title: Antibodies to platelets in patients with anti-phospholipid antibodies.
abstract: Binding of anti-phospholipid antibodies to circulating platelets and its consequences on platelet activation and aggregation was investigated in 11 patients with anti-phospholipid antibodies. Seven patients had mild thrombocytopenia. Nine healthy donors served as controls. Binding to platelets was investigated by performing enzyme-linked immunosorbent assays (ELISAs) with phospholipids as antigen on platelet eluates. Platelet activation was measured by flow cytofluorometry using monoclonal antibodies to an activation-specific lysosomal membrane protein. Findings in ELISA were compared with results of a conventional immunofluorescence method to detect platelet autoantibodies. In seven patients antibodies to negatively charged phospholipids were present in platelet eluates. In all thrombocytopenic patients and controls the platelets were not activated and aggregation was not impaired. There was a positive concordance of 50% between the results of immunofluorescence and ELISA. No apparent relation was found between the results of ELISA or immunofluorescence and platelet counts. It is concluded that anti-phospholipid antibodies can bind to circulating platelets. This binding is not associated with measurable aggregation abnormalities nor with platelet activation characterized by exposure of lysosomal membrane proteins. More studies are necessary to determine the exact role of anti-phospholipid antibodies in the pathogenesis of thrombocytopenia and thrombosis.
authors.affiliation: Department of Internal Medicine, University Hospital, Utrecht, The Netherlands.
authors.forename: H J
authors.initials: HJ
authors.lastname: Out
authors.forename: P G
authors.initials: PG
authors.lastname: de Groot
authors.forename: M
authors.initials: M
authors.lastname: van Vliet
authors.forename: G C
authors.initials: GC
authors.lastname: de Gast
authors.forename: H K
authors.initials: HK
authors.lastname: Nieuwenhuis
authors.forename: R H
authors.initials: RH
authors.lastname: Derksen
mesh_terms: D000328:Adult; D001323:Autoantibodies / Q000097:blood*; D001792:Blood Platelets / Q000276:immunology* / Q000502:physiology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007425:Intracellular Membranes / Q000276:immunology; D008180:Lupus Erythematosus, Systemic / Q000276:immunology; D008247:Lysosomes / Q000276:immunology; D008297:Male; D008875:Middle Aged; D010743:Phospholipids / Q000276:immunology*; D015539:Platelet Activation; D010974:Platelet Aggregation; D013921:Thrombocytopenia / Q000276:immunology
chemical_list: D001323:Autoantibodies; D010743:Phospholipids