title: The effect of monoclonal anti-human-platelet antibodies on platelet kinetics in a baboon model: IgG subclass dependency.
abstract: 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.
authors.affiliation: Department of Haematology and Cell Biology, University of the Orange Free State, Bloemfontein, South Africa. gnhmlmc@med.uovs.ac.za
authors.forename: L M
authors.initials: LM
authors.lastname: Coetzee
authors.forename: H
authors.initials: H
authors.lastname: Pieters
authors.forename: V
authors.initials: V
authors.lastname: van Wyk
authors.forename: S
authors.initials: S
authors.lastname: Cooper
authors.forename: J
authors.initials: J
authors.lastname: Roodt
authors.forename: S
authors.initials: S
authors.lastname: De Reys
authors.forename: P N
authors.initials: PN
authors.lastname: Badenhorst
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology*; D001792:Blood Platelets / Q000276:immunology* / Q000378:metabolism; D004195:Disease Models, Animal; D006801:Humans; D017099:IgG Deficiency; D010215:Papio; D015539:Platelet Activation; D013921:Thrombocytopenia / Q000276:immunology*
chemical_list: D000906:Antibodies