Complement activation in human autoimmune diseases and mouse models; employing a sandwich immunoassay specific for...

Area of Science:

• Immunology
• Biochemistry
• Clinical Diagnostics

Background:

• Low plasma levels of complement factors C3 and C4 are traditional but insensitive markers for complement activation in autoimmune diseases.
• Current methods for measuring the C3dg activation fragment are complex and difficult to standardize.

Purpose of the Study:

• To develop and validate a novel, sensitive, and specific immunoassay for detecting the C3dg fragment.
• To evaluate the utility of this assay for monitoring complement activation in autoimmune diseases and in preclinical research.

Main Methods:

• Development of a time-resolved immunoassay utilizing a monoclonal antibody specific for a neoepitope on the C3dg fragment.
• Validation of the assay's specificity and reproducibility using clinical samples.
• Assessment of the assay's ability to differentiate autoimmune diseases from controls.

Main Results:

• The developed immunoassay demonstrates high specificity (95%) and a positive likelihood ratio of 10 for detecting complement activation.
• The assay effectively distinguishes Systemic Lupus Erythematosus from healthy controls and other immune-mediated diseases like Rheumatoid Arthritis (86% specificity) and Spondyloarthritis (91% specificity).
• The assay is suitable for use in both clinical diagnostics and experimental research, including in vivo mouse models.

Conclusions:

• A novel, stable, and reproducible immunoassay for C3dg offers a superior method for evaluating complement activation compared to traditional C3 and C4 measurements.
• This assay has significant potential for improving patient follow-up in autoimmune diseases and advancing research in complement-mediated conditions.