IgA Structure Variations Associate with Immune Stimulations and IgA Mesangial Deposition

Area of Science:

• Immunology
• Nephrology
• Glycobiology

Background:

• Immunoglobulin A1 (IgA1) mesangial deposition characterizes IgA nephropathy and Henoch-Schönlein purpura, often post-infection.
• Previous studies noted deposited IgA as polymeric, J chain-associated, and hypogalactosylated, but lacked data on IgA repertoire or immune stimuli links to IgA structure.

Purpose of the Study:

• To investigate the influence of the IgA repertoire and immune stimuli on IgA structure and mesangial deposition in the α1KI mouse model.
• To explore the relationship between IgA features, polymerization, glycosylation, and deposition propensity.

Main Methods:

• Utilized the α1KI mouse model producing human IgA1 prone to mesangial deposition.
• Compared IgA deposition and serum IgA characteristics (polymerization, galactosylation) in mice under conventional, specific pathogen-free, and germfree conditions.
• Exposed wild-type, α1KI, and J chain-deficient mice to pathogens.
• Analyzed monoclonal IgA1 with different variable regions for deposition patterns.

Main Results:

• Specific pathogen-free conditions reduced IgA deposition, correlating with increased IgA galactosylation and decreased polymerization.
• Pathogen exposure increased polymeric serum IgA in wild-type, α1KI, and J chain-deficient mice.
• Germfree conditions delayed deposition but resulted in low serum IgA and monomeric IgA production.
• Variable regions, independent of glycosylation and polymerization, influenced IgA deposition, suggesting repertoire-dependent deposition.

Conclusions:

• IgA features, including quantity, post-translational modifications, and variable regions, modulate IgA deposition propensity.
• Changes in the IgA repertoire during immune responses are critical for deposition.
• These IgA characteristics are relevant to the initial IgA deposition step preceding clinical symptoms in IgA nephropathy.