Hypersialylated macromolecular serum immunoglobulin A1 in type 2 diabetes mellitus

Objectives: The origin of the elevation of serum immunoglobulin A1 (IgA1) in Type 2 diabetes mellitus (DM) is unsettled. The aim of this study was to address the carbohydrate changes of serum IgA1 from patients with Type 2 diabetes mellitus, as a possible cause of the elevation. Design and methods: IgA1 was purified from sera of 6 DM patients and 4 healthy matched controls by using highly acetylated-Sepharose 6B, anti-IgA-agarose, and jacalin-agarose columns, and further separated into jacalin low-affinity, medium, and high-affinity fractions. Hinge and Fc fragments from native IgA1 were obtained and analyzed by using Sambucus nigra, Maackia amurensis, Arachis hypogaea, Erythrina cristagalli, and Ricinus communis lectins. Results: The jacalin high-affinity fraction, mostly constituted by macromolecular IgA1, was more abundant in DM patients than in controls and also more reactive to Sambucus nigra, and Maackia amurensis lectins. Conclusions: Macromolecular serum IgA1 from DM patients is hypersialylated and this probably contributes to the high level of IgA1 in DM patients.