A MURINE MONOCLONAL-ANTIBODY THAT BLOCKS FIBRINOGEN BINDING TO NORMAL PLATELETS ALSO INHIBITS FIBRINOGEN INTERACTIONS WITH CHYMOTRYPSIN-TREATED PLATELETS

  • 1 January 1984
    • journal article
    • research article
    • Vol. 64  (1) , 59-63
Abstract
A monoclonal antibody, 10E5 was described that completely blocks ADP induced fibrinogen binding to platelets and aggregation induced by ADP, epinephrine and thrombin. Multiple lines of evidence indicate that 10E5 binds to platelet membrane glycoproteins IIb and/or IIa. Because platelets treated with chymotrypsin apparently aggregate when fibrinogen is added, the effect of 10E5 antibody on chymotrypsin-induced fibrinogen binding and platelet aggregation was tested. Aspirin-treated human platelets were washed in modified Tyrode''s buffer (pH 7.5), incubated for 5 min at 22.degree. C with 300 .mu.g/ml chymotrypsin, and washed again. The amount of 10E5 antibody bound to these platelets (37,232 .+-. 2,928 molecules/platelet; mean .+-. SEM [standard error of the mean], N = 9) was similar to that bound to unstimulated control platelets (36,910 .+-. 2,669) and did not differ significantly from the amount of antibody bound to ADP-treated platelets (P < .01, N = 5). The amount of 10E5 bound to chymotrypsin-treated platelets correlated directly with the amount of fibrinogen bound to separate aliquots of the same platelet samples (r = .876, P < .001). The 10E5 antibody caused virtually complete inhibition of both the binding of fibrinogen to chymotrypsin-treated platelets and the aggregation induced by exogenous fibrinogen. Immunoprecipitation studies of 125I-labeled chymotrypsin-treated platelets revealed that the 10E5 antibody bound proteins with MW characteristic of glycoproteins llb and ll1a. The fibrinogen receptor on chymotrypsin-treated platelets apparently is identical to that on ADP-treated platelets and this receptor is either near to, or on, the glycoprotein llb/ll1a complex.