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Zipfel PF, Heidenreich K. The 4 functional segments of Factor H: Role in physiological target recognition and contribution to disease. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2025:vkaf065. [PMID: 40356067 DOI: 10.1093/jimmun/vkaf065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2024] [Accepted: 03/07/2025] [Indexed: 05/15/2025]
Abstract
Factor H controls proximal complement activation, and its dysfunction leads to diseases that often manifest in the kidney. Structural and functional analyses have identified 4 distinct functional segments: an N-terminal regulatory unit, a cell binding unit, a segment with combined low-affinity C3b and heparin sites, and a C-terminal recognition or sensor unit with overlapping C3b/C3d and heparin sites. Three segments are linked to diseases. The regulatory segment is affected in C3 glomerulopathy and antineutrophil cytoplasmic antibody-associated vasculitis. The second segment includes the Y402H polymorphism of age-related macular degeneration, is associated with different types of cancer, and is targeted by pathogens. The C-terminal sensor segment is involved in atypical hemolytic uremic syndrome, in FHR1:FHR3 deficient and autoantibody-positive hemolytic uremic syndrome form and is exploited by pathogens. Factor H function is modulated by Factor H like protein 1 and FHR1, 2 plasma proteins that share segments with Factor H. This interplay is critical for fine-tuning local complement. Understanding Factor H's physiological role, as well as the impact of its absence, mutations, or autoantibody targeting, provides insights into disease mechanisms and provides opportunities for therapeutic intervention by using full-length Factor H, its fragments, or complement-modulatory compounds.
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Affiliation(s)
- Peter F Zipfel
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany
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Duan ZY, Zhang C, Chen XM, Cai GY. Blood and urine biomarkers of disease progression in IgA nephropathy. Biomark Res 2024; 12:72. [PMID: 39075557 PMCID: PMC11287988 DOI: 10.1186/s40364-024-00619-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2024] [Accepted: 07/12/2024] [Indexed: 07/31/2024] Open
Abstract
The prognosis of patients with IgA nephropathy (IgAN) is variable but overall not good. Almost all patients with IgAN are at risk of developing end-stage renal disease within their expected lifetime. The models presently available for prediction of the risk of progression of IgAN, including the International IgA Nephropathy Prediction Tool, consist of traditional clinical, pathological, and therapeutic indicators. Finding biomarkers to improve the existing risk prediction models or replace pathological indicators is important for clinical practice. Many studies have attempted to identify biomarkers for prediction of progression of IgAN, such as galactose-deficient IgA1, complement, a spectrum of protein biomarkers, non-coding RNA, and shedding cells. This article reviews the biomarkers of progression of IgAN identified in recent years, with a focus on those with clinical value, in particular the combination of multiple biomarkers into a biomarker spectrum. Future research should focus on establishing a model based primarily on biomarkers that can predict progression of IgAN and testing it in various patient cohorts.
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Affiliation(s)
- Zhi-Yu Duan
- Department of Nephrology, State Key Laboratory of Kidney Diseases, Beijing Key Laboratory of Kidney Diseases Research, First Medical Center of Chinese PLA General Hospital, National Clinical Research Center for Kidney Diseases, Beijing, 100853, China
| | - Chun Zhang
- Department of Nephrology, State Key Laboratory of Kidney Diseases, Beijing Key Laboratory of Kidney Diseases Research, First Medical Center of Chinese PLA General Hospital, National Clinical Research Center for Kidney Diseases, Beijing, 100853, China
| | - Xiang-Mei Chen
- Department of Nephrology, State Key Laboratory of Kidney Diseases, Beijing Key Laboratory of Kidney Diseases Research, First Medical Center of Chinese PLA General Hospital, National Clinical Research Center for Kidney Diseases, Beijing, 100853, China
| | - Guang-Yan Cai
- Department of Nephrology, State Key Laboratory of Kidney Diseases, Beijing Key Laboratory of Kidney Diseases Research, First Medical Center of Chinese PLA General Hospital, National Clinical Research Center for Kidney Diseases, Beijing, 100853, China.
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Dong L, Hu Y, Yang D, Liu L, Li Y, Ge S, Yao Y. Microangiopathy associated with poor outcome of immunoglobulin A nephropathy: a cohort study and meta-analysis. Clin Kidney J 2024; 17:sfae012. [PMID: 38333627 PMCID: PMC10851670 DOI: 10.1093/ckj/sfae012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Indexed: 02/10/2024] Open
Abstract
Background Microangiopathy (MA) lesions are not rare in immunoglobulin A nephropathy (IgAN) and have been suggested to have a potential role in increasing risk in renal function decline. However, this suggestion has not been universally accepted. We aimed to investigate its role in our cohort and in multiple studies through a systematic meta-analysis. Methods This cohort study included 450 IgAN patients, confirmed by renal biopsy, at Tongji Hospital, China, from January 2012 to December 2016. Clinical data were collected and analysed. We systematically searched PubMed and Web of Science for studies investigating the association between MA lesions and IgAN. Results In our cohort, IgAN patients with MA were significantly older and had higher blood pressure, more proteinuria, worse kidney function and increased uric acid levels compared with patients without MA. When comparing pathological features with the non-MA group, the MA group exhibited more global glomerulosclerosis and interstitial fibrosis/tubular atrophy. MA lesions were independently associated with a composite kidney outcome in IgAN patients {adjusted hazard ratio 2.115 [95% confidence interval (CI) 1.035-4.320], P = .040}. Furthermore, this relationship was validated in a meta-analysis involving 2098 individuals from five independent cohorts. The combined data showed a 187% adjusted risk of poor renal outcome in IgAN patients with MA compared with patients without MA [adjusted risk ratio 2.87 (95% CI 2.05-4.02; I2 = 53%). Conclusion MA lesions could serve as a valuable predictor for disease progression in patients with IgAN, extending beyond the widely recognized Oxford MEST-C score.
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Affiliation(s)
- Lei Dong
- Division of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yuncan Hu
- Division of Nephrology, Xiangyang Central Hospital, Affiliated Hospital of Hubei University of Arts and Science, Xiangyang, China
| | - Dan Yang
- Division of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Liu Liu
- Division of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yueqiang Li
- Division of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Shuwang Ge
- Division of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Ying Yao
- Division of Nephrology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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Duval A, Caillard S, Frémeaux-Bacchi V. The complement system in IgAN: mechanistic context for therapeutic opportunities. Nephrol Dial Transplant 2023; 38:2685-2693. [PMID: 37385820 DOI: 10.1093/ndt/gfad140] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Indexed: 07/01/2023] Open
Abstract
The complement system plays a crucial role in innate immunity, providing essential defense against pathogens. However, uncontrolled or prolonged activation of the complement cascade can significantly contribute to kidney damage, especially in cases of glomerulonephritis. Immunoglobulin A nephropathy (IgAN), the most prevalent form of primary glomerulonephritis, has growing evidence supporting the involvement of complement alternative and lectin pathways. In fact, patients with IgAN experience complement activation within their kidney tissue, which may be involved in the development of glomerular damage and the progression of IgAN. Complement activation has emerged as a significant area of interest in IgAN, with numerous complement-targeting agents currently being explored within this field. Nevertheless, the exact mechanisms of complement activation and their role in IgAN progression require comprehensive elucidation. This review seeks to contextualize the proposed mechanisms of complement activation within the various stages ("hits") of IgAN pathogenesis, while also addressing the clinical implications and anticipated outcomes of complement inhibition in IgAN.
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Affiliation(s)
- Anna Duval
- Centre de Recherche des Cordeliers, Inserm UMR S1138, Paris, France
- Department of Nephrology, Dialysis and Transplantation, University Hospital of Strasbourg, Strasbourg, France
| | - Sophie Caillard
- Department of Nephrology, Dialysis and Transplantation, University Hospital of Strasbourg, Strasbourg, France
| | - Véronique Frémeaux-Bacchi
- Centre de Recherche des Cordeliers, Inserm UMR S1138, Paris, France
- Service d'Immunologie Biologique, Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges Pompidou, Paris, France
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Rajasekaran A, Green TJ, Renfrow MB, Julian BA, Novak J, Rizk DV. Current Understanding of Complement Proteins as Therapeutic Targets for the Treatment of Immunoglobulin A Nephropathy. Drugs 2023; 83:1475-1499. [PMID: 37747686 PMCID: PMC10807511 DOI: 10.1007/s40265-023-01940-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/04/2023] [Indexed: 09/26/2023]
Abstract
Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis worldwide and a frequent cause of kidney failure. Currently, the diagnosis necessitates a kidney biopsy, with routine immunofluorescence microscopy revealing IgA as the dominant or co-dominant immunoglobulin in the glomerular immuno-deposits, often with IgG and sometimes IgM or both. Complement protein C3 is observed in most cases. IgAN leads to kidney failure in 20-40% of patients within 20 years of diagnosis and reduces average life expectancy by about 10 years. There is increasing clinical, biochemical, and genetic evidence that the complement system plays a paramount role in the pathogenesis of IgAN. The presence of C3 in the kidney immuno-deposits differentiates the diagnosis of IgAN from subclinical glomerular mesangial IgA deposition. Markers of complement activation via the lectin and alternative pathways in kidney-biopsy specimens are associated with disease activity and are predictive of poor outcome. Levels of select complement proteins in the circulation have also been assessed in patients with IgAN and found to be of prognostic value. Ongoing genetic studies have identified at least 30 loci associated with IgAN. Genes within some of these loci encode complement-system regulating proteins that can interact with immune complexes. The growing appreciation for the central role of complement components in IgAN pathogenesis highlighted these pathways as potential treatment targets and sparked great interest in pharmacological agents targeting the complement cascade for the treatment of IgAN, as evidenced by the plethora of ongoing clinical trials.
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Affiliation(s)
- Arun Rajasekaran
- Division of Nephrology, Department of Medicine, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Todd J Green
- Department of Microbiology, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Matthew B Renfrow
- Department of Biochemistry and Molecular Genetics, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Bruce A Julian
- Division of Nephrology, Department of Medicine, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Jan Novak
- Department of Microbiology, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Dana V Rizk
- Division of Nephrology, Department of Medicine, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA.
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