The effect of monoclonal anti-human-platelet antibodies on platelet kinetics in a baboon model: IgG subclass dependency

• Published in: Thrombosis and haemostasis Vol. 83; no. 1; p. 148
• Main Authors: Coetzee, L M, Pieters, H, van Wyk, V, Cooper, S, Roodt, J, De Reys, S, Badenhorst, P N
• Format: Journal Article
• Language: English
• Published: Germany 01.01.2000
• Subjects: Animals; Antibodies - immunology; Blood Platelets - immunology; Blood Platelets - metabolism; Disease Models, Animal; Humans; IgG Deficiency; Papio; Platelet Activation; Thrombocytopenia - immunology
• ISSN: 0340-6245
• DOI: 10.1055/s-0037-1613771

We assessed the in vivo effect of six intact anti-human antiplatelet antibodies of two major IgG subclasses on platelet kinetics in baboons. Five of the six antibodies tested caused thrombocytopenia of varying degree when injected at a precalculated threshold value. An agglutinating IgG1 antibody (MA-8L4A12) caused a long-lasting, mild thrombocytopenia with a predominant uptake of radiolabelled platelets in the spleen, while the four IgG2 antibodies tested (MA-13G8E1, MA-2M5A6, MA-21K2E8 and MA-22M10) caused a severe, transient thrombocytopenia with uptake of platelets in the liver. Two of the IgG2 antibodies (MA-13G8E1 and MA-2M5A6) caused platelet activation and aggregation in vitro, whilst the other two did not elicit a platelet aggregation response. The platelet survival time was shortened with all five of the thrombocytopenia-inducing antibodies, while only one antibody (MA-2M5A6) had a significant effect on the bleeding time. This study indicates that the IgG subclasss may be a determining factor in the outcome of platelet sequestration in immune-induced thrombocytopenia.