Immunological characterization of antigenic domains on human IL-2 receptor beta subunit: epitope-function relationships.
Five mAb directed at the IL-2R beta chain were analyzed for their binding and functional properties. They define three epitopes on a recombinant soluble beta chain or on the beta chain expressed at the surface of YT-2C2 cells. Epitope 1 (A41 and 6E8 mAb) is part of the IL-2 binding domain, whereas epitope 2 (CF1 and 6E10 mAb) is not involved in IL-2 binding. Epitope 3 (6B5 mAb) also partly overlaps the IL-2 binding domain but does not overlap epitopes 1 and 2. None of the mAb can by themselves inhibit IL-2 induced proliferation of a human activated T cell clone. Only epitope 1 mAb can synergize with an anti-alpha chain mAb to inhibit this proliferation. Using epitope 1 and 2 mAb as well as a purified, recombinant form of the IL-2R beta chain extracellular domain, an ELISA-based immunoassay was set up which allows the quantitative determination of soluble and detergent solubilized IL-2R beta chains. Epitopes 1 and 2 are in non-competitive interaction: the binding of a mAb to one epitope decreases the affinity of a mAb for the second epitope. Epitope 2 mAb have binding stoichiometries (approximately 16,000 sites/cell) which are approximately 80% higher than that of epitope 1 mAb and IL-2 itself (approximately 9000 sites/cell). Upon binding of epitope 2 mAb, the stoichiometries of epitope 1 mAb and IL-2 are increased to reach the stoichiometry of epitope 2 mAb.(ABSTRACT TRUNCATED AT 250 WORDS)
D000911:Antibodies, Monoclonal / Q000737:chemistry; D001666:Binding Sites, Antibody; D001667:Binding, Competitive; D018604:Epitope Mapping; D000939:Epitopes / Q000276:immunology* / Q000502:physiology*; D006689:Hodgkin Disease / Q000276:immunology; D006801:Humans; D007376:Interleukin-2 / Q000037:antagonists & inhibitors / Q000494:pharmacology; D007694:Killer Cells, Natural; D007938:Leukemia / Q000276:immunology; D008565:Membrane Proteins / Q000276:immunology; D015375:Receptors, Interleukin-2 / Q000737:chemistry* / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D000939:Epitopes; D007376:Interleukin-2; D008565:Membrane Proteins; D015375:Receptors, Interleukin-2; D011994:Recombinant Proteins