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Patient‐derived monoclonal antibodies directed towards beta 2 glycoprotein‐1 display lupus anticoagulant activity
Author(s) -
DIENAVAVERDOOLD I.,
BOONSPIJKER M. G.,
DE GROOT P. G.,
BRINKMAN H. J. M.,
VOORBERG J.,
MERTENS K.,
DERKSEN R. H. W. M.,
DE LAAT B.
Publication year - 2011
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1111/j.1538-7836.2011.04212.x
Subject(s) - lupus anticoagulant , antibody , monoclonal antibody , partial thromboplastin time , microbiology and biotechnology , antiphospholipid syndrome , immunoglobulin light chain , virology , antigen , phage display , biology , immunology , chemistry , platelet
Summary. Background: Patients with antiphospholipid syndrome (APS) display a heterogeneous population of antibodies with beta 2 glycoprotein‐1 (β 2 GP1) as the major antigen. Objectives: We isolated and characterized human mAbs directed against β 2 GP1 from the immune repertoire of APS patients. Methods: Variable heavy chain repertoires from B cells from two APS patients with anti‐β 2 GP1 antibodies were cloned into the pHEN1‐VLrep vector. Constructed full‐length IgG antibodies were tested for lupus anticoagulant (LAC) activity and binding to β 2 GP1 and its domains. Results: Two clones of each patient were selected on the basis of the reactivity of single chain Fv (scFv) fragments displayed on phages towards full‐length β 2 GP1 and its isolated domain I. The affinity of selected antibodies for β 2 GP1 was lost when transforming from phages to monovalent scFvs, and was regained when antibodies were constructed as complete IgG, indicating a role for bivalency in binding to β 2 GP1. Both selected clones from patient 2 recognized domain I of β 2 GP1, and for both clones selected from patient 1, binding required the presence of both domain I and domain II. All mAbs displayed LAC activity in both activated partial thromboplastin time‐based and dilute Russell’s viper venom test‐based clotting assays and in thrombin generation. Conclusions: In this study, we show successful cloning of patient‐derived mAbs that require domain I of β 2 GP1 for binding, and that display LAC activity that is dependent on their affinity for β 2 GP1. These antibodies can help us to gain more insights into the pathogenesis of APS, and may facilitate standardization of APS diagnosis.