von Willebrand factor-mediated platelet adhesion to collagen involves platelet membrane glycoprotein IIb-IIIa as well as glycoprotein Ib.
Monoclonal antibodies (MAbs) directed toward distinct functional domains of human von Willebrand factor (vWF) were used to probe the involvement of platelet membrane receptors glycoprotein Ib (GPIb) and glycoprotein IIb-IIIa (GPIIb-IIIa) in vWF-mediated platelet adhesion to collagen in flowing blood. Among nine MAbs to vWF, MAb H9 inhibits binding of vWF to GPIb, MAb 9 blocks binding of vWF to GPIIb-IIIa, and MAbs B200 through B204 inhibit binding of vWF to collagen. Collagen-coated cover slips were exposed to human citrated blood at shear rates varying from 200 to 2600 sec-1 in parallel-plate perfusion chambers. Blood was reconstituted with washed radiolabeled platelets, erythrocytes, and citrated autologous plasma previously incubated with MAb IgG or F(ab')2. Platelet-collagen interactions were estimated by radioactive counting and by quantitative morphometry. Inhibition of 70% of platelet adhesion was observed at a concentration of 20 micrograms/ml MAb 9, similar to that observed with MAbs H9 or B202. The effect of each MAb was dose dependent, and their inhibitory effect on platelet adhesion was also shear rate dependent. Virtually 100% inhibition was observed at 2600 sec-1 shear rate when a mixture of the MAbs (H9 + 9 + B202) was added to reconstituted blood. Thus, blocking three functional domains of vWF virtually abolishes platelet-collagen adhesion at high shear rates, indicating that normal adhesion to collagen is mediated through binding of vWF to collagen and to both platelet membrane GPIb and GPIIb-IIIa.
Fressinaud
E
E
INSERM U. 143, Hôpital de Bicêtre, Paris, France.
Baruch
D
D
Girma
J P
JP
Sakariassen
K S
KS
Baumgartner
H R
HR
Meyer
D
D
D000328:Adult; D000911:Antibodies, Monoclonal; D001792:Blood Platelets / Q000378:metabolism* / Q000648:ultrastructure; D003094:Collagen / Q000378:metabolism*; D000939:Epitopes / Q000276:immunology; D006801:Humans; D006825:Hybridomas; D008875:Middle Aged; D010973:Platelet Adhesiveness; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*; D014841:von Willebrand Factor / Q000276:immunology / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D000939:Epitopes; D010980:Platelet Membrane Glycoproteins; D014841:von Willebrand Factor; D003094:Collagen