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
