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Immunoglobulin G N-glycan sialylation in atopic children

Background: Immunoglobulin G (IgG) is considered one of modulators of immune responses in atopic diseases, acting mainly through activating and inhibitory Fcγ receptors (FcγRs) on immune effector cells. Each IgG heavy chain contains a single conserved N- glycosylation site and differential glycosylation of IgG Fc regions influences its affinity for FcγRs. Terminal sialic acid on IgG Fc glycans is known to act as a switch for IgG anti-inflammatory activity. The role of terminal sialic acid residues on IgG glycans in atopic diseases is still unknown. This is the first study investigating IgG glycosylation in atopic diseases, aiming at examining serum IgG sialylation profile in children suffering from atopic diseases. Methods: Peripheral blood was collected from 61 patients suffering from allergic asthma, allergic rhinitis, atopic dermatitis and/or food allergy and 74 healthy controls of both sexes aged 5-18 years. Patients' atopic status was confirmed by positive skin prick tests and elevated total serum IgE level. Plasma was separated by centrifugation and IgG isolated by affinity chromatography on CIMProtein G Monolithic Plate. IgG N glycans were released and processed by in-gel-block method, which included protein denaturation and N-glycan release by N-glycosydase F. IgG N glycans were then labelled with 2 aminobenzamide and examined by hydrophilic interaction ultra performance liquid chromatography (HILIC). Results: The percentage of sialylated structures in total IgG N-glycans was markedly higher in atopic children, with greater fraction of disialylated over monosialylated structures. Conclusion: The IgG N-glycan sialic acid level was higher in atopic group. This may mean that IgG in atopic children plays an anti- inflammatory role, probably aiming at modulation of mastocyte activation and allergic inflammation development. This feature has the potential to be developed into a predisposition, prognostic or diagnostic biomarker of atopic diseases.

immunoglobulin G; glycosylation; sialylation; atopy; children

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