Characterization of five monoclonal antibodies obtained after immunization in vitro with a synthetic 19-amino acid peptide of thyroglobulin

A 19-amino acid synthetic peptide representing the highly conserved amino terminus of thyroglobulin was used for the production of monoclonal antibodies after immunization of splenocytes in vitro. The properties of five of the antibodies were studied. One reacted only with the synthetic peptide. The others reacted with both the synthetic peptide and with thyroglobulin from all species tested so far, confirming that the amino terminus of thyroglobulin is highly conserved. Two of the five antibodies showed a positive reaction when tested on frozen sections of thyroid tissue, but with different reaction patterns. Monoclonal antibody F4 gave a positive reaction in the colloid, which contains mainly 19S thyroglubulin. In contrast, monoclonal antibody G4 gave a positive reaction only in the follicular cells. Monoclonal antibody G4 binds primarily to low molecular weight compounds in thyroglobulin preparations, possibly representing breakdown products of the protein.