Defining the complement biomarker profile of C3 glomerulopathy

Area of Science:

• Nephrology
• Immunology
• Complement System

Background:

• C3 glomerulopathy (C3G) is defined by C3 fragment deposition on kidney biopsy.
• Its primary cause is abnormal alternative complement pathway regulation.
• The full disease spectrum and specific complement abnormalities require further definition.

Purpose of the Study:

• To validate and define the association between complement dysregulation and C3G.
• To determine if specific complement pathway abnormalities can inform C3G disease definition.

Main Methods:

• 34 C3G patients (17 C3GN, 17 DDD) and 100 controls were analyzed.
• Nineteen complement biomarkers were measured in all samples.
• Results were compared between C3G subtypes and controls.

Main Results:

• C3G patients showed lower serum C3 and factor B, and higher C3d and Bb levels than controls.
• Terminal complement pathway analysis revealed suppressed C5 and elevated C5a in C3GN.
• C3 nephritic factor activity was higher in DDD than C3GN.

Conclusions:

• Complement biomarkers are significantly altered in C3G patients.
• These findings confirm the link between complement dysregulation and C3G.
• Specific complement biomarker patterns differentiate C3G subtypes.