title: Endothelial microparticle release is stimulated  in vitro  by purified IgG from patients with the antiphospholipid syndrome.
abstract: IgG antiphospholipid antibodies (aPL) exert direct effects on various cell types, contributing to the pathogenesis of thrombosis and pregnancy morbidity in patients with the antiphospholipid syndrome (APS). Some IgG samples from these patients activate endothelial cells (EC)  in vitro  as judged by surface expression of adhesion molecules such as E-selectin, which can promote thrombosis. Endothelial microparticles (EMP), which themselves are potentially prothrombotic, are released by activated EC. Though elevated circulating EMP levels have been reported in patients with APS, it is not known whether these EMP are released due to a direct effect of aPL on the cells. We tested the effect of purified polyclonal IgG from patients with APS (APS-IgG) and healthy controls (HC-IgG) upon cultured human umbilical vein EC (HUVEC). HUVEC exposed to APS-IgG produced significantly more EMP than those exposed to HC-IgG (p=0.0036) and a greater proportion of these EMP carried surface E-selectin (6.2% ± 4.0 for APS-IgG vs.  3.4% ± 2.0 for HC IgG, p=0.0172). This study therefore demonstrates that purified polyclonal APS-IgG can drive EMP release. We propose that EMP generation may be a useful measure of aPL-mediated pathogenic effects upon EC.
authors.affiliation: Centre for Rheumatology, Division of Medicine University College London, Rayne Institute, 4 th Floor, Room 422, 5 University Street, London. c.pericleous@ucl.ac.uk
authors.forename: Charis
authors.initials: C
authors.lastname: Pericleous
authors.forename: Lindsey A
authors.initials: LA
authors.lastname: Clarke
authors.forename: Paul A
authors.initials: PA
authors.lastname: Brogan
authors.forename: David S
authors.initials: DS
authors.lastname: Latchman
authors.forename: David A
authors.initials: DA
authors.lastname: Isenberg
authors.forename: Yiannis
authors.initials: Y
authors.lastname: Ioannou
authors.forename: Ian P
authors.initials: IP
authors.lastname: Giles
authors.forename: Anisur
authors.initials: A
authors.lastname: Rahman
mesh_terms: D000328:Adult; D017152:Antibodies, Antiphospholipid / Q000097:blood*; D016736:Antiphospholipid Syndrome / Q000097:blood / Q000276:immunology*; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D055252:Cell-Derived Microparticles / Q000276:immunology* / Q000378:metabolism; D002478:Cells, Cultured; D019040:E-Selectin / Q000378:metabolism; D005260:Female; D061307:Human Umbilical Vein Endothelial Cells / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D008875:Middle Aged; D013997:Time Factors
chemical_list: D017152:Antibodies, Antiphospholipid; D015415:Biomarkers; D019040:E-Selectin; D007074:Immunoglobulin G; C546936:SELE protein, human