow-up period; furthermore, it showed clear association with signs of complement overactivation and clinically meaningful clusters.ConclusionsOur observations raise the possibility that the FHR-5 protein plays a fine-tuning role in the pathogenesis of IC-MPGN/C3G.

scholarly journals CFH and CFHR Copy Number Variations in C3 Glomerulopathy and Immune Complex-Mediated Membranoproliferative Glomerulonephritis

2021 ◽  
Vol 12 ◽  
Author(s):  
Rossella Piras ◽  
Matteo Breno ◽  
Elisabetta Valoti ◽  
Marta Alberti ◽  
Paraskevas Iatropoulos ◽  
...  
Keyword(s):  
Immune Complex ◽  
Single Molecule ◽  
Copy Number ◽  
Membranoproliferative Glomerulonephritis ◽  
Alternative Pathway ◽  
Copy Number Variations ◽  
Factor H ◽  
Complement C3 ◽  
Complement Factor ◽  
C3 Glomerulopathy

C3 Glomerulopathy (C3G) and Immune Complex-Mediated Membranoproliferative glomerulonephritis (IC-MPGN) are rare diseases characterized by glomerular deposition of C3 caused by dysregulation of the alternative pathway (AP) of complement. In approximately 20% of affected patients, dysregulation is driven by pathogenic variants in the two components of the AP C3 convertase, complement C3 (C3) and Factor B (CFB), or in complement Factor H (CFH) and Factor I (CFI), two genes that encode complement regulators. Copy number variations (CNVs) involving the CFH-related genes (CFHRs) that give rise to hybrid FHR proteins also have been described in a few C3G patients but not in IC-MPGN patients. In this study, we used multiplex ligation-dependent probe amplification (MLPA) to study the genomic architecture of the CFH-CFHR region and characterize CNVs in a large cohort of patients with C3G (n = 103) and IC-MPGN (n = 96) compared to healthy controls (n = 100). We identified new/rare CNVs resulting in structural variants (SVs) in 5 C3G and 2 IC-MPGN patients. Using long-read single molecule real-time sequencing (SMRT), we detected the breakpoints of three SVs. The identified SVs included: 1) a deletion of the entire CFH in one patient with IC-MPGN; 2) an increased number of CFHR4 copies in one IC-MPGN and three C3G patients; 3) a deletion from CFHR3-intron 3 to CFHR3-3′UTR (CFHR34–6Δ) that results in a FHR3-FHR1 hybrid protein in a C3G patient; and 4) a CFHR31–5-CFHR410 hybrid gene in a C3G patient. This work highlights the contribution of CFH-CFHR CNVs to the pathogenesis of both C3G and IC-MPGN.

scholarly journals P0496THE IMPORTANCE OF COMPLEMENT LEVELS AND CLINICAL CHARACTERISTICS OF PRIMARY MEMBRANOPROLIFERATIVE GLOMERULONEPHRITIS IN TURKEY

2020 ◽  
Vol 35 (Supplement_3) ◽  
Author(s):  
Erhan Tatar ◽  
Deren Oygar ◽  
Nurhan Seyahi ◽  
Necmi Eren ◽  
Yağmur Cantürk ◽  
...  
Keyword(s):  
Nephrotic Syndrome ◽  
Immune Complex ◽  
Membranoproliferative Glomerulonephritis ◽  
C3 Glomerulopathy ◽  
Complex Type ◽  
Glomerular Diseases ◽  
Nephritic Syndrome ◽  
Pathological Evaluation ◽  
Chronicity Index ◽  
The Complement System

Abstract Background and Aims Membranoproliferative glomerulonephritis (MPGN) may be caused by disturbances in the complement system. Hypocomplementemia is a characteristic of MPGN. Among these patients frequency of hypocomplementemia and their relation with clinical and histopathological findings are still not clearly known. The aim of this study is to evaluate the hypocomplementemia frequency among the primary MPGN patients in Turkey and its relation with histopathological subtypes, findings and demographic characteristics. Method The data was obtained from national multicentered (47 centers) records of primary glomerular diseases in Glomerulonephritis Study Group of the Turkish Society of Nephrology database from May 2009 to June 2019. Primary MPGN cases were evaluated and divided into 2 groups with and without hypocomplementemia. Results In total, 193 cases were included in the study. The indications for renal biopsy were isolated nephrotic syndrome (55.4%), nephritic syndrome (21.2%), nephrotic syndrome with a nephritic component (6.2%) and asymptomatic urinary findings (17.2%). 34.2% of the cases were reported as immune complex type, another 34.2% of the cases were reported as C3 glomerulopathy. 31.6% of patients were not specified. 82 (42.4%) of the cases presented hypocomplementemia. Hypocomplementemic patients were younger (34±14 vs 41±15, p=0.002) and most frequently female (56% vs 41%, p=0.03). At same time, serum albumin and hemoglobin levels were lower and anemic patient rates were higher (p<0.001). In this group, the nephrotic syndrome rates were higher (72% vs 54%, p=0,01). Hypocomplementemia rate in the C3 glomerulopathy was 52% (in DDD 40%, in C3GN 55% ) whereas in immune complex type 41% and in non specified type 34%. In the pathological evaluation; among the hypocomplementemic group the endocapillary proliferation and glomerular exudative differentiation rates presented significant increase. However the chronicity index were lower in the kidney biopsy (Table 1). Conclusion This multicenter study provided important data about the epidemiology of MPGN with importance of hypocomplementemia in Turkey. Hypocomplementemia is associated with both subtypes of MPGN patern, anemia and nephrotic syndrome. At the same time, hypocomplementemia is a valuable parameter for active MPGN pattern in the histopathological evaluation. This may be important in determining the treatment.

MO085MONOCLONAL GAMMOPATHY OF UNKNOWN SIGNIFICANCE AMONG MEMBRANOPROLIFERATIVE GLOMERULONEPHRITIS PATIENTS

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
Marja Kovala ◽  
Minna Seppala ◽  
Kati Kaartinen ◽  
Seppo Meri ◽  
Eero Olavi Honkanen ◽  
...  
Keyword(s):  
Membranoproliferative Glomerulonephritis ◽  
Monoclonal Gammopathy ◽  
Cell Clone ◽  
Alternative Pathway ◽  
Significant Risk ◽  
Classical Pathway ◽  
Unknown Significance ◽  
Hematological Neoplasm ◽  
The Mean ◽  
Smoldering Myeloma

Abstract Background and Aims Monoclonal gammopathy is an entity where a B-cell or plasma cell clone produces monoclonal immunoglobulin. When paraproteinemia and a kidney disease is discovered without criteria for treatment of haematological malignangy, the entity is called monoclonal gammopathy of unknown significance (MGUS) or of renal significance (MGRS). It can cause variable histology, among which membranoproliferative glomerulonephritis (MPGN) has been described. Direct entrapment of paraprotein in glomeruli/tubules can be observed by immunofluorescence (IF), but IF can also be negative as paraprotein can cause complement-associated disease by acting as an activator of the classical pathway or as a dysregulator of the alternative pathway. Electron microscopy (EM) is needed to differentiate possible organized deposits. Method We investigated the prevalence, clinical parameters, histology, and the type of monoclonal gammopathy in biopsy-proven MPGN between 2006-2017. A total of 15 adult patients with a detected urine and/or serum paraprotein with concurrent biopsy-proven diagnosis were discovered among 60 patients (Figure 1). Two diagnostic biopsies were from transplants. Results MGUS was diagnosed in 15/60 (25%) of patients. Clinical variables are summarized in Table 1. The mean age at presentation was 59 years (37-79), 47-% were males. Smoldering myeloma was diagnosed in 2 (13%) patients and overt malignancy in 3 (20%) patients. Histological features are summarized in Table 2. There were 7 (47%) with dominant staining for C3 (6 with C3 glomerulonephritis, 1 Dense Deposition Disease) and 8 (53%) with dominant staining for Ig, of which 4 (31%) had mesangioproliferative, 4 (31%) membranoproliferative, 3 (23%) minimal change, 2 (15%) crescentic and 1 (8%) exudative pattern in light microscopy (LM). Seven (47%) biopsies, which did not stain for kappa or lambda light chains. The most common EM deposit location was subendothelial (69%). Conclusion MPGN was associated with a significant risk of underlying monoclonal gammopathy, as many (25%) patients were diagnosed with concurrent MGUS. When MPGN is observed, it should prompt investigations of the possible underlying monoclonal gammopathy and possibly, hematological neoplasm.

scholarly journals Complement protein levels and MBL2 polymorphisms are associated with dengue and disease severity

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ngo Truong Giang ◽  
Hoang van Tong ◽  
Do Quyet ◽  
Nghiem Xuan Hoan ◽  
Trinh Huu Nghia ◽  
...  
Keyword(s):  
Warning Signs ◽  
Severe Dengue ◽  
Healthy Controls ◽  
Complement Protein ◽  
Complement Proteins ◽  
Protein Levels ◽  
Study Population ◽  
Dengue With Warning Signs ◽  
The Complement System

Abstract The complement system may be crucial during dengue virus infection and progression to severe dengue. This study investigates the role of MBL2 genetic variants and levels of MBL in serum and complement proteins in Vietnamese dengue patients. MBL2 genotypes (− 550L/H, MBL2 codon 54), MBL2 diplotypes (XA/XO, YA/XO) and MBL2 haplotypes (LXPB, HXPA, XO) were associated with dengue in the study population. The levels of complement factors C2, C5, and C5a were higher in dengue and dengue with warning signs (DWS) patients compared to those in healthy controls, while factor D levels were decreased in dengue and DWS patients compared to the levels determined in healthy controls. C2 and C5a levels were associated with the levels of AST and ALT and with WBC counts. C9 levels were negatively correlated with ALT levels and WBC counts, and factor D levels were associated with AST and ALT levels and with platelet counts. In conclusions, MBL2 polymorphisms are associated with dengue in the Vietnamese study population. The levels of the complement proteins C2, C4b, C5, C5a, C9, factor D and factor I are modulated in dengue patients during the clinical course of dengue.

Schistosoma mansoni: complement activation in human and rodent sera by living parasites of various developmental stages

Parasitology ◽  
1983 ◽  
Vol 87 (1) ◽  
pp. 75-86 ◽  
Author(s):  
A. Ruppel ◽  
U. Rother ◽  
H. Vongerichten ◽  
H. J. Diesfeld
Keyword(s):  
Schistosoma Mansoni ◽  
Complement System ◽  
Developmental Stages ◽  
Alternative Pathway ◽  
Classical Pathway ◽  
Factor B ◽  
The Complement System ◽  
Dose Dependent ◽  
Living Adult

SUMMARYLiving Schistosoma mansoni of various developmental stages were studied with respect to their ability to activate the complement system in sera of humans, mice and rats. Immunofluorescence assays demonstrated that binding of human C3 occurred on fresh schistosomula as well as on schistosomula prepared from mouse lymph-nodes or lungs and on adult schistosomes. However, rodent C3 was deposited only on fresh schistosomula. Deposition of human C3 on the worms' surface required activation of the complement system. The alternative pathway was shown to be involved in deposition of human C3 on schistosomes of all ages, whereas activation of the classical pathway was demonstrable only with fresh schistosomula. Immunoelectrophoretic studies demonstrated a dose-dependent cleavage of human C3 and conversion of factor B by living adult schistosomes. The results demonstrate that the ability of living schistosomes to activate complement in vitro is dependent not only on their developmental stage but also on the species of the serum.

scholarly journals Development of a Novel Cytomedical Treatment that can Protect Entrapped Cells from Host Humoral Immunity

2002 ◽  
Vol 11 (8) ◽  
pp. 787-797 ◽  
Author(s):  
Ryo Suzuki ◽  
Yasuo Yoshioka ◽  
Etsuko Kitano ◽  
Tatsunobu Yoshioka ◽  
Hiroaki Oka ◽  
...  
Keyword(s):  
Humoral Immunity ◽  
Complement System ◽  
Alternative Pathway ◽  
Classical Pathway ◽  
Dependent Manner ◽  
Complement Components ◽  
Alternative Pathways ◽  
Low Cytotoxicity ◽  
The Complement System

Cell therapy is expected to relieve the shortage of donors needed for organ transplantation. When patients are treated with allogeneic or xenogeneic cells, it is necessary to develop a means by which to isolate administered cells from an immune attack by the host. We have developed “cytomedicine, ” which consists of functional cells entrapped in semipermeable polymer, and previously reported that alginate-poly-l-lysine-alginate microcapsules and agarose microbeads could protect the entrapped cells from injury by cellular immunity. However, their ability to isolate from humoral immunity was insufficient. It is well known that the complement system plays an essential role in rejection of transplanted cells by host humoral immunity. Therefore, the goal of the present study was to develop a novel cytomedical device containing a polymer capable of inactivating complement. In the screening of various polymers, polyvinyl sulfate (PVS) exhibited high anticomplement activity and low cytotoxicity. Murine pancreatic β-cell line (MIN6 cell) entrapped in agarose microbeads containing PVS maintained viability and physiological insulin secretion, replying in response to glucose concentration, and resisted rabbit antisera in vitro. PVS inhibited hemolysis of sensitized sheep erythrocytes (EAs) and rabbit erythrocytes by the complement system. This result suggests that PVS inhibits both the classical and alternative complement pathways of the complement system. Next, the manner in which PVS exerts its effects on complement components was examined. PVS was found to inhibit generation of C4a and Ba generation in activation of the classical and alternative pathways, respectively. Moreover, when the EAC1 cells, which were carrying C1 on the EAs, treated with PVS were exposed to C1-deficient serum, hemolysis decreased in a PVS dose-dependent manner. These results suggest that PVS inhibits C1 in the classical pathway and C3 convertase formation in the alternative pathway. Therefore, PVS may be a useful polymer for developing an anticomplement device for cytomedical therapy.

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