A radioimmunoassay for bradykinin based on monoclonal antibodies

We describe two monoclonal antibodies with recognise the peptides bradykinin and kallidin. These antibodies were used in a study to assess the feasibility of using monoclonal antibodies in place of conventional sera for radioimmunoassay. Antibody SBK1 recognises bradykinin with a Kd of 0.67 +/- 0.17 nM. It fails to recognise bradykinin from which any carboxyl terminal amino acid has been removed. Antibody SBK2 recognises bradykinin with a Kd of 58.11 +/- 7.55 nM; it recognises 1-8 and 1-7 bradykinin about 30% as effectively as the full-length sequence, and shorter carboxyl terminal truncated sequences with a progressively declining efficiency. In this model system, bradykinin concentrations of 0.2 nM could be reliably measured, and carboxyl truncated versions of the peptide could be distinguished from the parent molecule. The feasibility of using monoclonal antibodies to assay bradykinin and other small peptides is discussed in the light of these results.