Lupus anticoagulant antibodies: Recognition of phospholipid-binding protein complexes

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 autoimmune antiphospholipid antibodies is dependent upon beta 2-glycoprotein I.

Journal of Clinical Investigation ◽

10.1172/jci115926 ◽

1992 ◽

Vol 90 (3) ◽

pp. 1100-1104 ◽

Cited By ~ 148

Author(s):

R A Roubey ◽

C W Pratt ◽

J P Buyon ◽

J B Winfield

Keyword(s):

Antiphospholipid Antibodies ◽

Lupus Anticoagulant ◽

Anticoagulant Activity ◽

Glycoprotein I ◽

Beta 2

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Correlation between antiphospholipid antibodies that recognize domain I of β2-glycoprotein I and a reduction in the anticoagulant activity of annexin A5

Blood ◽

10.1182/blood-2006-07-030148 ◽

2006 ◽

Vol 109 (4) ◽

pp. 1490-1494 ◽

Cited By ~ 83

Author(s):

Bas de Laat ◽

Xiao-Xuan Wu ◽

Menno van Lummel ◽

Ronald H. W. M. Derksen ◽

Philip G. de Groot ◽

...

Keyword(s):

Antiphospholipid Antibodies ◽

Lupus Anticoagulant ◽

Anticoagulant Activity ◽

Annexin A5 ◽

Anionic Phospholipids ◽

Glycoprotein I ◽

Group A ◽

Group B ◽

Domain I ◽

American Authors

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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Inhibition of Lupus Anticoagulant Activity by Hexagonal Phase Phosphatidylethanolamine in the Presence of Prothrombin

Thrombosis and Haemostasis ◽

10.1055/s-0037-1615392 ◽

1998 ◽

Vol 80 (12) ◽

pp. 936-941 ◽

Cited By ~ 22

Author(s):

Marion Tannenbaum ◽

Carolyn Neville ◽

Paul Fortin ◽

Joyce Rauch

Keyword(s):

Systemic Lupus Erythematosus ◽

Lupus Erythematosus ◽

Lupus Anticoagulant ◽

Plasma Proteins ◽

Anticoagulant Activity ◽

Hexagonal Phase ◽

Annexin V ◽

Systemic Lupus ◽

Glycoprotein I ◽

No Inhibition

SummaryWe have previously demonstrated that lupus anticoagulant antibodies from patients with systemic lupus erythematosus (SLE) specifically recognize hexagonal (II) phase phosphatidylethanolamine (PE), but not bilayer PE (Thromb Haemost 1989; 62: 892). In those studies, the involvement of proteins in this recognition was not evaluated. To address this issue, we have isolated IgG lupus anticoagulant antibodies from the plasma of SLE patients and evaluated the inhibition of lupus anticoagulant activity by hexagonal (II) phase PE in the presence and absence of purified plasma proteins. All six of the IgG lupus anticoagulant antibodies tested were inhibited by hexagonal (II) phase PE in the presence, but not the absence, of human prothrombin. In contrast, little or no inhibition was observed with prothrombin alone or with PE in combination with either β2-glycoprotein I or annexin V. These data indicate that, for certain lupus anticoagulant antibodies, inhibition by hexagonal (II) phase PE is dependent on prothrombin, suggesting that these antibodies recognize a complex of PE and prothrombin.

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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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Antibodies to β2-Glycoprotein I Inhibit Phospholipid Dependent Coagulation Reactions

Thrombosis and Haemostasis ◽

10.1055/s-0038-1649635 ◽

1993 ◽

Vol 70 (04) ◽

pp. 598-602 ◽

Cited By ~ 15

Author(s):

John T Brandt

Keyword(s):

Lupus Anticoagulant ◽

Protein Complexes ◽

Recent Observation ◽

Anticoagulant Activity ◽

Specific Interaction ◽

Clinical Manifestations ◽

Dependent Manner ◽

Prothrombinase Complex ◽

Glycoprotein I

SummaryLupus anticoagulants are antibodies that inhibit phospholipid dependent coagulation reactions in vitro. These antibodies are of clinical interest because of their association with a variety of clinical manifestations characterized by microvascular thrombosis. Although these antibodies were originally thought to be directed at negatively charged phospholipid, recent studies have suggested that they may be directed at phospholipid-protein complexes. The effect of antibodies directed against β2-glycoprotein I (β2-GP I, apolipoprotein H) on phospholipid-dependent coagulation reactions has been studied. Polyclonal and monoclonal antibodies to β2-GP I were found to inhibit thrombin generation in a dose dependent manner. Inhibition of thrombin formation was due to specific interaction with β2-GP I. There was no evidence that inhibition was due to crossreactivity with other proteins involved in the prothrombinase complex. These findings document that antibodies directed against β2-GP I can have anticoagulant activity analogous to lupus anticoagulant activity and are consistent with the recent observation of such activity in lupus anticoagulant patient samples.

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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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Antibodies against Phospholipids other than Cardiolipin: Potential Roles for Both Phospholipid and Protein

Lupus ◽

10.1177/096120339600500534 ◽

1996 ◽

Vol 5 (5) ◽

pp. 498-502 ◽

Cited By ~ 15

Author(s):

J Rauch ◽

AS Janoff

Keyword(s):

Cell Membrane ◽

Lupus Anticoagulant ◽

Binding Proteins ◽

Annexin V ◽

Phospholipid Binding ◽

Antibody Recognition ◽

Cardiolipin Antibodies ◽

Phospholipid Structure ◽

Outer Membrane Leaflet

Autoantibodies to phospholipids other than cardiolipin have received less attention, to date, than anti-cardiolipin antibodies. This review focuses on these antibodies and potential roles for both phospholipid and protein in their reactivity. We review data in the literature indicating that antibodies to phosphatidylethanolamine and some lupus anticoagulant antibodies recognize phospholipid-binding proteins in association with phospholipid. Kininogens appear to be involved in the binding of antibodies to phosphatidylethanolamine, while phosphatidylserine-binding proteins, such as prothrombin and annexin V, have been implicated in lupus anticoagulant antibody recognition. These proteins bind to phospholipids that normally reside in the inner monolayer of the cell membrane, suggesting that exposure of these lipids is necessary for protein binding and antibody recognition to occur. In contrast, other autoantibodies, in particular those reactive with erythrocytes, appear to be directed at phospholipids that normally occur in the outer membrane leaflet, such as phosphatidylcholine. In summary, there is clearly accumulating evidence that antibodies to phospholipids other than cardiolipin recognize epitopes on phospholipid-binding proteins. It is not clear whether recognition of these epitopes is due to an increase in antigen density or a change in the protein or phospholipid structure, but it is likely that both protein and phospholipid structure play an important role in the in vivo interactions of these antibodies.

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Antiphospholipid Antibody Syndrome

Archives of Pathology & Laboratory Medicine ◽

10.5858/2010-0325-rsr.1 ◽

2011 ◽

Vol 135 (9) ◽

pp. 1092-1096 ◽

Cited By ~ 22

Author(s):

Nikhil A Sangle ◽

Kristi J Smock

Keyword(s):

Antiphospholipid Antibodies ◽

Lupus Anticoagulant ◽

Protein Complexes ◽

Anticardiolipin Antibodies ◽

Clinical Aspects ◽

Antiphospholipid Antibody ◽

Antiphospholipid Antibody Syndrome ◽

Pregnancy Morbidity ◽

Glycoprotein I ◽

Laboratory Results

Antiphospholipid antibodies are directed against phospholipid-protein complexes and include lupus anticoagulant, anticardiolipin antibodies, and anti–beta-2 glycoprotein I antibodies. Antiphospholipid antibody syndrome is a common cause of acquired thrombophilia and is characterized by venous or arterial thromboembolism or pregnancy morbidity and the presence of antiphospholipid antibodies. Antibodies should be demonstrable on at least 2 occasions separated by 12 weeks. Heterogeneity of the autoantibodies and absence of gold standard assays makes interpretation of laboratory results a challenge for both laboratorians and clinicians. This review discusses the key laboratory and clinical aspects of antiphospholipid antibody syndrome. Particular focus is given to lupus anticoagulant detection, in view of recently updated laboratory guidelines.

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