A monoclonal antibody specific for two-chain urokinase-type plasminogen activator. Application to the study of the mechanism of clot lysis with single-chain urokinase-type plasminogen activator in plasma.
A murine monoclonal antibody (MA-12E6A8) was raised against human urokinase-type plasminogen activator (u-PA), which, in an enzyme-linked immunosorbent assay (ELISA), reacted 15,000-fold better with recombinant two-chain u-PA (rtcu-PA) than with recombinant single-chain u-PA (rscu-PA). The antibody had no effect on the activity of rtcu-PA or on its inhibition by a chloromethylketone, but reduced the inhibition of rtcu-PA by recombinant plasminogen activator inhibitor-1 (rPAI-1) at least 10-fold. The dissociation constant of the rtcu-PA/MA-12E6A8 complex was 7 nmol/L. An ELISA was developed using MA-12E6A8 as capture antibody and a horseradish peroxidase conjugated u-PA specific antibody for tagging. It recognized free and active site blocked rtcu-PA but not rtcu-PA in complex with rPAI-1 or with alpha 2-antiplasmin. This ELISA was used to monitor the generation of rtcu-PA during fibrin clot lysis with rscu-PA in human plasma. Addition of 5 micrograms/mL rscu-PA to 3 mL plasma containing a 0.2 mL 125I-fibrin labeled plasma clot caused 50% clot lysis in 62 +/- 13 minutes (mean +/- SD, n = 6), at which time 99 +/- 28 ng/mL rtcu-PA was detected but no fibrinogen breakdown had occurred. Fifty percent fibrinogen breakdown did occur only when rtcu-PA had reached a level of 1,000 +/- 270 ng/mL (at 150 +/- 21 minutes). rscu-PA, 2 micrograms/mL, induced 50% clot lysis in 160 +/- 41 minutes (n = 6); no fibrinogen degradation occurred within 4 hours and rtcu-PA levels did not exceed 80 ng/mL. In the absence of a fibrin clot, 5 micrograms/mL rscu-PA added to human plasma did not result in significant generation of rtcu-PA (less than 50 ng/mL after 4 hours) and no fibrinogen degradation was observed. These results indicate that clot lysis with rscu-PA in a plasma milieu does not require extensive systemic conversion of rscu-PA to rtcu-PA, and that fibrinogen degradation occurs secondarily to systemic conversion of rscu-PA to rtcu-PA.
Center for Thrombosis and Vascular Research, University of Leuven, Belgium.
P J
PJ
Declerck
H R
HR
Lijnen
M
M
Verstreken
H
H
Moreau
D
D
Collen
D000818:Animals; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex / Q000032:analysis; D001777:Blood Coagulation; D004792:Enzyme Precursors / Q000276:immunology / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005340:Fibrinogen / Q000378:metabolism*; D005341:Fibrinolysin / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D051379:Mice; D008807:Mice, Inbred BALB C / Q000276:immunology; D010958:Plasminogen / Q000378:metabolism; D010960:Plasminogen Activators / Q000276:immunology / Q000378:metabolism*; D011994:Recombinant Proteins / Q000276:immunology / Q000378:metabolism; D014568:Urokinase-Type Plasminogen Activator / Q000276:immunology / Q000378:metabolism*; D000511:alpha-Macroglobulins / Q000378:metabolism
D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D004792:Enzyme Precursors; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D000511:alpha-Macroglobulins; C024668:plasmin-alpha(2)-macroglobulin complex; D005340:Fibrinogen; D010958:Plasminogen; D010960:Plasminogen Activators; D005341:Fibrinolysin; D014568:Urokinase-Type Plasminogen Activator