Monoclonal antibodies and synthetic peptides define the active site of FcepsilonRI and a potential receptor antagonist.
Defining the structure of the human high-affinity receptor for IgE, Fc,RI, is crucial to understand the receptor:ligand interaction, and to develop drugs to prevent IgE-dependent allergic diseases. To this end, a series of four anti-FcepsilonRI monoclonal antibodies (mAbs), including three new mAbs, 47, 54, and 3B4, were used in conjunction with synthetic FcepsilonRI peptides to define functional regions of the Fc IgE-binding site and identify an antagonist of IgE binding. The spatial orientation of the epitopes detected by these antibodies and their relationship to the IgE-binding region of FcepsilonRI was defined by a homology model based on the closely related FcepsilonRIIa. Using recombinant soluble FcRI-alpha as well as FcepsilonRI-alpha expressed on the cell surface, a series of direct and competitive binding experiments indicated that the mAbs detected nonoverlapping epitopes. One antibody (15-1), previously thought to be located close to the IgE-binding site, was precisely mapped to a single loop within the IgE-binding site by both mutagenesis and overlapping synthetic peptides encompassing the entire extracellular domain. A synthetic peptide epsilonRI-11, containing the amino acids 101-120 and the mAb 15-1 epitope, inhibited IgE binding and may form the basis for the development of a useful receptor-based therapy.
Helen M. Schutt Laboratory for Immunology, Austin Research Institute, Austin Repatriation Medical Centre, Heidelberg, Victoria, Australia.
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Rigby
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Trist
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Snider
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Hulett
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Hogarth
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Epa
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000378:metabolism*; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D001667:Binding, Competitive; D018604:Epitope Mapping; D000939:Epitopes / Q000378:metabolism; D006801:Humans; D007073:Immunoglobulin E / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000378:metabolism; D017455:Receptors, IgE / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D017452:Receptors, IgG / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000939:Epitopes; C080568:Fc gamma receptor IIA; D010455:Peptides; D017455:Receptors, IgE; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins; D007073:Immunoglobulin E