title: Modulating IgG effector function by Fc glycan engineering.
abstract: IgG antibodies contain a conservedN-glycosylation site on the Fc domain to which a complex, biantennary glycan is attached. The fine structures of this glycan modulate antibody effector functions by affecting the binding affinity of the Fc to diverse Fc receptor family members. For example, core fucosylation significantly decreases antibody-dependent cellular cytotoxicity (ADCC), whereas terminal α2,6-sialylation plays a critical role in the anti-inflammatory activity of human i.v. immunoglobulin therapy. The effect of specific combinations of sugars in the glycan on ADCC remains to be further addressed, however. Therefore, we synthesized structurally well-defined homogeneous glycoforms of antibodies with different combinations of fucosylation and sialylation and performed side-by-side in vitro FcγR-binding analyses, cell-based ADCC assays, and in vivo IgG-mediated cellular depletion studies. We found that core fucosylation exerted a significant adverse effect on FcγRIIIA binding, in vitro ADCC, and in vivo IgG-mediated cellular depletion, regardless of sialylation status. In contrast, the effect of sialylation on ADCC was dependent on the status of core fucosylation. Sialylation in the context of core fucosylation significantly decreased ADCC in a cell-based assay and suppressed antibody-mediated cell killing in vivo. In contrast, in the absence of fucosylation, sialylation did not adversely impact ADCC.
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742.
authors.forename: Tiezheng
authors.initials: T
authors.lastname: Li
authors.affiliation: Laboratory of Molecular Genetics and Immunology, The Rockefeller University, New York, NY 10065.
authors.forename: David J
authors.initials: DJ
authors.lastname: DiLillo
authors.affiliation: Laboratory of Molecular Genetics and Immunology, The Rockefeller University, New York, NY 10065.
authors.forename: Stylianos
authors.initials: S
authors.lastname: Bournazos
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742.
authors.forename: John P
authors.initials: JP
authors.lastname: Giddens
authors.affiliation: Laboratory of Molecular Genetics and Immunology, The Rockefeller University, New York, NY 10065 ravetch@mail.rockefeller.edu wang518@umd.edu.
authors.forename: Jeffrey V
authors.initials: JV
authors.lastname: Ravetch
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742; ravetch@mail.rockefeller.edu wang518@umd.edu.
authors.forename: Lai-Xi
authors.initials: LX
authors.lastname: Wang
mesh_terms: D000818:Animals; D000920:Antibody-Dependent Cell Cytotoxicity; D006031:Glycosylation; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D007074:Immunoglobulin G / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D011134:Polysaccharides / Q000378:metabolism*; D015202:Protein Engineering; D011961:Receptors, Fc / Q000276:immunology
chemical_list: D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D011134:Polysaccharides; D011961:Receptors, Fc
keywords: Fc receptor; IgG; glycosylation