title: Fc:Fc interactions revealed by spin-labeled IgG heterosaccharides in model immune complexes.
abstract: Dynamic properties of spin-labelled heterosaccharides in the Fc-region of murine monoclonal antihapten immunoglobulin G were studied in model immune complexes (IC) as a function of the IC size. Model IC dimers, trimers and oligomers were formed using bivalent photoaffinity antigens. The ESR spectrum exhibits two components. The rotational correlation time of the less-immobilized species is shorter than 10(-10) sec, and that of the more-immobilized component is in the order to 10(-9) approximately 10(-8) sec depending on the IC size. Fraction of the more-immobilized spin labels increases, and the mobility of this component decreases with increase in IC size (i.e., mobility: monomers approximately equal to dimers greater than trimers much greater than immune-complex precipitates). These data strongly suggest the existence of Fc:Fc interactions in IC, and provide the basis for a model in which such interactions underlie the initial mechanism by which the information of antigen binding to Fab region is transferred into organized Fc:Fc association structure for IgG effector activities.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D004136:Dinitrobenzenes / Q000276:immunology; D004578:Electron Spin Resonance Spectroscopy; D006023:Glycoproteins; D007141:Immunoglobulin Fc Fragments; D007128:Immunoglobulin Fragments; D007074:Immunoglobulin G; D046911:Macromolecular Substances; D051379:Mice; D009844:Oligosaccharides; D013113:Spin Labels
chemical_list: D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D004136:Dinitrobenzenes; D006023:Glycoproteins; D007141:Immunoglobulin Fc Fragments; D007128:Immunoglobulin Fragments; D007074:Immunoglobulin G; D046911:Macromolecular Substances; D009844:Oligosaccharides; D013113:Spin Labels