Localization of the receptor binding site of IFN-alpha 2b

The receptor binding site of IFN-alpha is not precisely known. To further characterize this site, mAb against IFN-alpha 2b were selected that block the binding of radiolabeled IFN-alpha 2b to its cell surface receptor. These antibodies also neutralized the anti-viral and anti-proliferative properties of IFN-alpha 2b. A subset of these antibodies (group 1) do not recognize IFN-alpha 2a, either in solid-phase immunoassays or functional assays, whereas a second subset (group 2), with no cross-reactivity with group 1, recognizes both IFN-alpha subtypes. Because IFN-alpha 2b and IFN-alpha 2a differ by only alpha Arg23-Lys23 substitution, group 1 antibodies must recognize an epitope within the receptor binding region of IFN-alpha 2b that includes Arg23. Group 2 antibodies recognize a separate and distinct epitope within the binding site that does not include Arg23.