Monoclonal Antibodies Towards the Fast Inhibitor of Tissue Plasminogen Activator from Human Plasma and Serum

Summary

Hybridoma cells were produced by fusing mouse myeloma cells (SP 2/0 - Ag 14) with spleen cells from a Balb/c mouse, previously immunized with the partially purified complex between tissue plasminogen activator (t-PA) and its fast inhibitor from human plasma (serum). Screening with a radioimmunoassay revealed a number of hybridomas secreting antibodies directed towards the complex. Of these, about 1/3 reacted both with the complex and t-PA, whereas about 2/3 reacted only with the complex. Three of the latter hybridomas, producing antibodies directed towards the inhibitor-moiety in the complex have been cloned and the antibodies were studied in detail. PA-inhibitor activity in plasma or serum and t-PA/PA-inhibitor complex could be specifically adsorbed on all three insolubilized monoclonal antibodies (MCI, MC2 and MC3). None of the antibodies seems to be directed against structures of vital importance for the functional activity of the PA-inhibitor. In accordance with this finding the antibody with the highest avidity (MCI) reacts equally well with the PA-inhibitor alone or in complex with t-PA. A radioimmunoassay was devloped with this antibody and significant displacement was obtained with samples with PA-inhibitor concentrations above 2 AU/mL. In 13 plasma samples with different levels of PA-inhibitory activity a significant correlation was obtained when comparing this activity with the PA-inhibitor antigen as measured with the radioimmunoassay (r = 0.88).

Keywords

Plasminogen activator inhibitor - Monoclonal antibodies - Radioimmunoassay

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