BACKGROUND: Antiphospholipid antibodies (aPL) show great heterogeneity. Different phospholipids, with or without protein cofactor(s), and phospholipid binding proteins alone have been proposed as the target molecules for aPL. In order to determine the influence of phospholipid degradation products on the binding of aPL, sera from 6 patients with the antiphospholipid syndrome were studied. METHODS: Fresh and aged phosphatidylserine and cardiolipin were used as coating reagents in solid-phase immunoassay procedures. Antibody reactivity was tested by enzyme-linked immunosorbent assay in the sera and in eluates from columns packed with polystyrene scrapings coated with either cardiolipin or phoshatidylserine. RESULTS: Three reaction patterns of affinity-purified antibodies were seen: (1) reactivity with phosphatidylserine but not with cardiolipin or degraded phosphatidylserine, (2) reactivity with cardiolipin and degraded phosphatidlyserine, and (3) reactivity with all three phospholipid antigens. CONCLUSIONS: Striking differences in the antiphospholipid antibody reactivity with cardiolipin, phosphatidylserine and degraded phosphatidylserine in the presence of serum proteins were observed among patients with venous thromboembolism. The analyses showed that the degradation of phosphatidylserine influences the binding of aPL in in vitro assays.
BACKGROUND: Antiphospholipid antibodies (aPL) show great heterogeneity. Different phospholipids, with or without protein cofactor(s), and phospholipid binding proteins alone have been proposed as the target molecules for aPL. In order to determine the influence of phospholipid degradation products on the binding of aPL, sera from 6 patients with the antiphospholipid syndrome were studied. METHODS: Fresh and aged phosphatidylserine and cardiolipin were used as coating reagents in solid-phase immunoassay procedures. Antibody reactivity was tested by enzyme-linked immunosorbent assay in the sera and in eluates from columns packed with polystyrene scrapings coated with either cardiolipin or phoshatidylserine. RESULTS: Three reaction patterns of affinity-purified antibodies were seen: (1) reactivity with phosphatidylserine but not with cardiolipin or degraded phosphatidylserine, (2) reactivity with cardiolipin and degraded phosphatidlyserine, and (3) reactivity with all three phospholipid antigens. CONCLUSIONS: Striking differences in the antiphospholipid antibody reactivity with cardiolipin, phosphatidylserine and degraded phosphatidylserine in the presence of serum proteins were observed among patients with venous thromboembolism. The analyses showed that the degradation of phosphatidylserine influences the binding of aPL in in vitro assays.