INFLUENCE OF DEGRADED PHOSPHATIDYLSERINE ON BINDING OF ANTIPHOSPHOLIPID ANTIBODIES

Background: Antiphospholipid antibodies (aPL) show great heterogeneity . Different phospholipids, with or without protein cofactor(s), and ph ospholipid binding proteins alone have been proposed as the target mol ecules for aPL. In order to determine the influence of phospholipid de gradation products on the binding of aPL, sera from 6 patients with th e antiphospholipid syndrome were studied. Methods: Fresh and aged phos phatidylserine and cardiolipin were used as coating reagents in solid- phase immunoassay procedures. Antibody reactivity was tested by enzyme -linked immunoabsorbent assay in the sera and in eluates from columns packed with polystyrene scrappings coated with either cardiolipin or p hosphatidylserine. Results: Three reaction patterns of affinity-purifi ed antibodies were seen: (1) reactivity with phosphatidylserine but no t with cardiolipin or degraded phosphatidylserine, (2) reactivity with cardiolipin and degraded phosphatidylserine, and (3) reactivity with all three phospholipid antigens. Conclusions: Striking differences in the antiphospholipid antibody reactivity with cardiolipin, phosphatidy lserine and degraded phosphatidylserine in the presence of serum prote ins were observed among patients with venous thromboembolism. The anal yses showed that the degradation of phosphatidylserine influences the binding of aPL in in vitro assays.