Production and characterisation of monoclonal antibodies to parathyroid hormone-related protein

The production and characterisation of 17 monoclonal antibodies to human parathyroid hormone-related protein (PTH-rP) 1-34 is described. Five of the antibodies were shown to be of high avidity (Ka 4 X 10(10)-1.9 X 10(11) L/M) and able to detect 15-100 pg PTH-rP 1-34 per tube by RIA. None cross-reacted with PTH 1-34, and inhibition studies with peptide subfragments of PTH-rP 1-34 indicated that all recognise a central region extending from residues 9-18 to between residues 23 and 34. All antibodies tested cross-reacted with native PTH-rP in culture fluids from keratinocytes and squamous cancer cell lines and in human and bovine milk. The concentrations of PTH-rP 1-34 (ng/ml) in these fluids as determined by RIA were: keratinocytes 1-3, squamous cancer 0.2-2.5, human milk, up to 80. Selected antibodies coupled to Sepharose 4B were used to extract PTH-rP from biological fluids with high yields.