N-linked glycans and sialic acid residues are essential for the anaphylactic activity of murine IgG1 antibodies

SILVA, S.R; JACYSYN, J.F; BUTERA, D; FAVORETTO, B.C; MOURA DA SILVA; MACEDO, M.S; CASABUONO, A.C; COUTO, A.S; FAQUIM-MAURO.E.L

Rio de Janeiro-Brasil

Congreso; ICI 2007 - International Congress of Immunology; 2007

ICI 2007

N-linked glycans and sialic acid residues are essential for the anaphylactic activity of murine IgG1 antibodies SILVA, S.R.1; JACYSYN, J.F. 1; BUTERA, D. 2;.FAVORETTO, B.C.2; MOURA DA SILVA, A.M.2; MACEDO, M.S. 1; CASABUONO, A.C3.; COUTO, A.S.3; FAQUIM-MAURO.E.L2. 1 Institute of Biomedical Science, University of São Paulo, São Paulo, 2, Butantan Institute, São Paulo, Brazil, 3Department of Organic Chemistry, Buenos Aires University, Buenos Aires, Argentina. Introduction: Antibodies are functional molecules that following the formation of complexes with the antigen may trigger the immune mechanisms of antigen elimination, through interactions of their Fc region with specific ligands. Glycosylation of the IgG-Fc region is essential for the recognition and activation of Fcγ receptors. However, it is not completely clear how differences in the N-linked oligosaccharide structure impact the biological activity of antibodies. Objective: We investigated the influence of the N-linked oligosaccharide chain and the contribution of individual sugar residues on the ability of the murine IgG1 antibody to elicit anaphylaxis. Methods: Two monoclonal IgG1 antibodies with the same antigenic specificity, one with in vivo anaphylactic activity and the other a non-anaphylactic IgG1 were used to characterize the N-linked oligosaccharide chains. Results: Both antibodies express the same amino acid sequence in the CH2 and CH3 domains of the heavy chain. Lectin-binding assays showed difference on the monosaccharide content, mainly of sialic acid, of the two IgG1 antibodies. The affinity chromatography using Triticus vulgaris lectin and the analysis of the oligosaccharide chains by HPAEC-PAD revealed minimal sialic acid residues in the carbohydrate chain from non-anaphylactic IgG1 compared with anaphylactic IgG1. The enzymatic removal of the carbohydrate chain or of the terminal sialic acid residues in anaphylactic IgG1 resulted in loss or reduction, respectively, of the antibody ability to trigger mast cell degranulation and in vivo anaphylactic reaction. Conclusion: The N-linked oligosaccharide chain and the sialic acid residues attached to the IgG1-Fc region are essential for the IgG1 anaphylactic activity. Supported by FAPESP and CAPES