Rarer clinical associations of antiphospholipid antibodies

Detection of antiphospholipid antibodies (aPL) are central to the definition of the antiphospholipid (antibody) syndrome (APS). Thrombosis in certain vascular beds, such as the cerebral circulation, the veins of the lower legs and cutaneous vessels, and/or fetal loss, are common manifestations of APS. However, aPL have been found in association with a large range of other clinical conditions-these conditions constitute a rather heterogeneous group and are the subject of this review. Thus, aPL may rarely be found in association with thromboses of vascular beds other than those commonly associated with APS. The combination of thrombosis and aPL still satisfies the criteria for APS, and management of this group of patients is the same as that of APS associated with the more common manifestations of the disease. Alternatively, aPL may be detected in a range of conditions where thrombosis cannot be clearly demonstrated, such as duodenal ulcer or transverse myelopathy. The approach to management of patients who have aPL in association with these conditions is less clear, although in some cases interventions to remove the associated antibody have been associated with amelioration of the condition. Finally, in several studies, aPL have been detected in a proportion of patients with conditions occurring commonly in the normal population-these findings have to be treated with caution in view of inconsistent findings between the reported results and methodological limitation of studies purporting to show positive results.     

Pathogenic role of antiphospholipid antibodies

The antiphospholipid antibody syndrome (APS) is characterized by recurrent arterial and venous thrombosis and/or pregnancy in association with antiphospholipid (aPL) antibodies. The pathogenic mechanisms in APS that lead to in vivo injury are incompletely understood. Recent evidence suggests that APL antibodies alter regulation of haemostasis and induce activation of complement. We will discuss the current knowledge on how aPL antibodies trigger increased inflammation and enhanced thrombotic tendency, and thereby lead to tissue damage.     

Antiphospholipid syndrome, “the best prophet of the future”

The antiphospholipid syndrome (APS) is an autoimmune disorder characterized by the occurrence of venous and arterial thromboses, often multiple, and obstetric-related adverse events in the presence of antiphospholipid antibodies (aPL). APS, first described in 1983, as thrombosis, abortion and cerebral disease, is nowadays recognised as a systemic disease with a wide constellation of clinical manifestations related to acute and chronic vascular lesions. The presence of aPL is the serological hallmark of APS representing a heterogeneous population of autoantibodies with many antigenic specificities directed to phospholipid-binding proteins, either alone or in combination with phospholipids. Many assays have been developed for aPL detection. Particularly, anticardiolipin antibodies, anti-β2-glycoprotein I antibodies and lupus anticoagulant are essential tools for APS diagnosis. The cumulative evidence indicates that aPL are pathogenic autoantibodies binding to target cells and promoting thrombosis and pregnancy complications through a wide range of pathological mechanisms not yet fully understood. Finally, the recognition of the important role of aPL to assess the individual risk of thrombosis or pregnancy complications has expanded the concept of aPL, and currently aPL profile is regarded as a major risk factor for clinical thrombotic events.     

The relation between antiphospholipid syndrome-related pregnancy morbidity and non-gravid vascular thrombosis: A review of the literature and management strategies

The antiphospholipid syndrome (APS) is associated with pregnancy morbidity and vascular thrombosis in the presence of circulating antiphospholipid (aPL) antibodies. Clinical manifestations of aPL antibodies represent a spectrum (asymptomatic, pregnancy events, vascular events, or both pregnancy and vascular events), and APS should not be considered a single disease with a predictable outcome. Patients with aPL antibodies are at increased risk of vascular thrombotic events during pregnancy, the postpartum period, and even during long-term follow-up after an APS-related pregnancy event. Therefore, the purpose of this paper is to review the relation between APS-related pregnancy morbidity and vascular thrombosis, and to address the importance of prophylactic therapy during and after APS pregnancies to prevent maternal thrombotic complications. During pregnancy, low-dose aspirin (LDA) should be considered for all patients with aPL antibodies and heparin should be added to LDA in patients fulfilling the Sapporo criteria for definite APS. During delivery, especially with caesarian section, periods without anticoagulation should be kept to an absolute minimum. Some data suggest that LDA might be effective against future non-gravid vascular thrombosis in patients with APS and a history of only pregnancy morbidity.     

Identification of an Fc gamma receptor-independent mechanism by which intravenous immunoglobulin ameliorates antiphospholipid antibody-induced thrombogenic phenotype

OBJECTIVE: Patients with the antiphospholipid antibody syndrome (APS) often experience recurrent arterial and venous thrombosis and pregnancy losses. Intravenous immunoglobulin (IVIG) therapy has prevented pregnancy loss in some women with APS and has reversed fetal resorption rates in murine models of pregnancy loss. Although the basis for these effects is unknown, effector mechanisms of pathogenic antibodies often involve receptors for IgG (Fc gamma receptors [Fc gammaR]). We examined the potential mechanisms of action of WIG in an in vivo murine model of antiphospholipid antibody (aPL)-induced thrombosis and endothelial cell activation. METHODS: Mice infused with IgG containing human anticardiolipin antibodies (aCL) were treated with IVIG (36 microg i.v.), saline, or ovalbumin. Surgically induced thrombus formation and in vivo leukocyte adhesion to endothelial cells were measured. Circulating levels of aCL were measured by enzyme-linked immunosorbent assay. To determine whether Fc gammaR are required for the effects of IVIG, we treated mice deficient in stimulatory Fc gammaR. To examine the effects of IVIG on endogenously generated antibody, we treated mice immunized with beta2-glycoprotein I (beta2GPI). RESULTS: IVIG treatment inhibited aPL-induced endothelial cell activation and enhancement of thrombosis in mice passively infused with human aPL-containing IgG, and this was associated with a decrease in aPL levels. Similarly, IVIG lowered aPL levels and inhibited thrombogenesis in mice immunized with beta2GPI. The thrombophilic effects of aPL were evident in Fc gammaR-deficient mice. CONCLUSION: Treatment with IVIG inhibits the thrombogenic effects of aPL in vivo and reduces the levels of aCL in the circulation. Blockade of stimulatory Fc gammaR on inflammatory cells is not necessary for this effect. The mechanism of action of IVIG is more likely saturation of the IgG transport receptor, leading to accelerated catabolism of pathogenic aPL. These results have implications in the management of thrombosis in APS and may have applications for pregnant patients with a history of APS.     

Epilepsy as part of systemic lupus erythematosus and systemic antiphospholipid syndrome (Hughes syndrome)

The antiphospholipid syndrome (APS) is defined by the presence of antiphospholipid antibodies (aPL), demonstrated by ELISAs for antibodies against phospholipids and associated phospholipid-binding cofactor proteins and/or a circulating lupus anticoagulant (LA) together with diverse systemic clinical manifestations such as thrombosis, and recurrent spontaneous abortions. According to the criteria set out in Sydney the only neurological manifestations that can be suitable as APS classification criteria are ischemic events (stroke and transient ischemic attacks). However, other neurological manifestations, including seizures in particular, have been repeatedly reported in APS patients. The present review will summarize recent research on the association of aPL, as well as other autoantibodies, with seizure disorders, with or without concomitant SLE.     

Novel considerations in the pathogenesis of the antiphospholipid syndrome: involvement of the tissue factor pathway of blood coagulation

The antiphospholipid syndrome (APS) is characterized by clinical manifestations such as venous and arterial thrombosis, thrombocytopenia and/or recurrent pregnancy loss, as well as the persistent presence of laboratory markers of antiphospholipid (aPL) antibodies detected in laboratory assays. Though it is generally accepted that aPL antibodies, such as anticardiolipin (aCL), anti-beta2 glycoprotein I (anti-beta2GPI), and lupus anticoagulants (LA) contribute to the pathogenesis of APS, precise mechanism(s) are yet to be fully described. It is probable that aPL antibodies bind to a range of cellular targets (e.g., platelets, endothelial cells, and monocytes), leading to thrombosis and obstetric complications. There is now increasing evidence that alterations to the tissue factor (TF) pathway of blood coagulation contribute toward hypercoagulability in patients with aPL antibodies. This article reviews current evidence that suggests changes and/or interference to the major pathway of blood coagulation may represent a novel mechanism that contributes to the development of APS.     

What have we learned about antiphospholipid syndrome from patients and antiphospholipid carrier cohorts?

Venous or arterial thrombosis or pregnancy morbidity in the presence of circulating antiphospholipid antibodies (aPL) define the antiphospholipid syndrome (APS). In terms of accepted APS criteria, aPL are detected by one coagulation test (lupus anticoagulant; LAC) and two immunoassays (anticardiolipin antibodies and anti-β2-glycoptrotein I antibodies). In patients with APS, a single positive test carries a much lower risk of thrombosis recurrence or new pregnancy loss than does multiple (or triple) positivity. The same holds true for aPL carriers, namely subjects with laboratory tests but without clinical criteria for APS. Thus, very different risk categories exist among patients with APS as well as in carriers of aPL. Triple positivity apparently identifies the pathogenic autoantibody (antidomain I-II of β2-glycoptrotein I); it is in this category of patients that trials on new therapeutic strategies should focus.     

Pathogenetic mechanisms of antiphospholipid antibody production in antiphospholipid syndrome

Antiphospholiipid syndrome (APS) is an autoimmune disease characterized by the pathological action of antiphospholipid antibodies (aPL), that leads to recurrent pregnancy loss and thrombosis. Despite limited evidence, it is clear that there are both inherited and acquired components of the ontogeny of these antibodies. Animal genetic studies and human familial and population studies highlight the influence of genetic factors in APS, particularly human leukocyte antigen associations. Similarly, both animal and human studies have reported the importance of acquired factors in APS development and infectious agents in particular have a great impact on aPL production. Bacterial and viral agents have been implicated in the induction of autoimmune responses by various mechanisms including molecular mimicry, cryptic autoantigens exposure and apoptosis. In this review we highlight the latest updates with regards to inherited and acquired factors leading to the manufacturing of pathogenic antibodies and APS.     

Interpretation and recommended testing for antiphospholipid antibodies

The antiphospholipid syndrome (APS) is defined by the association of arterial and/or venous thrombosis and/or pregnancy complications with the presence of at least one of the main laboratory-detected antiphospholipid antibodies (aPL) (i.e., lupus anticoagulants [LA], IgG and/or IgM anticardiolipin antibodies [aCL], and IgG and/or IgM anti-β2-glycoprotein I antibodies [aβ2GPI]). During the last decade efforts have been made to improve the harmonization and reproducibility of laboratory detection of aPL and guidelines have been published. The prognostic significance of aPL is being clarified through the fine elucidation of their antigenic targets and pathogenic mechanisms. Several clinical studies have consistently reported that LA is a stronger risk factor for both arterial and venous thrombosis compared with aCL and aβ2GPI. In particular, LA activity dependent on the first domain of β2-glycoprotein I and triple aPL positivity are prognosticators of the thrombotic and obstetric risks. Hopefully, this increasing knowledge will help improve diagnostic and treatment strategies for APS.     

The Roll of Toll-like Receptors in the Antiphospholipid Syndrome

The antiphospholipid syndrome (APS) is an autoimmune disease characterized by thrombosis, recurrent fetal loss, and the presence of antiphospholipid antibodies (aPL). Recent data support the idea that the thrombotic activity in APS patients is attributed to enhanced cytokine release via activation of certain Toll-like receptors. To investigate these mechanisms more precisely, different experimental approaches were used to investigate this connection in detail. IgG fractions and/or monoclonal aPL, either generated from murine or human B cells were intensely used for stimulation experiments of monocytes, endothelial cells, or dendritic cells. All these stimuli induced an enhanced expression and secretion of cytokines, especially tumor necrosis factor (TNF)-α, caused by specific regulation or activation of Toll-like receptors. Using specific agonists or inhibitors could confirm the causal connection of these stimulatory effects. This review focuses on these recent developments, connecting the binding of aPL with the activity of Toll-like receptors, especially in monocytes, endothelial cells, and dendritic cells.     

Antiphospholipid antibodies and antiphospholipid syndrome in 57 children and adolescents with systemic lupus erythematosus

The presence of antiphospholipid (aPL) antibodies and antiphospholipid syndrome (APS) was researched in 57 children and adolescents with systemic lupus erythematosus (SLE). The frequency of aPL antibodies was 75.4% (anticardiolipin 70.2% and lupus anticoagulant 29.1%). The positivity for these antibodies fluctuated during the course of the disease. No association was found between aPL antibodies and clinical or laboratory manifestations or the autoantibodies studied, nor with the activity or gravity of the SLE. APS was diagnosed in 14% of the cases (eight patients), on average three years after the diagnosis of SLE. Four patients had arterial thrombosis (stroke, three; transient ischaemic attack, one; amaurosis fugax, two; renal, one), one presented with deep vein thrombosis (DVT) and three had involvement of small calibre vessels (osteonecrosis, two; transverse myelitis, one). Recurrences were observed in three of the eight cases (37.5%), with a mean interval of 13 months between the events. The presence of APS was associated with haemolytic anaemia, leukopenia, thrombocytopenia, coagulation abnormalities, ischaemic cerebrovascular accidents, amaurosis fugax, osteonecrosis and interstitial pneumonitis. A negative association was observed between APS and the presence of anti-Ro antibodies.     

Stroke and antiphospholipid syndrome: the treatment debate

Antiphospholipid syndrome (APS) is one of the most frequent acquired thrombophilias. Thromboses can be at both the venous and arterial level, are usually recurrent and frequently affect cerebral circulation. Although it is difficult to predict which patients with antiphospholipid antibodies (aPL) will develop thrombosis, once a thrombotic event has taken place, secondary prevention is mandatory. Recommendations for treatment of APS have long been based on studies with a retrospective design. Recently, three prospective studies (two controlled and one uncontrolled small series) have addressed the role of antiaggregant and anticoagulant therapy in patients with stroke and aPL. However, results from prospective and retrospective studies are not in full agreement. In addition to the obvious differences in design, other factors such as the important variability in the study groups account for the discrepancy. While future investigation must better define homogeneous subsets of patients with APS, current secondary prophylaxis of thrombosis in these patients must be tailored according to individual estimated risk of recurrences, risk of haemorrhage and severity of potential recurrent events. Due to the often devastating consequences of stroke, we believe there is a place for prolonged, high-intensity anticoagulation in patients with APS and cerebral arterial thrombosis.     

Syndrome des antiphospholipides « séronégatif » : mythe ou réalité ?

The antiphospholipid syndrome (APS) is a systemic autoimmune disease characterized by thrombosis and/or obstetrical manifestations and the persistent presence, at least 12 weeks apart, of antiphospholipid antibodies (aPL) such as lupus anticoagulant (LA) and/or anticardiolipin antibodies (ACL) and/or anti-β2 glycoprotein I antibodies (aβ2GPI). The finding of patients with clinical profile highly suggestive of APS but who are negative for conventional biological criteria has led to the concept of seronegative APS. In the last few years, new antigen targets and methodological approaches have been employed to more clearly identify this syndrome in patients with thrombosis or obstetrical complications without conventional aPL. Although seronegative APS is still controversial, there is increasing recognition of the existence of this subgroup. However, clinical relevance of non conventional aPL need to be confirmed by efforts toward standardizing new biological tools and longitudinal studies involving large cohort of patients.     

Risk of thrombosis in patients with antiphospholipid antibodies and factor V Leiden mutation

OBJECTIVE: Antiphospholipid antibodies (aPL) are thrombophilic risk markers in patients with systemic lupus erythematosus (SLE) or primary antiphospholipid syndrome (APS). The risk factors for recurrent venous or arterial thrombosis and indications for longterm anticoagulation therapy are debated. We hypothesized that carrying a second thrombophilic defect, factor V Leiden mutation, would increase the risk for thrombosis in patients with aPL. METHODS: Seventy-five patients with primary APS and 83 with SLE and aPL with or without thrombosis followed at 2 university hospitals were studied. Factor V mutation rate was analyzed in patients and in 200 healthy blood donors by polymerase chain reaction analysis. RESULTS: The prevalence of factor V Leiden mutation in patients with SLE and aPL or primary APS was similar to controls. Patients with deep vein thrombosis or arterial thrombosis did not have a significantly increased rate of factor V mutation compared to controls or to patients with aPL without thrombosis. CONCLUSION: Factor V Leiden mutation is not significantly associated with vein thrombosis in patients with aPL. However, due to the sample size we cannot rule out synergy between both factor V Leiden and aPL. A trend toward increased risk for thrombosis was detected in patients with the mutation and this should be analyzed in a larger study.     

Gene polymorphisms of tissue plasminogen activator and plasminogen activator inhibitor-1 in patients with antiphospholipid antibodies

OBJECTIVE: Impaired fibrinolytical outcomes may be one of the pathogenic factors for thrombotic events in patients with antiphospholipid antibodies (aPL). We investigated the consequences of the gene polymorphisms of tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) in patients positive for aPL. METHODS: Seventy-seven Japanese and 82 British patients with aPL were examined for Alu-repeat insertion (I)/deletion (D) polymorphism of the tPA gene by polymerase chain reaction (PCR), and 4G/5G polymorphism in the PAI-1 promoter gene by site-directed mutagenesis-PCR and restriction fragment length polymorphism analysis. Correlations between these polymorphisms and clinical symptoms of antiphospholipid syndrome (APS) (arterial thrombosis, venous thrombosis, miscarriage) were analyzed. RESULTS: Significant differences in the allele frequencies of these genes did not exist between patients and controls. There was no significant correlation between these gene polymorphisms and clinical symptoms of APS in patients with aPL. CONCLUSION: Polymorphisms of the tPA or PAI-1 genes probably do not significantly influence the risk of anerial thrombosis, venous thrombosis, or pregnancy morbidity in patients with aPL.     

Genetics of antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by recurrent arterial or venous thrombosis or fetal loss and the presence of antiphospholipid antibodies (aPL). Genetic factors are thought to play a role in the susceptibility to APS. Similar to many other polygenic autoimmune diseases, human leukocyte antigen associations have been reported. The genetics of β₂-glycoprotein I, one of the most representative target antigens of aPL, has been extensively studied. Additional genetic risk factors for the development of thrombosis in patients with aPL have also been discussed. However, the genes involved in APS have not been identified because antigen specificity of aPL and the pathophysiology of APS are highly heterogeneous and multifactorial. Genomewide linkage analysis and larger cohort studies would lead to better understanding of the genes that might be involved in APS.     

Examining the non-linear relationship between monoclonal antiphospholipid antibody sequence, structure and function

In the antiphospholipid syndrome (APS), pathogenic antiphospholipid antibodies (aPL) that cause thrombosis or pregnancy morbidity are characterized by binding to anionic phospholipids (PL) and beta2-glycoprotein I (beta(2)GPI). Sequence analysis of human monoclonal aPL has shown that high affinity for these antigens is associated with the presence of three particular amino acids: arginine (Arg), asparagine and lysine in the complementarity determining regions (CDRs) of their heavy and light chains. In vitro expression systems have been used to create variants of the antibodies in which these amino acids have been altered. In general, removal of Arg residues reduces affinity for anionic PL and beta(2)GPI. Arg at different positions in the sequence, however, have different effects on binding affinity and effects on binding are not always mirrored by effects on pathogenicity. This review will focus upon the sequence motifs that have been found to distinguish pathogenic from non-pathogenic aPL, and whether these or other properties may help to identify distinct pathogenic subsets of aPL. In particular, we will focus on our recent work in which we are trying to develop a better understanding of the molecular mechanisms involved in activation of target cells by pathogenic aPL. These studies, together with molecular models of antigen/antibody complexes, help us to understand exactly how pathogenic antibodies interact with antigens. Ultimately, this understanding may aid the design of more powerful diagnostic/prognostic assays and targeted therapeutic agents to block the pathogenic effects of these antibodies.     

Pathophysiology of the antiphospholipid syndrome: roles of anticardiolipin antibodies in thrombosis and fibrinolysis

Antiphospholipid antibodies (aPL) (anticardiolipin antibodies and lupus anticoagulant) are associated with thrombosis and pregnancy morbidity, the antiphospholipid syndrome (APS). Despite the clear association between aPL and those manifestations, the precise underlying disease mechanisms remain unclear. APL may affect the normal procoagulant and anticoagulant reactions occurring on cell membranes, and also may interact with certain cells, altering the expression and secretion of procoagulant substances. In this article, we review the immunological characteristics of anticardiolipin antibodies and their potential effects on the coagulation and fibrinolytic systems implicated in the development of thrombotic complications in patients with APS.