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Increased N ‐Linked Glycosylation Leading to Oversialylation of Monomeric Immunoglobulin A 1 from Patients with Sjögren's Syndrome
Author(s) -
Basset,
Durand,
JAmin,
Clément,
Pennec,
Youinou,
Dueymes,
Roitt
Publication year - 2000
Publication title -
scandinavian journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.934
H-Index - 88
eISSN - 1365-3083
pISSN - 0300-9475
DOI - 10.1046/j.1365-3083.2000.00685.x
Subject(s) - sialic acid , glycosylation , immunoglobulin a , antibody , lectin , agglutinin , glycan , chemistry , oligosaccharide , nephelometry , immunoglobulin g , fucosylation , microbiology and biotechnology , immunology , glycoprotein , biochemistry , biology
Increased serum immunoglobulin A (IgA) level is a common finding in primary Sjögren's syndrome (pSS). IgA might not be properly eliminated because of an abnormal glycosylation. We reported previously that IgA 1 from patients with pSS was oversialylated. We extend this finding by showing that monomeric IgA 1 contains more sialic acid (SA) in patients than in controls, as determined by enzyme‐linked immunosorbent assay (ELISA) and Western blot with Sambucus nigra agglutinin (SNA), a lectin specific for SA. To localize this excess of SA on the N ‐ and/or O ‐linked oligosaccharides, we analysed them separately, using N ‐ and O ‐linked oligosaccharide profiling kits based on fluorophore‐assisted carbohydrate electophoresis. N ‐linked, but not O ‐linked, oligosaccharides of patients' IgA 1 were oversialylated, and this seemed to be linked to an excess of SA on the same number of polysaccharides as normal IgA 1 . To localize the abnormality to the Fab and/or Fc fragments, monomeric IgA 1 was digested with protease, separated and transferred to nitrocellulose, where SA was identified by SNA. Both Fab and Fc fragments appeared to be oversialylated. Oversialylation of N ‐linked oligosaccharides of IgA 1 from patients with pSS might prevent the recognition of IgA by receptors that are responsible for their clearance, resulting in an excess of serum IgA and related immune complexes.