The specific detection of IgA in immune complexes

Area of Science:

• Immunology
• Clinical Chemistry

Background:

• Circulating immune complexes (IC) play a role in various autoimmune and inflammatory diseases.
• Accurate detection of specific immunoglobulin A (IgA)-containing IC is crucial for diagnosis and monitoring.

Purpose of the Study:

• To develop and validate a sensitive assay for detecting IgA in circulating immune complexes.
• To evaluate the assay's performance using purified immunoglobulins and patient sera.

Main Methods:

• Development of an anti-IgA inhibition assay (a-IgA-InhA) utilizing low avidity goat IgM against human IgA.
• Testing specificity with aggregated and monomeric IgA, and sensitivity with sera from Henoch-Schönlein purpura patients and healthy controls.
• Utilizing sucrose density ultracentrifugation and polyethylene glycol precipitation for sample analysis.

Main Results:

• The assay specifically detected aggregated IgA and IgA-containing IC, not monomeric IgA.
• Large IgA constituents (>19S) were identified in Henoch-Schönlein purpura sera.
• Smaller IgA polymers (7S-19S) in both patient and normal sera interfered with IC detection; polyethylene glycol precipitation resolved this issue.

Conclusions:

• The developed anti-IgA inhibition assay (a-IgA-InhA) is a sensitive method for detecting IgA-containing IC.
• Polyethylene glycol precipitation enhances the detection of IgA-containing IC, particularly in Henoch-Schönlein purpura.
• This assay holds potential for improved diagnosis and management of diseases associated with IgA immune complexes.