Production and characterisation of monoclonal antibodies to parathyroid hormone (1-34)

Monoclonal antibodies to the biologically active N terminal region of parathyroid hormone (PTH) suitable for use in the measurement of circulating PTH concentrations have proved difficult to produce. In this study, no serum PTH antibody titres could be detected in mice using synthetic human PTH (1-34) (free or coupled to albumin) or PTH (1-10) (coupled to keyhole limpet haemocyanin) as immunogen. A consistent response to PTH (1-34) peptide was obtained in DA rats. We have produced five monoclonal antibodies to PTH (1-34) derived from the fusion of DA rat spleen cells and the mouse myeloma line X63 Ag.8.653. Bulk production of the antibodies was achieved using congenitally athymic mice for ascites production. Antibody assessment studies revealed the antibodies to be sensitive to the oxidation state of the methionine residues in PTH (1-34). Two of the antibodies, 3B3 and 6E3, were shown to be of potential use in measuring circulating PTH (1-84) when used in combination with available antibodies to C terminal PTH. A third antibody, 4G3, which failed to recognise PTH (1-84) when used in combination with 3B3, formed the basis of a specific assay for PTH (1-34).