B2 glycoprotein I (B2GPI) containing IgM immune-complexes (B2GPI-IgM IC) in patients with IgM anticardiolipin antibodies (aCL IgM).

ALBERTO MF; SÁNCHEZ-LUCEROS A; MESCHENGIESER SS; LAZZARI MA

USA

Congreso; XXII Congress of the International Society on Thrombosis and Haemostasis; 2009

International Society on Thrombosis and Haemostasis

Patients with antiphospholipid syndrome (APS) suffer occasional thrombosis despite the persistent presence of antiphospholipid antibodies (aPL). aPL are only capable to induce cellular activation when BGPI is presented as dimmers forming the IC. In the current study we thought to investigate the prevalence of B2GPI- IgM IC in a group of patients (pts) with or without aCL IgM. One hundred fifty three pts with clinical criteria of APS were included. Sixty three pts without any detectable aPL, were divided en three groups: 27/63 pregnancy loss (PL aPL-), 16/63 arterial thrombosis (AT aPL-), 20/63 venous thrombosis (VT aPL-). Ninety pts with aCL IgM over cut-off value (<15 MPL), aCL IgG -, with or without lupus anticoagulant activity (LA) were divided in three groups: 44/90 pregnancy loss (PL IgM+), 31/90 arterial thrombosis (AT IgM+) and 15/90 venous thrombosis (VT IgM+).  Fifty four healthy controls age and sex matched were included. aCL antibodies were determined with a commercial kit (Binding Site).LA was evaluated according to the guidelines of SSCISTH. To determine B2GPI- IgM IC we set up an ELISA employing and affinity purified anti-human B2GPI as immunocapture phase.Bound IgM IC were detected by means of alkaline phosphatase- anti-human IgM. Results are shown in the table. Control PL aPL- AT aPL- VT aPL- PL IgM+ AT IgM+ VT IgM+ 0.23±0.06 0.30±0.15 0.26±0.11 0.22±0.06 0.51±0.16 0.44±0.21 0.26±0.1 Numbers represent mean 405 OD ± 1SD Higer values of B2GPI- IgM IC were statistically significant in PL IgM+ and AT IgM+ vs Controls, PL aPL- and AT aPL-  (p<0.05). AL activity was not related to B2GPI- IgM IC. The presence of B2GPI- IgM IC was associated with PL, AT rather than VT only in pts with aCL IgM+. Activation of the complement system is related to pathological effects of aPL in  PL and AT. IgM is a good complement activator. B2GPI- IgM IC could be a pathogenic marker and highlights a risk population in pts with clinical manifestation of APS with or without serological criteria.