Urinary complement biomarkers in immune-mediated kidney diseases.

Area of Science:

• Immunology
• Nephrology
• Biomarker Discovery

Background:

• The complement system, a key innate immunity component, significantly contributes to immune-mediated kidney diseases.
• Both systemic and local kidney synthesis/activation of complement pathways (classical, alternative, mannose-binding lectin) can cause kidney injury.
• Emerging evidence highlights intra-renal complement synthesis and activation, directly impacting kidney damage.

Purpose of the Study:

• To review current knowledge on urinary complement biomarkers for kidney diseases.
• To explore the role of complement in immune complex deposition and alternative pathway activation kidney diseases.
• To identify limitations and future directions in urinary complement biomarker research.

Main Methods:

• Literature review of studies on complement pathways in kidney diseases.
• Analysis of urinary complement biomarkers in conditions like lupus nephritis, IgA nephropathy, C3 glomerulopathy, and ANCA-associated vasculitis.
• Discussion of the advantages of urinary biomarkers over serum biomarkers for assessing intra-renal inflammation.

Main Results:

• Urinary complement biomarkers may better reflect kidney inflammation than serum markers, which are affected by systemic inflammation.
• Urinary biomarkers are non-invasive and easily accessible, offering a practical diagnostic approach.
• Specific complement pathways are implicated in various kidney diseases, including lupus nephritis, IgA nephropathy, C3 glomerulopathy, and ANCA-associated vasculitis.

Conclusions:

• Urinary complement biomarkers are promising for assessing kidney disease activity and guiding treatment.
• Further research is needed to overcome current limitations and discover novel urinary biomarkers.
• Understanding complement's role in kidney diseases is critical for developing targeted therapies.