Interaction between endothelial cell-derived extracellular vesicles and monocytes: A potential link between vascular thrombosis and pregnancy-related morbidity in antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune disease driven by a wide group of autoantibodies primarily directed against phospholipid-binding proteins (antiphospholipid antibodies). APS is defined by two main kinds of clinical manifestations: vascular thrombosis and pregnancy-related morbidity. In recent years, in vitro and in vivo assays, as well as the study of large groups of patients with APS, have led some authors to suggest that obstetric and vascular manifestations of the disease are probably the result of different pathogenic mechanisms. According to this hypothesis, the disease could be differentiated into two parallel entities: Vascular APS and obstetric APS. Thus, vascular APS is understood as an acquired thrombophilia in which a generalised phenomenon of endothelial activation and dysfunction (coupled with a triggering factor) causes thrombosis at any location. In contrast, obstetric APS seems to be due to an inflammatory phenomenon accompanied by trophoblast cell dysfunction. The recent approach to APS raises new issues; for instance, the mechanisms by which a single set of autoantibodies can lead to two different clinical entities are unclear. This review will address the monocyte, a cell with well-known roles in haemostasis and pregnancy, as a potential participant in vascular thrombosis and pregnancy-related morbidity in APS. We will discuss how in a steady state the monocyte-endothelial interaction occurs via extracellular vesicles (EVs), and how antiphospholipid antibodies, by inducing endothelial activation and dysfunction, may disturb this interaction to promote the release of monocyte-targeted procoagulant and inflammatory messages.     

Current status and future prospects for the treatment of antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a prothrombotic disease characterized by thrombosis and pregnancy morbidity in the presence of antiphospholipid antibodies (apL). Management of thrombosis is based on long-term oral anticoagulation and patients with arterial events should be treated aggressively. Primary thrombo-prophylaxis is recommended in patients with systemic lupus erythromatosus (SLE) and obstetric APS. Obstetric APS care is based on high-risk management and treatment with aspirin and heparin. Possible future therapies include statins, hydroxychloroquine, rituximab, and new anticoagulant drugs. Current research is focused on targeting components of the complement system, interfering with aPL–mediated cell activation and using tailored peptides to block the pathogenic subpopulation of aPL.     

Relative importance of different human aPL derived heavy and light chains in the binding of aPL to cardiolipin

INTRODUCTION: Previous studies have suggested the importance of somatic mutations and arginine, asparagine and lysine residues in the complementarity determining regions (CDRs) of antiphospholipid antibodies (aPL) implicated in the pathogenesis of the antiphospholipid antibody syndrome. The relative contributions of the heavy and light chains of aPL in binding to cardiolipin (CL) were assessed by pairing the heavy and light chains of two IgG, beta(2)GPI dependent aPL (IS4 and CL24) with different partner chains from other IgG, beta(2)GPI independent aPL (UK4) and anti-DNA antibodies (B3 and 33H11). METHODS: Four heavy (V(H)) and five light (V(L)) chain variable sequences from three aPL and two anti-DNA antibodies were cloned into expression vectors containing appropriate gamma(1), lambda or kappa constant region cDNA. Paired combinations of heavy and light chain expression plasmids were transfected into COS-7 cells allowing transient expression of whole IgG molecules, which were harvested and tested for the ability to bind CL and DNA by enzyme-linked immunosorbant assay (ELISA). RESULTS: Whole IgG was produced from 19 heavy/light chain combinations. IS4V(H) was dominant in conferring the ability to bind CL with four of the five V(L) tested. The identity of the V(L) region paired with IS4V(H) was important in determining the strength of binding to CL. IS4V(H) contains multiple arginine residues in CDR3, which may have accumulated due to antigen driven selection. It is likely that these arginine residues may interact with CL. The combination B3V(H)/B3V(L) also bound CL, but none of the other 14 combinations showed any binding in this assay. CONCLUSION: Whole IgG molecules capable of binding CL were produced by in vitro expression in COS-7 cells. Arginine residues play important roles in binding to CL and double-stranded DNA. However, different patterns of mutation to arginine are associated with binding to each of these antigens.     

Abstract 21-30

21. Nodular regenerative hyperplasia of the liver as the presenting manifestation of primary APS. A case report22. Prevalence of antiphospholipid and antinuclear antibodies in patients with active lupus nephritis23. IgM anticardiolipin antibodies and antiphospholipid syndrome24. Antiphospholipid antibodies(APLA)-possible markers in accelerated atherosclerosis25. Qinacrine added to ongoing therapeutic regimens is highly beneficial in active SLE and attenuates anticardiolipin antibody production26. Induction of pathogenic APL by CMV peptides27. Successful pregnancy outcome in a patient with Gaucher's disease and anti-phospholipid syndrome28. Antiphospholipid antibody levels in intravenous immunoglobulin (IVIg) preparations29. Transverse myelitis in patients with antiphospholipid antibodies: The importance of early diagnosis and treatment30. Antiphospholipid syndrome, antiphospholipid antibodies and atherosclerosis     

Structural and functional characterization of a human IgG monoclonal antiphospholipid antibody

Antiphospholipid antibodies (aPL) are likely involved in the pathogenesis of the antiphospholipid syndrome (APS). This study analyzes the structural and functional characteristics of a human monoclonal aPL (HL7G) from the IgG2 subtype with λ light chains generated from a patient with primary APS and recurrent cerebral microemboli. DNA encoding the variable region of heavy and light chains of the antibody was sequenced, analyzed, and compared to HL5B a previously described monoclonal aPL from the same patient. Both antibodies are derived from the same germline genes. HL7G had similar but more extensive somatic mutations in the CDR1 and 2 regions than HL5B, indicating that both antibodies are closely related and derived by a T cell-dependent antigen driven process. In ELISA assays HL7G bound to cardiolipin and several other phospholipid antigens in the absence of protein cofactors. Different from HL5B this aPL bound to β2-glycoprotein I (β2GPII). This suggests that reactivity of aPL against β2GPI is determined by only few specific amino acid exchanges. HL7G was able to induce tissue factor (TF) as one of the procoagulant effects of aPL. Our data suggest that the binding specificity of aPL is only of limited value to predict the biological effect and the pathophysiological impact of the antibodies.     

Antiphospholipid antibodies

The concept of antiphospholipid syndrome(APS) has been widely accepted. Antiphospholipid antibodies originally included anticardiolipin antibodies and lupus anticoagulants as serological marker of APS. However, recent advances have shown that most pathogenic antiphospholipid antibodies are directed to phospholipid binding proteins such as beta 2-glycoprotein I and prothrombin as well as phospholipids. The preliminary classification criteria for definite APS have been advocated as the "Sapporo criteria". Further prospective investigations are required to re-evaluate the clinical significance of so-called antiphospholipid antibodies.     

Antiphospholipid syndrome: From pathogenesis to novel immunomodulatory therapies

Antiphospholipid syndrome (APS) is characterized by recurrent thrombosis and pregnancy morbidity in association with the persistent presence of circulating antiphospholipid antibodies (aPL). APS remains the most frequent cause of acquired hypercoagulability and recurrent miscarriage. Long-term anticoagulation therapy is the only treatment with proven benefit in the APS. Anticoagulation is not effective in all patients and carries a risk of bleeding. Recent improvements in the understanding of the pathogenic mechanisms have led to the identification of potential targets and future therapies for APS. In contrast to non-specific anticoagulation, the emergence of immunomodulatory drugs provides the possibility of interfering with specific pathogenic pathways. Novel therapies might be used in the future for APS.     

Orthopedic Involvement in Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is a common autoimmune disease, manifested by vascular thrombosis and fetal loss in the presence of antiphospholipid antibodies. Orthopedic involvement is a relatively novel and underrecognized feature of APS. In this article we review the association of primary, secondary, and catastrophic APS with diverse orthopedic conditions, including osteonecrosis in adult and pediatric patients, bone marrow necrosis, nontraumatic fractures, and some other disorders.     

14th International Congress on Antiphospholipid Antibodies Task Force. Report on antiphospholipid syndrome laboratory diagnostics and trends

Current classification criteria for definite Antiphospholipid Syndrome (APS) require the use of three laboratory assays to detect antiphospholipid antibodies (aCL, anti-β2GPI and LA) in the presence of at least one of the two major clinical manifestations (i.e. thrombosis or pregnancy morbidity) of the syndrome. However, several other autoantibodies shown to be directed to other proteins or their complex with phospholipids have been proposed to be relevant to APS but their clinical utility and their diagnostic value remains elusive.This report summarizes the findings, conclusions and recommendations of the “APS Task Force 3—Laboratory Diagnostics and Trends” meeting that took place during the 14th International Congress on Antiphospholipid Antibodies (APLA 2013, September 18–21, Rio de Janeiro, RJ, Brazil).     

Characterization of monoclonal anti-beta2-glycoprotein-I and anti-prothrombin antibody fragments generated by phage display from a patient with primary antiphospholipid syndrome

The molecular structure of antibodies associated with autoimmune thrombosis is beginning to be understood. We describe the binding specificities and sequence analysis of anti-beta2-glycoprotein-I (anti-beta2GP-I) or anti-prothrombin (anti-PT) antibody fragments generated by phage display from a patient with primary antiphospholipid syndrome (APS). We obtained 39 positive clones, two that had the correct size reacted with beta2GP-I (Beta 1 and Beta 2). Ten clones with the same restrictive pattern recognized PT (Prot 1) and cross-reacted with beta2GP-I. All three clones recognized anionic and zwitterionic phospholipids. The V(H) regions of both anti-beta2GP-I clones are members of the VH4 family. Prot 1 has a V(H) segment of the VH3 family. The Beta 1 J(H) segments are J(H)5b and J(H)4b for Beta 2 and Prot 1. V(L) genes are V(lambda)1, 3 and 1, respectively. No J(L) was identified for Beta 1, while Beta 2 and Prot 1 carry J(lambda)3b genes. Beta 1 and Beta 2 carry highly conserved germ-line V(H) and V(L) genes. Mutations of the Prot 1 gene appear to be antigen-dependent, most are hotspot mutations located in the CDR 1 and 2 regions. Our work suggests that some anti-beta2GP-I from patients with primary APS are natural autoantibodies. Our work may also help to explain the frequent coexistence of anti-beta2GP-I and anti-PT in the same patient.     

Bovine IgM antibodies with exceptionally long complementarity-determining region 3 of the heavy chain share unique structural properties conferring restricted VH + Vlambda pairings

Naturally occurring antibody repertoires of cattle (Bos taurus) include a group of IgMlambda antibodies with exceptionally long complementarity-determining region 3 of the heavy chain (CDR3H) segments, containing multiple Cys residues. These massive CDR3H segments will greatly influence the tertiary and quaternary structures of the bovine IgM combining sites. As an antibody's combining site is formed by both heavy and light chains, we have analyzed the nucleotide sequences and structural properties of the lambda-light chains that pair with micro -heavy chains containing exceptionally long CDR3H. There appears to be an exquisite selective pressure for the use of three V(lambda)1 genes (V(lambda)1x and two new V(lambda)1d and V(lambda)1e genes) in IgM with unusually long CDR3H. The V(lambda)1d and V(lambda)1e genes are similar to each other, but diverge from the other V(lambda)1 genes into two closely related subfamilies. The available bovine V(lambda) genes are classified into three V(lambda) gene families: V(lambda)1, V(lambda)2 and V(lambda)3 based on nucleotide similarity >/=80%. Further, analysis of total Ser content and positions of Ser residues in the sequences was found to be sufficient to classify the cattle V(lambda)1 subfamilies. Patterns of Ser residues differ for V(lambda) domains from ruminant species (e.g. cattle, sheep and goats) and other mammals (e.g. humans and mice). These 'Ser signatures' can be used to track divergent evolution in lambda-light chains. Interestingly, Ser90L in complementarity-determining region 3 of the light chain (CDR3L) occurred in all V(lambda) domains that pair with V(H) regions containing exceptionally long CDR3H. A structural role for Ser90L was revealed in homology models of V(lambda) domains, i.e. to hold the ascending polypeptide of CDR3L in a relatively tight space between the N-terminal segment and residues from CDR1L. The CDR3L of V(lambda) domains also occupied smaller volumes if paired to V(H) domains with extremely long CDR3H (>/=48 residues), and were more variable in their conformation and filled larger volumes if CDR3Hs were 相似文献   

Systemic Antiphospholipid Syndrome and Atherosclerosis

Atherosclerosis (AT) is a metabolic, systemic inflammatory/immune disease characterized by lipoproteins metabolism alteration that leads to immune/inflammatory system activation with the consequent proliferation of smooth-muscle cells, narrowing arteries and atheroma formation. Antiphospholipid syndrome (APS) is a systemic autoimmune disease characterized by thrombophilic state and circulating antiphospholipid antibodies (aPL) including anti β2-GPI. Experimental studies and human observations suggest that APS is associated with AT. In fact, innate and adaptive immune responses participate in the pathogenesis of both diseases. Anti-oxLDL, anti-aPL, anti β2GPI, anti-HSP antibodies, among others, has been found in patients with APS and AT. Endothelial dysfunctions, oxidative stress, increase of cell adhesion molecules, active platelets, are common findings in both diseases. Macrophages, dendritic cells, T-cell activation, CD40–CD40 ligand interaction, are considered as pathogenic mechanism of AT and APS. Premature AT may be the first symptom of APS. Thrombophilia, aPL antibodies, and APS may be present in patients with premature AT. An association between AT and venous thrombosis (a clinical hallmark of APS) has been proposed in unselected patients with deep venous thrombosis of the legs without symptomatic AT. Asymptomatic AT, defined in terms of carotid intima media thickness and lumen diameter decrease, was observed in patients with APS. Premenopausal female patients with PAPS have a higher prevalence of cerebrovascular disease in comparison with male patients. Accelerated AT and hormones could be the explanation of these findings. High levels of aCLs, significantly predict the risk of future ischemic stroke in women but not in men. AT is one of the main features of systemic APS and offer opportunities for new treatment strategies.     

Antiphospholipid Syndrome Infectious Origin

Antiphospholipid syndrome (APS) is characterized by the presence of pathogenic autoantibodies against beta 2-glycoprotein-I (beta 2GPI). The factors causing production of anti-beta 2GPI remain unidentified, but an association with infectious agents has been reported. Studies on experimental APS models proved that molecular mimicry between beta 2GPI-related synthetic peptides and structures within bacteria, viruses, tetanus toxoid, and CMV are a cause for experimental APS. Any explanation of how microbial infections might set off APS must take into account the observation that all individuals appear to harbor potentially autoreactive lymphocytes, as well as natural antiphospholipid antibodies, but that these cells or antibodies remain innocuous unless somehow activated. Herein, we discuss the association of antiphospholipid antibodies in the infectious state, molecular mimicry as a proposed cause for development of APS, and the contribution of the database to this topic.     

Pathogenic roles of anti-beta2-GPI antibody in patients with antiphospholipid syndrome]

Antiphospholipid syndrome (APS) is characterized by arterial and/or venous thrombosis and pregnancy morbidity in the presence of antiphospholipid antibodies (aPL). Beta2-glycoprotein I (beta2-GPI) and prothrombin are representative autoantigens, the former more extensively investigated. Anti-beta2-GPI antibodies are not only markers of APS, but also are considered to be pathogenic. Possible roles of anti-beta2-GPI antibodies are, 1) enhancement the binding of beta2-GPI to anionic phospholipid and inhibition of protein C activation/activated protein C, 2) to form anti-beta2-GPI antibody-beta2-GPI-oxidized LDL complex and to promote uptake by sub-endothelial macrophage, resulting in atherosclerosis, 3) to dimerize beta2-GPI on the surface of platelets and to activate platelets via apoE receptor 2 and subsequent signal transduction, 4) stimulation of monocytes via p38 MAP kinase pathway and induction of tissue factor production. In pregnancy morbidity, activation of complement cascade plays an important role. These findings may provide a novel target in the management of APS.     

Antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a disease characterized by venous and arterial thromboses or spontaneous abortions and the repeated detection of antiphospholipid antibodies (aPL). APS may be associated with another autoimmune disease (secondary APS), particularly systemic lupus erythematosus (SLE), or unrelated to an underlying disease (primary APS). APS affects almost all organs. In addition to the clinical criteria, lupus anticoagulant testing and immunological aPL determinations are required to establish the diagnosis of APS.     

Autoantibody explosion in antiphospholipid syndrome

Antiphospholipid syndrome (APS) is characterized by thrombosis and pregnancy loss in the presence of antiphospholipid antibodies (aPL), mainly anticardiolipin, anti-beta2-glycoprotein I and lupus anticoagulant. However, similar to systemic lupus erythematosus, APS is also characterized by multiple other autoantibodies including 'non-classical' aPL, as well as other antibodies. Herein we describe the autoantigen properties, prevalence and clinical importance of 30 different antibodies in APS. Among the other antibodies characterizing APS are autoantibodies directed to platelets, glycoproteins, various coagulation factors, lamins, mitochondrial antigens and cell surface markers. Few of these autoantibodies are correlated with the presence of other antibodies, and some may have an additive role in the pro-thrombotic tendency of the syndrome. This autoantibody explosion might be important in early identification of the syndrome and its manifestations.     

Ocular manifestations in antiphospholipid syndrome

Antiphospholipid syndrome (APS) is characterized by increased hypercoagulability and divergent symptoms including ocular manifestations. In APS patients arterial and/or venous thromboses and repeated fetal loss are diagnosed in presence of antiphospholipid (aPL) antibodies. Antiphospholipid antibodies are heterogeneous group of immunoglobulins with different antigenic structure. Primary APS is defined in the absence of underlying disease, while secondary APS is seen within another pathological condition. In both primary and secondary APS ocular and neuroophthalmic manifestations, such as retinal arteritis, retinal venous occlusion, ischemic optic neuropathy, transient loss of vision - amaurosis fugax, diplopia and others can be diagnosed. In secondary APS occlusion of central retinal artery and vein (OACR, OVCR) is the most common finding, thus when found in younger patients it should be considered indicative of APS. Bilateral ocular changes are considered more significant since they affect both ocular function and life prognosis.     

Antiphospholipid antibodies and thrombosis: the putative mechanisms of hypercoagulable state in patients with anticardiolipin antibody

Antiphospholipid antibodies are well recognized as associated with serious clinical complications such as arterial and venous thrombosis and recurrent spontaneous abortion. These complications are collectively called antiphospholipid syndrome(APS). The mechanisms responsible for the thrombosis are unclear. We reported three mechanisms. beta 2-glycoprotein I(beta 2GPI) inhibited activated protein C(APC) activity and, furthermore, APC activity decreased by the addition of monoclonal aCL and beta 2GPI. Monoclonal anticardiolipin antibodies(aCL) seemed to enhance the inhibition of APC procoagulant activity caused by beta 2GPI. Monoclonal aCL in the presence of beta 2GPI also increased the activity of plasminogen activator inhibitor(PAI)-1 in the mixture of tissue-plasminogen activator(t-PA) and PAI-1 by inhibiting the function of beta 2GPI, which increased the remaining t-PA activity in the mixture. The formation of thrombin-antithrombin complexes(TAT) in APS was impaired. The level of TAT in APS did not increase, however the level of prothrombin fragment 1 + 2 (F1 + 2) increased. Therefore, free thrombin present in patients' blood may contribute to thrombosis in APS. These reports indicate that thrombosis in APS may be caused by several thrombogenic factors that stimulate aCL.     

Anti-beta 2-glycoprotein I and antiphosphatidylserine antibodies are predictors of arterial thrombosis in patients with antiphospholipid syndrome

The predictive value (PV) and association of 4 antiphospholipid antibodies with clinical manifestations of the antiphospholipid syndrome (APS) were evaluated in 90 patients with systemic lupus erythematosus (SLE) and 100 with APS. Patients with APS were classified into arterial thrombosis, venous thrombosis, and pregnancy morbidity subgroups. IgG, IgM, and IgA anticardiolipin (aCL), antiphosphatidylserine (aPS), anti-beta 2-glycoprotein I (anti-B2GPI), and antiprothrombin (aPT) antibodies were determined by enzyme-linked immunosorbent assay. Individually, anti-B2GPI and aPS antibodies had the strongest PV for APS (86.4%-94.1%; P < .001) in patients with SLE. The PV for APS reached 100% when 2 or more antibodies were present. Similarly, anti-B2GPI and aPS antibodies had a stronger PV and association for arterial thrombosis (87%-95%; P < .001) compared with venous thrombosis (80%-92%; P = .01). Weak PV and association with pregnancy morbidity were seen with all antibodies. These results suggest an important pathogenic role of anti-B2GPI antibodies in arterial thrombosis. In addition, anti-B2GPI and aPS antibodies seem to provide the best diagnostic value for the laboratory assessment of APS.