Effect of anti plasminogen monoclonal antibodies on whole blood clot lysis.

Abstract

Several monoclonal antibodies (MABs) against specific parts of the plasminogen molecule were developed. One of them, MPW1PG, recognizes only the native form Glu-plasminogen, while the other one, MPW2PG, reacts equally well with Glu-plasminogen and its proteolytically degraded derivative Lys-plasminogen as confirmed by immunoblotting experiments. Both MABs do not alter the cleavage of the low molecular weight substrate S-2251 by plasmin in a purified system but rather increase the rate of plasmin formation by urokinase and t-PA in a system without fibrin. In the presence of fibrin MPW1PG has no effect on plasmin formation by t-PA, while MPW2PG exhibits mixed type inhibition. To investigate whether this effect can also be seen in a whole blood clot lysis system, the Chandler loop was used (PVC tubes, 4 mm inner diameter, 28 mm length), 125I-fibrinogen was added to citrated whole blood (0.36% sodium citrate) to about 5,000 cpm/10 microliter sample. 1.5 ml of the mixture were pipetted into each tube, the tubes were closed, put on a rotary plate, tilted to an angle of 23 degrees, and rotated at 16 rpm. 10 microliter samples were taken for radioactive counting before clotting by addition of 10 microliter 3.02M CaCl2 (100%-value), 45 min after clotting (0%-value), and 30, 60, 120, 180, 360 minutes after addition of activators. Lysis was started one hour after recalcification. Different amounts of MABs were added either 30 min before recalcification (MAB endogen) or together with the activator (MAB exogen) Percent lysis was calculated from the radioactivity released into the fluid phase. Double determinations were done in all experiments.(ABSTRACT TRUNCATED AT 250 WORDS)