Identification of human nonpancreatic-type ribonuclease by antibodies obtained against a synthetic peptide

An antibody that recognizes human nonpancreatic-type ribonuclease was obtained by immunizing a rabbit with a 14-residue synthetic peptide corresponding to the N-terminal sequence of eosinophil-derived neurotoxin which is identical to human liver ribonuclease. This amino acid sequence is unique to this protein. The anti N-peptide antibody was purified by protein A-Sepharose and by using ELISA and SDS-PAGE immunoblot techniques, the antibody reactivity against EDN and partially purified nonpancreatic-type ribonucleases from human plasma and urine was observed. Cross-reactivity with bovine pancreatic ribonuclease A and other proteins was not detected. In addition, the activity of the nonpancreatic-type ribonuclease was not affected by the antibody. The immune response was elicited without the need for a carrier protein showing that the N-terminal sequence of nonpancreatic ribonuclease contains a specific epitope. This antibody can be used for the immunological identification of both the native and denatured forms of this type of enzyme.