Identification of antigenic determinants on insulin recognized by monoclonal antibodies

The specificities of nine monoclonal antibodies raised to bovine insulin were investigated. The probable binding sites of the antibodies were determined by correlation of cross-reactivity with heterologous insulins and amino acid differences in the primary structures. Most antibodies recognized topographic determinants composed of both A- and B-chain residues but were capable of binding either one or both free chains independently. Only one antibody was completely conformation-dependent. A number of antibodies showed heteroclitic binding to particular insulin variants. All the antibodies were autoreactive in that they recognized rat insulin which has the same primary sequence as the mouse molecule.