title: Impact of immune complex size and glycosylation on IgG binding to human FcγRs.
abstract: IgG molecules are widely used as therapeutic agents either in the form of intact Abs or as Fc fusion proteins. Although efficient binding of the IgG Fc fragment to cellular FcγRs may be essential to achieve a high cytolytic activity, it may be advantageous for other applications to limit or abolish this interaction. Genetic or biochemical approaches have been used to generate these non-FcγR-binding IgG variants. By using soluble versions of FcγRs and monomeric versions of these altered IgG molecules, it was demonstrated that these IgG variants no longer bind to FcγRs. Importantly, however, these assays do not reflect the physiologic interaction of IgG with low-affinity cellular FcγRs occurring in the form of multimeric immune complexes. In this study, we investigated how the size of an immune complex can affect the interaction of normal and various versions of potentially non-FcγR-binding IgG variants with cellular FcγRs. We show that neither the D265A mutation nor EndoS treatment resulting in IgG molecules with only one N-acetylglucosamine and a fucose residue was fully able to abolish the interaction of all IgG subclasses with cellular FcγRs, suggesting that IgG subclass-specific strategies are essential to fully interfere with human FcγR binding.
authors.affiliation: Department of Biology, University of Erlangen-Nuremberg, 91058 Erlangen, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Lux
authors.forename: Xiaojie
authors.initials: X
authors.lastname: Yu
authors.forename: Chris N
authors.initials: CN
authors.lastname: Scanlan
authors.forename: Falk
authors.initials: F
authors.lastname: Nimmerjahn
mesh_terms: D000483:Alleles; D000818:Animals; D000936:Antigen-Antibody Complex / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001666:Binding Sites, Antibody / Q000235:genetics / Q000276:immunology*; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D006026:Glycoside Hydrolases / Q000494:pharmacology; D006031:Glycosylation; D057809:HEK293 Cells; D006801:Humans; D007074:Immunoglobulin G / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009154:Mutation / Q000276:immunology; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase / Q000494:pharmacology; D017452:Receptors, IgG / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000936:Antigen-Antibody Complex; C445323:FCGR2A protein, human; C496124:FCGR3A protein, human; D007074:Immunoglobulin G; D017452:Receptors, IgG; D011994:Recombinant Proteins; D006026:Glycoside Hydrolases; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase