Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P02749 (beta2-glycoprotein I)
 836 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Thrombosis in the antiphospholipid syndrome has been associated with acquired deficiency of the anticoagulant protein S. We sought evidence that beta2-glycoprotein I, a major target antigen for antiphospholipid antibodies, is involved in regulation of protein S activity. Incubation of purified protein S or plasma with beta2-glycoprotein I reversed functional modulation of protein S by its plasma inhibitor, the C4b-binding protein. In a plasma-free ELISA, beta2-glycoprotein I prevented the binding of protein S and C4b-binding protein when preincubated with immobilized protein S but not when similarly preincubated with C4b-binding protein. beta2-glycoprotein I in fluid phase interfered with precipitation of protein S by sepharose-bound C4b-binding protein. Effects of beta2-glycoprotein I on protein S function were inhibited by one of four monoclonal anti-beta2-glycoprotein 1 antibodies. These data suggest that beta2-glycoprotein I helps maintain adequate plasma levels of circulating free, active protein S. Antiphospholipid (anti-beta2-glycoprotein I) antibodies might cause sporadic thrombosis, at least in part, by impairing this novel regulatory mechanism.
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PMID:Enhancement of protein S anticoagulant function by beta2-glycoprotein I, a major target antigen of antiphospholipid antibodies: beta2-glycoprotein I interferes with binding of protein S to its plasma inhibitor, C4b-binding protein. 1036 49

The antigen specificity of anti-phospholipid antibodies in infectious mononucleosis (IM) was studied using ELISA for the detection of anti-beta2-glycoprotein I (beta2-GPI), anti-annexin V, anti-protein S and anti-prothrombin antibodies and TLC immunostaining for the detection of anti-phospholipid antibodies. This technique enabled us to look at antibodies reacting to 'pure' phospholipid antigens in the absence of protein contamination. Sera from 46 patients with IM, 18 with systemic lupus erythematosus (SLE), 21 with primary anti-phospholipid antibody syndrome (PAPS), 50 with Helicobacter pylori infection and 30 healthy blood donors were tested. This study highlights anti-phospholipid antibodies in patients with IM as specific 'pure' anti-cardiolipin antibodies, while in PAPS and SLE patients anti-phosphatidylserine and anti-phosphatidylethanolamine antibodies were also found. This investigation also shows that the anti-cardiolipin antibodies found in IM can be present with anti-cofactor protein antibodies. The higher prevalence of anti-cofactor antibodies found in IM sera than in Helicobacter pylori sera may be due to the immunostimulatory effect and/or the polyclonal activation often observed in course of Epstein-Barr virus infection. However, anti-beta2-GPI and, to a lesser extent, anti-prothrombin antibodies occur with a significantly lower prevalence in IM than in PAPS patients. This finding suggests that these antibodies should be regarded as the expression of the broad autoimmune syndrome involving the phospholipid-binding plasma proteins.
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PMID:Specificity of anti-phospholipid antibodies in infectious mononucleosis: a role for anti-cofactor protein antibodies. 1079 80

Anti-beta2-glycoprotein I antibodies are considered as a specific marker for the antiphospholipid syndrome. In contrast to lupus circulating anticoagulant and anticardiolipin (aCL) antibodies, they are usually not found at significant levels in infections. We report a case of pulmonary embolism in an adult with varicella. Transient significant levels of aCL antibodies and of IgM anti-beta2-GPI antibodies were observed. No other prothrombotic factor, including free protein S antigen deficiency, was found. The direct pathogenic role of these transient antibodies on the thrombotic event may then be suspected. They are probably associated with VZV acute infection and are absent two months after varicella.
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PMID:Pulmonary embolism and transitory anti-beta2-GPI antibodies in an adult with chicken pox. 1103 26

Congenital and acquired thrombophilia are associated with an increased risk of pregnancy-associated venous thrombosis and fetal loss. Two hundred eighty-nine patients with a history of recurrent spontaneous abortion were subjected to screening examinations for the etiology of these abortions. Endocrine abnormality (28.0%), uterine abnormality (10.4%), autoimmune diseases (1.4%), antiphospholipid antibody syndrome (4.5%), and balanced type chromosome translocation (4.2%) were found as underlying causes of recurrent abortions, and the remaining 55.0% of the 289 patients were classified as having an unexplained etiology. Congenital thrombophilia such as protein C (PC) deficiency, protein S (PS) deficiency, antithrombin deficiency, and factor V Leiden mutation was not frequently detected; only one patient had PS deficiency. A reduced factor XII activity was found at a frequency of 4.2%. The frequency of methylene tetrahydrofolate reductase gene C677T mutation in recurrent aborters (0.38) was the same as that found in a fertile control group. Although the prevalence of anti-beta2-glycoprotein I antibody (abeta2-GPI) syndrome was very low (1.7%), patients with a high titer of immunoglobulin G (IgG) class abeta2-GPI, despite anticoagulation therapy, experienced severe fetomaternal complications in subsequent pregnancies. The rate (13.8%) of positive tests for serum IgA class abeta2-GPI in patients with unexplained etiology was higher than that in the controls (0%) (P < .05). We conclude that congenital thrombophilia is rare in Japanese patients who had experienced consecutive spontaneous abortions.
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PMID:Recurrent pregnancy loss: etiology of thrombophilia. 1137 65

The presence of lupus anticoagulants (LAC) in plasma is a major risk factor for thrombosis. An attractive hypothesis to explain a LAC-mediated thrombotic tendency is that LAC interfere with activation of protein C, a natural antithrombotic in plasma. We investigated the relationship between LAC and protein C activation in vivo. We selected 20 patients with systemic lupus erythematosus (SLE) with LAC (and not using oral anticoagulants), 36 patients with SLE without LAC and 25 healthy volunteers. In these, we measured circulating levels of activated protein C (APC), prothrombin (FII), free protein S, C4BP, protein C, and antibodies to protein C, protein S, FII and beta2-glycoprotein I (beta2GPI). In SLE patients (n = 56), mean levels of APC, FII and free protein S were significantly (P < 0.001) lower than those in healthy volunteers (respectively 13%, 17% and 14%). Mean protein C levels and C4BP levels were similar for SLE patients and healthy volunteers. In contrast to the above hypothesis, the decreased levels of APC could not be attributed to the presence of LAC. Levels of APC were correlated with both FII levels and protein C levels. Decreased levels of APC, FII, protein C and free protein S were related to the presence of anti-FII antibodies. None of the patients had antibodies against protein C or protein S. In conclusion, although the mean levels of APC, FII and free protein S were significantly decreased in SLE patients, no correlation with LAC was found. However, anti-FII antibodies were related to decreased levels of APC, FII, protein C, free protein S and C4BP. As FII levels, and not protein C levels, were decreased in SLE patients and correlated with APC levels, we conclude that the decreased FII levels are responsible for the low levels of APC.
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PMID:Low levels of activated protein C in patients with systemic lupus erythematosus do not relate to lupus anticoagulants but to low levels of factor II. 1202 41

The antiphospholipid syndrome (APS) is a thrombotic disorder leading to spontaneous abortions, venous thromboses, myocardial infarctions and strokes. Although the syndrome is associated with characteristic autoantibodies, these tests have poor predictive value for thrombosis. The aim of the study was to determine whether the combined presence of two types of antiphospholipid antibodies can be associated with a high-risk subset of thrombosis-prone patients. One hundred and thirty-four sera from a lupus clinic were tested for antibodies to beta2-glycoprotein I (beta2GPI), protein S and prothrombin. In a group of 29 patients for whom plasma was available, free (functional) protein S levels were also measured. Autoantibodies to beta2GPI and protein S are associated with each other. Dual reactivity to beta2GPI and protein S correlates with increased history of thrombotic events (69% of doubly reactive patients) when compared to either type of autoantibody alone (37% of patients with only anti-beta2GPI and 38% with only anti-protein S, P=0.04 and P=0.01, respectively) or neither reactivity (37%). Among 29 patients tested for free (functional, anticoagulant) protein S levels, the lowest levels were found in patients with antibodies to beta2GPI and/or protein S, and all four patients with a history of thrombosis had below-normal free protein S levels. These associations were not found with antiprothrombin antibodies. In conclusion dual autoantibodies to beta2GPI and protein S are associated with increased history of thrombosis in the antiphospholipid syndrome.
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PMID:Dual antibody reactivity to beta2-glycoprotein I and protein S: increased association with thrombotic events in the antiphospholipid syndrome. 1204 84

Anti-phospholipid (aPL) antibodies (Abs) are well known to be associated with thromboembolic events in patients with systemic lupus erythematosus (SLE). However, the clinical relevance of a PL Abs in patients without SLE (non-SLE) who have venous thromboembolism remains unclear. We evaluated 143 non-SLE patients with a first episode of clinically suspected deep vein thrombosis (DVT) by using objective tests for diagnosing DVT and laboratory tests including the activated protein C resistance (APC-R) test, the factor V Leiden test, and various aPL Abs. The prevalence of acquired APC-R, in which case there was no factor V Leiden mutation, was significantly higher in patients with DVT (15/58 cases, 25.9%, p < 0.0001) than in those without DVT (3/80 cases, 3.7%), and confirmed that acquired APC-R was a strong risk factor for DVT (odds ratio [OR], 8.95; 95% confidence intervals [CI], 2.45-32.7; p < 0.001). Multivariate logistic analysis revealed that the presence of LA, aCL, anti-beta2-glycoprotein I, anti-prothrombin and anti-protein C Abs was not reliable as a risk factor for DVT in non-SLE patients, and that the presence of anti-protein S Abs was the most significant risk factor for DVT (OR, 5.88; 95% CI, 1.96-17.7; p < 0.002). Furthermore, the presence of anti-protein S Abs was strongly associated with acquired APC-R (OR, 57.8; 95% CI, 8.53-391; p < 0.0001). These results suggest that acquired APC-R may reflect functional interference by anti-protein S Abs of the protein C pathway, which action may represent an important mechanism for the development DVT in non-SLE patients.
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PMID:Acquired activated protein C resistance associated with anti-protein S antibody as a strong risk factor for DVT in non-SLE patients. 1242 83

A number of previous studies have shown that anti-phospholipid(aPL) antibodies(Abs) do not bind primarily to the negatively-charged phospholipid itself but rather to complexes of the phospholipid and plasma proteins, and that the most common antigenic targets are beta 2-glycoprotein I recognized by anticardiolipin Abs and prothrombin recognized by most lupus anticoagulants. However, resent studies suggest that other phospholipid-binding proteins, particularly protein C, protein S, and annexin V, may be important targets as well. To clarify the association between the various types of aPL Abs and thrombotic complications in patients with systemic lupus erythematosus(SLE), we examined the prevalence of aPL Abs to various phospholipid-binding proteins(beta 2-glycoprotein I, prothrombin, protein C, protein S, and annexin V). We found that anti-beta 2-glycoprotein I Abs may be associated primarily with cerebral infarction and femoral artery thrombosis, and that anti-protein S Abs may be associated primarily with venous thromboembolism and renal thrombotic microangiopathy. Furthermore, anti-annexin V Abs might be closely related to fetal loss. These findings suggest that thrombotic complications in SLE depend on the antigenic specificities of aPL Abs, alone or in combination.
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PMID:[Association between anti-phospholipid antibodies and thrombotic complications in systemic lupus erythematosus]. 1270 97

Thrombophilia can be defined as an increased tendency to thrombosis. There are several defined risk factors for thrombosis, and these are generally separated into acquired and congenital factors. Congenital risk factors include deficiencies or defects in natural anticoagulants, such as antithrombin, protein C and protein S, and genetic polymorphisms such as prothrombin G20210A and the cleavage-resistant factor mutation, factor V Leiden, which leads to a condition known as activated protein C resistance. Acquired risk factors include antiphospholipid antibodies, detected as lupus anticoagulants, and/or anticardiolipin or anti-beta2-glycoprotein I antibodies. Elevated homocysteine, immobility, increasing age, surgery, cancer, poor nutrition, pregnancy, high levels of clotting factors, and use of oral contraceptives and hormone replacement therapy comprise other risk factors. Each of these constitutes an element of increased risk, which is compounded when concomitant. There is ongoing debate regarding relative and compound risks, the value of laboratory screening, whom to screen for with these markers, and the form and duration of clinical management. This report briefly explores, from a scientist's perspective, some important issues that are sometimes overlooked.
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PMID:Diagnostic issues in thrombophilia: a laboratory scientist's view. 1570 70

To assess the clinical significance of lupus anticoagulants (LAs) and antiphospholipid antibodies (aPLs) toward thrombosis and abortions, we measured them in 112 patients whose samples were available at enrollment in the warfarin in the antiphospholipid syndrome (WAPS) study. Enzyme-linked immunosorbent assay (ELISA) and coagulation test values in the highest and lowest tertiles were compared. When considered separately, IgG antibodies to beta2-glycoprotein I (abeta2GPI) and prothrombin (aPT) were associated with anamnestic arterial and venous thrombosis, respectively, and those to annexin AV (aAnAV) with abortions. IgM antibodies to protein S and the lupus ratio of the dilute prothrombin time were associated with prospective thrombosis. No other association for IgM antibodies was seen. LA-positive patients who carried abeta2GPI antibodies were at risk of anamnestic arterial and total thrombosis and aPT antibodies to that of anamnestic venous and total thrombosis. LA-positive patients who carried IgG abeta2GPI and aAnAV antibodies were at risk for both anamnestic abortion and prospective thrombosis. Overall, these data support the inclusion of abeta2GPI antibodies in and suggest the removal of anticardiolipin antibodies from the laboratory criteria of the antiphospholipid syndrome. They also suggest that the measurement of aPT and aAnAV antibodies is useful in some selected situations and that there is little role for IgM antibody detection.
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PMID:Clinical significance of different antiphospholipid antibodies in the WAPS (warfarin in the antiphospholipid syndrome) study. 1744 49


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