Phosphattdyl Serine-Dependent Antiprothrombin Antibody Is Exclusive to Patients With Lupus Anticoagulant

Abstract

We conducted this study to determine whether antiprothrombin antibody (aPT) [to prothrombin (PT) alone or PT/phosphatidyl serine (PS) complex] actually existed in patients with lupus anticoagulant (LA) and/or anticardiolipin antibody (aCL). aPT to PT alone was positive in 2/7 LA-positive (29%) and 3/7 LA/aCL-positive (43%) patients. aPT to PT/PS complex was positive in 4/7 LA-positive (57%) and 4/7 LA/aCL-positive (57%) patients in the presence of Ca2+. However, none of the aCL-positive patients without LA or the LA/aCL-negative patients were positive for aPT and aPT/PS. Thus, we confirmed the existence of aPT and aPT/PS specifically among LA-positive patients. However, the clinicopathological significance of aPT and aPT/PS in this clinical setting is yet to be clarified.

Anti-beta2-glycoprotein I (beta2GPI) monoclonal antibodies with lupus anticoagulant-like activity enhance the beta2GPI binding to phospholipids.

“…In this regard, we reported recently that ␤2GPI itself functions as an inhibitor of phospholipid-dependent anticoagulant activity of APC (49). The clustering mechanism proposed in this study may also explain the anti-APC activity of anti-␤2GPI antibodies observed in previous studies (64)(65)(66), and indeed, anti-␤2GPI mAbs used in the current study were found to have a potent inhibitory activity against the anticoagulant activity of APC (our unpublished data).…”

Anti‐endothelial cell antibodies to the endothelial hybridoma cell line (EAhy926) in systemic lupus erythematosus patients with antiphospholipid antibodies

“…Furthermore, aPT was exclusively positive in patients with LA (6/15, 40 . 0%), further suggesting that PT may be the target antigen of LA and that aPT may be the same entity as LA as previously reported (Matsuda et al, 1996).…”

“…This speculation may be further supported by the evidence that both aCL/AECA-positive sera absorbed with cardiolipin liposome/b 2 -GPI became aCL-negative, but still retained AECA reactivity. Furthermore, both aPT/AECA-positive sera absorbed with phosphatidylserine-liposome/prothrombin, which is regarded as the target antigen of LA (Beevers et al, 1991;Oosting et al, 1993;Matsuda et al, 1996), still retained AECA reactivity.…”

Buffer may be the critical factor in measurement of anti-prothrombin antibody on a γ-ray-irradiated plate by enzyme-linked immunosorbent assay

“…We also confirmed the existence of aPT in 40% of systemic lupus erythematosus (SLE) patients with LA by ELISA, employing a non-y-ray-irradiated plain plate, but we failed to detect aPT when we employed a y-ray-irradiated plate [2,3].…”