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J Am Soc Nephrol. 2016 Sep;27(9):2748-61. doi: 10.1681/ASN.2015080911. Epub 2016 Jan 29.

IgA Structure Variations Associate with Immune Stimulations and IgA Mesangial Deposition.

Author information

1
Limoges University Hospital Dupuytren, Centre National de la Recherche Scientifique, Limoges University, Limoges, France;
2
Genetics and Development Instittute, Rennes University, Centre National de la Recherche Scientifique, Rennes, France;
3
B Cell Design, Limoges, France;
4
Immunology Group, Lund University, Lund, Sweden;
5
Centre National de la Recherche Scientifique, Laboratory of Structural and Functional Glycobiology, University of Lille 1, France; and.
6
Instituto Gulbenkian de Ciência, Oeiras, Portugal.
7
Limoges University Hospital Dupuytren, Centre National de la Recherche Scientifique, Limoges University, Limoges, France; cogne@unilim.fr.

Abstract

IgA1 mesangial deposition is the hallmark of IgA nephropathy and Henoch-Schönlein purpura, the onset of which often follows infections. Deposited IgA has been reported as polymeric, J chain associated, and often, hypogalactosylated but with no information concerning the influence of the IgA repertoire or the link between immune stimuli and IgA structure. We explored these issues in the α1KI mouse model, which produces polyclonal human IgA1 prone to mesangial deposition. Compared with mice challenged by a conventional environment, mice in a specific pathogen-free environment had less IgA deposition. However, serum IgA of specific pathogen-free mice showed more galactosylation and much lower polymerization. Notably, wild-type, α1KI, and even J chain-deficient mice showed increased polymeric serum IgA on exposure to pathogens. Strict germfree conditions delayed but did not completely prevent deposition; mice housed in these conditions had very low serum IgA levels and produced essentially monomeric IgA. Finally, comparing monoclonal IgA1 that had different variable regions and mesangial deposition patterns indicated that, independently of glycosylation and polymerization, deposition might also depend on IgA carrying specific variable domains. Together with IgA quantities and constant region post-translational modifications, repertoire changes during immune responses might, thus, modulate IgA propensity to deposition. These IgA features are not associated with circulating immune complexes and C3 deposition and are more pertinent to an initial IgA deposition step preceding overt clinical symptoms in patients.

KEYWORDS:

IgA; IgA deposition; IgA nephropathy; Immunology and pathology; transgenic mouse

PMID:
26825533
PMCID:
PMC5004660
DOI:
10.1681/ASN.2015080911
[Indexed for MEDLINE]
Free PMC Article

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