Serum anti-beta2-glycoprotein-I and anticardiolipin antibodies during thrombosis in systemic lupus erythematosus patients

Deciphering the clinical significance of longitudinal antiphospholipid antibody titers

In antiphospholipid syndrome (APS), the risk of clinical manifestations increases with higher titers of antiphospholipid antibodies (aPL). Despite the adoption of aPL titers in the classification approach to aPL-positive subjects, the value of longitudinal monitoring of those titers in the follow-up is still debated, being well studied only in systemic lupus erythematosus (SLE). The literature suggests that the rate of aPL positivity decreases during follow-up in primary APS, estimating that seroconversion occurs in between 8.9 and 59% of patients over time. Negativisation of aPL occurs more frequently in asymptomatic aPL carriers than in patients with full-blown APS as well as in subjects with single aPL positivity or low aPL antibody titers. In patients with SLE, aPL typically behave fluctuating from positive to negative and back again in the course of follow-up. The few studies assessing the longitudinal course of aPL positivity with no associated systemic connective tissue disease reported a progressive decrement of aPL titers over time, in particular of antibodies against β2 glycoprotein I (antiβ2GPI) and cardiolipin (aCL) of IgG isotype. After a thrombotic event, aPL titers tend to decrease, as emerged from cohorts of both primary and secondary APS. Hydroxychloroquine has been identified as the most effective pharmacological agent to reduce aPL titers, with multiple studies demonstrating a parallel reduction in thrombosis rate. This review addresses available evidence on the significance of aPL titer fluctuation from clinical, therapeutic and pathogenic perspectives.

Antiphospholipid Antibodies Are Not Associated with Clinical Parameters or Prognostic Outcomes in Patients with Non-Hodgkin's Lymphoma

BACKGROUND

 Antiphospholipid antibodies (APAs) are found quite frequently in patients with non-Hodgkin's lymphoma (NHL). However, the clinical significance of these antibodies is largely unknown. This study aims to delineate the clinical and prognostic role of APAs in NHL patients.

PATIENTS AND METHODS

  Consecutive patients of NHL were screened for lupus anticoagulant (LA), IgG/IgM anticardiolipin antibody, and IgG/IgM anti-β2-glycoprotein I at the time of diagnosis. Baseline investigations, staging, and treatment were done as per institutional protocol. Patients were followed up until the last known outpatient visit or death. All were screened at each visit for any thromboembolic event. The association of APA status with baseline NHL characteristics and treatment response was evaluated by univariate analysis. Kaplan-Meier survival analysis was used to compare the final outcome in patients with or without APAs. Patients who were initially APA positive were retested for the corresponding antibody at the end of chemotherapy.

RESULTS

 Twenty-four out of 105 patients (22.8%) were APA positive at diagnosis. The presence of APA was not significantly associated with NHL stage, histology, International Prognostic Index score, activated partial thromboplastin time, or treatment response. The median duration of follow-up was 15 months. Only four patients developed venous thrombosis; none was APA positive. There was no statistically significant difference in overall survival between the two groups (p = 0.471). Patients, who were APA positive initially, tested negative at the end of treatment, irrespective of treatment response.

CONCLUSION

 APAs are encountered more frequently in NHL patients than in the general population. However, APAs do not correlate with disease severity, thrombosis risk, treatment outcome, or overall survival.

Antiphospholipid Syndrome in Greece: Clinical and Immunological Study and Review of the Literature

The aim of this paper is to analyze the epidemiologic, clinical, and immunologic characteristics of the antiphospholipid syndrome (APS), primary or secondary, in autoimmune patients from Northern Greece. Sixty-seven patients with APS were included (9 men, 13.4%, and 58 women, 86.6%). Fifty-two (77.6%) patients had secondary APS and 15 had primary APS (22.4%). The mean age was 46.0 ±15.4 years and the mean follow-up period was 62.7 ±15.0 months. Medical records were retrospectively analyzed from January 1994 until December 2001, according to a preestablished protocol. Eight patients (11.9%) had arterial thrombosis, 12 (17.9%) had vein thrombosis, 12 (17.9%) had thrombocytopenia, 20 (29.8%) had neurologic disorders, and 51.6% of the women in reproductive age had, at least 2 fetal losses (higher frequency in primary APS). Thirty-six patients (53.7%) had increased levels of both immunoglobulin G (IgG) and IgM anticardiolipin antibodies (ACA), 19 (28.4%) had IgG ACA only, and 12 (17.7%) had IgM ACA only. Antinuclear antibodies (ANA) were detected in 46 (68.6%) patients, and antineutrophil cytoplasmic antibodies (ANCA) in 29 (43.3%). All patients were prophylactically treated with aspirin (50-100 mg/day) and low-molecular-weight heparin and/or intravenous immunoglobulins-IVIGs occasionally (pregnant women). The findings of this study are, generally, similar to those described by others. Miscarriages seem to be more frequent in women with primary APS (p<0.05), compared to other studies. Differences between these findings and those described by others concerning epidemiologic, clinical, or immunologic data are discussed.

Cardiovascular involvement in autoimmune diseases

Autoimmune diseases (AD) represent a broad spectrum of chronic conditions that may afflict specific target organs or multiple systems with a significant burden on quality of life. These conditions have common mechanisms including genetic and epigenetics factors, gender disparity, environmental triggers, pathophysiological abnormalities, and certain subphenotypes. Atherosclerosis (AT) was once considered to be a degenerative disease that was an inevitable consequence of aging. However, research in the last three decades has shown that AT is not degenerative or inevitable. It is an autoimmune-inflammatory disease associated with infectious and inflammatory factors characterized by lipoprotein metabolism alteration that leads to immune system activation with the consequent proliferation of smooth muscle cells, narrowing arteries, and atheroma formation. Both humoral and cellular immune mechanisms have been proposed to participate in the onset and progression of AT. Several risk factors, known as classic risk factors, have been described. Interestingly, the excessive cardiovascular events observed in patients with ADs are not fully explained by these factors. Several novel risk factors contribute to the development of premature vascular damage. In this review, we discuss our current understanding of how traditional and nontraditional risk factors contribute to pathogenesis of CVD in AD.

Cardiovascular disease in latin american patients with systemic lupus erythematosus: a cross-sectional study and a systematic review

Objective. This study was performed to determine the prevalence of and associated risk factors for cardiovascular disease (CVD) in Latin American (LA) patients with systemic lupus erythematosus (SLE). Methods. First, a cross-sectional analytical study was conducted in 310 Colombian patients with SLE in whom CVD was assessed. Associated factors were examined by multivariate regression analyses. Second, a systematic review of the literature on CVD in SLE in LA was performed. Results. There were 133 (36.5%) Colombian SLE patients with CVD. Dyslipidemia, smoking, coffee consumption, and pleural effusion were positively associated with CVD. An independent effect of coffee consumption and cigarette on CVD was found regardless of gender and duration of disease. In the systematic review, 60 articles fulfilling the eligibility criteria were included. A wide range of CVD prevalence was found (4%-79.5%). Several studies reported ancestry, genetic factors, and polyautoimmunity as novel risk factors for such a condition. Conclusions. A high rate of CVD is observed in LA patients with SLE. Awareness of the observed risk factors should encourage preventive population strategies for CVD in patients with SLE aimed at facilitating the suppression of cigarette smoking and coffee consumption as well as at the tight control of dyslipidemia and other modifiable risk factors.

Antiphospholipid syndrome: laboratory testing and diagnostic strategies

The antiphospholipid syndrome (APS) is diagnosed in patients with recurrent thromboembolic events and/or pregnancy loss in the presence of persistent laboratory evidence for antiphospholipid antibodies. Diagnostic tests for the detection of antiphospholipid antibodies include laboratory assays that detect anticardiolipin antibodies, lupus anticoagulants, and anti-β(2)-glycoprotein I antibodies. These assays have their origins beginning >60 years ago, with the identification of the biologic false positive test for syphilis, the observation of "circulating anticoagulants" in certain patients with systemic lupus erythematosus, the identification of cardiolipin as a key component in the serologic test for syphilis, and the recognition and characterization of a "cofactor" for antibody binding to phospholipids. Although these assays have been used clinically for many years, there are still problems with the accurate diagnosis of patients with this syndrome. For example, lupus anticoagulant testing can be difficult to interpret in patients receiving anticoagulant therapy, but most patients with a thromboembolic event will already be anticoagulated before the decision to perform the tests has been made. In addition to understanding limitations of the assays, clinicians also need to be aware of which patients should be tested and not obtain testing on patients unlikely to have APS. New tests and diagnostic strategies are in various stages of development and should help improve our ability to accurately diagnose this important clinical disorder.

Pediatric cerebellar stroke associated with elevated titer of antibodies to β2-glycoprotein

Antibodies to 2-glycoprotein I (anti-2GPI) have been associated with recurrent thrombosis and pregnancy morbidity. However, the prevalence of anti-2GPI in children suffering from cerebral and cerebellar infarction is unknown. We report on a 10-month-old boy who had an ischemic cerebellar stroke, secondary to antiphospholipid syndrome with high titers of immunoglobulin G anti-2GPI (first titer: 132U) anticardiolipin antibodies and lupus anticoagulant tests were negative. All other causes of infarction were excluded. To our knowledge, this is the first reported case of childhood cerebellar ischemic stroke with only anti-2GPI but no antibodies detectable in standard antiphospholipid assays.

The geoepidemiology of the antiphospholipid antibody syndrome

Antiphospholipid antibodies (aPL) can be detected by functional (lupus anticoagulant) and/or by solid phase assays (anti-cardiolipin and anti-beta2 glycoprotein I). Although detectable in 1-5% of asymptomatic apparently healthy subjects, persistent aPL are significantly associated with recurrent arterial/venous thrombosis and with pregnancy morbidity. Such an association is the formal classification tool for the antiphospholipid syndrome (APS). The prevalence of the syndrome with no associated systemic connective tissue diseases (primary APS) in the general population is still a matter of debate since there are no sound epidemiological studies in the literature so far. aPL display higher prevalence in systemic lupus erythematosus and rheumatoid arthritis than in other systemic autoimmune diseases. However not all the aPL positive lupus patients display the clinical manifestations. Comparable findings may be found in the paediatric population, although anti-beta2 glycoprotein I antibodies are detected in healthy children more frequently than in adults. High prevalence of aPL has been also reported in clinical manifestations that are not formal APS classification criteria: heart valve disease, livedo reticular, nephropathy, neurological manifestations, and thrombocytopenia. Antiphospholipid antibodies can be associated with infectious processes, active vaccination, drug administration and malignancies. Their prevalence and titres are lower and the relationship with the APS clinical manifestations are less strong than in the previously mentioned conditions. Ethnicity was also reported to influence the prevalence of aPL.

Pathogenesis of neuropsychiatric systemic lupus erythematosus and potential biomarkers

Systemic lupus erythematosus is a chronic, multisystemic, autoimmune disease that may involve the central, peripheral, and autonomic nervous systems and can present with a wide variety of neurological and psychiatric manifestations. In this article, we review the recent literature pertaining to the pathogenesis of neuropsychiatric systemic lupus erythematosus (NPSLE). We searched the PUBMED database with no chronological constraints using the following terms: "neuropsychiatric systemic lupus erythematosus" cross-referenced with the terms "pathogenesis" and "biomarkers" for full-text articles in English. The etiology of NPSLE is as yet unknown, though numerous autoantibodies and cytokines have been suggested as possible mediators. Of the numerous autoantibodies and biomarkers examined, anti-phospholipid, anti-ribosomal P, anti-neuronal, anti-glial fibrillary acidic protein (GFAP), anti-endothelial cell, anti-N-methyl-D: -aspartate (NMDA), microtubule-associated protein 2 (MAP-2), and matrix metalloproteinase-9 (MMP-9) appear to be elevated in patients with NPSLE. Cytokines that may be involved in the pathology of NPSLE include interleukin (IL)-2, IL-6, IL-8, IL-10, tumor necrosis factor (TNF)-alpha, and interferons (IFN)-alpha and -gamma. With continued advances in immunological research, new insights into the pathophysiologic mechanisms of NPSLE may lead to the development of biomarkers and new treatment strategies.

Antiphospholipid syndrome and vascular ischemic (occlusive) diseases: an overview

Antiphospholipid syndrome (APS) is primarily considered to be an autoimmune pathological condition that is also referred to as "Hughes syndrome". It is characterized by arterial and/or venous thrombosis and pregnancy pathologies in the presence of anticardiolipin antibodies and/or lupus anticoagulant. APS can occur either as a primary disease or secondary to a connective tissue disorder, most frequently systemic lupus erythematosus (SLE). Damage to the nervous system is one of the most prominent clinical constellations of sequelae in APS and includes (i) arterial/ venous thrombotic events, (ii) psychiatric features and (iii) other non- thrombotic neurological syndromes. In this overview we compare the most important vascular ischemic (occlusive) disturbances (VIOD) with neuro-psychiatric symptomatics, together with complete, updated classifications and hypotheses for the etio-pathogenesis of APS with underlying clinical and laboratory criteria for optimal diagnosis and disease management.

Cerebrovascular disease associated with antiphospholipid antibodies: more questions than answers

Neurological syndromes occur in a significant number of patients with antiphospholipid antibodies. The optimal management for these patients however remains uncertain.

Our study is a descriptive analysis looking retrospectively at 45 patients who presented to the principal tertiary referral centre in the Australian Capital Territory, with either cerebral arterial or venous thrombosis for which there was no obvious cause for their presentation when initially reviewed. The diagnosis was based on the clinical findings made by one of three neurologists attached to our centre. Radiological findings and the presence of either IgM or IgG anticardiolipin antibodies, IgG anti-beta-2 glycoprotein 1 antibodies or a lupus anticoagulant were then documented.

In this group of patients three subgroups were identified:

1. Individuals that fulfilled the Sapporo Classification Criteria

2. Individuals with transiently positive antiphospholipid antibodies and

3. Individuals with persistently low positive antiphospholipid antibodies.

The most interesting of these three groups are those individuals with transiently positive antiphospholipid antibodies. A potential cause for presentation was identified in only one patient of this group with documented infective endocarditis and bacteraemia. Comparison with the other two groups suggested that there was little in terms of clinical presentation, radiological findings or intercurrent risk factors for thrombotic disease to distinguish between them. With disappearance of antiphospholipid antibodies, the individuals within this group have not had further thrombotic events.

Our observations emphasise the problems that continue to exist in relation to the occurrence of cerebrovascular disease in the context of antiphospholipid antibodies and the optimal management of these stratified groups. Our findings also raise an as yet unanswered question as to the signficance of these transiently positive antiphospholipid antibodies. In the absence of significant intercurrent risk factors our findings would suggest that in the group we describe that they are likely to be of clinical significance.

Autoantibodies against the fibrinolytic receptor, annexin 2, in antiphospholipid syndrome

The association of thrombosis and gestational morbidity with antiphospholipid antibodies is termed antiphospholipid syndrome (APS). Annexin 2 (A2) is a profibrinolytic endothelial cell surface receptor that binds plasminogen, its tissue activator (tPA), and beta(2)-glycoprotein I (beta2GPI), the main antigen for antiphospholipid antibodies. Here, we evaluate A2 as a target antigen in APS. Serum samples from 434 individuals (206 patients with systemic lupus erythematosus without thrombosis, 62 with APS, 21 with nonautoimmune thrombosis, and 145 healthy individuals) were analyzed by enzyme-linked immunosorbent assay (ELISA) and immunoblot for antiphospholipid and A2 antibodies. Anti-A2 antibodies (titer > 3 SDs) were significantly more prevalent in patients with APS (22.6%; venous, 17.5%; arterial, 34.3%; and mixed thrombosis, 40.4%) than in healthy individuals (2.1%, P < .001), patients with nonautoimmune thrombosis (0%, P = .017), or patients with lupus without thrombosis (6.3%, P < .001). Anti-A2 IgG enhanced the expression of tissue factor on endothelial cells (6.4-fold +/- 0.13-fold SE), blocked A2-supported plasmin generation in a tPA-dependent generation assay (19%-71%) independently of beta2GPI, and inhibited cell surface plasmin generation on human umbilical vein endothelial cells (HUVECs) by 34% to 83%. We propose that anti-A2 antibodies contribute to the prothrombotic diathesis in antiphospholipid syndrome.

Avidity of Anti-β2-Glycoprotein I and Thrombosis or Pregnancy Loss in Patients with Antiphospholipid Syndrome

We aimed to evaluate avidity of anti-beta(2)-glycoprotein I antibodies (anti-beta(2)-GPIs) in patients with antiphospholipid syndrome (APS) at the time of acute thrombotic events or pregnancy loss as compared with clinical event-free periods. To do so, 69 sera samples from 16 patients (6 with primary APS and 10 with APS secondary to systemic lupus erythematosus ) were selected on the basis of anti-beta(2)-GPI positivity. Avidity of IgG anti-beta(2)-GPIs was determined by chaotropic enzyme-linked immunosorbent assay (ELISA), using increased NaCl concentration during antibody binding. High, heterogeneous, and low-avidity anti-beta(2)-GPIs were measured in APS patients, with no clear pattern regarding the time of thrombotic events or pregnancy failure. In general, anti-beta(2)-GPI avidity did not change substantially during disease course. We concluded that avidity of anti-beta(2)-GPIs appears to be a rather stable parameter in an individual APS patient. Considering the previously shown association of high-avidity anti-beta(2)-GPIs with venous thrombosis, avidity of anti-beta(2)-GPIs may be a better predictor of predisposition to thrombosis and unsuccessful pregnancy than levels of antiphospholipid antibodies, which may fluctuate over time owing to several factors.

Capillary electrophoresis-based analysis of phospholipid and glycosaminoglycan binding by human beta2-glycoprotein I

Human beta2-glycoprotein I (beta2gpI) is a phospholipid and heparin binding plasma glycoprotein involved in autoimmune diseases characterized by blood clotting disturbances (thrombosis) together with the occurrence of autoantibodies against beta2gpI. With the final goal of assessing autoantibody influence on binding interactions of beta2gpI we have studied the development of capillary electrophoresis (CE)-based assays for interactions of negatively charged ligands with beta2gpI. In the development of suitable conditions for analysis at neutral pH of this basic protein (pI about 8) we found the pH hysteresis behavior of fused silica surfaces useful since the protonated surface after an acid pre-wash counteracted protein adsorption efficiently in contrast to more laborious procedures including acrylamide/dimethylacrylamide coatings that did not permit analysis of this particular protein. This simple approach made estimates of heparin-beta2gpI interactions possible and the principle was shown also to work for detection of betagpI binding to anionic phospholipids. Utilizing the pH hysteresis effect may be a simple solution to the adsorption problems often encountered in analyses of proteins by CE.

Current debates in antiphospholipid syndrome: the acquired antibody-mediated thrombophilia

Antiphospholipid (APL) syndrome is the most common form of acquired thrombophilia. It can cause significant morbidity and even mortality. The term "APL antibodies" represents a heterogeneous group of antibodies associated with this disorder. Currently no single assay can identify every APL antibody. Clinically relevant APL antibodies are mainly anticardiolipin antibodies (ACA) detected by solid phase enzyme-linked immunosorbent assay (ELISA) and lupus anticoagulants (LA) demonstrated by in vitro coagulation assay. However, there are some other antibodies associated with the APL syndrome (i.e., subgroup APL antibodies). ACAs, LAs, and subgroup APL antibodies represent intersecting, but non-identical, subsets of autoantibodies. Thus, those autoantibodies may coexist or may occur independently. Any organ system and any size of vessel can be affected during the clinical course of the disease. Therefore, the APL syndrome can manifest itself in a wide variety of clinical thrombotic features. Fetal loss and pregnancy morbidity represent a specific challenge. Despite tremendous advances in the understanding of the pathogenesis of APL syndrome during the past decade, the mainstay of management is still anticoagulation. However, there is no general agreement regarding the duration and intensity of anti-coagulant therapy. In this review, we focused on the current dilemmas and their present clarifications in the wide clinicopathologic spectrum of APL syndrome and APL antibody-related distinct pathologic conditions.

Prophylaxis of the antiphospholipid syndrome: a consensus report

Hypothetical circumstances that may require prophylaxis for a potential antiphospholipid syndrome (primary prophylaxis), or in some instances when there already had been some manifestations ofthe syndrome (secondary prophylaxis), were presented to a panel of experts for their consideration on potential prophylactic intervention. These were subsequently presented to the participants in the First International Consensus on Treatment of the Antiphospholipid Syndrome. In most instances there was consensus in adding low dose aspirin, an exception being aspirin allergy when other antiaggregants could be used in nonpregnant subjects. General measures to prevent thrombosis and other vasoprotective actions should also be provided. Higher risk of fetal loss or thrombosis called for anticoagulation with coumadin in nonpregnant subjects or subcutaneous low molecular weight heparin in pregnant ones. When indicated, prophylaxis of the antiphospholipid syndrome should be provided in systemic lupus erythematosus patients who are being treated for their disease. In no instance should corticosteroids or immunosuppresants be given as prophylactic of an antiphospholipid syndrome.

Anti-beta2-glycoprotein I antibodies and ischemic stroke in a 20-month-old boy

Antibodies to beta2-glycoprotein I (anti-beta2GPI) have been associated with recurrent thrombosis and pregnancy morbidity. However, the prevalence of anti-beta2GPI in children suffering from cerebral infarction is unknown. We report on a 20-month-old boy who had an ischemic stroke, secondary to antiphospholipid syndrome with high titers of immunoglobulin G anti-beta2GPI (first titer: 132 U; second titer 6 weeks later: 350 U; normal range: 0-100 U). Anticardiolipin antibodies and lupus anticoagulant tests were negative. All other causes of infarction were excluded. Laboratory studies showed anti-beta2GPI IgG levels of 164 U and 216 U at 6 months and 2 years, respectively, after the onset. The patient received treatment with low-dose aspirin. To our knowledge, this is the first reported case of childhood ischemic stroke with only anti-beta2GPI but no antibodies detectable in standard antiphospholipid assays. This case supports the recommendation of others to search for these antibodies in the presence of strong clinical suspicion of antiphospholipid syndrome, when anticardiolipin antibodies and lupus anticoagulant tests are negative.

Antiphospholipid syndrome: why and how should we make the diagnosis?

Antiphospholipid syndrome (APLS) is characterized by recurrent thrombosis and/or pregnancy loss associated with persistently elevated levels of autoantibodies to phospholipids or plasma proteins. APLS occurs both as a primary disease and as a condition secondary to lupus and other autoimmune diseases. Awareness of the polymorphic presentations of APLS is vital given the risk of life-threatening thrombosis associated with this condition. Anticoagulant therapy is effective in preventing recurrent thrombosis. New biological markers have been developed, including autoantibodies to beta-2-glycoprotein 1 (anti-beta2GP1), phosphatidylethanolamine (PE), and annexin-V. These autoantibodies are not listed in the new diagnostic criteria set (Sapporo, 1999) because their usefulness needs to be validated and their detection standardized. Nevertheless, they may be helpful as part of a biological evaluation strategy for APLS. Progress can be expected in the near future, particularly regarding prediction of thrombosis. Although no marker predicts thrombosis with complete certainty, persistent high titers of the IgG variants of one or more antiphospholipid antibodies (particularly circulating anticoagulant and anti-beta2GP1) indicate a high risk of thrombosis. Evaluation of other thrombogenic factors such as inherited thrombophilia is probably useful in patients with APLS. Improvements in our ability to predict the risk of thrombosis may lead to novel strategies for prevention and treatment. New drugs such as complement factor (C3) inhibitors are being developed.

Antiphospholipid antibodies in Chilean patients with systemic lupus erythematosus

Antiphospholipid antibodies (aPLs) are a heterogeneous family of antibodies found in autoimmune disorders, infectious diseases, and other situations. The presence of different aPLs has been associated with various clinical manifestations of the antiphospholipid syndrome (APS). The objective of this study was to investigate the prevalence of aPLs in a group of 90 Chilean patients with systemic lupus erytematosus (SLE) and 90 healthy controls. We measured anticardiolipin antibodies (aCLs), antiphosphatidylserine antibodies (aPSs), anti-beta(2) glycoprotein I antibodies (anti-beta(2)GPIs), and antiprothrombin antibodies (aPTs) with an enzyme-linked immunosorbent technique using "in-house" assays. Fifty-four of 90 SLE patients (60.0%) had some type of aPL. Forty of 90 (44.4%) were positive for aCLs, 9 of 61 (14.8%) had aPSs, 21 of 90 (23.3%) had anti-beta(2)GPIs, and 18 of 90 (20.0%) had aPTs. In the control group, prevalences were as follows: aCLs, 3.3%; aPSs, 1.1%; anti-beta(2)GPIs, 1.1%; aPTs, 2.2%. In most cases, values were in the low-positive range. Of all aPL detected, 29.5% was of the IgG isotype, 37.5% IgM, and 33.0% IgA. We observed a correlation between aCLs and aPSs and of these antibodies with anti-beta(2)GPIs and aPTs but not between anti-beta(2)GPIs and aPTs. Our results show a high prevalence of aPLs in SLE patients. An association between different specificities and isotypes of aPLs was also observed.

Catastrophic antiphospholipid syndrome in the intensive care unit

CAPS is characterized by development of widespread microvascular thrombosis. Patients at risk are those with positive aCL or LA factor. Precipitating events, such as infection, trauma, surgical procedures, or reduction in anticoagulation therapy, may contribute to the development of CAPS. Presentation to the ICU can be dramatic, with progressive multiorgan failure and need for rapid institution of life-supporting measures. Cardiopulmonary failure has been the major contributor to mortality. A variety of therapeutic modalities have been used in an attempt to offset the widespread thrombosis and organ damage from high aCL levels. Anticoagulation therapy and high dosages of steroids seem to have a positive effect on survival.

Molecular and genetic characterizations of five pathogenic and two non-pathogenic monoclonal antiphospholipid antibodies

Antiphospholipid syndrome (APS) is an autoimmune disease that is characterized by thrombosis, recurrent fetal loss and thrombocytopenia. Antiphospholipid antibodies, detected by enzyme-linked immunoabsorbent assays (aCL) and/or in vitro blood clotting assays (LAC) are strongly associated with APS. Both the molecular structures used by pathogenic antiphospholipid antibodies and the genetic mechanisms leading to their production are unknown. We describe here the variable region genes of seven IgG antiphospholipid antibodies derived from two APS patients. Of these, five are pathogenic as defined in a mouse model of thrombosis and two are not. Analyses of the expressed variable region genes show no preferential V gene usage. However, similar to anti-DNA antibodies, pathogenic antiphospholipid antibodies contain an increased number of arginine residues in the third complimentarity-determining region (CDR3) of their H chains. The increased accumulation of arginine residues in the V(H) CDR3 may act to enhance antigen binding, promote disease and point to the importance of the H chain in the pathogenic potential of certain antiphospholipid antibodies.

Anticardiolipin and anti-beta2-glycoprotein-I antibodies in hypertensive disorders of pregnancy

BACKGROUND

This study was undertaken in order to determine the frequency of anticardiolipin (aCL) and anti-beta2-glycoprotein-I antibodies (anti-beta2 GP-I) in patients with hypertensive disorders of pregnancy.

METHODS

We studied aCL (IgG and IgM) and IgG anti-beta 2 GP-I by ELISA in the serum and IgG aCL and anti-beta 2 GP-I in the urine of 125 women with hypertensive disorders of pregnancy (cases) (75 had preeclampsia, 25 had eclampsia, and 25 had chronic hypertension). One hundred and twenty seven normal women were used as controls. Antibody positivity was defined as above the 90(th) percentile of the controls.

RESULTS

We found no differences in frequency of serum anti-beta 2 GP-I or serum and urinary aCL between cases and controls. In contrast, we found that frequency of IgG anti-beta 2 GP-I was higher in the urine of cases (26.1%) compared to controls (9.4%, p = 0.001). Strength of association was stronger for urinary anti-beta2-glycoprotein-I in women with preeclampsia (odds ratio [OR] = 4.3, 95% confidence limit [CI 95%] = 1.95-9.62, p <0.0001). Cases and the subgroup of preeclamptic patients also had higher titers of urinary IgG anti-beta 2 GP-I than control women (p <0.0001).

CONCLUSIONS

Our work suggests that urine testing is necessary in order to ascertain whether antibodies to beta(2)GP-I are associated with preeclampsia.

Phospholipid Autoantibodies and the Antiphospholipid Antibody Syndrome: Diagnostic Accuracy of 23 Methods Studied by Variation in ROC Curves with Number of Clinical Manifestations

Background: We analyzed the diagnostic accuracies for the diagnosis of antiphospholipid syndrome (APS) of 23 antiphospholipid antibody (APL-Ab) assays targeted at different antigen preparations and immunoglobulin isotypes.

Methods: In 144 patients with suspected APS, anti-cardiolipin (aCL) and anti-β2-glycoprotein I (aβ2GPI) antibodies were measured with 23 different ELISAs from three manufacturers. Data were analyzed by ROC curves. In the absence of an accepted criterion standard, the endpoint “diagnosis of APS” was varied according to the number (two through five) of signs and symptoms of APS.

Results: Although the presence of lupus anticoagulant was associated significantly with APL-Ab in 10 of 23 assays (P = 0.01–10−4) and recurrent arterial or venous occlusions were significantly associated with APL-Ab of IgM isotype in 5 of 6 assays (P = 0.02–10−4), sensitivity for detection of APS did not exceed 67%. With the exception of IgA APL-Ab, the diagnostic accuracy of the assays improved when the diagnosis of APS was based on an increasing number of simultaneous features of APS. For most methods, areas under the ROC curves were &gt;0.8 irrespective of the method’s subclass specificity and antigen preparation (aCL or aβ2GPI), if the clinical diagnosis of APS was based on four or more signs and symptoms of APS.

Conclusion: Despite considerable heterogeneity in the individual test results, a single test of IgG or IgM isotype targeted at either aCL or aβ2GPI antibodies has excellent diagnostic accuracy when the criterion for diagnosis requires four or more typical manifestations of APS.

Prevalence and clinical significance of anticardiolipin and anti-beta2-glycoprotein-I antibodies in patients with non-Hodgkin's lymphoma

The association of antiphospholipid antibodies (APA) has been reported in several cases of patients with non-Hodgkin's lymphoma (NHL) with or without thromboembolic complications. The purpose of this study was to analyse systematically the prevalence of APA and its clinical significance in lymphoma patients. Sera of 90 consecutive unselected patients with NHL were tested for the presence of anticardiolipin (aCL) antibodies and anti-beta2-glycoprotein-I (anti-beta2-GPI) antibodies. The patients were followed up over a median period of 14 months to note the occurrence of thromboembolism. We found APA in 24 out of 90 NHL patients (26.6%). Elevated APA were more often detected in women and in the elderly. The presence of elevated APA was not correlated with the histology and the stage of the lymphoma. None of the 24 patients with elevated APA developed a thromboembolic event in the follow-up period. Thromboembolic events were observed in 12 patients (13.3%), all with negative APA. High APA titres and the combination of positive aCL- and anti-beta2-GPI antibodies, features which are known to be more strongly correlated with thrombosis among patients with antiphospholipid syndrome and systemic lupus erythematous (SLE), were very uncommon in our cohort of NHL patients (3.3%). Vessel compression by lymphoma but not elevated APA remains the main cause of thrombosis in NHL patients.

Decreases in anti-double-stranded DNA levels are associated with concurrent flares in patients with systemic lupus erythematosus

OBJECTIVE

To determine the degree to which changes in anti-double-stranded DNA (anti-dsDNA), as determined by Crithidia and enzyme-linked immunosorbent assays (ELISAs), precede or coincide with changes in systemic lupus erythematosus (SLE) activity, as measured by 5 clinical indices, the physician's global assessment (PGA), modified SLE Disease Activity Index (M-SLEDAI), modified Lupus Activity Index (M-LAI), Systemic Lupus Activity Measure (SLAM), and the modified British Isles Lupus Assessment Group (M-BILAG).

METHODS

Disease activity and anti-dsDNA were measured monthly in 53 SLE patients who were followed up for 1 year. Lupus flare was defined as an increase in PGA of > or = 1.0, M-SLEDAI > or = 3, M-LAI > or = 0.1, SLAM > or = 3, and M-BILAG > or = 4 within a 1-month period. Flare rates were calculated for groups, which were defined by "previous" (1 month prior to the flare) or "concurrent" (at the time of the flare) changes in anti-dsDNA. Logistic regression models were used to determine the significance of the association between recent changes in anti-dsDNA and flare, controlling for the prednisone dosage.

RESULTS

Flares occurred at 12% of visits, based on the PGA measure of disease activity. Using the other indices, flare rates were 19% (M-SLEDAI), 25% (M-LAI), 13% (SLAM), and 12% (M-BILAG). A concurrent decrease in anti-dsDNA (ELISA) was associated with significantly higher flare rates based on PGA (18 of 84, 21%; P = 0.0014), M-SLEDAI (27 of 89, 30%; P = 0.0019), M-LAI (37 of 89, 42%; P = 0.0001), and M-BILAG (19 of 89, 21%; P = 0.0264) scores. Flare rates were also significantly higher after a previous increase in anti-dsDNA (ELISA) based on M-SLEDAI (26 of 93, 30%; P = 0.0022) and M-LAI (34 of 93, 37%; P = 0.0117) scores. Flare rates tended to be lowest when there was a concurrent increase in anti-dsDNA (ELISA). Analysis of specific organ systems showed that a concurrent decrease in anti-dsDNA (ELISA) was significantly associated with increases in renal disease activity. Similar results were obtained using the Crithidia assay.

CONCLUSION

A previous increase in anti-dsDNA levels occurred before SLE flares, as measured by the M-SLEDAI and M-LAI only. However, during lupus flares, including the subset of renal flares, anti-dsDNA levels frequently decreased. We hypothesize that this decrease in anti-dsDNA represents deposition in tissue at the time of flare.

A decrease in complement is associated with increased renal and hematologic activity in patients with systemic lupus erythematosus

OBJECTIVE

To determine the degree to which changes in C3 and C4 precede or coincide with changes in systemic lupus erythematosus (SLE) activity, as measured by 5 global activity indices, the physician's global assessment (PGA), modified SLE Disease Activity Index (M-SLEDAI), modified Lupus Activity Index (M-LAI), Systemic Lupus Activity Measure (SLAM), and the modified British Isles Lupus Assessment Group (M-BILAG), and to evaluate the association between changes in C3 and C4 levels and SLE activity in individual organ systems.

METHODS

Fifty-three lupus patients were observed monthly for 1 year in a longitudinal study. Lupus disease activity and complement levels were measured at each visit. Lupus flare was defined as a 1.0 (or greater) increase in the PGA, a 3-point increase in the M-SLEDAI, a 0.1 increase in the M-LAI, a 3-point increase in the SLAM, or a 4-point increase in the M-BILAG within a 1-month period. Flare rates were calculated for subgroups defined by previous (1 month before) or concurrent changes in complement levels. Logistic regression models were used to determine the significance of the association between recent changes in complement levels and flare, controlling for prednisone dosage. Similar models were used to assess the association between changes in C3 or C4 levels and increased SLE activity in specific organ systems.

RESULTS

Lupus flares occurred at 12% of visits based on the PGA, 19% based on the M-SLEDAI, 25% based on the M-LAI, 13% based on the SLAM, and 12% based on the M-BILAG. Recent changes in C3 and C4 levels were not associated with flares based on 3 of the 5 activity indices. Flares defined by the M-LAI were more frequent when there was a concurrent decrease in C3 (odds ratio [OR] 1.9, 95% confidence interval [95% CI] 1.1-3.1) or C4 (OR 2.1, 95% CI 1.3-3.6). Higher flare rates, as defined by the SLAM, were associated with previous increases in C3 (OR 1.6, 95% CI 1.0-2.6) and C4 (OR 2.2, 95% CI 1.2-3.9). When individual organ systems were analyzed, decreases in C3 and C4 were associated with a concurrent increase in renal disease activity (OR 2.2, 95% CI 1.4-3.5 and OR 1.9, 95% CI 1.1-3.4, respectively). Decreases in C3 were also associated with concurrent decreases in the hematocrit (OR 4.6, 95% CI 1.7-12.3), platelet (OR 2.5, 95% CI 1.5-4.1), and white blood cell (OR 2.2, 95% CI 1.3-3.6) counts. Previous increases in C3 levels were associated with a decrease in platelets (OR 1.7, 95% CI 1.1-2.7). A decrease in C4 was associated with a concurrent decrease in the hematocrit level (OR 3.2, 95% CI 1.3-7.5) and platelet count (OR 1.6, 95% CI 1.0-2.5).

CONCLUSION

Decreases in complement levels were not consistently associated with SLE flares, as defined by global measures of disease activity. However, decreasing complement was associated with a concurrent increase in renal and hematologic SLE activity.

Prevalence and isotype distribution of antiphospholipid antibodies in Chilean patients with systemic lupus erythematosus (SLE)

Previous studies have demonstrated that ethnicity plays a role in the prevalence, isotype distribution, and clinical significance of anticardiolipin (aCL) and anti-beta2 glycoprotein I (abeta2-GPI) antibodies in systemic lupus erythematosus (SLE) patients. Few studies have been done in Latin American populations. Serum samples from 129 Chilean SLE patients were tested for IgG, IgM and IgA aCL and abeta2-GPI by ELISA. Clinical data were reviewed with the focus on clinical manifestations of antiphospholipid syndrome (APS). Positivity for at least one isotype of aCL was found in 30% of patients, while only 10% were positive for at least one isotype of abeta2-GPI. IgG was the most prevalent isotype for aCL (16%), and the isotype distribution was similar (4%) for abeta2-GPI. In general, the presence of aCL was significantly associated with the presence of abeta2-GPI, but a number of samples were positive for only one antibody, some of them associated with clinical manifestations of APS. ACL antibodies at medium-high titers were significantly correlated with thrombosis (P = 0.0007) and fetal loss (P = 0.009); however, the sensitivity of abeta2-GPI for detecting thrombosis and fetal loss was lower than aCL (19 and 17% vs 56 and 50%, respectively), and the specificity slightly higher (91 and 90% vs 84 and 82%). In Chilean SLE patients, aCL and abeta2-GPI antibodies are important in the evaluation of patients with APS. However, the utility of abeta2-GPI antibodies was limited by the low prevalence of these antibodies in comparison with other ethnic groups. Further studies are needed to define the basis of the observed differences among ethnic groups.

The clonal analysis of anticardiolipin antibodies in a single patient with primary antiphospholipid syndrome reveals an extreme antibody heterogeneity

The mechanism underlying the prothrombotic state that characterizes the primary antiphospholipid syndrome proves to be difficult to define mainly because of the variety of the phospholipid and protein targets of antiphospholipid antibodies that have been described. Much of the debate is related to the use of polyclonal antibodies during the different antiphospholipid assays. To better describe the antiphospholipid antibodies, a strategy was designed to analyze the reactivity of each one antibody making up the polyclonal anticardiolipin activity, breaking down this reactivity at the clonal level. This was performed in a single patient with primary antiphospholipid syndrome by combining (1) the antigen-specific selection of single cells sorted by flow cytometry using structurally bilayered labeled anionic phospholipids and (2) the cloning of immunoglobulin (Ig) variable (V) region genes originating from individual IgG anticardiolipin-specific B cells by a single-cell polymerase chain reaction technique. The corresponding V regions were cloned in order to express human recombinant antibodies in insect cells by a baculovirus expression system. The molecular analysis, the fine specificity, and the protein cofactor dependency of the first 5 monoclonal IgG anticardiolipins are reported here. This clonal analysis reveals the extreme heterogeneity of these antibodies, which could account for the difficulties in the previous attempts to define the pathogenic antiphospholipid response. This approach should help to unravel the complex antiphospholipid immune response and the mechanism of the prothrombotic state associated with these antibodies, but it could also shed some light on their possible origins. (Blood. 2001;97:3820-3828)

[Non-simultaneous malignant lymphoma and antiphospholipid syndrome: 4 cases]

OBJECTIVE

We report four cases of non-synchronous antiphospholipid syndrome (APS) and malignant lymphoma, which highlight the complex relationship that seems to exist between these illnesses.

METHODS

In a retrospective study conducted in two departments (internal medicine and clinical hematology) of a university hospital, we collected all observations of patients with both APS and malignant lymphoma diagnosed throughout the past decade.

RESULTS

An association of APS with malignant lymphoma was recorded in three female and one male patient, median age 42.5 years at the time of diagnosis of the first disease. In each case, the primary APS was diagnosed, with arterial thrombotic events in three cases and venous thrombotic events in one case. One patient had isolated IgG anticardiolipin antibody, whereas the others had a combination of IgG anticardiolipin antibody and lupus anticoagulant with or without IgG anti-beta 2 glycoprotein I antibody. One patient also had an acquired inhibitor to factor VIII:C and a chronic C virus hepatitis. The mean time apparently separating the two illnesses ranged from 18 months to 9 years, but in two cases the diagnosis of APS was delayed due to a progressive, atypical, neurological onset. In two instances, the APS took place at a distance from a cured malignant lymphoma (Hodgkin's disease and nodal large cell B-cell lymphoma), whilst in the others it preceded a B-cell lymphoma (nodal and cutaneous, small cells and primary hepatic, large cells). Treatment resulted in complete haematological response in both cases, with disappearance of anticardiolipin antibody and lupus anticoagulant in the latter following a double autologous peripheral blood stem cell transplantation. In addition, late carcinomas (breast, kidney, thyroid) were seen in two patients.

CONCLUSIONS

Our data indicate that the diagnosis of a malignant lymphoma should be considered in patients with a primary APS and peripheral lymph node enlargement or unexplained constitutional symptoms. Conversely, a late onset of arterial or venous thrombotic diathesis after a malignant lymphoma may indicate not only late relapse of malignant lymphoma but also a subsequent APS.

Management of thrombosis in women with antiphospholipid syndrome

1) Antiphospholipid antibody syndrome may be associated with unusual sites of thrombosis. 2) Laboratory evaluation involves testing for antiphospholipid antibodies: lupus anticoagulant and anticardiolipin antibodies. 3) Acute management of thrombosis involves immediate anticoagulation. Low-molecular-weight heparins are as safe and effective as unfractionated heparin in this setting. Arterial events may require emergent thrombolytic therapy. Monitoring of the APTT with unfractionated heparin in the presence of a lupus anticoagulant is ineffective; these patients require monitoring of antifactor Xa levels or the use of LMWH, which does not require monitoring. 4) The pharmacokinetics of LMWH change in pregnancy, resulting in a shorter plasma half-life and larger volume of distribution. Monitoring of antifactor Xa levels is necessary. 5) Chronic anticoagulation is best achieved with warfarin, with significantly decreased rates of recurrent events when the INR is > or = 3.0. Long-term, if not life-long, anticoagulation is often necessary. Warfarin is teratogenic, and individuals desiring pregnancy will need to convert to therapeutic, not prophylactic, doses of either unfractionated heparin or LMWH. 6) As part of optimal management of thrombosis in APS, additional risk factors for thrombosis should be eliminated or reduced. These include comorbid illnesses such as hypertension and hyperlipidemia, as well as smoking. 7) Tamoxifen, raloxifene, oral contraceptives, and hormone replacement therapy are all associated with an increased risk of DVT in the general population. In APS patients receiving therapeutic anticoagulation, the addition of these drugs should not increase thrombosis risk. In APS patients not receiving anticoagulant therapy, these hormonal therapies may increase the thrombosis risk.

Acquired thrombophilic syndromes

As the biochemical mechanisms of hypercoagulable states are revealed, the syndromes of venous thromboembolism have been increasingly associated with specific aberrations. Most of these changes involve an increase in procoagulant potential, for example, by activation of the coagulation cascade, or by a defect or decrease in natural inhibitors of clotting. Similar abnormalities of the fibrinolytic pathways may contribute, as can loss of inhibitory mechanisms of endothelial cells, as well as changes in vascular anatomy and rheologic patterns of blood flow. All of these factors can directly influence thrombus formation and/or the physiologic response to the thrombus.(1)

'Catastrophic' antiphospholipid syndrome

When 'catastrophic' is applied as an adjective to the antiphospholipid syndrome, it implies a characteristic presentation due to predominantly small blood vessel thrombosis leading to rapidly progressive failure of multiple organs and a frequently fatal outcome. We present the case of a 48-year-old woman who presented with the 'catastrophic' antiphospholipid syndrome without previous history of coagulation disorder or connective tissue disease that illustrates the difficulties in diagnosing and managing this disorder. We also review the factors that have been reported to have a role in the development of this condition and show how this case throws light on its pathogenesis.

An unusual increase of blood anti-beta 2-glycoprotein-I antibody but not antiphospholipid antibody in cerebral ischemia--a case report

An abnormal increase in anti-beta2-glycoprotein I antibodies (abeta2GPI) is capable of producing thrombosis and the vasculopathy-simulating antiphospholipid antibody (aPL). However, it is rarely described in cerebral ischemia without an association with aPL. The authors report a middle-aged man who experienced recurrent cerebral ischemia and diffuse cerebral stenosis without the apparent traditional cardiovascular risk factor. He was free of antiphospholipid/cofactor syndrome (APCS) and systemic lupus erythematosus (SLE). An increase of blood abeta2GPI was detected in serial measurements. The aPL, Venereal Disease Research Laboratory (VDRL) test, Coombs' test, and antinuclear factor were negative. Activated partial thromboplastin time was normal. This patient is a reminder to consider abeta2GPI in an unexplained recurrent cerebral thrombosis and cerebral artery stenosis even when the typical clinical manifestation or laboratory data of APCS is absent.

Anti-beta2 glycoprotein I antibodies prevent the De-activation of platelets and sustain their phagocytic clearance

Exposure to phosphatidylserine (PS) tags dying and senescent cells for removal and identifies activated platelets. In this study we followed the fate of PS-exposing platelets in the presence of antibodies purified from Systemic Lupus Erythematosus (SLE) and primary Anti-phospholipid Syndrome (APS) patients' sera by beta2GPI affinity chromatography. Thrombin-activated platelets exposed PS and associated to beta2GPI. Both events were required for recognition by antibodies. Human monocyte-derived macrophages phagocytosed activated platelets only. Each macrophage internalized an average of 3.16+/-0.2 platelets after 60 min at 37 degrees C. Phagocytosis did not increase after longer incubations (4.65+/-0.26 platelets internalized by each macrophage after 300 min). Recognition of platelets by anti-beta2GPI antibodies significantly increased phagocytosis (P< 0.01). Upon withdrawal of thrombin, platelets downregulated PS (PS exposure t(1/2): 242 min) and the ability to be recognized by macrophages. Purified beta2GPI bound to PS-exposing platelets (association t(1/2): 250 min). Phosphatidyl serine exposure and beta2GPI association had virtually identical kinetics. Antibody binding prolonged the exposure of the beta2GPI/PS complex (t(1/2): >1200 min). The ability to phagocytose opsonized platelets was accordingly sustained (5.3+/-0.2 opsonized platelets were internalized by each macrophage after 60 min and 9.4+/-0.3 after 300 min). Anti-beta2GPI antibodies therefore poise activated platelets in a PS-exposing status, preventing the recycling of their function and favoring their phagocytic clearance.

Update on antiphospholipid antibodies

The association of antibodies with an apparent specificity for anionic phospholipids with thrombosis, fetal loss, thrombocytopenia, and certain other clinical manifestations is now well-recognized as the antiphospholipid syndrome (APS). Recent advances in our understanding of the antibodies and antigens involved include discovery of the crystal structure of beta2-glycoprotein I, (beta2GPI), genetic studies of beta2GPI polymorphisms, and the development of anti-beta2GPI and antiprothrombin immunoassays as clinical laboratory tests. The identification of antigen-specific T cells in APS patients has stimulated interest in the role of the cellular immune response in the syndrome. Clinical research in APS will also benefit from the development of preliminary classification criteria.

Which are the best biological markers of the antiphospholipid syndrome?

The diagnosis of antiphospholipid syndrome (APS) requires the presence of both clinical and biological features. Due to the heterogeneity of anti-phospholipid antibodies (aPL) the laboratory approach for their detection includes clotting-based tests for lupus anticoagulant (LA) as well as solid-phase assays for anticardiolipin antibodies (aCL). In addition, as it has been shown that autoimmune aPL recognize epitopes on phospholipid (PL)-binding plasma proteins, assays detecting antibodies to beta 2-glycoprotein I (beta 2-GPI) or prothrombin have been developed. The association between venous or arterial thrombosis and recurrent fetal loss with the presence of conventional aPL (LA and/or aCL) has been confirmed by many studies. The LA and IgG aCL at moderate/high titre seem to exhibit the strongest association with clinical manifestations of the APS. Several reports indicate that LA is less sensitive but more specific than aCL for the APS. Assays against PLs other than CL as well as the use of mixtures of PLs have been proposed to improve the detection of APS-related aPL. Concerning antibodies to PL-binding proteins (detected in the absence of PLs), there is evidence that anti-beta 2-GPI are closely associated with thrombosis and other clinical features of the APS. Moreover, these antibodies may be more specific in the recognition of the APS and in some cases may be present in the absence of aPL detected by standard tests. Many issues are still under debate and are discussed in this review, such as the problems of standardization of anti-beta 2-GPI assays, detection of the IgA isotype of aCL and anti-beta 2-GPI, the coagulation profiles of LA in the recognition of the thrombotic risk and the association of particular markers with subsets of patients with APS.

Antiphospholipid syndrome: antibodies and antigens

Elucidation of the antibodies and antigens involved in the antiphospholipid syndrome has provided many new insights and research opportunities. The major autoantibodies associated with the syndrome and detected in clinical laboratory assays for antiphospholipid antibodies are directed against prothrombin and beta2-glycoprotein I beta2GPI), a phospholipid-binding plasma protein whose physiological function is unknown. Recent advances in our understanding of these antibodies and antigens include discovery of the crystal structure of beta2GPI, identification of a plasmin cleavage site in beta2GPI, genetic studies of beta2GPI polymorphisms, development of clinical laboratory assays using purified protein antigens, and the identification of antigen specific T cells.

Anti-beta2-glycoprotein I (GPI) autoantibodies, annexin V binding and the anti-phospholipid syndrome

We examined the role of autoantibodies to beta2-GPI and prothrombin (PT) in the inhibition of annexin V binding to cardiolipin (CL) and the association with clinical manifestations of the anti-phospholipid syndrome (APS). Plasma samples from 59 patients with anti-phospholipid (aPL) antibodies were studied. Affinity purification of total IgG and IgG anti-ss2-GPI antibodies was performed using staphylococcal protein A and phospholipid liposomes. Annexin V binding to CL was significantly inhibited by 31/59 (53%) aPL+ plasma samples. There was a significant association between annexin V inhibition and elevated levels of IgG anti-cardiolipin (aCL) (r = -0.62; P < 0.001), IgG anti-ss2-GPI (r = -0.67; P < 0. 001) and a weaker association with lupus anti-coagulant (r = -0.27; P = 0.05). There was no association with other isotypes of aCL and anti-ss2-GPI or with anti-PT of any isotype. In patients with clinical manifestations of the APS there were higher levels of IgG aCL (median (range) Z score): 10.0 (0-17.6) versus 5.0 (0-16.1); P = 0.03), IgG anti-ss2-GPI (4.5 (0-11.3) versus 0.9 (0-9.7); P = 0.02) and greater inhibition of annexin V binding to CL (-3.4 (-11.4-0.6) versus -1.1 (-10.8-1.2); P = 0.22). Odds ratios for the laboratory assays and the presence of clinical manifestations of the APS varied between 0.38 and 4.16, with the highest values for IgG aCL (4.16), IgG anti-ss2-GPI (3.28) and annexin V inhibition (2.85). Additional experiments with affinity-purified IgG antibodies indicated that inhibition of annexin V binding was dependent upon the concentration of ss2-GPI and anti-ss2-GPI antibodies. These results indicate that inhibition of annexin V binding to procoagulant phospholipid surfaces is dependent upon anti-ss2-GPI antibodies and suggest a role for annexin V in the pathogenesis of the APS.

Phosphatidylserine expression on cell surfaces promotes antibody-dependent aggregation and thrombosis in beta2-glycoprotein I-immune mice

Beta-2-glycoprotein I (beta2GP1) has been implicated as the primary antigenic target in antiphospholipid syndrome. To study the role beta2GP1 antibodies play in thrombosis associated with this syndrome, the clearance and binding of phosphatidylserine (PS)-containing target membranes were monitored in beta2GP1-immune mice. Clearance in immune mice (T(1/2)4.8 min) was faster than in normal mice (T(1/2)11.0 min). Analysis of PS vesicles recovered from immune mice by sequencing and Western blotting showed the presence of bound beta2GP1 and autologous antibody, respectively. Bleeding times in immune mice were approximately 30% shorter than in control mice. In vitro clotting times, however, were the same in both populations. To determine if the in vivo results could be attributed to the interaction of autoantibodies with the vascular endothelium, the binding of PS-containing target membranes to normal and apoptotic endothelial cells was studied. While endothelial cells bound PS vesicles, beta2GP1 reduced uptake by approximately 50% in both normal and apoptotic endothelium. In the presence of beta2GP1 antibodies, however, uptake in apoptotic cells, but not normal cells, increased by more than two-fold. These results suggest that thrombosis in antiphospholipid syndrome could, in part, be due to antibody-dependent cross-linking of beta2GP1 bound to PS-expressing cells and the vascular endothelium.

[Aspirin and antiphospholipid syndrome]

INTRODUCTION

Antiphospholipid syndrome is the most frequent cause of acquired thrombophilia. Aspirin may have some indications. CURRENT KONWLEDGE AND KEY POINTS: The usefulness of low doses of aspirin is now well demonstrated in the prevention of obstetric complications associated with antiphospholipid antibodies (especially pregnancy loss). When heparin is combined with low-dose aspirin, the recurrent rate of fetal loss is lower than 30%. In patients with arterial or venous thrombosis, there is a high rate of recurrence during the two first years except if high-dose warfarin was used (i.e., INR > or = 3). The association warfarin-aspirin in secondary prevention of thrombosis may be evaluated in prospective studies. It is not so clear in the literature and in our experience that warfarin is superior to aspirin in stroke recurrence prevention in patients with antiphospholipid antibodies, except in Sneddon's syndrome. There are no guidelines in primary thrombosis prevention in patients with antiphospholipid antibodies. In lupus patients, aspirin may not be sufficient after many years of follow-up in preventing a first episode of thrombosis. Prospective studies may be undertaken. Atherosclerotic patients with antiphospholipid antibodies are particularly exposed to the risk of thrombosis after revascularisation or angioplasty and stent implantation. Aspirin may have a place in those patients but these must be evaluated. FUTUR PROSPECTS AND PROJECTS: Except in prevention of obstetric complications, the usefulness of aspirin in patients with antiphospholipid antibodies must be evaluated in prospective studies.

The anti-phospholipid antibody syndrome: clinical and serological aspects

The association of thromboses and/or cytopenias with anti-phospholipid antibodies (aPL), the anti-phospholipid syndrome (APS), is well recognized. The syndrome may be primary or occur within systemic lupus erythematosus (SLE). The notion of the syndrome occurring within SLE is important since patients found to have aPL may be at risk for developing APS manifestations, those who develop some manifestations may be at risk for developing others and, finally, SLE patients with this syndrome may need special treatment. There are subtle differences between the primary and the secondary forms, mostly due to the frequently higher and more persistent autoantibody levels in the primary and the influence of lupus in the secondary. These syndromes may be related to various antigen/antibody systems in which phospholipids participate either directly or through their effect on the proteins that bind them. Similar clinical manifestations also occur in patients who have serum antibodies to such proteins (e.g. beta2-glycoprotein-I) in the absence of phospholipid. Some of these antibodies may even be more important pathogenically than the antibodies against cardiolipin that were originally described. Testing for the latter is, however, still the first choice when suspecting an antiphospholipid syndrome. If this is negative in this situation, a search for the other autoantibodies is indicated.

The anti-phospholipid antibody syndrome (Hughes syndrome): therapeutic aspects

Despite the enormous amount of work focused on the pathogenesis and clinical manifestations of the Hughes or anti-phospholipid syndrome (APS), there is little published on management. Usually, the diagnosis of APS is made after the first thrombotic event, when a thrombophilia screen is performed. These patients have a high risk of recurrent thromboses and current therapy centres on the use of thromboprophylaxis with warfarin. However, a number of clinical questions keep recurring: do arterial and venous thrombosis require the same intensity of anti-coagulation? When should warfarin be stopped? Should patients who develop thrombosis when other risk factors (oral contraceptive pill, prolonged resting etc.) are present be treated like those without any risk factors but the presence of anti-phospholipid antibodies (aPL)? How to manage a patient with recurrent thrombosis despite a high intensity anti-coagulation (International normalized ratio (INR) between 3.0-4.0)? Since many of the patients with aPL are fertile women, a substantial group of patients are diagnosed after recurrent pregnancy loss. Low-dose aspirin for those patients without previous thrombosis and aspirin plus heparin for patients with a history of thrombotic events are the current therapeutic options. However, some questions remain unanswered: does the addition of heparin to low-dose aspirin in women with first trimester recurrent miscarriage but without previous thrombosis improve foetal outcome over and above aspirin alone? Which is the best therapeutic regime during pregnancy for patients with aPL-associated stroke? When should high-dose intravenous gammaglobulin be considered? Finally, very little is known about the risk of thrombosis in individuals positive for aPL but still free of thrombosis. Should these individuals receive any treatment? If so, which one? In this review we attempt to address some of these questions taking into account available data from retrospective and prospective studies and our own clinical experience.

Therapeutic plasma exchange for the acute management of the catastrophic antiphospholipid syndrome: beta(2)-glycoprotein I antibodies as a marker of response to therapy

We describe two patients with the catastrophic antiphospholipid syndrome associated with elevation of beta(2)-glycoprotein I antibodies and fulminant thrombotic diatheses. Both patients were treated with therapeutic plasma exchange (TPE), which resulted in a marked decrease in antibody titer accompanied by an improved clinical outcome in one patient (IgG antibody). In the second patient, the outcome was poor despite TPE (IgA antibody). There were no significant complications of TPE in either case. Because of the fulminant nature of the catastrophic antiphospholipid syndrome, we conclude that a trial of TPE is warranted for the acute management. Further studies are needed to clarify which patients may benefit from this treatment.

Relapsing catastrophic antiphospholipid antibody syndrome: a mimic for thrombotic thrombocytopenic purpura?

SUMMARY

The catastrophic antiphospholipid antibody syndrome (CAPS) is an uncommon disorder characterized by widespread micro- and macrovascular changes due to intravascular thrombosis. This complication of the antiphospholipid antibody syndrome is often fatal and recurrences are very rare. The differential diagnosis of CAPS includes thrombotic thrombocytopenic purpura (TTP) and this distinction may be difficult, but essential, for appropriate therapy. Plasmapheresis is effective in both conditions, but anticoagulation, a mainstay in the treatment of CAPS, could be disastrous in TTP. We present the case of an elderly woman who survived two episodes of CAPS four years apart and whose clinical findings were also suggestive of TTP. The characteristics of TTP and CAPS are compared and the importance of accurate diagnosis is emphasized.