Lupus anticoagulant activity of autoimmune antiphospholipid antibodies is dependent upon beta 2-glycoprotein I.

Abstract The paradoxical correlation between thrombosis and the lupus anticoagulant (LAC) effect is an enigmatic feature of the antiphospholipid (aPL) syndrome. The Dutch authors previously reported that thrombosis-related anti–β2-glycoprotein I (β2GPI) antibodies recognize domain I and cause LAC. The American authors reported that aPLs disrupt an anticoagulant annexin A5 (AnxA5) crystal shield. We investigated whether antidomain I antibodies correlate with disruption of AnxA5-anticoagulant activity. We studied a well-characterized group of 33 patients including subgroups with β2GPI-dependent LAC that recognize domain I (n = 11), with β2GPI-independent LAC (n = 12), and lacking LAC (n = 10). The effects on AnxA5-anticoagulant activity were determined with an AnxA5 resistance assay that measures coagulation times with and without AnxA5. Patients with β2GPI-dependent LAC (group A, all with thrombosis) had significantly lower AnxA5-anticoagulant ratios than those with β2GPI-independent LAC (group B, thrombosis n = 4; 157.8% versus 235.6%, P < .001) and those without LAC (group C, thrombosis n = 2; 157.8% versus 232.5%, P < .001). There was no difference in the ratios between groups B and C (P = .92). Plasmas with β2GPI-dependent LAC that recognize domain I displayed significantly increased AnxA5 resistance, suggesting that specifically anti-β2GPI antibodies compete with AnxA5 for anionic phospholipids. These results are consistent with a model in which aPL antibodies may promote thrombosis by interfering with the anticoagulant activity of AnxA5.

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Prothrombin as cofactor for antiphospholipids

Lupus ◽

10.1177/096120339800700209 ◽

1998 ◽

Vol 7 (2_suppl) ◽

pp. 37-40 ◽

Cited By ~ 19

Author(s):

M Galli ◽

T Barbui

Keyword(s):

Clinical Relevance ◽

Antiphospholipid Antibodies ◽

Lupus Anticoagulant ◽

Anticoagulant Activity ◽

Low Risk ◽

Immune Recognition ◽

Clotting Time ◽

Glycoprotein I ◽

Russell’S Viper ◽

Kaolin Clotting Time

Prothrombin is a common antigenic target of antiphospholipid antibodies, since anti-prothrombin antibodies are detected in about 50-90% of the patients. To allow proper immune recognition, prothrombin must be adsorbed on suitable anionic surfaces. The epitope(s) have not yet been identified: the majority of anti-prothrombin antibodies appear to be of poly- or oligoclonal nature. Anti-prothrombin antibodies, either alone or in combination with anti-β2-glycoprotein I antibodies, are responsible for the lupus anticoagulant activity of about 75% of the cases of phospholipid-dependent inhibitors of coagulation. The two antibodies may be discriminated by means of specific coagulation profiles generated by the comparison of the ratio of the Kaolin Clotting Time (KCT) and the dilute Russell's Viper Venom Time (dRVVT): the KCT profile, which mainly reflects the presence of anti-prothrombin antibodies and the dRVVT profile, which is mostly associated with anti-β2-glycoprotein I antibodies. This distinction, although somewhat artificial, may be clinically useful, since the KCT profile identifies patients at low risk to develop thrombosis. Similarly, most of the studies that measured anti-prothrombin antibodies by ELISA failed to find a significant association with thrombosis. In conclusion, the clinical relevance of these antibodies has not yet been established.

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Laboratory methods to detect antiphospholipid antibodies

Hematology ◽

10.1182/asheducation-2014.1.321 ◽

2014 ◽

Vol 2014 (1) ◽

pp. 321-328 ◽

Cited By ~ 18

Author(s):

Steven A. Krilis ◽

Bill Giannakopoulos

Keyword(s):

Clinical Significance ◽

Antiphospholipid Antibodies ◽

Lupus Anticoagulant ◽

Solid Phase ◽

Evidence Based ◽

Diagnostic Utility ◽

Laboratory Methods ◽

Detailed Review ◽

Glycoprotein I ◽

Beta 2

Abstract This chapter reviews several important themes pertaining to the antiphospholipid syndrome (APS), including a description of the clinical features, a discussion of the main autoantigen, beta 2-glycoprotein I (β2GPI), and insights into the characteristics of the pathogenic anti-β2GPI autoantibodies. Evidence-based considerations for when to test for APS are explored, along with the clinical significance of patients testing positive on multiple APS assays, so-called triple positivity. A detailed review of recently published laboratory guidelines for the detection of lupus anticoagulant and the solid-phase anticardiolipin and anti-β2GPI ELISAs is undertaken. Finally, a brief review of nonclassification criteria laboratory assays with potential future diagnostic utility is presented.

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Lupus Anticoagulant Activity Is Frequently Dependent on the Presence of β2-Glycoprotein I

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648480 ◽

1992 ◽

Vol 67 (05) ◽

pp. 499-502 ◽

Cited By ~ 127

Author(s):

Janine D Oostin ◽

Ronald H W M Derksen ◽

H Tanja I Entjes ◽

Bonno N Bouma ◽

Philip G de Groot

Keyword(s):

Dose Response ◽

Plasma Levels ◽

Antiphospholipid Antibodies ◽

Lupus Anticoagulant ◽

Response Curve ◽

Anticoagulant Activity ◽

False Negative ◽

Coagulation Assays ◽

Glycoprotein I ◽

Deficient Patient

SummaryAntiphospholipid antibodies (aPL) are defined by anticardioli-pin antibody (aCL) ELISA and prolongation of phospholipid dependent coagulation assays (lupus anticoagulant; LAC). For the binding of aCL to cardiolipin a cofactor, β2-glycoprotein I (β2-GPI), is necessary. We have investigated whether the same cofactor is essential for LAC activity. Plasma from 6 LAC positive patients and 3 controls was depleted from β2-GPI by means of affinity chromatography. From the 6 LAC positive plasmas, 4 became LAC negative (tested with dRWT) when β2-GPI was depleted and became positive again when purified β2-GPI (200 μg/ml) was added. A dose response curve showed that addition of 50 μg/ml β2-GPI to β2-GPI deficient patient plasma, led to a positive dRWT. Depletion of, and addition of β2-GPI to plasma from controls had no effect on the dRWT. Measurement of β2-GPI plasma levels in 19 LAC positive patients, 40 LAC negative patients and 15 controls showed no difference in β2-GPI levels.These results show that a combination of aPL and β2-GPI is essential not only for binding to cardiolipin, but also for LAC activity and imply that low β2-GPI levels (<50 μg/ml) can lead to false negative LAC tests. These observations may lead to new insights in the pathophysiological complications associated with aPL.

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Functional and binding studies of the roles of prothrombin and beta 2- glycoprotein I in the expression of lupus anticoagulant activity

Blood ◽

10.1182/blood.v83.10.2878.2878 ◽

1994 ◽

Vol 83 (10) ◽

pp. 2878-2892 ◽

Cited By ~ 93

Author(s):

P Permpikul ◽

LV Rao ◽

SI Rapaport

Keyword(s):

Calcium Ions ◽

Lupus Anticoagulant ◽

Anticoagulant Activity ◽

Protein A ◽

Inhibitory Effect ◽

Factor X ◽

Glycoprotein I ◽

Normal Plasma ◽

Beta 2 ◽

Factor X Activation

Abstract We present functional and binding data relevant to the reported roles for prothrombin and beta 2-glycoprotein I (beta 2GPI) in the expression of lupus anticoagulant activity. In a purified system containing human prothrombin, Xa, Va, and a rate-limiting concentration of phosphatidylserine (PS)/phosphatidylcholine (PC) vesicles, the preliminary incubation of vesicles with protein A separated IgG preparations from 10 lupus anticoagulant plasmas, calcium, and prothrombin enhanced the inhibitory effect of all IgG preparations upon thrombin generation. Experiments in a purified factor X activation system provided supporting data that a similar preliminary incubation with prothrombin enhanced the inhibitory effect of many of the IgG preparations upon factor X activation. However, we could not obtain unequivocal evidence that prothrombin was an obligatory cofactor for lupus anticoagulant IgG to inhibit procoagulant phospholipid function, because lupus anticoagulant IgG separated by protein A chromatography contained traces of prothrombin. The binding of many IgG preparations to immobilized PS was enhanced by prothrombin when calcium ions were present. beta 2GPI enhanced binding of many of the IgG preparations to immobilized PS both in the presence and absence of calcium, yet beta 2GPI failed to enhance the ability of the IgG preparations to inhibit phospholipid function in purified prothrombin and factor X assays. Moreover, the IgG preparations prolonged the dilute Russell's viper venom time (dRVVT) of beta 2GPI-depleted normal plasma. Nine of 10 IgG preparations bound to prothrombin on Western blots in the absence of calcium and phospholipid, whereas no preparation bound to beta 2GPI. Passage of five citrated lupus anticoagulant plasmas through a prothrombin affinity column in the absence of added calcium and phospholipid removed most of the activity prolonging the dRVVT of normal plasma, and IgG in the pass-through plasma no longer bound to PS in the presence of prothrombin and calcium ions. IgG in prothrombin column eluates had strikingly enhanced specific lupus anticoagulant activity and also specific PS binding activity in the presence of prothrombin and calcium ions. Thus, lupus anticoagulant plasmas were shown to contain IgG binding to prothrombin, in the absence of calcium ions and phospholipid, which could also, in the presence of calcium ions and prothrombin, bind to PS and express lupus anticoagulant activity.

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Lupus anticoagulant antibodies: Recognition of phospholipid-binding protein complexes

Lupus ◽

10.1177/096120339800700207 ◽

1998 ◽

Vol 7 (2_suppl) ◽

pp. 29-31 ◽

Cited By ~ 15

Author(s):

J Rauch

Keyword(s):

Antiphospholipid Antibodies ◽

Lupus Anticoagulant ◽

Binding Proteins ◽

Protein Complexes ◽

Binding Protein ◽

Anticoagulant Activity ◽

Annexin V ◽

Antibody Activity ◽

Phospholipid Binding ◽

Glycoprotein I

Lupus anticoagulant antibodies form a heterogeneous group of antiphospholipid antibodies with rather poorly defined antigens. The role that phospholipid-binding proteins play in lupus anticoagulant antibody activity is a subject of current investigation. Several candidate proteins have been proposed, including β2-glycoprotein I (β2GPI), prothrombin, and annexin V. As β2GPI-dependent lupus anticoagulants will be reviewed elsewhere in this issue, this paper will focus on the involvement of prothrombin and annexin V in lupus anticoagulant activity. Evidence for a role for these proteins in the reactivity and induction of lupus anticoagulant antibodies will be discussed, as well as an apparent requirement for both phospholipid and phospholipid-binding protein. The data presented here suggest that some lupus anticoagulant antibodies recognize and may be induced by complexes of phospholipid and phospholipid-binding proteins, in particular, phospholipid and prothrombin or annexin V.

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Lupus anticoagulant activity of some antiphospholipid antibodies against phospholipid bound 2 glycoprotein I

Journal of Clinical Pathology ◽

10.1136/jcp.46.10.976-b ◽

1993 ◽

Vol 46 (10) ◽

pp. 976-976

Keyword(s):

Antiphospholipid Antibodies ◽

Lupus Anticoagulant ◽

Anticoagulant Activity ◽

Glycoprotein I

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dRVVT Is more Sensitive than KCT or TTI for Detecting Lupus Anticoagulant Activity of Anti-β2-glycoprotein I Autoantibodies

Thrombosis and Haemostasis ◽

10.1055/s-0037-1614453 ◽

1999 ◽

Vol 81 (02) ◽

pp. 256-258 ◽

Cited By ~ 53

Author(s):

A. Biasiolo ◽

P. Rampazzo ◽

T. Brocco ◽

V. Pengo

Keyword(s):

Lupus Anticoagulant ◽

Anticoagulant Activity ◽

Test System ◽

Clotting Time ◽

Lupus Anticoagulants ◽

Glycoprotein I ◽

Tissue Thromboplastin ◽

The Mean ◽

Kaolin Clotting Time ◽

Antibody Preparations

SummaryAnti-β2-glycoprotein I (β2-GPI) antibodies behave as classical Lupus Anticoagulants (LA), as they inhibit phospholipid-dependent coagulation reactions and their activity disappears in the presence of excess exogenous phospholipids (PLs). We have recently shown that a certain amount of PLs in the dilute Russell Viper Venom Time (dRVVT) test system is required to express LA activity of anti β2-GPI antibodies. We have now extended this observation to two other tests, i.e., Kaolin Clotting Time (KCT) in which PLs are not added, and Tissue Thromboplastin Inhibition test (TTI) in which PLs are extremely diluted. In fact, affinity-purified antibody preparations from 5 patients with antiphospholipid syndrome did not express or only weakly expressed anticoagulant activity in both tests; the mean ratios of coagulation times obtained with purified antibodies and that of control buffer were 1.11 and 1.0 for KCT and TTI, respectively. On the contrary, the mean ratios in dRVVT were 1.31 and 1.49 at a PLs dilution of 1:8 and 1:64, respectively. Therefore, the presence of LA activity due to autoantibodies to β2-GPI is characterized by a positive dRVVT and negative or only weakly positive KCT and TTI.

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Hemostasis system and immunomorphologic state of placenta under presence of antiphospholipid antibodies in plasma with consideration of their class and pregnancy outcome

Journal of obstetrics and women s diseases ◽

10.17816/jowd86971 ◽

2004 ◽

Vol 53 (1) ◽

pp. 22-26

Author(s):

N. G. Kosheleva ◽

L. В. Zubzhitskaia ◽

О. N. Arzhanova ◽

О. V. Tyshkevich ◽

Y. Gromyko ◽

...

Keyword(s):

Pregnancy Outcome ◽

Antiphospholipid Antibodies ◽

Lupus Anticoagulant ◽

Recurrent Miscarriage ◽

Anticardiolipin Antibodies ◽

Research Groups ◽

Hemostasis System ◽

Autoimmune Antibodies ◽

Glycoprotein I ◽

Tissue Damages

The present study was undertaken to investigate hemostasis system of 197 women with recurrent miscarriage: Analysis placentas by immunomorphology are studied of 41 women and of 52 women with autoimmune antibodies to 2-glycoprotein-I (2-GPI) in placenta. There was exposed hyperactivation platelets blood of all women with antiphospholipid antibodies irrespective of groups with significantly was increased at the beginning of pregnancy and progressed with growing gestation. As result of investigation it is determined certain connection between outcome of pregnancy and activation degree platelets blood in vasculars. Was found absence influence anticardiolipin antibodies (aCL) on plasmocoagulative link hemostasis. The circulation of lupus anticoagulant (LA) was accompanied indication of hypercoagulation. In all research groups was determined significant oppression of fibrinolisis. Analysis placentas by immunomorphology was determined significantly tissue damages with LA and 2-GPI-dependent aCL.

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