A novel radioimmunoassay for human erythropoietin using a synthetic NH2-terminal polypeptide and anti-peptide antibodies.

Antibodies prepared by immunizing rabbits with a synthetic polypeptide representing the first 26 amino acids of the proposed NH2-terminal sequence of human erythropoietin cross-react with peptide, highly purified 125I-labeled erythropoietin and biologically active erythropoietin. We have now developed a rapid and convenient radioimmunoassay for the hormone using 125I-labeled peptide and anti-peptide antibodies. This peptide/anti-peptide approach completely circumvents the relative lack of availability of highly purified 125I-labeled erythropoietin and of erythropoietin for immunization purposes and makes a radioimmunoassay for the hormone universally available to investigators. This concept may be applied as a general method for designing radioimmunoassays of molecules available in severely restricted quantities.