Production and characterization of monoclonal antibodies to anti-human chorionic somatomammotropin by immunization with two free synthetic peptides.

The peptides corresponding to the fragments 135-140 and 166-174 of human chorionic somatomammotropin (hCS) were synthesized, and used to raise monoclonal antibodies to the native hCS molecule. The synthetic peptides were injected into BALB/c mice in the free form, i.e. not conjugated to a carrier, and the spleens were fused with Sp2/01Ag8 myeloma line to produce monoclonal antibodies. The antibodies produced belonged to the IgM and IgG classes and, once purified by affinity chromatography on hCS-Sepharose, they were covalently coupled to macroporous polystyrene beads and characterized by competitive radioimmunoassay. Their affinity constants were determined by elaborating the radioimmunoassay data by nonlinear regression analysis and they were found to range from 10(5) to 10(6) M-1. The evaluation of the affinity constant of the antibodies produced is always important as a measure of the immunogenicity of an antigen, particularly when synthetic peptides are used as immunogens.