Mechanism of platelet aggregation induced by a monoclonal antibody requiring Fc portion

• Published in: Thrombosis research Vol. 70; no. 1; pp. 51 - 65
• Main Authors: Yu, Ai-Xin, Wu, Xiao-Wei, Li, Jia-Zeng, Lian, Eric C.-Y.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Ltd 01.04.1993; Elsevier Science
• Subjects: aggregation; Animals; Antibodies, Monoclonal; Antigen-Antibody Reactions; Biological and medical sciences; Blood coagulation. Blood cells; Epitopes; Fundamental and applied biological sciences. Psychology; Immunoglobulin Fab Fragments; Immunoglobulin G; Mice; Mice, Inbred BALB C; Molecular and cellular biology; Monoclonal antibody; Platelet; Platelet Aggregation - drug effects; Platelet Aggregation - immunology; Platelet Aggregation Inhibitors - pharmacology; platelet glycoprotein IIb-IIIa; Platelet Membrane Glycoproteins - immunology; Receptors, Fc - immunology; aggregation; Monoclonal antibody; platelet glycoprotein IIb-IIIa; Aggregation; Human; Platelet; Integrin; Fc-Fragment; Biological receptor
• ISSN: 0049-3848; 1879-2472
• DOI: 10.1016/0049-3848(93)90223-B

A monoclonal antibody designated Apt4, which is IgGl, was produced by fusion of mouse myeloma cells to spleen cells from a BALB/c mouse immunized with normal human platelets. Apt4 whole IgG caused the aggregation of both platelet rich plasma (PRP) and washed platelets from normal subjects and a patient with Bernard Soulier syndrome but not those from two patients with the Type 1 Glanzmann's thrombasthenia. No aggregation was observed when Apt4 F(ab′) 2 fragments were used. Immunofluorescence study showed that both whole IgG and F(ab′) 2 fragments of Apt4 bound to fresh or formalin fixed platelets from normal subjects and a patient with Bernard Soulier syndrome but not to those from two patients with Glanzmann's thrombasthenia. Aggregation induced by Apt4 IgG was inhibited by EDTA (10 mM), PGE 1 (1 mM), 2-deoxy-D-glucose /antimycin (1.4 uM), and apyrase (20 units/ml). Preincubation of normal PRP with monoclonal anti-GPIIb/IIIa or anti-GPIb antibodies completely or partially inhibited the Apt4-induced aggregation, whereas anti-GPIIIa antibodies have no effects on this activation. Monoclonal ant-FcγRII antibody (IV.3) inhibited Apt4 induced aggregation. Immunoprecipitation of 125I-labeled platelet membrane lysate by Apt4 IgG showed two protein bands with a molecular weight of 145,000 and 95,000 daltons respectively under nonreducing condition, which are corresponding to GPIIb and GPIIIa. In conclusion, Apt4 antibody binds to GPIIb/IIIa complex and induces aggregation, requiring energy metabolism, calcium, ADP release and Fc portion of IgG to interact with Fc receptor, but independent of thromboXane A 2 formation.