Circulating beta 2 glycoprotein I-IgG anti- beta 2 glycoprotein I immunocomplexes in patients with definite Antiphospholipid Syndrome

Beta2-glycoprotein I ( beta 2GPI), a relevant antigen in Antiphospholipid Syndrome (APS), binds anionic macromolecules including heparin (Hep). A possible formation of ternary complexes between beta 2GPI, antibodies and Hep in APS is thus possible. The aim of this study was to evaluate Hep- beta 2GP...

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Published in:Lupus 2012-06, Vol.21 (7), p.784-786
Main Authors: Banzato, A, Frasson, R, Acquasaliente, L, Bison, E, Bracco, A, Denas, G, Cuffaro, S, Hoxha, A, Ruffatti, A, Iliceto, S, De Filippis, V, Pengo, V
Format: Article
Language:English
Subjects:
Affinity chromatography
antiphospholipid syndrome
Enzyme-linked immunosorbent assay
fluorescence spectroscopy
glycoprotein I
Glycoproteins
Heparin
Immunoglobulin G
Macromolecules
Sodium chloride
Thromboembolism
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Summary:Beta2-glycoprotein I ( beta 2GPI), a relevant antigen in Antiphospholipid Syndrome (APS), binds anionic macromolecules including heparin (Hep). A possible formation of ternary complexes between beta 2GPI, antibodies and Hep in APS is thus possible. The aim of this study was to evaluate Hep- beta 2GPI interaction in patients with APS. The affinity of Heps of different length, including unfractionated Hep (UFH), low-molecular weight Hep (enoxaparin) and pentasaccharide (fondaparinux), to human beta 2GPI was estimated by fluorescence spectroscopy, yielding dissociation constant (Kd) values of 1.1, 24.0 and 89.4 mu M, demonstrating that the longer UFH binds to beta 2GPI far more tightly than the shorter ones. Plasma and protein G-purified IgGs from eight patients with APS (i.e. five with thromboembolic disease and three with catastrophic APS), were fractionated by affinity chromatography using a Hep (UFH)-bound column, eluted with a linear NaCl gradient. For each chromatographic analysis, fractions were collected in the whole NaCl gradient and tested by ELISA for the presence of beta 2GPI and anti- beta 2GPI IgG. The results of Hep-affinity chromatography and ELISAs concurrently indicate that either beta 2GPI and anti- beta 2GPI IgG elute from the Hep column in the same chromatographic peak, at a retention time identical to that of the purified, isolated beta 2GPI, thus suggesting that circulating immunocomplexes containing beta 2GPI are present in patients with APS.
ISSN:0961-2033
DOI:10.1177/0961203312440347