Anti-phosphatidyl-serine/prothrombin antibodies (aPS/PT) in isolated lupus anticoagulant (LA): is their presence linked to dual test positivity?

OBJECTIVES: Anti phosphatidylserine/prothrombin antibodies (aPS/PT) are often present in patients with antiphospholipid syndrome (APS) and might be relevant in the pathogenesis of this condition. They are major determinant of lupus anticoagulant (LA) in triple-positive antiphospholipid (aPL) profile. Whether they are present and pathogenic in patients with isolated LA [negative anticardiolipin (aCL) and anti ß2-glycoprotein I (aß2GPI) antibodies] is a matter of debate. METHODS: We measured aPS/PT in a large number of isolated LA with the aim to ascertain whether there is a link between the way isolated LA is assessed and the presence of these antibodies. APS/PT were measured in 86 patients with isolated LA (aCL- and abeta2GPI-). LA was assessed by two test systems, the dilute Russell Viper Venom Time (dRVVT) and the Silica Clotting Time (SCT). RESULTS: Sixty-six (77%) individuals with isolated LA were positive for aPS/PT (IgM 44, IgG and IgM 15, IgG in 7). Diagnosis of LA was made based on positive results in both dRVVT and SCT in 40 patients (Group 1) and based on only one positive test in the remaining 46 patients (Group 2). The rate of positive aPS/PT antibodies was significantly higher in Group 1 (OR=7.2, 95% CI 1.9-27.0, p<0.002). Moreover, the titre of IgM aPS/PT was significantly increased in Group 1 as compared to Group 2 (137 U, IQR 64-179 vs. 43 U, IQR 11-120, p=0.008). CONCLUSIONS: These data indicate an association between LA based on two positive coagulation tests and the presence of aPS/PT antibodies, especially of IgM isotype.

Presence of lupus anticoagulant in an asymptomatic Nigerian.

BACKGROUND: The lupus anticoagulant (LA) is one of the antiphospholipid antibodies (aPL), which prolong phospholipid- dependent coagulation tests by interfering with coagulation reactions that depend on protein - phospholipid complexes in vitro. METHOD: A 25 year old 'healthy' male Nigerian was screened for the presence of any coagulation abnormality using the KCT, PT and platelet count; after volunteering for his plasma to be used in the preparation of normal pooled plasma in a study. RESULTS: He was discovered to have a prolonged KCT, PT and normal platelet count. Based on the prolonged KCT his plasma was subjected to mixing studies with various concentration of normal pooled plasma; the KCT index was calculated and a curve was plotted. His KCT index was 1.6 and the curve convex in the left axis suggesting the presence of LA. His past medical history and physical examination were not remarkable. Three months after the initial study, a repeat KCT index was 1.4 and the subject asymptomatic. CONCLUSION: From literature review this is the first report of LA in an asymptomatic adult Nigerian; the importance of this finding is discussed.

Effect of anti-beta2glycoprotein I Lupus Anticoagulants on fibrin polymerization and fibrinolysis.

Anti-beta2-Glycoprotein I (beta2GPI) autoantibodies are the prominent laboratory feature of Hughes syndrome. By prolonging some coagulation tests in the presence of exogenous phospholipids (PL), they behave as classical Lupus Anticoagulants (LA). We investigated the effect of 3 affinity-purified anti-beta2GPI IgG preparations from patients with Hughes syndrome on fibrin polymerization and fibrinolysis of normal plasma, measured by comparing the optical densities of assay mixtures in the presence of the autoantibodies or normal IgG. The presence of anti-beta2GPI IgG in diluted Russell Viper Venom Time (dRVVT) assays, carried out using a PL dilution of 1:8 or 1:64, resulted in a delay in the onset of polymerization by 30-40 and 60-70s, respectively. Fibrin polymerization was complete after 250s for both anti-beta2GPI IgG and normal IgG. The inhibitory effect of the anti-beta2GPI antibodies was not observed in the presence of excess PL, as expected for LA. Anti-beta2GPI IgG increased the plateau level of polymerization when dRVVT was performed in the presence of 1.5 nM recombinant tissue plasminogen activator, but did not impair the fibrinolytic process, which was almost complete after 250 min. The autoantibodies did not delay the onset of fibrin polymerization in tests carried out using recombinant tissue factor. On the contrary, the autoantibodies enhanced polymerization in prothrombin time assays, and accelerated it in tissue thromboplastin inhibition tests, with no effect on fibrinolysis. These data provide evidence that anti-beta2GPI LA may act as either anticoagulants or procoagulants in different in vitro coagulation tests.

Purification and characterization of lupus anticoagulant like protein from Agkistrodon halys brevicaudus venom.

By means of CM-Sephadex C-25, DEAE-Sephadex A-50, Sephadex G-200, and Sephadex G-75 chromatographies, a lupus anticoagulant like protein (LALP) from Agkistrodon halys brevicaudus was purified. On SDS-PAGE, the purified LALP had a molecular weight of 25,500 daltons under non-reducing condition and 15,000 daltons under reducing condition. The isoelectric point was pH 5.6. Its N terminal amino acid sequencing revealed a mixture of 2 sequences: DCP(P/S)(D/G)WSSYEGH(C/R)(Q/K). It was devoid of phospholipase A, fibrino(geno)lytic, 5'-nucleotidase, L-amino acid oxidase, phosphomonoesterase, phosphodiesterase and thrombin-like activities, which were found in crude venom. In the presence of LALP, PT, aPTT, and dRVVT of human plasma were markedly prolonged and its effects were concentration-dependent but time-independent. The inhibitory effect of LALP on the plasma clotting time was enhanced by decreasing phospholipid concentration in TTI test. The individual clotting factor activity was not affected by LALP when higher dilutions of LALP-plasma mixture were used for assay. Russell's viper venom time was shortened when high phospholipid confirmatory reagent was used. Therefore, the protein has lupus anticoagulant property.

Transient hemorrhagic diathesis associated with an inhibitor of prothrombin with lupus anticoagulant in a 1 1/2-year-old girl: report of a case and review of the literature.

Acquired inhibitors of coagulation causing bleeding manifestations are rare in children, particularly without an associated underlying disorder such as autoimmune disease. We describe an otherwise healthy 1 1/2-year-old girl who had extensive spontaneous bruising and prolonged bleeding from venipuncture sites. Prothrombin time (PT) and activated partial thromboplastin time (APTT) were prolonged, with evidence of an immediate-acting inhibitor. Thrombin clotting time, fibrinogen, and platelets were normal. Biologic assay of factors II, V, VII, and X were all low, with increasing values at higher dilutions. However, by immunoassay and/or chromogenic assays, only factor II was reduced. An antibody which failed to neutralize prothrombin activity in vitro was detected against radiolabeled prothrombin. Coagulation studies normalized in parallel with clinical recovery and disappearance of the antibody. This case demonstrates acute hypoprothrombinemia-lupus anticoagulant syndrome as a rare presentation of bleeding diathesis in a healthy young child.

Purification of anticardiolipin and lupus anticoagulant activities by using cardiolipin immobilized on agarose beads.

We describe a novel method for the purification of aPL, in which pure CL is immobilized on octyl-sepharose beads by hydrophobic interaction. No lipid contamination was present in eluates, and the system could be reutilized three times without loosing extracting capacity. Four patients with antiphospholipid syndrome were studied. A marked decrease in aCL and LA activities was found in all patient plasmas after the passage through a CL-octyl-sepharose column. Both activities were recovered in eluates which contained beta 2-GP-I and IgGs. beta 2-GP-I was also present in normal plasma eluates, which showed no aCL and slight LA activity. This method represents an improvement in the purification of aPL, and could be useful in explaining the mechanism of action of antibodies that are obtained using pure phospholipid as extracting matrix.

[Antiphospholipid syndrome: a new clinical entity? Part 1: antiphospholipid antibodies: specificity and methodological problems]. / Le syndrome des antiphospholipides: une nouvelle entité clinique? Partie 1: Anticorps antiphospholipides: spécificité et problèmes méthodologiques.

A new clinical entity, the antiphospholipid syndrome, has recently been described. It is based on the detection of antiphospholipid antibodies either by coagulation tests or by ELISA assay. The precise epitopes towards which these antibodies are directed is a matter of controversy. It is even possible that the name antiphospholipid is inappropriate. The diagnosis of lupus like anticoagulant (LA) detected by coagulation tests requires a three step procedure after appropriate processing of plasma samples. Antiphospholipid antibodies can also be identified by ELISA; this assay is simpler, but there is still a need for standardization. LA and antiphospholipid antibodies identified by ELISA are similar, but not identical; they have similar clinical implications. Due to the heterogeneity of the antibodies and the antigens it is necessary to use a panel of tests to establish or exclude the presence of antiphospholipid antibodies. In the future a better knowledge of antibodies' specificity should help in selecting the most useful test for clinical purposes.

Anticardiolipin antibodies block the inhibition by beta 2-glycoprotein I of the factor Xa generating activity of platelets.

Antiphospholipid antibodies, defined either by lupus anticoagulant (LA) activity or positive anticardiolipin immunoabsorbent assay (ACA) are associated with a predisposition to thromboses, recurrent fetal loss or thrombocytopenia. The mechanisms for these predispositions remain undefined. We have enriched immunoglobulin fractions from two patient plasmas to obtain antibodies with LA activity but no ACA, or conversely, with ACA positivity but no LA, in order to investigate in vitro characteristics which might explain a thrombotic propensity. beta 2-glycoprotein I (beta 2-GPI), the plasma cofactor required for ACA binding to negatively charged phospholipid, has previously been shown to inhibit prothrombinase generation in the presence of activated platelets (8). We now report that beta 2-GPI, at physiological concentrations, inhibits the generation of factor Xa in the presence of activated gel-filtered platelets. Further, ACA interferes with this inhibition, resulting in protracted, unopposed factor Xa generation. This interference with beta 2-GPI, a natural anticoagulant component of plasma, is potentially prothrombotic. LA immunoglobulins behave differently and inhibit factor Xa generation in a manner similar to beta 2-GPI. These findings provide the basis for a previously unsuspected mechanism for thrombosis in patients with aPL.

Beta 2-glycoprotein I is a requirement for anticardiolipin antibodies binding to activated platelets: differences with lupus anticoagulants.

Antiphospholipid (aPL) antibodies are of major interest not only because the lupus anticoagulant (LA) causes an inhibition of in vitro blood coagulation, but also because the presence of aPL antibodies confers a risk of thrombosis. The inhibition of in vitro phospholipid-dependent coagulation (LA) is thought to be caused by the binding of LA to procoagulant phospholipid surfaces, thus impeding the clotting process. Another class of aPL antibodies are those originally described to be directed against negatively charged phospholipids, in particular cardiolipin (ACA). ACA are usually directed against a complex antigen consisting of negatively charged phospholipid and a plasma protein, beta 2-glycoprotein I (beta 2-GPI). Further, there is antibody heterogeneity even within individual patients so that ACA and LA are separable using physicochemical techniques such as ion exchange chromatography and chromatofocusing. Using such techniques we have enriched Ig fractions for LA and ACA from two patient plasmas. The majority of Ig with LA activity had a pI of 7.2 to 7.3 whereas ACA had a pI of 5.0 to 5.2. Using these enriched fractions labeled with [125I]-iodine we have shown that LA binds to platelets in a specific and saturable manner. Binding is dependent on thrombin activation. [125I]-ACA behaves differently. Like LA, binding is specific and dependent on thrombin activation but in this case requires the presence of beta 2-GPI. ACA, in the presence of beta 2-GPI, competes for binding with LA suggesting the same or contiguous site. There is no cross-reactivity of these antibodies with GPIIb/IIIa and the most likely binding site is phospholipid. In neither case does LA nor ACA have an effect on thrombin-induced release of serotonin or beta-thromboglobulin nor do they affect platelet aggregation induced by a number of agonists. This antibody binding may play an etiological role in thrombocytopenia associated with aPL, but does not explain thrombosis on the basis of hyperaggregability or increased platelet release.

Anticoagulante lúpico: análisis clínico y de laboratorio de 45 pacientes

El anticoagulante lúpico (ACL) es un anticuerpo antifosfolipídico que prolonga las pruebas de coagulación dependientes de fosfolípidos como el tiempo de tromboplastina parcial activado (TTPa). El objetivo del presente estudio es informar la experiencia clínica y de laboratorio con 45 pacientes portadores de esta anomalía que clásicamente se manifiesta por trombosis, abortos a repetición y trombocitopenia. Los 45 pacientes se estudiaron en un período de 67 meses y represetan el 1.76 por ciento de todos los pacientes evaluados hemostáticamente en este tiempo. Cuarenta por ciento de los casos de ACL se presentó en pacientes con lupus eritematoso sistemico (LES); 25 por ciento en pacientes con neoplasia hematológica y 35 por ciento restante en pacientes con enfermedades benignas. Hubo 15 episodios de trombosis en 13 pacientes (28.8 por ciento de la muestra), ocho de estos tenian LES (44.4 por ciento). Dos pacientes con LES dieron historia de abortos a repetición (4.5 por ciento) y cuatro casos presentaron fenómenos hemorragiparos (9 por ciento). El estudio sugiere como grupo de riesgo elevado para trombosis a los pacientes con LES y VDRL falso positivo.

Anticoagulante lúpico: paradoja de la medicina

El anticoagulante lúpico es un inhibidor de la coagulación sanguínea adquirido espontáneamente que interfiere con la activación de la protrombina por el complejo activador. Este inhibidor, una inmunoglobulina, aparece más comúnmente en el plasma de pacientes con desórdenes autoinmunes incluyendo el lupus eritematoso sistémico, pero también ha sido asociado con enfermedades no relacionadas directamente con el sistema inmune y en pacientes sin ninguna enfermedad demostrable. Los pacientes con este "anticoagulante" usulamente están libres de sangrado a pesar de las anormalidades en su coagulación. Paradójicamente, han sido reportados episodios de trombosis venosa profunda, trombosis arterial u oclusión cerebrovascular, embolismo pulmonar y trombosis en la circulación renal. El mecanismo de estas asociaciones es desconocido, pero su comprensión será necesaria para un mejor diagnóstico y tratamiento de esta nueva entidad