title: Dimeric FcγR Ectodomains as Probes of the Fc Receptor Function of Anti-Influenza Virus IgG.
abstract: Ab-dependent cellular cytotoxicity, phagocytosis, and Ag presentation are key mechanisms of action of Abs arising in vaccine or naturally acquired immunity, as well of therapeutic mAbs. Cells expressing the low-affinity FcγRs (FcγRII or CD32 and FcγRIII or CD16) are activated for these functions when receptors are aggregated following the binding of IgG-opsonized targets. Despite the diversity of the Fc receptor proteins, IgG ligands, and potential responding cell types, the induction of all FcγR-mediated responses by opsonized targets requires the presentation of multiple Fc regions in close proximity to each other. We demonstrated that such "near-neighbor" Fc regions can be detected using defined recombinant soluble (rs) dimeric low-affinity ectodomains (rsFcγR) that have an absolute binding requirement for the simultaneous engagement of two IgG Fc regions. Like cell surface-expressed FcγRs, the binding of dimeric rsFcγR ectodomains to Ab immune complexes was affected by Ab subclass, presentation, opsonization density, Fc fucosylation, or mutation. The activation of an NK cell line and primary NK cells by human IgG-opsonized influenza A hemagglutinin correlated with dimeric rsFcγRIIIa binding activity but not with Ab titer. Furthermore, the dimeric rsFcγR binding assay sensitively detected greater Fc receptor activity to pandemic H1N1 hemagglutinin after the swine influenza pandemic of 2009 in pooled human polyclonal IgG. Thus these dimeric rsFcγR ectodomains are validated, defined probes that should prove valuable in measuring the immune-activating capacity of IgG Abs elicited by infection or vaccination or experimentally derived IgG and its variants.
authors.affiliation: Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria 3004, Australia; Department of Immunology, Monash University Central Clinical School, Melbourne, Victoria 3004, Australia; Department of Pathology, The University of Melbourne, Melbourne, Victoria 3052, Australia;
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Wines
authors.affiliation: Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Parkville, Victoria 3052, Australia;
authors.forename: Hillary A
authors.initials: HA
authors.lastname: Vanderven
authors.affiliation: Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria 3004, Australia;
authors.forename: Sandra E
authors.initials: SE
authors.lastname: Esparon
authors.affiliation: Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Parkville, Victoria 3052, Australia;
authors.forename: Anne B
authors.initials: AB
authors.lastname: Kristensen
authors.affiliation: Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Parkville, Victoria 3052, Australia; Australian Research Council Centre of Excellence in Convergent Bio-Nano Science and Technology, The University of Melbourne, Parkville, Victoria 3052, Australia; and Melbourne Sexual Health Centre, Infectious Diseases Department, Alfred Health, Monash University Central Clinical School, Melbourne, Victoria 3004, Australia.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Kent
authors.affiliation: Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria 3004, Australia; Department of Immunology, Monash University Central Clinical School, Melbourne, Victoria 3004, Australia; Department of Pathology, The University of Melbourne, Melbourne, Victoria 3052, Australia; mark.hogarth@burnet.edu.au.
authors.forename: P Mark
authors.initials: PM
authors.lastname: Hogarth
mesh_terms: D000914:Antibodies, Viral / Q000032:analysis* / Q000276:immunology; D000936:Antigen-Antibody Complex / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis* / Q000276:immunology; D007158:Immunologic Techniques / Q000379:methods*; D053118:Influenza A Virus, H1N1 Subtype; D011961:Receptors, Fc / Q000276:immunology*; D017452:Receptors, IgG / Q000276:immunology*
chemical_list: D000914:Antibodies, Viral; D000936:Antigen-Antibody Complex; D007074:Immunoglobulin G; D011961:Receptors, Fc; D017452:Receptors, IgG