Summary
Polyclonal antibodies have been raised against the inhibitor moiety in the purified
complex between tissue plasminogen activator and its fast inhibitor (PA-inhibitor)
in human plasma/ serum. A radioimmunoassay for quantitation of PA-inhibitor antigen
was developed. The polyclonal antiserum and a previously described monoclonal antibody
against the PA-inhibitor (14) have been used to study the immunological relationship
between PA-inhibitors from plasma, serum, platelets, placenta extract and conditioned
media from Hep G2 and HT 1080 cells. It was demonstrated that the ratio between PA-inhibitor
activity and antigen varied considerably between the different sources. In the plasma
samples studied, similar activity and antigen concentrations were found, suggesting
that the PA-inhibitor in these samples mainly was in an active form. On the other
hand the other sources seemed to contain variable amounts of inactive PA-inhibitor
forms. Immunoadsorption experiments revealed that the PA-inhibitor (activity and antigen)
from all the sources were specifically bound to the insolubilized antibodies (polyclonal
and monoclonal). In no case, however, could active PA-inhibitor be eluted from the
immunoadsorption columns. Also the competitive radioimmunoassays suggested that the
PA-inhibitors from the different sources studied, were closely immunologically related.
Keywords
Plasminogen activator inhibitors - Immunoadsorption - Radioimmunoassay - Blood - Cell
cultures
