title: Enrichment of sialylated IgG by lectin fractionation does not enhance the efficacy of immunoglobulin G in a murine model of immune thrombocytopenia.
abstract: Intravenous immunoglobulin G (IVIg) is widely used against a range of clinical symptoms. For its use in immune modulating therapies such as treatment of immune thrombocytopenic purpura high doses of IVIg are required. It has been suggested that only a fraction of IVIg causes this anti immune modulating effect. Recent studies indicated that this fraction is the Fc-sialylated IgG fraction. The aim of our study was to determine the efficacy of IVIg enriched for sialylated IgG (IVIg-SA⁺) in a murine model of passive immune thrombocytopenia (PIT). We enriched IVIg for sialylated IgG by Sambucus nigra agglutinin (SNA) lectin fractionation and determined the degree of sialylation. Analysis of IVIg-SA⁺ using a lectin-based ELISA revealed that we enriched predominantly for Fab-sialylated IgG, whereas we did not find an increase in Fc-sialylated IgG. Mass spectrometric analysis confirmed that Fc sialylation did not change after SNA lectin fractionation. The efficacy of sialylated IgG was measured by administering IVIg or IVIg-SA⁺ 24 hours prior to an injection of a rat anti-mouse platelet mAb. We found an 85% decrease in platelet count after injection of an anti-platelet mAb, which was reduced to a 70% decrease by injecting IVIg (p<0.01). In contrast, IVIg-SA⁺ had no effect on the platelet count. Serum levels of IVIg and IVIg-SA⁺ were similar, ruling out enhanced IgG clearance as a possible explanation. Our results indicate that SNA lectin fractionation is not a suitable method to enrich IVIg for Fc-sialylated IgG. The use of IVIg enriched for Fab-sialylated IgG abolishes the efficacy of IVIg in the murine PIT model.
authors: Sanquin Research and Landsteiner Laboratory, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors: Theresa
authors: T
authors: Guhr
authors: Judith
authors: J
authors: Bloem
authors: Ninotska I L
authors: NI
authors: Derksen
authors: Manfred
authors: M
authors: Wuhrer
authors: Anky H L
authors: AH
authors: Koenderman
authors: Rob C
authors: RC
authors: Aalberse
authors: Theo
authors: T
authors: Rispens
mesh_terms: D000818:Animals; D005591:Chemical Fractionation; D002846:Chromatography, Affinity; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D006031:Glycosylation; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D016756:Immunoglobulins, Intravenous / Q000008:administration & dosage / Q000627:therapeutic use; D056747:Immunomodulation / Q000276:immunology*; D013058:Mass Spectrometry; D051379:Mice; D019158:N-Acetylneuraminic Acid / Q000378:metabolism*; D037121:Plant Lectins / Q000378:metabolism*; D010976:Platelet Count; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000188:drug therapy / Q000276:immunology*; D051381:Rats; D054788:Ribosome Inactivating Proteins / Q000378:metabolism*
chemical_list: D007074:Immunoglobulin G; D016756:Immunoglobulins, Intravenous; D037121:Plant Lectins; C050600:Sambucus nigra lectins; D054788:Ribosome Inactivating Proteins; D019158:N-Acetylneuraminic Acid