Antigenicity of the carboxyl terminus of insulin: isolation of human insulin-specific monoclonal antibodies.

Monoclonal technology was used to isolate antibodies binding the B30 (carboxy) terminal residue in the polyclonal-provoked immune response to human insulin. Although both spleen and lymph node cell fusions were carried out, only the latter were successful in isolating monoclonal antibodies that bound the carboxy terminal of human insulin. The binding of such antibodies was abolished or diminished by substitutions of the B30 residue. Studies with insulin species variants showed that the molecular binding between antibody and insulin may be critically determined by a subresidue feature, e.g. presence or absence of a single methyl group, as shown by the binding of the monoclonal antibody D10 to human insulin (threonine at B30) but not to rabbit insulin (serine at B30). Such studies are of interest in the study of the molecular basis of antibody-antigen interaction.