[Studies on monoclonal antibodies directed against human C-peptide]

By comparison, it was shown that ascaris protein as carrier was far more effective than BSA and mouse serum albumin to make human c-peptide (HCP) immunogenicity in mice. Twelve monoclonal antibodies (McAb) were obtained after fusion of NS-1 myeloma cells with spleen cells from two BALB/c mice immunized with HCP-ascaris protein conjugate. Eight McAb were characterized and all of them were of IgG1 subclass. Affinities of the McAb for HCP were in the range of 0.03-0.85 X 10(9) mol-1. Although all 8 McAb reacted with both HCP and human proinsulin (HPI), they could specifically recognize human insulin from HPI and were highly species specific without cross-reaction with proinsulin, insulin and c-peptide of other species tested. Through analysis of binding with different HCP fragments, their antigenic determinants were located at either N or C terminal of HCP. The results of plasma HCP radioimmunoassay in 20 normal fasting human adults showed that the value (0.47 +/- 0.16 pmol/ml) determined by rabbit PcAb (R2303) against BSA-HCP was significantly higher than that (0.29 +/- 0.13 pmol/ml) determined by McAb-1.