A newly identified biomarker, complement factor H-related protein 1 (CFHR1), is showing promise in understanding and potentially treating IgA nephropathy, a common autoimmune kidney disease. Researchers have found elevated levels of CFHR1 in patients with the condition, suggesting it plays a key role in the formation of damaging immune complexes within the kidneys. This discovery, published in December 2025 in Scientific Reports, could lead to earlier diagnosis, more targeted therapies, and improved outcomes for those at risk of kidney failure.
IgA nephropathy affects an estimated 2.8 to 13.8 per 100,000 people globally, though prevalence varies significantly by ethnicity, with higher rates observed in Asian populations. According to the National Kidney Foundation, the disease is characterized by deposits of immunoglobulin A (IgA) antibodies in the glomeruli, the kidney’s filtering units. Over time, this leads to inflammation and scarring, potentially progressing to end-stage renal disease requiring dialysis or a kidney transplant.
Unraveling the Role of the Complement System
For years, researchers have understood that IgA-containing immune complexes (IgA-ICs) are central to the development of IgA nephropathy. Though, the precise mechanisms driving their formation and deposition in the kidneys remained unclear. Recent investigations, led by Professor Kazuo Takahashi from the Department of Biomedical Molecular Sciences at Fujita Health University School of Medicine in Japan, have focused on the complement system – a crucial part of the immune response.
“The key IgA-IC-associated molecules and pathways involved in the development of glomerulonephritis remain unclear,” Professor Takahashi stated in the published research. To address this, his team conducted a proteomic analysis of kidney tissue samples and circulating IgA-ICs from patients with IgA nephropathy, comparing them to samples from healthy individuals. The results revealed a significant overexpression of several complement pathway proteins, including CFHR1, CFHR2, CFHR3, CFHR5, C1q chains B and C, and properdin, in the affected kidneys.
CFHR1: A Potential Diagnostic and Therapeutic Target
The findings pinpoint CFHR1 as particularly noteworthy. Researchers observed higher levels of CFHR1 not only within the kidney tissue but likewise within the circulating IgA-ICs of patients with IgA nephropathy compared to healthy controls. Further analysis, using double immunofluorescence staining, confirmed that CFHR1 colocalized with IgA deposits in kidney biopsies, strengthening the link between the protein and disease pathology.
Longitudinal studies added another layer of insight. The research team found that CFHR1 levels in circulating IgA-ICs significantly decreased in patients receiving immunosuppressive treatment over a two-year period. However, no significant change was observed in patients receiving only supportive care. Interestingly, serum CFHR1 levels remained stable in both groups, suggesting that measuring CFHR1 within the IgA-ICs, rather than in the serum alone, may be more indicative of disease activity and treatment response.
Professor Takahashi hypothesizes that elevated CFHR1 in circulating IgA-ICs may promote the formation of these damaging complexes, potentially by catalyzing their assembly around abnormal IgA molecules. “Elevated circulating total CFHR1 levels in patients with IgA nephropathy may reflect activation of the alternative complement pathway upon exposure to mucosal microbial antigens bound to IgA,” he explained.
Implications for Treatment and Future Research
The identification of CFHR1 as a biomarker opens up several exciting possibilities. “The quantification of CFHR1 within circulating IgA immune complexes holds promise as a novel diagnostic and prognostic biomarker for IgA nephropathy,” Professor Takahashi noted. This could allow for earlier and more accurate diagnosis, potentially identifying individuals at higher risk of disease progression.
CFHR1 could serve as a target for new therapies. Several complement-targeting drugs are currently under development and clinical evaluation for IgA nephropathy, and CFHR1 may help identify patients most likely to benefit from these treatments. The research team emphasizes the need for a deeper understanding of the molecular mechanisms driving IgA-IC formation, including the specific roles played by complement pathway proteins, to optimize patient management and improve treatment outcomes.
Current treatment strategies for IgA nephropathy, guided by the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines, focus on managing blood pressure, reducing protein in the urine, and controlling cardiovascular risk factors. Immunosuppressive agents are used in some cases, but concerns about side effects limit their widespread application. A more precise understanding of the disease process, facilitated by biomarkers like CFHR1, could pave the way for more personalized and effective therapies.
Researchers are now focused on validating these findings in larger, multi-center studies and exploring the potential of CFHR1-targeted therapies. The next steps will involve refining the CFHR1 assay for clinical use and conducting clinical trials to assess its predictive value and therapeutic potential.
This article is for informational purposes only and is not a substitute for professional medical advice. If you have concerns about kidney health, please consult with a qualified healthcare provider.
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