anti-beta2GPI IgG Research Articles

Both IgG and IgM anti-beta2 glycoprotein I antibodies assays are clinically useful to the antiphospholipid syndrome diagnosis

Objectives:The aim of our study was to evaluate the clinical values of anti-beta2 glycoprotein I antibodies (anti-beta2GPI) IgG and IgM comparing with lupus anticoagulant (LA), anticardiolipin antibodies (aCL) in the two clinical groups of antiphospholipid syndrome (APS), vascular thrombosis (VT) and pregnancy morbidity (PM).Methods:Eighty patients who fulfilled the APS clinical criteria, VT n = 34; PM n = 40, both VT and PM n = 6 were included. LA, aCL and three anti-beta2GPI ELISA kits were tested.Results:Sensitivities of LA, aCL and anti-beta2GPI assays were found respectively 62, 26 and 41% in VT, and 28, 28 and 30% in PM. The sensitivity for the APS diagnosis could reach to 63% using triple tests. The presence of LA (P<0·01, OR = 4·3) or anti-beta2GPI IgG alone (P<0·05, OR = 8·4) was significantly associated with VT. IgM isotype was found more frequent in PM (92%) than in VT (57%) among all positive anti-beta2GPI cases.Conclusion:Both IgG and IgM anti-beta2GPI assays were useful when clinical features of APS presented, even its standardization is ongoing. A decreased by half sensitivity of LA in PM compared with that in VT underlines the importance of adding anti-beta2GPI in PM of APS, especially IgM isotype although recent review questioned its significance.

Drug-induced lupus: simvastatin or amiodarone? A case report in elderly

Reports of systemic lupus erythematosus (SLE) seen during treatment with amiodarone are rare in the literature. SLE or immunological abnormalities induced by treatment with statins are more frequent. In this issue we report a case of a 81-year-old male who, after a 2-year therapy with amiodarone, developed a clinical and serologic picture of drug-induced SLE (DILE). He was admitted for congestive heart failure in mechanical aortic valve prosthesis, permanent atrial fibrillation (anticoagulation with warfarin), hypercholesterolaemia, and hypothyroidism. Amiodarone was started two years earlier for polymorphic ventricular tachycardia, statin and L-thyroxine the following year. At admission he presented pleuro-pericardical effusion detected by CT-scan (also indicative of interstitial lung involvement) and echocardiography. Serological main indicative findings were: elevation of inflammatory markers, ANA (Anti-Nuclear Antibodies) titers = 1:320 (indirect immune-fluorescence – IIF – assay on HEp-2), homogeneous/fine speckled pattern, anti-dsDNA titers = 1:80 (IIF on Crithidia luciliae), negative ENA (Extractable Nuclear Antigens) and antibodies anti-citrulline, rheumatoid factor = 253 KU/l, normal C3-C4, negative HbsAg and anti-HCV, negative anticardiolipin antibodies IgG and IgM, negative anti-beta2GPI IgG and IgM. Amiodarone was discontinued and methylprednisolone was started, since the patient was severely ill. At discharge, after a month, the patient was better and pleuro-pericardical effusion was reduced. Readmitted few weeks later for bradyarithmia and worsening of dyspnoea, pericardial effusion was further reduced but he died for refractory congestive heart failure and pneumonia. Clinical picture (sierositis, neither skin nor kidney involvement), other typical side effects of amiodarone (hypothyroidism and lung interstitial pathology) and serological findings are suggestive of amiodarone-induced SLE.

Auto-anticorpos anti-β2-glicoproteína I e síndrome metabólica

FUNDAMENTO: A síndrome metabólica (SM) é uma entidade pró-aterogênica. Autoanticorpos tais como β2-glicoproteína I (β2-gpI) podem influenciar o aparecimento de ateromas. Estudos anteriores confirmaram uma associação entre anticorpos IgA anti-β2-gpI e isquemia cerebral, infarto do miocárdio, doença arterial periférica e doença da carótida. OBJETIVO: O objetivo desse estudo de caso-controle foi avaliar uma possível associação entre anticorpos anti-β2-gpI e anticardiolipina (aCL) com SM não-complicada. MÉTODOS: Pacientes com SM sem histórico de eventos vasculares e indivíduos-controle, consistindo em pacientes da Enfermaria de Ortopedia admitidos devido a doenças musculoesqueléticas foram incluídos no estudo. Idade, sexo, etnia, histórico de hipertensão, tabagismo, hipercolesterolemia e diabetes mellitus foram avaliados como fatores de risco em ambos os grupos. Anticorpos IgG, IgM, e IgA anti-β2-gpI e aCL foram detectados através de imunoensaios enzimáticos. RESULTADOS: Um total de 68 pacientes com SM e 82 controles foram estudados. Os pacientes com SM tinham média de idade superior à dos controles (P = 0,001), enquanto homens (P = 0,003; OR 0,31; IC95%: 0,15-0,16) e etnia caucasiana (P = 0,004; OR 0,25; IC95%:0,10-0,60) eram predominantes nos controles. Histórico de hipertensão, hipercolesterolemia e diabetes mellitus foi mais prevalente nos pacientes com SM do que nos controles (P < 0.05). A frequência de anticorpos aCL (todos os isotipos) e do IgG e IgM anti-β2 gpI não diferiu de forma significante nos pacientes com SM e controles. Anticorpos IgA anti-β2-gpI foram significantemente mais frequentes nos pacientes com SM (42,2%) do que nos controles (10,9%) (P < 0,001). O OR ajustado para anticorpos IgA anti-β2-gpI foi 3,60 (IC95%: 1,55-8,37; P = 0,003). CONCLUSÃO: O presente estudo mostra que níveis elevados de autoanticorpos IgA para β2-gpI podem estar independentemente associados com SM.

Anti-β2 glycoprotein-I antibody increases the risk of pregnancy-induced hypertension: a case-controlled study

The aim of this study was to evaluate whether anti-beta2 glycoprotein-I antibody (anti-beta2GPI) of the IgG or IgM classes is associated with the development of pregnancy-induced hypertension (PIH) or preeclampsia in the Japanese population. In a case-controlled cohort study, peripheral blood was obtained at 8-14 weeks of gestation from a consecutive series of 1155 women. The case group comprised 36 patients who later developed PIH during the pregnancy. Of the 36 PIH patients, 13 had severe PIH, 18 had preeclampsia and 11 had severe preeclampsia. One hundred and eleven age- and parity-matched women whose pregnancies ended in normal delivery without obstetric complications were selected as controls. We found that a titer of anti-beta2GPI IgG>or=1.0 U/ml was a risk factor for severe PIH (P=0.023, OR 5.7 95%CI 1.4-22.8). In addition, titers of anti-beta2GPI IgM>or=1.2 U/ml was found to be a risk factor for PIH (P=0.001, OR 8.8 95%CI 1.6-47.5). In women positive for anti-beta2GPI but negative for lupus anticoagulant, anti-cardiolipin, phosphatidylserine-dependent anti-prothrombin, or kininogen-dependent anti-phosphatidylethanolamine antibodies, the presence of anti-beta2GPI was not a significant risk factor for development of PIH or preeclampsia. In conclusion, the presence of anti-beta2GPI antibody represents a risk factor for developing PIH and severe PIH. This finding supports the utility of anti-beta2GPI determination as one of the laboratory criteria for anti-phospholipid syndrome classification. The usefulness of anti-beta2GPI measurement among women without other anti-phospholipid antibodies requires further study.

The association between circulating antibodies against domain I of beta2-glycoprotein I and thrombosis: an international multicenter study.

Diagnosis of the antiphospholipid syndrome (APS) is difficult as a result of limited specificity of existing assays for detecting clinically relevant antiphospholipid antibodies. Anti-beta2-glycoprotein I (beta 2GPI) antibodies play a central role in the disease process of APS. We have investigated the relation between antiphospholipid antibodies with specificity for domain I of beta 2GPI and thrombosis/pregnancy morbidity in an international multicenter study. Four hundred and seventy-seven patients derived from nine different centres met the inclusion criterion of having anti-beta 2GPI antibodies in their plasma/serum. Clinical data and results of tests for lupus anticoagulant, anti-cardiolipin antibodies and anti-beta 2GPI antibodies were established at the different centres of inclusion. After being re-tested for the presence of IgG and/or IgM anti-beta 2GPI antibodies, the samples were tested for the presence of IgG-directed against domain I of beta 2GPI and results were correlated with the thrombotic and obstetric history. Re-testing for the presence of anti-beta 2GPI antibodies resulted in inclusion of 442/477 patients. IgG class anti-domain I antibodies were present in plasma of 243/442 patients (55%). 201/243 (83%) had a history of thrombosis. This resulted in an odds ratio of 3.5 (2.3-5.4, 95% confidence interval) for thrombosis. Anti-domain I IgG antibodies were also significantly correlated with obstetric complications [odds ratio: 2.4 (1.4-4.3, 95% confidence interval)]. In this multicenter study, the detection of IgG antibodies that are directed against domain I of beta 2GPI proved to be more strongly associated with thrombosis and obstetric complications than those detected using the standard anti-beta 2GPI antibody assay.

Prospective Study on Autoantibodies Against Apolipoprotein H (β2GPI) in Several Clinical Parameters From Patients With Terminal Renal Failure and Functioning Renal Transplants

Renal transplantation is the best therapeutic option for patients with end-stage renal disease. However, long-term results have not been very encouraging because of patient deaths due to cardiovascular disease and chronic transplant nephropathy (CTN), which includes vascular damage similar to arteriosclerosis injury. Several autoantibodies have been related to vasculopathy in the transplant such as anti-beta2GPI IgA, IgG, and IgM autoantibodies. We analyzed the levels of these autoantibodies among a cohort of 176 transplant recipients and a control group of 80 healthy subjects using enzyme-linked immunosorbent assay (ELISA). We collected data concerning the cardiovascular status of the patients, such as age, sex, diabetes mellitus, biopsy-confirmed CTN, schemic cardiopathy, cholesterol, triglycerides, and renal status by Modification of Diet in Renal Disease (MDRD) clearance and proteinuria. We also selected other characteristics, including hepatitis C virus infection and systolic/diastolic arterial pressures. The proportion of patients with high levels of IgG and IgM anti-beta2GPI autoantibodies did not differ from that observed in the control group, whereas the difference became significant in the case of anti-beta2GPI IgA autoantibodies (19.88% vs 1%). These results for the presence of anti-beta2GPI IgA autoantibodies were related to clinical data through a multivariate analysis, where the only parameter influenced by the presence of these autoantibodies seemed to be proteinuria, which in most cases was due to CTN.

Antiphospholipid Antibodies with LAC Activity That Bind beta2-Glycoprotein I Cause Increased Resistance Against Activated Protein C.

Background: The antiphospholipid syndrome is characterized by the occurrence of vascular thrombosis combined with the presence of antiphospholipid antibodies (aPL) in plasma of patients. Recently it was published that aPL with lupus anticoagulant activity (LAC), caused by anti-beta2-glycoprotein I (beta2GPI) antibodies, highly correlate with a history of thrombosis. aPL-related resistance against activated protein C (APC) is one of the proposed mechanism responsible for thrombosis. We investigated a possible correlation between a beta2GPI-dependent LAC and increased APC-resistance in a population of 22 plasma samples with LAC activity.Methods: Twenty-two LAC-positive plasma samples were tested for beta2GPI-dependence (titration of cardiolipin into an APTT-based assay), increased APC-resistance, anti-beta2GPI IgG/IgM antibodies, anti-prothrombin IgG/IgM antibodies and anti-protein C IgG/IgM antibodies. In addition, a monoclonal anti-beta2GPI antibody and patient-purified IgG (both with LAC activity) were diluted in plasma with/without protein C and tested for occurrence of a beta2GPI-dependent LAC (normalization of clotting time by the addition of cardiolipin). To study aPL-induced APC-resistance in more detail, surface plasmon resonance analysis was used to investigate binding between APC and beta2GPI in the presence/absence of a mouse-derived monoclonal anti-beta2GPI antibody.Results: Eleven plasma samples that displayed a beta2GPI-dependent LAC also showed increased APC resistance. In contrast, only 1 of the 11 plasma samples with a beta2GPI-independent LAC displayed increased APC-resistance. None of the other serological parameters (antibodies against beta2-glycoprotein I, prothrombin or protein C) displayed the same association with increased APC resistance as a beta2-glycoprotein I dependent LAC. Furthermore, we found a linear correlation between the potency of a beta2GPI-dependent LAC and the level of APC-resistance. When a monoclonal anti-beta2GPI antibody and a patient-purified IgG were tested for a beta2GPI-dependent LAC, both antibodies did not display a beta2GPI-dependent LAC when diluted in protein C deficient plasma. In literature it has been proposed that direct binding of beta2GPI to APC results in a decreased activity of APC. By using surface plasmon resonance analysis, we found that beta2GPI displayed a higher affinity for coated APC in the presence of the monoclonal anti-beta2GPI antibody (4 nM) compared to beta2GPI alone (400 nM).Conclusion: The results of this study indicate that by adding cardiolipin into an APTT-based clotting assay, one can detect beta2GPI-dependent LAC based on increased resistance against APC. Increased resistance against activated protein C might result from direct binding of beta2GPI to activated protein C. In conclusion, our observations indicate a direct correlation between a major clinical symptom of APS (thrombosis), a diagnostic assay (beta2GPI-dependent LAC) and a potential mechanism responsible for thrombosis in the antiphospholipid syndrome (increased APC-resistance).

Anti-beta 2 glycoprotein I antibodies and the risk of myocardial infarction in young premenopausal women.

Contrasting data have been reported on the association between the presence of anti-phospholipid antibodies (aPL) and arterial thrombotic events, particularly those in coronary arteries. This discrepancy is perhaps related to the confounding effect of traditional risk factors. Among them, coronary atherosclerosis appears to be the most important in studies conducted in middle-aged and elderly patients. To minimize such confounding effects, a multicenter case-control study on the association between aPL and myocardial infarction (MI) was carried out in a rare cohort of young premenopausal women. We evaluated 172 cases hospitalized for a first MI before the age of 45 years and 172 controls individually matched with cases for age, sex and geographical origin. Clinical and laboratory data were collected and levels of anti-cardiolipin (aCL), anti-beta2 glycoprotein I (anti-beta2GPI) and anti-nuclear antibodies (ANA) were measured. A significant association between MI and IgG/IgM anti-beta2GPI antibodies was observed; the results were confirmed after adjusting for smoking and hypertension (anti-beta2GPI IgG OR = 2.47, 95% CI 1.81-3.38; anti-beta2GPI IgM 4th quartile OR 3.68, 95% CI 1.69-8.02). The association between anti-beta2GPI antibodies and MI was detected in both subgroups with and without coronary artery stenosis. Whereas the association of aCL IgG with MI was modest, ANA showed no significant association with MI. No aPL were found in unselected patients (mainly males) who recently developed acute MI. Anti-beta2GPI antibodies are a significant risk factor for MI in young premenopausal women independently of other risk factors, including the degree of coronary artery stenosis.

Antibodies to β2-glycoprotein I and annexin V in women with early and late idiopathic recurrent spontaneous abortions

Anti-phospholipid antibodies (APA) are heterogeneous group of autoantibodies that target phospholipid or phospholipid-binding proteins. APAs were previously shown to induce several thrombotic states, including idiopathic recurrent spontaneous abortion (RSA). Unlike the contribution of the classical lupus anticoagulant (LAC) and anticardiolipin antibodies (ACA), the contribution of anti-beta2 glycoprotein 1 (beta2GPI) and anti-annexin V antibodies to RSA risk remain poorly understood. We assessed anti-beta2GPI and anti-annexin V IgM and IgG antibodies as RSA risk factors for RSA in 172 Tunisian women with >3 consecutive idiopathic pregnancy losses, together with 173 matched control women. The prevalence of anti-beta2GPI IgG (P=0.41, OR=1.64) and IgM (P=0.50, OR=1.70) were comparable between cases and controls. Higher anti-annexin V IgG (P=0.02, OR=5.28), but not IgM (P=0.25, OR=1.78), levels were seen in cases. Regression analysis showed that anti-beta2GPI IgM (OR=8.90; 95% CI=1.23-64.63) was associated with early RSA, while anti-annexin V IgG (OR=9.35, 95% CI=1.44-60.86) was associated with late RSA. For combined early + late RSA, the only variable selected was BMI (OR=0.93; 95% CI=0.87-0.99), and neither anti-annexin V nor anti-beta2GPI IgM and IgG were associated with early + late RSA. Anti-annexin V and anti-beta2GPI appear to be independent risk markers of RSA.

Frequency of antiphospholipid antibodies in patients with infectious diseases using three different ELISA methods

OBJECTIVE: The standard enzyme-linked immunosorbent assay (ELISA) for anticardiolipin (aCL) antibodies is the most important test for the diagnosis of antiphospholipid syndrome (APS). However, the test is also positive in some infectious diseases and other non-related syndromes. It has been suggested that the detection of antibodies to a mixture of phospholipids or to beta2-glycoprotein I (beta2-GP I) has higher specificity for APS than the standard aCL ELISA. The aim of the present work is to compare the diagnostic specificity of three different antiphospholipid (aPL) assays in patients with infectious diseases. METHODS: Antiphospholipid antibodies were searched by three ELISA techniques, namely standard aCL, APhL® ELISA kit and anti-beta2-GP I, in sera of patients with infectious diseases, including syphilis (69), leptospirosis (33) and visceral leishmaniasis (30). RESULTS: The frequency of positivity of IgG aPL in patients with syphilis, leptospirosis and Kala-azar was 13/69 (19%), 9/33 (27%) and 2/30 (6%), respectively, using standard ELISA, versus only 1/69 (1.4%), 0/33 (0%) and 0/30 (0%) positivity by the APhL® ELISA kit. The positivity of the isotype IgM aPL was 10/69 (14%), 4/33 (12%) and 1/30 (3%), respectively, by the standard ELISA, and 1/69 (1.4%), 0/33 (0%) and 0/30 (0%) by the APhL® ELISA kit. The presence of significant levels of IgG anti-beta2GPI was observed in 14/69 cases of syphilis (20%), 6/33 cases of leptospirosis (18%) and 16/30 cases of Kala-azar (53%). The APhL® ELISA kit had superior performance showing the highest specificity: 97% (95% CI: 92%-99%) for IgG compared to 81% (95% CI: 74%-87%) for standard ELISA and 72% (95% CI: 64%-79%) for anti-beta2 GPI assay. CONCLUSIONS: The APhL® ELISA kit proved to be significantly more specific than the aCL standard ELISA and the anti-beta2GPI ELISA, and it should be used to help in the diagnosis and confirmation of APS.

A prospective study of antibodies to β2‐glycoprotein I and prothrombin, and risk of thrombosis

Antiphospholipid syndrome (APS) is a clinical autoimmune disorder characterized by thrombosis/pregnancy morbidity associated with the persistence of lupus anticoagulant (LA) and/or anticardiolipin (aCL) antibodies. We assessed the contribution of antibodies to beta2-glycoprotein I (anti-beta2GPI) and prothrombin (anti-PT) to the thrombotic risk in a cohort of 194 consecutive patients with persistent LA and/or aCL. Median follow-up was 45 months. A total of 39 patients (20.1%) had one documented episode of thrombosis during follow-up. Eleven of these patients had no previous thrombosis before enrollment in the study and 28 had recurrences of thrombosis. There were 21 venous and 18 arterial thrombotic events and the overall incidence of thrombosis was 5.6% per patient-year. After multivariate analysis, the male sex (P = 0.025), a previous thrombosis (P < 0.01), the presence of anti-beta2GPI (P = 0.001), and the presence of anti-PT (P = 0.03) remained as independent risk factors for recurrent thrombosis. Only IgG anti-beta2GPI and anti-PT were associated with an increased risk of thrombosis (P < 0.01 and P = 0.005). Patients testing positive for anti-beta2GPI had a higher rate of thrombosis than did antiphospholipid patients without anti-beta2GPI (8.0% vs. 3.1% per patient-year). Similarly, a higher rate of thrombosis was found in patients with positive anti-PT compared with patients without anti-PT (8.6% vs. 3.5% per patient-year). Considering only the group of 142 LA positive patients, the highest incidence of thrombosis was found in LA patients positive for both anti-beta2GPI and anti-PT (8.4% per patient-year). In conclusion, the presence of IgG anti-beta2GPI and anti-PT in patients with LA and/or aCL and mainly in those with LA predicts a higher risk of thromboembolic events.

Intravenous immunoglobulin treatment of four patients with juvenile polyarticular arthritis associated with persistent parvovirus B19 infection and antiphospholipid antibodies

Children with rheumatic oligoarthritis and polyarthritis frequently establish persistent parvovirus B19 infections that may be associated with the production of antiphospholipid antibodies (anti-PL IgG). In this study we analysed the influence of high-dose intravenous immunoglobulin (IVIG) therapy on virus load, on the level of anti-PL IgG and its potential capacity to improve the patients' clinical status. Four juvenile patients with long-lasting polyarticular rheumatic diseases and persistent parvovirus B19 infection, associated in three cases with the presence of antibodies against β2-glycoprotein I (anti-β2GPI IgG), were treated with two cycles of IVIG on five successive days (0.4 g/kg per day). Clinical parameters including scores of disease activity, virus load and anti-PL IgG levels were determined before, during and after treatment. Two patients showed a complete remission that has lasted 15 months. During that period they showed neither clinical nor laboratory signs of inflammation. Viral DNA was not detectable in serum, and a decrease in anti-β2GPI IgG was observed. As assessed by the Childhood Health Assessment Questionnaire and the Health-related Quality of Life Questionnaire for Children, both patients were no longer restricted in their activities of daily living and no impact on the health-related quality of life was observed. In one patient the therapy failed: there was no improvement of symptoms and no decrease in virus load or inflammatory parameters. In the fourth patient, clinical and laboratory parameters did not improve despite a decrease in both viral load and anti-PL IgG. Our results show that the use of IVIG to treat parvovirus B19-triggered polyarticular rheumatic disease of childhood might offer an opportunity to improve this disabling condition.

Immunization of naive BALB/c mice with human beta2-glycoprotein I breaks tolerance to the murine molecule.

Immunization of naive mice with beta2-glycoprotein I (beta2GPI) leads to the generation of pathogenic anticardiolipin antibodies associated with clinical manifestations of the antiphospholipid syndrome (APS). The aim of this study was to determine whether immunization of naive mice with human beta2GPI, which shares homology with mouse beta2GPI molecules, breaks tolerance to murine beta2GPI and leads to the generation of anti-mouse beta2GPI. Twenty-four female BALB/c mice were immunized in the footpads with 10 microg of human beta2GPI. Twelve age- and sex-matched BALB/c mice were immunized in the same manner with Freund's complete adjuvant and served as controls. The reactivity of whole sera, polyclonal IgG, and affinity-purified anti-beta2GPI IgG antibodies against human, bovine, and mouse beta2GPI was evaluated by enzyme-linked immunosorbent assay. High titers of anti-human beta2GPI IgG antibodies were detected 1 month after immunization. Progressively increasing titers against murine and bovine beta2GPI were recorded 1-4 months after injection. Immunization of mice with human beta2GPI resulted in the generation of antibodies reacting with human, bovine, and murine beta2GPI. The loss of tolerance to mouse beta2GPI is attributable to the high interspecies homology of beta2GPI. These results may point to molecular mimicry as a possible cause of APS.

Prevalence of anti-beta2 glycoprotein-I antibody in patients with primary or secondary immune thrombocytopenia

We determined the prevalence of antibodies to beta2 glycoprotein-I (beta2 GPI) in sera of 57 patients with primary or secondary immune thrombocytopenia positive for platelet antibody (PAIgG) and in 16 healthy control subjects. Both isotypes (IgG and IgM) of anti-beta2 GPI were detected by means of semiquantitative ELISA and platelet antibodies were measured by means of flow cytometry using FITC-labeled anti-human IgG. Six (10.5%) of 57 patients with immune thrombocytopenia had anti-beta2 GPI, whereas none of the 16 healthy subjects had anti-beta2 GPI. Four were positive for IgM anti-beta2 GPI, one for IgG anti-beta2 GPI, and one was positive both for IgM and IgG anti-beta2 GPI. There was no significant association between the presence of anti-beta2 GPI and the severity of thrombocytopenia. Our findings suggest that some patients with immune thrombocytopenia have anti-beta2 GPI in addition to the increased PAIgG; however, the results do not support a major role for anti-beta2 GPI in the pathogenesis of immune thrombocytopenia.

Anti-beta2-glycoprotein I, anti-prothrombin and anticardiolipin antibodies in a longitudinal study of patients with systemic lupus erythematosus and the antiphospholipid syndrome

To determine anti-beta2 glycoprotein-I (anti-beta2GPI) and anti-prothrombin (anti-ProT) antibody levels, and the IgG subclass distribution of anti-beta2GPI antibodies, in serial samples from patients with systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS) having initial or recurrent thrombotic/neurological (T/N) events during the study period. To investigate the correlations between these antibodies and beta2GPI antigen, anticardiolipin antibody (aCL), anti-double-stranded (ds) DNA, C3 levels and disease activity. Fifty serum samples were identified from seven patients with SLE who had had T/N events during the follow-up from a cohort under long-term follow-up. IgG anti-beta2GPI, anti-ProT, aCL, IgG subclasses of anti-beta2GPI and beta2GPI antigen levels were determined by ELISA. Corresponding disease activity [British Isles Lupus Assessment Group (BILAG)], anti-dsDNA and C3 levels were compared. IgG anti-beta2GPI antibody levels were elevated in six of the patients before and after the T/N events with less marked fluctuations than aCL antibody levels. The predominant subclass of anti-beta2GPI antibodies was IgG2 before and after the T/N events. IgG anti-ProT antibodies were negative in all cases. There was a significant but weak correlation between anti-beta2GPI and aCL antibodies. No correlation was found between disease activity and IgG anti-beta2GPI antibody and beta2GPI antigen levels. There were fluctuations in beta2GPI antigen levels and a trend to increase after T/N events was observed in some patients. Most of the patients with a T/N event during the study period had IgG anti-beta2GPI, but not IgG anti-ProT antibodies. Many IgG aCL-negative samples were found to have IgG anti-beta2GPI activity during the follow-up period. The predominant subclass of IgG anti-beta2GPI was IgG2, which may have importance in the pathogenesis of APS. beta2GPI antigen levels were found to be increased in some patients with SLE after T/N events. IgG anti-beta2GPI antibodies may be used as an adjunctive marker of future T/N events in patients with SLE and APS with aCL antibodies and lupus anticoagulant.

Arterial disease in lupus and secondary antiphospholipid syndrome: association with anti-beta2-glycoprotein I antibodies but not with antibodies against oxidized low-density lipoprotein.

The prevalence and clinical significance of antibodies against beta2-glycoprotein I (anti-beta2GPI) and antibodies against oxidized low-density lipoprotein (anti-ox-LDL) were evaluated as potential indicators of arterial disease in patients with systemic lupus erythematosus (SLE) and SLE with secondary antiphospholipid syndrome (APS). IgG anti-beta2GPI and IgG anti-ox-LDL were measured by enzyme-linked immunosorbent assay (ELISA) in serum samples from 118 patients with SLE, including 40 with secondary APS. IgG anti-beta2GPI were positive in 17% (20/118) of SLE patients. The presence and titres of IgG anti-beta2GPI were strongly associated with a history of arterial thrombosis. Haemolytic anaemia was also significantly associated with the presence of IgG anti-beta2GPI. The prevalence of IgG anti-ox-LDL was 53% (63/118), but there was no association with arterial thrombosis. No correlation between the values of anti-ox-LDL and those of anti-beta2GPI was found. These results suggest that IgG anti-beta2GPI could be a marker for arterial thrombosis in SLE patients, while IgG anti-ox-LDL were not associated with arterial disease in this group of lupus patients.

Immunologic characterization and functional properties of murine antibodies raised against deleted mutants of human beta 2-glycoprotein I.

beta 2-Glycoprotein I (beta 2GPI) is a 50 kDa molecule proposed as a principal target of 'autoimmune' antiphospholipid antibodies (aPL). We have used deleted mutants (DM) representing different domains of beta 2GPI (I-IV, IV-V and V) for immunization of naive mice and studied the characteristics of the respective murine IgG preparations in comparison with affinity-purified IgG from two patients with primary antiphospholipid syndrome. Immunization with beta 2GPI and with the DM produced anti-beta 2GPI antibodies, part of which reacted with negatively charged phospholipids (PL), whereas reactivity with cardiolipin was evident only in the IgG from mice immunized with beta 2GPI. These results are consistent with the presumption that aPL are induced following the in vivo association of beta 2GPI (used for immunization) with resident negatively charged PL. Accordingly, DM which either lack the PL binding site or aPL attachment locus did not elicit, upon immunization, antibodies reactive with PL. Further, murine anti-beta 2GPI IgG and human 'autoimmune' aPL were similar, albeit not identical, in terms of DM requirement for PL binding and charge dependency. Murine antibodies and human aPL, regardless of their binding characteristics, were found to bind significantly to platelets upon their activation with thrombin and to promote platelet activation. The results of the current study emphasize the dissimilarities between human 'autoimmune' aPL and murine anti-beta 2GPI. Thus, anti-beta 2GPI antibodies to different DM as well as human aPL are capable of binding and activating human platelets provided beta 2GPI is present.

Antibodies to beta 2-glycoprotein I and clinical manifestations in patients with systemic lupus erythematosus.

To investigate whether anticardiolipin antibodies (aCL) in patients with systemic lupus erythematosus (SLE) bind to beta 2-glycoprotein I (beta 2GPI), and to search for a relationship between the presence of IgG and/or IgM anti-beta 2GPI antibody and clinical manifestations in SLE patients. IgG and IgM anti-beta 2GPI in 308 Japanese SLE patients were measured using phospholipid-independent enzyme immunoassays. Relationships to clinical histories and to various laboratory data were examined. The values of anti-beta 2GPI and aCL, as measured by conventional enzyme immunoassay, showed a strong correlation, but the anti-beta 2GPI assay was more useful in distinguishing beta 2GPI-dependent aCL from beta 2GPI-independent aCL. The presence of IgG anti-beta 2GPI was associated with an increased frequency of a history of thrombosis. Comparisons of various laboratory data suggested that the titer of anti-beta 2GPI may fluctuate with disease activity. The results suggest that pathogenic aCL is directed against structurally altered beta 2GPI and that enzyme immunoassay for anti-beta 2GPI may prove useful in evaluating the risk of thrombosis and monitoring the clinical course in patients with SLE.

Binding of beta 2 glycoprotein I to activated polystyrene and its recognition by human IgG autoantibodies.

Beta 2 glycoprotein I (apolipoprotein H, beta 2GPI) is involved in the formation of epitope(s) recognized by clinically relevant autoantibodies from patients with antiphospholipid syndrome. We studied the binding of beta 2GPI to chemically activated polystyrene in a microtitre plate format. Adsorption isotherms (at 37 degrees C) were generated for beta 2GPI on activated polystyrene and on unactivated polystyrene, with both human serum antibodies and rabbit polyclonal IgG antibodies as probes, and horseradish peroxidase (HRP)-tagged anti-IgG to detect binding. Additionally, beta 2GPI was biotinylated and isotherms were developed by using HRP-streptavidin as the recognition sequence. Human serum autoantibodies, which did not precipitate beta 2GPI in solution, yielded a characteristic chemisorption isotherm on activated polystyrene but did not recognize beta 2GPI bound to untreated polystyrene. The rabbit IgG, which did precipitate beta 2GPI in solution, detected beta 2GPI bound to both activated polystyrene and, to a lesser extent, to untreated polystyrene. The binding of beta 2GPI to untreated polystyrene was confirmed by the use of biotinylated beta 2GPI. To assess the prevalence of IgG anti-beta 2GPI autoantibodies, we surveyed 113 sera submitted to our laboratory for anticardiolipin antibody (aCL) testing. Only nine (8%) had anti-beta 2GPI activity greater than two standard deviations above the mean for those sera in which aCL activity was within normal limits. We conclude that epitope presentation of beta 2GPI for human autoantibody binding is dependent on surface properties of the polystyrene, and that beta 2GPI autoantibodies are found only in a subpopulation of sera positive for aCL.