Monoclonal antibodies against human platelet membrane glycoprotein IIIa and collagen-induced platelet activation.
Two monoclonal antibodies against human platelet membrane glycoprotein IIIa (GPIIIa) were obtained. One monoclonal antibody, designated as 1B1, was found to inhibit both collagen-induced platelet aggregation and release reactions. This antibody also inhibited the binding of 125I-labeled collagen to human platelets. On the other hand, the other antibody, designated as B10, had no effect on platelet activation induced by a number of physiological stimulants including collagen. Direct binding studies involving 125I-labeled 1B1 or B10 demonstrated that the binding sites for these antibodies on unstimulated platelets have dissociation constants of 4.2 and 14.0 nM, respectively. The binding of 125I-labeled 1B1 or B10 to platelets was not inhibited by the other antibody. Purified 1B1 and B10 were covalently coupled to Affi-Gel and then proteolytic fragments of GPIIIa were applied to the Affi-Gel immunoadsorbent columns. Of the several proteolytic fragments, the 56 kilodaltons (kDa) fragment obtained on digestion with V8 protease bound to both of the columns. The 69 and 55 kDa fragments obtained with BrCN bound to only the 1B1 Affi-Gel column, while the 63 kDa fragment obtained with chymotrypsin only bound to the B10-Affi-Gel column. Based on the partial amino acid sequences of these fragments and the amino acid sequence of GPIIIa (C. A. Fitzgerald, B. Steiner, S. C. Rall, Jr., S. Lo and D. R. Phillips, J. Biol. Chem., 262, 3936 (1987), the epitopes for 1B1 and B10 were concluded to be located at amino acids 335 to 582 and 206 to 335, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Kawashima
H
H
Tomaru
A
A
Yamamoto
K
K
Tsuji
T
T
Osawa
T
T
D000818:Animals; D000911:Antibodies, Monoclonal; D001792:Blood Platelets / Q000276:immunology / Q000378:metabolism*; D003094:Collagen / Q000494:pharmacology*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D010980:Platelet Membrane Glycoproteins / Q000276:immunology*
D000911:Antibodies, Monoclonal; D010980:Platelet Membrane Glycoproteins; D003094:Collagen