A RAPID LATEX IMMUNOASSAY FOR THE DETECTION OF PLASMIN ALPHA(2)-PLASMIN INHIBITOR COMPLEX - UTILIZATION OF 2 MONOCLONAL-ANTIBODIES DIFFERENTIALLY RECOGNIZING RESPECTIVE COMPONENTS OF THE COMPLEX

Among six monoclonal antibodies raised against the human plasmin-alpha (2)-plasmin inhibitor complex (PPI), three antibodies were found to re cognize the plasmin part (group 1) and another three the alpha(2)-plas min inhibitor (alpha(2)-PI) part (group 2) of the complex, One of the group-1 monoclonal antibodies, designated JIPPI-3, specifically reacte d with a segment of plasmin containing kringles 2 and 3. Although all three group 2 antibodies reacted with both alpha(2)-PI and PPI on immu noblotting and ELISA, one of them, JIPPI-50, was unable to react with alpha(2)-PI, when the antibody had been covalently conjugated to Sepha rose 4B gels and tested for reactivity against the antigens in solutio n. The results indicated that the epitope for this antibody had been b uried in nascent alpha(2)-PI, but had been exposed by complex formatio n with plasmin or by possible conformational changes induced in the al pha(2)-PI molecule on insolubilization to nitrocellulose membranes or immunoplates. By utilizing a set of JIPPI-3 and JIPPI-50, individually coated onto latex beads, PPI could be measured in plasma in the range of 0.8-100 mu g/ml without interference by coexisting plasminogen (12 0-200 mu g/ml) or alpha(2)-PI (alpha(2) mu g/ml). This measurable rang e seems to cover the level of PPI clinically observed under hyperfibri nolytic states.