Antiphospholipid antibodies affect trophoblast gonadotropin secretion and invasiveness by binding directly and through adhered β2-glycoprotein I

Abstract

Objective. To investigate the in vitro ability of antiphospholipid antibodies (aPL) to bind human trophoblast cells and to affect gonadotropin secretion and invasiveness.Methods. Antiphospholipid antibody IgG from women with recurrent miscarriages, ␤ 2 -glycoprotein I (␤ 2 GPI)-independent IgG aPL human monoclonal antibody (mAb) (519), and IgM anti-␤ 2 GPI human mAb (TM1G2) were investigated for their binding to trophoblasts cultured for various amounts of time, their ability to affect invasiveness of Matrigel-coated filters, and their release of human chorionic gonadotropin (hCG).Results. Polyclonal IgG aPL, as well as mAb 519 and TM1G2, bound to trophoblasts, the highest binding being found when cells displayed the greatest amount of syncytium formation. TM1G2 binding was found to be ␤ 2 GPI dependent. Both polyclonal and monoclonal aPL, but not the controls, significantly reduced hCG release and Matrigel invasiveness.Conclusion. These findings suggest that aPL recognition of both anionic PL and adhered ␤ 2 GPI on trophoblast cell structures might represent a potential pathogenetic mechanism for defective placentation in women with the antiphospholipid syndrome.

Anti-beta 2 glycoprotein I antibodies in centenarians

“…The remaining aCL positive sera from centenarians displayed comparable results (data not shown). As previously reported, sera from APS patients reacted with plates coated with anionic but not with neutral or positive PLs (data not shown) (Di Simone et al, 2000;Harris et al, 1985).…”

“…Anti-anionic (PS), -neutral (PE, PC), -cationic PL (Sph) activity was evaluated by ELISA as described (Allegri et al, 1990;Tincani et al, 1996;Di Simone et al, 2000).…”

“…b2GPI was purified from NHS, and anti-b2GPI antibodies were detected by ELISA as described (Tincani et al, 1996;Di Simone et al, 2000;Balestrieri et al, 1995). Sera were considered positive if OD values were higher than the 95th percentile of 50 normal healthy controls (0.130 for IgG and 0.280 for IgM, respectively).…”

“…To evaluate the b2GPI-dependence of aCL positive sera, aCL assays were performed in the absence of FCS, using gelatin only (0.5%; Sigma-Aldrich) in the blocking buffer as well as after addition of human b2GPI (5 mg/ml) or FCS (10%) as described (Di Simone et al, 2000).…”

How do antiphospholipid antibodies bind β2‐glycoprotein I?

“…In contrast, nonpathogenic aPL, which are not associated with the development of clinical features of APS, do not recognize ␤ 2 GPI and bind both neutral and negative phospholipids without any cofactor dependence (21). Binding to ␤ 2 GPI, although undoubtedly important, is not an absolute requirement in determining the pathogenicity of aPL, since human monoclonal IgG aPL that bind phospholipids in the absence of ␤ 2 GPI have been isolated and shown to be highly pathogenic in vivo (13,22).…”