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Composition of IgA-containing circulating immune complexes in IgA nephropathy.
L A van Es1, A W van den Wall Bake, R M Valentijn
1Department of Nephrology, Leiden University Hospital, The Netherlands.
Summary
Macromolecular immunoglobulin A (IgA) is common in IgA nephropathy (IgAN) patients, indicating a recent immune response. This suggests microbial triggers may activate the mucosal immune system, contributing to IgAN pathogenesis.
Area of Science:
- Nephrology
- Immunology
- Pathology
Background:
- Macromolecular IgA, including polymeric IgA and IgA-containing immune complexes, is frequently detected in patients with IgA nephropathy (IgAN).
- The presence of polymeric IgA suggests a recent immune response, potentially linked to mucosal immune system overactivity observed in IgAN patients.
Purpose of the Study:
- To investigate the composition and implications of macromolecular IgA in IgA nephropathy (IgAN).
- To explore potential triggers and alternative mechanisms in the pathogenesis of IgAN.
Main Methods:
- Analysis of serum samples from IgAN patients.
- Sucrose density ultracentrifugation to characterize macromolecular IgA components.
- Review of vaccination and infection data in relation to disease exacerbations.
Main Results:
- Macromolecular IgA, comprising polymeric IgA and/or IgA-containing immune complexes, is prevalent in IgAN sera.
- Patients with IgAN exhibit a more vigorous mucosal immune response compared to controls, particularly after infections.
- Macromolecular IgA may contain IgG, IgA rheumatoid factor, and C3; however, specific causative antigens remain unidentified.
Conclusions:
- While IgG and IgA rheumatoid factor may play a role, they don't fully explain IgAN pathogenesis in all cases.
- Alternative mechanisms, such as intermittent polymeric IgA or IgA complexes, are proposed for patients without detectable IgA complexes.
- Local IgA antibody binding to mesangial antigens can lead to IgA deposits, even without circulating IgA complexes.