The inhibition of protein C anticoagulant activity by anti-[beta]2-glycoprotein I ([beta]2GPI) antibodies isolated from patients with antiphospholipid syndrome by chromatography methods

• Published in: Modern rheumatology 2002-03, Vol.12 (1), p.44
• Main Authors: Ieko, M, Nakabayashi, T, Takeda, M, Naitoh, S, Atsumi, T, Koike, T
• Format: Article
• Language: English
• Subjects: Chromatography; Glycoproteins; Health risk assessment; Medical disorders
• ISSN: 1439-7595; 1439-7609
• DOI: 10.1007/s101650200007

Antiphospholipid antibodies (aPL) are associated with an increased risk of thrombosis; however, the mechanism remains unknown. Recent studies have focused on the impediment of protein C anticoagulant activity by anti-#2-glycoprotein I (#2GPI) antibodies (a#2GPI Ab). We purified IgG fractions containing a high concentration of a#2GPI Ab from patients with antiphospholipid syndrome (APS) and then investigated the effect of purified a#2GPI Ab on the activity of activated protein C (APC). Using a three-step chromatography method (DEAE-sepharose column, phosphatidylserine polyacrylamide gel column dependent on the presence of #2GPI, and protein G column chromatography), we successfully isolated anti-#2GPI IgG from nine patients with APS. Seven of nine samples inhibited APC activity in a concentration-dependent manner only in the presence of #2GPI, as observed by a chromogenic assay that was able to determine thrombin activity even in the presence of APC. The extent of APC inhibition by these fractions appeared to be related to a#2GPI Ab titers of the purified IgG. However, the inhibitory effect of IgG from patients was not detected in the absence of #2GPI. IgG purified from three normal subjects did not affect APC activity. Herein, we show a useful method for the isolation of IgG containing a high concentration of a#2GPI Ab. Moreover, the present findings indicate that inhibition by a#2GPI Ab on APC anticoagulant activity could explain one of the mechanisms for the thrombotic state in APS. [PUBLICATION ABSTRACT]