Complement activation in patients with primary antiphospholipid syndrome

Opposite Profiles of Complement in Antiphospholipid Syndrome (APS) and Systemic Lupus Erythematosus (SLE) Among Patients With Antiphospholipid Antibodies (aPL)

APS is the association of antiphospholipid antibodies (aPL) with thromboses and/or recurrent pregnancy loss (RPL). Among patients with SLE, one-third have aPL and 10–15% have a manifestation of secondary APS. Animal studies suggested that complement activation plays an important role in the pathogenesis of thrombosis and pregnancy loss in APS. We performed a cross-sectional study on complement proteins and genes in 525 patients with aPL. Among them, 237 experienced thromboses and 293 had SLE; 111 had both SLE and thromboses, and 106 had neither SLE nor thrombosis. Complement protein levels were determined by radial immunodiffusion for C4, C3 and factor H; and by functional ELISA for mannan binding lectin (MBL). Total C4, C4A and C4B gene copy numbers (GCN) were measured by TaqMan-based realtime PCR. Two to six copies of C4 genes are frequently present in a diploid genome, and each copy may code for an acidic C4A or a basic C4B protein. We observed significantly (a) higher protein levels of total C4, C4A, C4B, C3, and anticardiolipin (ACLA) IgG, (b) increased frequencies of lupus anticoagulant and males, and (c) decreased levels of complement factor H, MBL and ACLA-IgM among patients with thrombosis than those without thrombosis (N = 288). We also observed significantly lower GCNs of total C4 and C4A among aPL-positive patients with both SLE and thrombosis than others. By contrast, aPL-positive subjects with SLE had significantly reduced protein levels of C3, total C4, C4A, C4B and ACLA-IgG, and higher frequency of females than those without SLE. Patients with thrombosis but without SLE (N = 126), and patients with SLE but without thrombosis (N = 182) had the greatest differences in mean protein levels of C3 (p = 2.6 × 10⁻⁶), C4 (p = 2.2 × 10⁻⁹) and ACLA-IgG (p = 1.2 × 10⁻⁵). RPL occurred in 23.7% of female patients and thrombotic SLE patients had the highest frequency of RPL (41.0%; p = 3.8 × 10⁻¹⁰). Compared with non-RPL females, RPL had significantly higher frequency of thrombosis and elevated C4 protein levels. Female patients with homozygous C4A deficiency all experienced RPL (p = 0.0001) but the opposite was true for patients with homozygous C4B deficiency (p = 0.017). These results provide new insights and biomarkers for diagnosis and management of APS and SLE.

Blood Cell-Bound C4d as a Marker of Complement Activation in Patients With the Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is a chronic and disabling condition characterized by recurrent thrombosis and miscarriages mediated by antibodies against phospholipid-binding proteins (aPL), such as beta₂glycoprotein I (β₂GPI). Complement is involved in APS animal models and complement deposits have been documented in placenta and thrombotic vessels despite normal serum levels. Analysis of circulating blood cells coated with C4d displays higher sensitivity than the conventional assays that measure soluble native complement components and their unstable activation products in systemic lupus erythematosus (SLE). As C4d-coated blood cell count has been reported to be more sensitive than serum levels of complement components and their activation products in systemic lupus erythematosus (SLE) patients, we decided to evaluate the percentage of C4d positive B lymphocytes (BC4d), erythrocytes (EC4d), and platelets (PC4d) in primary APS patients and asymptomatic aPL positive carriers as marker of complement activation in APS. We assessed by flow cytometry the percentages of BC4d, EC4d, and PC4d in primary APS (PAPS; n. 23), 8 asymptomatic aPL positive carriers, 11 APS-associated SLE (SAPS), 17 aPL positive SLE, 16 aPL negative SLE, 8 aPL negative patients with previous thrombosis, 11 immune thrombocytopenia (ITP) patients, and 26 healthy subjects. In addition, we used an in vitro model to evaluate the ability of a monoclonal anti-β₂GPI antibody (MBB2) to bind to normal resting or activated platelets and fix complement. EC4d and PC4d percentages were significantly higher in PAPS and aPL carriers as well as aPL positive SLE and SAPS than in aPL negative controls. The highest values were found in PAPS and in SAPS. The EC4d and PC4d percentages were significantly correlated with serum C3/C4 and anti-β₂GPI/anti-cardiolipin IgG. In vitro studies showed that MBB2 bound to activated platelets only and induced C4d deposition. The detection of the activation product C4d on circulating erythrocytes and platelets supports the role of complement activation in APS. Complement may represent a new therapeutic target for better treatment and prevention of disability of APS patients.

Complement Therapeutics in Autoimmune Disease

Many autoimmune diseases are characterized by generation of autoantibodies that bind to host proteins or deposit within tissues as a component of immune complexes. The autoantibodies can activate the complement system, which can mediate tissue damage and trigger systemic inflammation. Complement inhibitory drugs may, therefore, be beneficial across a large number of different autoimmune diseases. Many new anti-complement drugs that target specific activation mechanisms or downstream activation fragments are in development. Based on the shared pathophysiology of autoimmune diseases, some of these complement inhibitory drugs may provide benefit across multiple different diseases. In some antibody-mediated autoimmune diseases, however, unique features of the autoantibodies, the target antigens, or the affected tissues may make it advantageous to block individual components or pathways of the complement system. This paper reviews the evidence that complement is involved in various autoimmune diseases, as well as the studies that have examined whether or not complement inhibitors are effective for treating these diseases.

Complement in the Pathophysiology of the Antiphospholipid Syndrome

The antiphospholipid syndrome (APS) is characterized by thrombosis and pregnancy morbidity in the presence of antiphospholipid antibodies (aPL). Complement is a system of enzymes and regulatory proteins of the innate immune system that plays a key role in the inflammatory response to pathogenic stimuli. The complement and coagulation pathways are closely linked, and expanding data indicate that complement may be activated in patients with aPL and function as a cofactor in the pathogenesis of aPL-associated clinical events. Complement activation by aPL generates C5a, which induces neutrophil tissue factor-dependent procoagulant activity. Beta-2-glycoprotein I, the primary antigen for pathogenic aPL, has complement regulatory effects in vitro. Moreover, aPL induce fetal loss in wild-type mice but not in mice deficient in specific complement components (C3, C5). Antiphospholipid antibodies also induce thrombosis in wild type mice and this effect is attenuated in C3 or C6 deficient mice, or in the presence of a C5 inhibitor. Increased levels of complement activation products have been demonstrated in sera of patients with aPL, though the association with clinical events remains unclear. Eculizumab, a terminal complement inhibitor, has successfully been used to treat catastrophic APS and prevent APS-related thrombotic microangiopathy in the setting of renal transplant. However, the mechanisms of complement activation in APS, its role in the pathogenesis of aPL related complications in humans, and the potential of complement inhibition as a therapeutic target in APS require further study.

Secondary thrombotic microangiopathy in systemic lupus erythematosus and antiphospholipid syndrome, the role of complement and use of eculizumab: Case series and review of literature

INTRODUCTION

Thrombotic microangiopathy (TMA) is a life-threatening, albeit infrequent, complication of systemic lupus erythematosus (SLE) and anti-phospholipid syndrome (APS). Recommendations for the treatment of SLE- and APS-related secondary TMA are currently based solely on case reports and expert opinion. Unfortunately, interventions may not yield timely results or effectively halt the progression of TMA. Since complement activation plays a key role in the pathogenesis of secondary TMA due to SLE, APS, a therapy that targets the complement pathway is an attractive intervention. Eculizumab, a recombinant, fully humanized IgG2/IgG4 monoclonal antibody inhibits C5 activation and is FDA-approved for PNH and atypical HUS (aHUS). However, limited case reports are available on its use in treatment of secondary TMA.

CASE PRESENTATION AND RESULTS

We present the largest case series to date that includes 9 patients with SLE and/or APS who were successfully treated with eculizumab for refractory secondary TMA. In this case series, we report significant responses in hematology values, renal function and other organs following treatment with eculizumab. At 4 weeks, 75% improvement in platelet counts was observed in 78% of patients. Two-thirds of patients demonstrated >75% improvement of haptoglobin and LDH at four weeks. At 4 weeks, eGFR improved by 25% in half of the patients, and 43% had reductions in proteinuria. Two of 3 patients that required hemodialysis were able to be taken off hemodialysis.

CONCLUSION

Based on these observations, we suggest that eculizumab may be a potential treatment option for acutely ill patients with secondary TMA due to SLE and/or APS who have failed standard of care. A collective approach is needed to better elucidate the role and optimal timing of eculizumab use in the management of TMA complicating SLE and/or APS.

Differences in plasma fibrin clot composition in patients with thrombotic antiphospholipid syndrome compared with venous thromboembolism

The prothrombotic fibrin clot phenotype has been reported in patients with thrombotic antiphospholipid syndrome (APS) and venous thromboembolism (VTE). Protein composition of plasma fibrin clots in APS has not been studied. We evaluated 23 patients with thrombotic APS, 19 with VTE alone, and 20 well-matched controls. A proteomic analysis of fibrin clots generated from citrated plasma was based on liquid chromatography-mass spectrometry. Plasma levels of thrombospondin-1 (TSP1), apolipoprotein(a), A-I, and B-100, complement components (C)3a, C5b-C9, histidine-rich glycoprotein (HRG), and prothrombin were evaluated using immunoenzymatic tests. In plasma fibrin clots of APS patients, compared with VTE subjects and controls, we identified decreased amounts of (pro)thrombin, antithrombin-III, apolipoprotein A-I, and HRG with no differences in plasma levels of antithrombin, prothrombin, along with lower plasma HRG and apolipoprotein A-I. In APS patients, plasma HRG positively correlated with amounts of clot-bound HRG, while apolipoprotein A-I was inversely associated with clot-bound levels of this protein. The most predominant proteins within the clots of APS patients were bone marrow proteoglycan, C5-C9, immunoglobulins, apolipoprotein B-100, platelet-derived proteins, and TSP1. Our study is the first to demonstrate differences in the protein composition of fibrin clots generated from plasma of thrombotic APS patients versus those with VTE alone.

Clinical profiles and risk assessment in patients with antiphospholipid antibodies

INTRODUCTION

Antiphospholipid syndrome (APS) is an acquired autoimmune thrombophilia associated with the presence of persistent antiphospholipid antibodies (aPL). Owing to recent studies, not only APS patients but also incidentally-identified, asymptomatic aPL carriers are able to be stratified in terms of the risk of future thrombotic events, according to the variety and the titer of positive aPL tests and to the non-thrombotic, aPL-associated clinical manifestations. Areas covered: Here, we critically review (1) criteria manifestations of APS, (2) non-criteria manifestations of APS, (3) risk assessment in patients with APS and in aPL carriers, and (4) the potential role of primary thrombosis prophylaxis in aPL carriers. In addition, we discuss what we are currently able to do and what we need to do in the future for primary prophylaxis against a first thrombotic event. Expert commentary: We suggest a comprehensive algorithm to stratify thrombotic risk in aPL carriers, including criteria aPL, non-criteria aPL, their scoring systems, and non-criteria manifestations. However, further studies, particularly prospective randomized controlled trials, are highly warranted to establish an effective and tolerable treatment regimen for high risk aPL carriers.

Therapeutic response to glucocorticoids, anticoagulation and plasma exchange in a patient with primary antiphospholipid syndrome presenting with purpura fulminans

We report the case of a 25-year-old female patient who presented with purpura fulminans as a manifestation of primary antiphospholipid syndrome. Purpura fulminans is considered a rare cutaneous manifestation of antiphospholipid syndrome. Most frequently, it occurs in the context of catastrophic antiphospholipid syndrome and is associated with significant morbidity and mortality, either due to loss of affected extremities or thromboembolic damage to internal organs. After insufficient efficacy of parenteral anticoagulation and oral glucocorticosteroid treatment, we escalated treatment to high-dose intravenous glucocorticosteroid and five consecutive sessions of plasma exchange with good and sustained clinical response. At follow-up six months after admission, skin manifestations had healed with scarring, and no additional thrombotic events had occurred. Plasma exchange may hold promise as a therapeutic option in refractory or severe cases of antiphospholipid syndrome-related purpura fulminans with extensive cutaneous necrosis, although evidence is limited.

The anti-thrombotic effects of vitamin D and their possible relationship with antiphospholipid syndrome

The importance of the immunomodulatory effects of vitamin D has recently been associated with autoimmune and chronic inflammatory diseases. Vitamin D deficiency has been linked to the development of autoimmune conditions. Antiphospholipid syndrome is an autoimmune disease characterized by thrombotic events and obstetric complications in patients with antiphospholipid antibodies. Current data show that patients with antiphospholipid syndrome have a high prevalence of vitamin D deficiency even without classic risk factors. Several studies have suggested vitamin D may have anti-thrombotic functions. In antiphospholipid syndrome, low vitamin D serum levels have been associated with thrombotic manifestations, suggesting a possible protective role of vitamin D in antiphospholipid syndrome. This literature review presents current evidence on the haemostatic functions of vitamin D and their possible relationship with the clinical manifestations of antiphospholipid syndrome.

Obstetric antiphospholipid syndrome

The present clinical and laboratory classification criteria for antiphospholipid syndrome (APS) were established in Sydney, Australia, in 2006. In this review, we focus on the obstetric subset of APS (OAPS), defined by persistent positivity for antiphospholipid antibodies together with either early recurrent pregnancy loss, early fetal death, stillbirth or premature birth <34 gestational weeks due to pre-eclampsia, eclampsia and placental insufficiency. It is important to diagnose these cases since most women suffering from OAPS can, when given appropriate treatment, have successful pregnancies. Furthermore, patients with OAPS may, depending on the antibody profile, be at enhanced risk of thrombotic events later in life. We present an update on the present knowledge of possible underlying pathogenesis, risk factors and risk estimations for adverse pregnancy outcomes before and during pregnancy, current treatment concepts, and long-term outcomes for women with OAPS and their children.

Complement Consumption in Systemic Lupus Erythematosus Leads to Decreased Opsonophagocytosis In Vitro

OBJECTIVE

Infections remain a major cause of morbidity and mortality in patients with systemic lupus erythematosus (SLE). The high prevalence of infections in SLE is attributed to both the disease and its treatments. The complement system plays an important role in host immune responses against invading microorganisms. We sought to provide the experimental and clinical evidence supporting the hypothesis that low levels of complement factors cause defective complement-mediated opsonization in patients with SLE.

METHODS

Staphylococcus aureus was opsonized with sera from healthy individuals (n = 16), SLE patients with normal (n = 5) or low complement (n = 8) levels. Phagocytosis of S. aureus by healthy human neutrophils was analyzed by an imaging flow cytometry-based method. We retrospectively examined the infection incidence in relation to complement levels in a cohort of 165 patients with SLE during a 1.5-year period. The association was analyzed for infection incidence and disease-related variables.

RESULTS

Uptake of S. aureus by neutrophils was decreased when S. aureus was opsonized with sera from SLE patients with low complement levels compared to sera from healthy individuals and SLE patients with normal complement. In our SLE cohort, 44% of patients had at least 1 infection during the 1.5 years. No significant association was observed between complement levels and infection risk. Importantly, high-dose glucocorticoids (GC; prednisone ≥ 10 mg/day) were the most important predictive factor for infections in patients with SLE.

CONCLUSION

Low complement levels affect bacterial opsonization in SLE blood and lead to downregulated phagocytosis by neutrophils. High-dose GC increase the infection risk in patients with SLE.

Pathogenic Role of Complement in Antiphospholipid Syndrome and Therapeutic Implications

Antiphospholipid syndrome (APS) is an acquired autoimmune disease characterized by thromboembolic events, pregnancy morbidity, and the presence of antiphospholipid (aPL) antibodies. There is sound evidence that aPL act as pathogenic autoantibodies being responsible for vascular clots and miscarriages. However, the exact mechanisms involved in the clinical manifestations of the syndrome are still a matter of investigation. In particular, while vascular thrombosis is apparently not associated with inflammation, the pathogenesis of miscarriages can be explained only in part by the aPL-mediated hypercoagulable state and additional non-thrombotic effects, including placental inflammation, have been described. Despite this difference, evidence obtained from animal models and studies in APS patients support the conclusion that complement activation is a common denominator in both vascular and obstetric APS. Tissue-bound aPL rather than circulating aPL-beta2 glycoprotein I immune complexes seem to be responsible for the activation of the classical and the alternative complement pathways. The critical role of complement is supported by the finding that complement-deficient animals are protected from the pathogenic effect of passively infused aPL and similar results have been obtained blocking complement activation. Moreover, elevated levels of complement activation products in the absence of abnormalities in regulatory molecules have been found in the plasma of APS patients, strongly suggesting that the activation of complement cascade is the result of aPL binding to the target antigen rather than of a defective regulation. Placental complement deposits represent a further marker of complement activation both in animals and in patients, and there is also some suggestive evidence that complement activation products are deposited in the affected vessels. The aim of this review is to analyze the state of the art of complement involvement in the pathogenesis of APS in order to provide insights into the role of this system as predictive biomarker for the clinical manifestations and as therapeutic target.

Cellular and Molecular Mechanisms of Anti-Phospholipid Syndrome

The primary anti-phospholipid syndrome (APS) is characterized by the production of antibodies that bind the phospholipid-binding protein β2 glycoprotein I (β2GPI) or that directly recognize negatively charged membrane phospholipids in a manner that may contribute to arterial or venous thrombosis. Clinically, the binding of antibodies to β2GPI could contribute to pathogenesis by formation of immune complexes or modification of coagulation steps that operate along cell surfaces. However, additional events are likely to play a role in pathogenesis, including platelet and endothelial cell activation. Recent studies focus on neutrophil release of chromatin in the form of neutrophil extracellular traps as an important disease contributor. Jointly, the participation of both the innate and adaptive arms of the immune system in aspects of the APS make the complete understanding of crucial steps in pathogenesis extremely difficult. Only coordinated and comprehensive analyses, carried out in different clinical and research settings, are likely to advance the understanding of this complex disease condition.

Alternative pathway activation due to low level of complement factor H in primary antiphospholipid syndrome

INTRODUCTION

Although complement activation has been proposed as a possible thrombophilic mechanism in antiphospholipid syndrome (APS), the origin of complement activation in APS remains unclear. Here, we focused on complement regulatory factors (CRF), which control the complement system to prevent damage to host tissue. We evaluated the function of two major CRF, membrane cofactor protein (MCP) and factor H (FH), in APS patients.

MATERIALS AND METHODS

In this study, we analyzed preserved serum samples from 27 patients with primary APS (PAPS), 20 with APS complicated with SLE (APS + SLE), 24 with SLE (SLE), and 25 with other connective tissue diseases (Other CTD). Serum MCP and FH levels were tested by ELISA. Autoantibodies against FH were determined by both ELISA and western-blotting.

RESULTS

Serum complement levels of PAPS were lower than those of other CTD (median C3: 82 vs 112 mg/dL, p < 0.01, C4: 15 vs 22 mg/dL, p < 0.05). Serum MCP levels did not significantly differ among the groups. Serum FH levels were significantly lower in PAPS patients compared with SLE or other CTD (median 204, 1275, and 1220 μg/mL, respectively, p < 0.01). In PAPS patients, serum FH levels were positively correlated with serum C3 levels (p < 0.01, R = 0.55), but no correlation was found with serum C4 levels (p = 0.22, R = 0.33). Autoantibodies against FH were not detected in any of our patients.

CONCLUSIONS

Activation of the alternative complement pathway due to low level of FH is one of the possible thrombophilic mechanisms in PAPS.

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.

Complement activation predicts adverse pregnancy outcome in patients with systemic lupus erythematosus and/or antiphospholipid antibodies

OBJECTIVE

Studies in mouse models implicate complement activation as a causative factor in adverse pregnancy outcomes (APOs). We investigated whether activation of complement early in pregnancy predicts APOs in women with systemic lupus erythematosus (SLE) and/or antiphospholipid (aPL) antibodies.

METHODS

The PROMISSE Study enrolled pregnant women with SLE and/or aPL antibodies (n=487) and pregnant healthy controls (n=204) at <12 weeks gestation and evaluated them monthly. APOs were: fetal/neonatal death, preterm delivery <36 weeks because of placental insufficiency or preeclampsia and/or growth restriction <5th percentile. Complement activation products were measured on serial blood samples obtained at each monthly visit.

RESULTS

APO occurred in 20.5% of SLE and/or aPL pregnancies. As early as 12-15 weeks, levels of Bb and sC5b-9 were significantly higher in patients with APOs and remained elevated through 31 weeks compared with those with normal outcomes. Moreover, Bb and sC5b-9 were significantly higher in patients with SLE and/or aPL without APOs compared with healthy controls. In logistic regression analyses, Bb and sC5b-9 at 12-15 weeks remained significantly associated with APO (OR_adj=1.41 per SD increase; 95% CI 1.06 to 1.89; P=0.019 and OR_adj=1.37 per SD increase; 95% CI 1.05 to 1.80; P=0.022, respectively) after controlling for demographic and clinical risk factors for APOs in PROMISSE. When analyses were restricted to patients with aPL (n=161), associations between Bb at 12-15 weeks and APOs became stronger (OR_adj=2.01 per SD increase; 95% CI 1.16 to 3.49; P=0.013).

CONCLUSION

In pregnant patients with SLE and/or aPL, increased Bb and sC5b-9 detectable early in pregnancy are strongly predictive of APOs and support activation of complement, particularly the alternative pathway, as a contributor to APOs.

Antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by the presence of antiphospholipid antibodies, such as lupus anticoagulant, anticardiolipin antibodies and anti-β2-glycoprotein 1 antibodies. APS can present with a variety of clinical phenotypes, including thrombosis in the veins, arteries and microvasculature as well as obstetrical complications. The pathophysiological hallmark is thrombosis, but other factors such as complement activation might be important. Prevention of thrombotic manifestations associated with APS includes lifestyle changes and, in individuals at high risk, low-dose aspirin. Prevention and treatment of thrombotic events are dependent mainly on the use of vitamin K antagonists. Immunosuppression and anticomplement therapy have been used anecdotally but have not been adequately tested. Pregnancy morbidity includes unexplained recurrent early miscarriage, fetal death and late obstetrical manifestation such as pre-eclampsia, premature birth or fetal growth restriction associated with placental insufficiency. Current treatment to prevent obstetrical morbidity is based on low-dose aspirin and/or low-molecular-weight heparin and has improved pregnancy outcomes to achieve successful live birth in >70% of pregnancies. Although hydroxychloroquine and pravastatin might further improve pregnancy outcomes, prospective clinical trials are required to confirm these findings.

IgA anti-β2 glycoprotein I antibodies: Experience from a large center

OBJECTIVE

IgG and IgM antibodies directed at β2-glycoprotein I are included in the classification criteria for the antiphospholipid syndrome (APS) while the IgA antibodies against β2-glycoprotein I (IgA aβ2GPI) are not. Conflicting data about the significance of IgA aβ2GPI and APS manifestation can be found and more studies are necessary in order to define the diagnostic value of IgA aβ2GPI. In the present article, we investigated the possible role of IgA aβ2GPI as marker of APS.

METHODS

A cohort of 314 patients with APS and systemic autoimmune disease was investigated for the presence of IgA aβ2GPI and its association with clinical manifestation of APS.

RESULTS

Eighty-nine patients presented IgA aβ2GPI, 68 cases associated with others antiphospholipid antibodies (aPL) and in 21 cases being the only aPL present. In primary APS IgA aβ2GPI are highly coincidental with other aPL (92,2%) while most of the isolated IgA aβ2GPI were present in the SLE group (16/21). No association between IgA aβ2GPI and APS manifestations: thrombosis and pregnancy morbidity was found, while a positive association between IgA aβ2GPI and the presence of anti-nDNA, anti-RNP, anti-Sm, anti-SSA, anti-SSB antibodies was encountered.

CONCLUSION

Our study does not show association between IgA aβ2GPI and APS manifestations and does not support the inclusion of IgA aβ2GPI as a classification criteria for APS.

Complement activation in patients with isolated antiphospholipid antibodies or primary antiphospholipid syndrome

The antiphospholipid syndrome (APS) is the association of thrombosis and recurrent pregnancy loss and/or pregnancy morbidity with persistent antiphospholipid antibodies (aPL). Increased complement activation has been implicated in the pathogenesis of APS in animal models. It was our objective to evaluate complement activation in patients with aPL or primary antiphospholipid syndrome (PAPS). We measured complement activation products, fragments Bb and C3a–desArg by ELISA in 186 aPL/PAPS patients and 30 healthy controls. All patients with aPL had significantly increased levels of complement activation products. Fragment Bb levels (mean, 95% CI); (thrombotic APS 0.54 units/ml, 0.31–0.83, obstetric APS 0.60 units/ml,0.39–1.02, isolated aPL 0.48 units/ml, 0.29–0.85, overall 0.39 units/ml, 0.33–0.47) and C3a–desArg levels (mean, 95% CI): (thrombotic APS 261 ng/ml, 219–311, obstetric APS 308 ng/ml, 243–391, isolated aPL 258 ng/ml, 193–337, overall 225 ng/ml, 202–251) were significantly higher compared to controls (fragment Bb 0.06 units/ml, 0.03–0.11, C3a–desArg 69 ng/ml, 50–92). There were correlations between Fragment Bb and C3a–desArg levels in all patients with aPL. Receiver operator characteristic (ROC) analysis showed increased fragment Bb and C3a–desArg levels had strong associations with the presence of persistent lupus anticoagulant (area under ROC: Bb 0.89, and C3a–desArg 0.90), dual and triple aPL positivity (Bb 0.71–0.82, C3a–desArg 0.71–0.80) but not with high titre anti-cardiolipin antibodies (Bb 0.62, C3a–desArg 0.65), or anti β2-glycoprotein 1 antibodies (Bb 0.66, C3a–desArg 0.67). Complement activation is present in all patient groups within this large cohort of patients aPL. This suggests it may have a major role in the pathogenesis of APS and merits further study.

Evaluation of the alternative classification criteria of systemic lupus erythematosus established by Systemic Lupus International Collaborating Clinics (SLICC)

OBJECTIVE

To evaluate the performance of the 2012 Systemic Lupus International Collaborating Clinics criteria (SLICC-12) on classifying systemic lupus erythematosus (SLE) in an uncontrolled multi-centered study with real-life scenario of the patients in Japan.

METHODS

This study comprised 495 patients with SLE or non-SLE rheumatic diseases and allied conditions from 12 institutes in Japan. Chart review of each patient was performed by the 27 expert rheumatologists and diagnosis of 487 cases reached to the consensus. Value of the SLICC-12 on SLE classification was analyzed comparing with the 1997 revised American College of Rheumatology SLE classification criteria (ACR-97) employing the expert-consented diagnoses.

RESULTS

Compared to the ACR-97, the SLICC-12 had a higher sensitivity (ACR-97 vs. SLICC-12: 0.88 vs. 0.99, p < .01) and comparable specificity (0.85 vs. 0.80). The rate of misclassification (0.14 vs. 0.11) or the area under the receiver operating characteristic curves (0.863 vs. 0.894) was not statistically different. In the cases that diagnoses corresponded in high rates among experts, both criteria showed high accordance of SLE classification over 85% with the expert diagnoses.

CONCLUSION

Although employment of SLICC-12 for the classification for SLE should be carefully considered, the SLICC-12 showed the higher sensitivity on classifying SLE in Japanese population.

The Evolving Landscape for Complement Therapeutics in Rheumatic and Autoimmune Diseases

The complement system is increasingly understood to play major roles in the pathogenesis of human inflammatory and autoimmune diseases. Because of this situation, there are rapidly expanding commercial efforts to develop novel complement inhibitors and effector pathway-modulating drugs. This review provides insights into the evolving understanding of the complement system components, mechanisms of activation within and across the 3 pathways (classical, alternative, and lectin), how the pathways are normally controlled and then dysregulated in target tissues, and what diseases are known to be, in large part, complement-dependent through the successful development and approval of complement therapeutics in patients. Mechanisms of complement activation in rheumatoid arthritis, lupus, and thrombotic microangiopathies are also illustrated. In addition, the specific therapeutic drugs that are both approved and under development are discussed in the context of both nonrheumatic and rheumatic diseases. Finally, the methods by which the complement system can be assessed in humans through biomarker studies are outlined, with the goal of understanding, in specific patients, how the system is functioning.

The impact of antibody profile in thrombosis associated with primary antiphospholipid syndrome

Triple positivity (TP) for antiphospholipid antibodies(aPL) may identify aPL carriers with poorer prognosis. The clinical impact of TP in primary antiphospholipid syndrome(PAPS) remains unclear and further clinical evidences are needed to validate TP as a marker of severity. The aim of this study was to evaluate the impact of TP on the clinical course of PAPS with thrombosis(t-PAPS). We performed a retrospective analysis of a cohort of t-PAPS patients, comparing groups of patients with TP and non-TP profiles according to their demographic, clinical and laboratory features. We included 105 patients with t-PAPS, the median follow-up time of 3.7 years. Twenty-two patients(21%) had TP; the demographic distribution, the presence of cardiovascular risk factors and the site of thrombosis were similar between TP and non-TP patients. The frequency of thrombotic events did not differ between TP and non-TP patients during the study period. Pregnancy morbidities were more frequent in women with t-PAPS and TP than in those with non-TP profile (80% vs. 52.8%, P = 0.05). Patients with t-PAPS and TP presented, at diagnosis, higher dRVVT ratio (median R = 2.44 vs. 1.57, P < 0.0001), higher aCL titer (median = 50UI vs. 35 UI, P < 0.0001), lower C3 levels (median = 1.08 vs. 1.30 mg dL^-1 , P = 0.001), lower C4 levels (median = 0.22 vs. 0.25 mg dL^-1 , P = 0.05) and higher frequency of positive ANA test (50% vs. 20%, P = 0.008) than patients with t-PAPS and non-TP. Lower-than-normal levels of C3 was independently associated with TP (OR = 5.1, P = 0.02). The presence of TP in patients with t-PAPS was associated with immune derangement, with no effect on the clinical course of the disease.

Complement C5-inhibiting therapy for the thrombotic microangiopathies: accumulating evidence, but not a panacea

Thrombotic microangiopathy (TMA), characterized by organ injury occurring consequent to severe endothelial damage, can manifest in a diverse range of diseases. In complement-mediated atypical haemolytic uraemic syndrome (aHUS) a primary defect in complement, such as a mutation or autoantibody leading to over activation of the alternative pathway, predisposes to the development of disease, usually following exposure to an environmental trigger. The elucidation of the pathogenesis of aHUS resulted in the successful introduction of the complement inhibitor eculizumab into clinical practice. In other TMAs, although complement activation may be seen, its role in the pathogenesis remains to be confirmed by an interventional trial. Although many case reports in TMAs other than complement-mediated aHUS hint at efficacy, publication bias, concurrent therapies and in some cases the self-limiting nature of disease make broader interpretation difficult. In this article, we will review the evidence for the role of complement inhibition in complement-mediated aHUS and other TMAs.

Altered β2 -glycoprotein I expression on microparticles in the presence of antiphospholipid antibodies

Essentials β2 glycoprotein-I (β2 GPI) is a scavenger molecule that binds to microparticles (MPs). β2 GPI expression on MPs was measured in systemic lupus erythematosus (SLE) patients and controls. β2 GPI positive MPs is depressed among SLE patients positive for antiphospholipid antibodies. Complex formation between β2 GPI on MPs and patients own anti-β2 GPI may disturb MP clearance. Click to hear an ISTH Academy presentation on antiphospholipid antibody syndrome by Drs de Laat and Bertolaccini SUMMARY: Background Antiphospholipid antibodies (aPLs) together with thrombosis and/or pregnancy morbidities characterize the antiphospholipid syndrome. β2 -Glycoprotein I (β2 GPI), the most important antigen for aPLs, is a scavenger molecule that specifically binds to phosphatidylserine (PS) expressed on microparticles (MPs). Objectives To evaluate β2 GPI-expressing MPs in patients with systemic lupus erythematosus (SLE) stratified for aPL status, and in healthy controls. Patients/Methods We investigated 18 aPL/anti-β2 GPI-positive and 22 aPL-negative patients from a large SLE cohort and 19 healthy controls. β2 GPI-positive MPs and IgG-positive MPs were detected by flow cytometry. We measured plasma levels of β2 GPI, and performed in vitro experiments to investigate the binding properties of β2 GPI on MPs. Results SLE patients had more MPs and IgG-positive MPs than controls. We observed fewer β2 GPI-positive MPs in aPL/anti-β2 GPI-positive patients than in aPL/anti-β2 GPI-negative patients and controls (approximately two-fold). β2 GPI levels in plasma did not differ with aPL/anti-β2 GPI status in patients; however, controls had slightly higher levels of β2 GPI than aPL/anti-β2 GPI-positive patients. In vitro experiments revealed that β2 GPI preferentially binds to PS-positive MPs. Conclusions Despite abundant total MPs and MPs in immune complexes, β2 GPI-positive MPs were depleted in SLE patients, and the levels were especially low in aPL/anti-β2 GPI-positive patients. We suggest that anti-β2 GPI antibodies bind to β2 GPI-PS complexes expressed on MPs. Consequent loss of β2 GPI-PS expression on MPs may impair scavenging and contribute to the accumulation of circulating PS-negative MPs, a possible source of autoantigens. Autoantibodies delaying MP clearance may thus constitute an important mechanism underlying autoimmunity.

Diagnosing antiphospholipid syndrome: 'extra-criteria' manifestations and technical advances

First described in the early 1980s, antiphospholipid syndrome (APS) is a unique form of acquired autoimmune thrombophilia in which patients present with clinical features of recurrent thrombosis and pregnancy morbidity and persistently test positive for the presence of antiphospholipid antibodies (aPL). At least one clinical (vascular thrombosis or pregnancy morbidity) and one lab-based (positive test result for lupus anticoagulant, anticardiolipin antibodies and/or anti-β2-glycoprotein 1 antibodies) criterion have to be met for a patient to be classified as having APS. However, the clinical spectrum of APS encompasses additional manifestations that can affect many organs and cannot be explained exclusively by patients being in a prothrombotic state; clinical manifestations not listed in the classification criteria (known as extra-criteria manifestations) include neurologic manifestations (chorea, myelitis and migraine), haematologic manifestations (thrombocytopenia and haemolytic anaemia), livedo reticularis, nephropathy and valvular heart disease. Increasingly, research interest has focused on the development of novel assays that might be more specific for APS than the current aPL tests. This Review focuses on the current classification criteria for APS, presenting the role of extra-criteria manifestations and lab-based tests. Diagnostic approaches to difficult cases, including so-called seronegative APS, are also discussed.

Antibodies Against Complement Components: Relevance for the Antiphospholipid Syndrome-Biomarkers of the Disease and Biopharmaceuticals

PURPOSE OF REVIEW

Laboratory criterion for the diagnosis of antiphospholipid syndrome (APS) is the presence of antiphospholipid antibodies (aPL Abs). Complement system has a role in mediating aPL Abs-induced thrombosis in animal models. The importance of antibodies against complement components (potential biomarkers of APS) and the importance of antibodies with beneficial anti-complement effects in APS (as biopharmaceuticals) are reviewed.

RECENT FINDINGS

Antibodies against complement components described in APS patients, so far, are anti-C1q and anti-factor H Abs, although anti-factor B Abs and anti-C5a Abs were described in animal models of APS. Clinical studies in APS patients are limited to a small number of case reports. Studies that would confirm potential role of Abs against complement components (as potential biomarkers of APS) are lacking. Lack of randomized clinical trials (that would provide complete data for confirmation of beneficial effects of biopharmaceuticals in complement inhibition) in APS is alarming.

A novel 2-stage approach that detects complement activation in patients with antiphospholipid antibody syndrome

INTRODUCTION

The antiphospholipid syndrome (APS) is marked by autoantibodies that recognize anionic phospholipids in a cofactor-dependent manner. A role for complement has been implicated in the pathophysiology, however, elevations of complement activation markers have not been consistently demonstrated in clinical studies. We therefore designed a proof-of-principle study to determine whether complement activation might be detectable in APS by first exposing plasmas to phospholipid vesicles.

METHODS

We examined complement activation markers in patients with APS, non-APS thrombosis, systemic lupus erythematosus, cancer, patients with antiphospholipid antibodies without thrombosis (APL) and healthy controls. Direct measurements of plasma C5a and sC5b-9 levels were compared to levels that were generated in normal serum by phospholipid vesicles that had been pre-incubated with the same plasmas. We then determined the effects of the C5 inhibitor, eculizumab, examined the complement pathways involved, and determined whether the effects could be reproduced with purified IgGs and β2-glycoprotein I (β2GPI).

RESULTS

Plasma levels of C5a and sC5b-9 were higher, but not significantly increased in APS patients compared to healthy controls. In contrast, phospholipid vesicles pre-incubated with APS plasmas generated significantly higher levels than healthy controls and the other groups, except for APL patients. Complement activation was abrogated by addition of eculizumab. The results with substrate sera indicated that the alternative and classical/lectin pathways were involved. The results were reproducible with purified IgGs and β2GPI.

CONCLUSION

This proof-of-principle study confirms a role for complement in APS and opens the possibility of monitoring complement activation by including phospholipid vesicles in assay systems.

Up-regulated Complement 3 Production by Toll-like receptor 9/ Transforming Growth Factor-Beta 1/Complement 3 Pathway in Whole Blood Cells of Lupus Thrombocytopenia

Objectives

This study aims to assess the complement 3 (C3) expressions in whole blood cells and verify a pathway toll-like receptor 9 (TLR9)/ transforming growth factor-beta 1 (TGF-β1)/C3 for C3 regulation in mediating thrombocytopenia (TCP) in patients with systemic lupus erythematosus (SLE).

Patients and methods

The study included 63 newly diagnosed SLE patients (2 males, 61 females; mean age 39.5 years; range 15 to 67 years). Whole blood messenger ribonucleic acid expression for C3, TLR9 and TGF-β1 were measured by quantitative reverse transcription real-time polymerase chain reaction in SLE patients with TCP (n=38) and age- and sex-matched SLE patients without TCP (n=25) at baseline and in 10 SLE patients with TCP after four weeks of treatment. Whole blood cells from SLE patients with TCP were cultured in the presence of TLR9 ligand cytosine-phosphate- guanine, recombinant human TGF-β1, TGF-β receptor inhibitor/activin receptor-like kinase inhibitor SB431542. TGF-β1 and C3 levels in whole blood cells cultures were determined by quantitative reverse transcription real-time polymerase chain reaction and enzyme-linked immunosorbent assay.

Results

Whole blood cells from SLE patients with TCP displayed an enhanced gene expression for C3, TLR9 and TGF-β1 compared with that of SLE patients without TCP (p<0.01 for C3, p<0.05 for TLR9 and TGF-β1). SLE patients with TCP had decreased plasma levels of C3 suggesting excessive consumption. In whole blood cell culture, engagement of TLR9 led to the increased gene expression of C3. Furthermore, TGF-β1 inhibitor abolished TLR9 stimulation on C3 gene expression.

Conclusion

These results suggest that blood cells are the source of extra-hepatic synthesis of C3 in SLE patients with TCP and this synthesis of C3 was up-regulated by TLR9 via induction of TGF-β1. Thus TLR9/TGF-β1/C3 pathway might be in operation mediating lupus thrombocytopenia.

Pathogenesis and management of antiphospholipid syndrome

Antiphospholipid antibodies are a heterogeneous group of autoantibodies that have clear associations with thrombosis and pregnancy morbidity, and which together constitute the 'antiphospholipid syndrome' (APS). However, the pathophysiology of these complications is not well understood and their heterogeneity suggests that more than one pathogenic process may be involved. Diagnosis remains a combination of laboratory analysis and clinical observation but there have been significant advances in identifying specific pathogenic features, such as domain I-specific anti-β2-glycoprotein-I antibodies. This in turn has pointed to endothelial and complement activation as important factors in the pathogenesis of APS. Consequently, although anticoagulation remains the standard treatment for thrombotic APS and during pregnancy, the realisation that these additional pathways are involved in the pathogenesis of APS has significant implications for treatment: agents acting outside the coagulation system, such as hydroxychloroquine for pregnancy complications and sirolimus as an inhibitor of the mammalian target of rapamycin (mTOR) pathway, are now under evaluation and represent a radical change in thinking for haematologists. Conventional anticoagulation is also under challenge from new, direct acting anticoagulants. This review will provide a comprehensive overview of the evolving understanding of APS pathogenesis and how this and novel therapeutics will alter diagnosis and management.

Potential influences of complement factor H in autoimmune inflammatory and thrombotic disorders

Complement system homeostasis is important for host self-protection and anti-microbial immune surveillance, and recent research indicates roles in tissue development and remodelling. Complement also appears to have several points of interaction with the blood coagulation system. Deficiency and altered function due to gene mutations and polymorphisms in complement effectors and regulators, including Factor H, have been associated with familial and sporadic autoimmune inflammatory - thrombotic disorders, in which autoantibodies play a part. These include systemic lupus erythematosus, rheumatoid arthritis, atypical haemolytic uremic syndrome, anti-phospholipid syndrome and age-related macular degeneration. Such diseases are generally complex - multigenic and heterogeneous in their symptoms and predisposition/susceptibility. They usually need to be triggered by vascular trauma, drugs or infection and non-complement genetic factors also play a part. Underlying events seem to include decline in peripheral regulatory T cells, dendritic cell, and B cell tolerance, associated with alterations in lymphoid organ microenvironment. Factor H is an abundant protein, synthesised in many cell types, and its reported binding to many different ligands, even if not of high affinity, may influence a large number of molecular interactions, together with the accepted role of Factor H within the complement system. Factor H is involved in mesenchymal stem cell mediated tolerance and also contributes to self-tolerance by augmenting iC3b production and opsonisation of apoptotic cells for their silent dendritic cell engulfment via complement receptor CR3, which mediates anti-inflammatory-tolerogenic effects in the apoptotic cell context. There may be co-operation with other phagocytic receptors, such as complement C1q receptors, and the Tim glycoprotein family, which specifically bind phosphatidylserine expressed on the apoptotic cell surface. Factor H is able to discriminate between self and nonself surfaces for self-protection and anti-microbe defence. Factor H, particularly as an abundant platelet protein, may also modulate blood coagulation, having an anti-thrombotic role. Here, we review a number of interaction pathways in coagulation and in immunity, together with associated diseases, and indicate where Factor H may be expected to exert an influence, based on reports of the diversity of ligands for Factor H.

Recent advances in understanding antiphospholipid syndrome

Antiphospholipid syndrome (APS), also known as Hughes Syndrome, is a systemic autoimmune disease characterized by thrombosis and/or pregnancy morbidity in the presence of persistently positive antiphospholipid antibodies. A patient with APS must meet at least one of two clinical criteria (vascular thrombosis or complications of pregnancy) and at least one of two laboratory criteria including the persistent presence of lupus anticoagulant (LA), anticardiolipin antibodies (aCL), and/or anti-b2 glycoprotein I (anti-b2GPI) antibodies of IgG or IgM isotype at medium to high titres in patient’s plasma. However, several other autoantibodies targeting other coagulation cascade proteins (i.e. prothrombin) or their complex with phospholipids (i.e. phosphatidylserine/prothrombin complex), or to some domains of β2GPI, have been proposed to be also relevant to APS. In fact, the value of testing for new aPL specificities in the identification of APS in thrombosis and/or pregnancy morbidity patients is currently being investigated.

Rivaroxaban limits complement activation compared with warfarin in antiphospholipid syndrome patients with venous thromboembolism

Essentials Complement activation has a pathogenic role in thrombotic antiphospholipid syndrome (APS). Coagulation proteases such as factor Xa can activate complement proteins. Complement activation markers were elevated in anticoagulated thrombotic APS patients. Complement activation decreased in APS patients switching from warfarin to rivaroxaban.

SUMMARY

Background Complement activation may play a major role in the pathogenesis of thrombotic antiphospholipid syndrome (APS). Coagulation proteases such as factor Xa can activate complement proteins. Aims To establish whether rivaroxaban, a direct factor Xa inhibitor, limits complement activation compared with warfarin in APS patients with previous venous thromboembolism (VTE). Methods A total of 111 APS patients with previous VTE, on warfarin target INR 2.5, had blood samples taken at baseline and at day 42 after randomization in the RAPS (Rivaroxaban in Antiphospholipid Syndrome) trial. Fifty-six patients remained on warfarin and 55 switched to rivaroxaban. Fifty-five normal controls (NC) were also studied. Markers of complement activation (C3a, C5a, terminal complement complex [SC5b-9] and Bb fragment) were assessed. Results APS patients had significantly higher complement activation markers compared with NC at both time-points irrespective of the anticoagulant. There were no differences between the two patient groups at baseline, or patients remaining on warfarin at day 42. In 55 patients randomized to rivaroxaban, C3a, C5a and SC5b-9 were lower at day 42 (median (ng mL-1 ) [confidence interval] 64 [29-125] vs. 83 [35-147], 9 [2-15] vs. 12 [4-18] and 171 [56-245] vs. 201 [66-350], respectively) but levels of Bb fragment were unchanged. There were no correlations between rivaroxaban levels and complement activation markers. Conclusions APS patients with previous VTE on warfarin exhibit increased complement activation, which is likely to occur via the classical pathway and is decreased by rivaroxaban administration. Rivaroxaban may therefore potentially provide an additional benefit to its anticoagulant effect in this patient group by limiting complement activation.

TNF-alpha and annexin A2: inflammation in thrombotic primary antiphospholipid syndrome

Antiphospholipid syndrome (APS) is characterized by thromboses and/or pregnancy losses. Laboratory criterion for the diagnosis of APS is the presence of antiphospholipid antibodies (anticardiolipin, anti-beta2-glycoprotein I (aβ2gpI) and lupus anticoagulant). On the one hand, the latest classification criteria for the diagnosis of APS emphasized that thrombotic manifestations of the syndrome should be without any signs of an inflammatory process, while on the other hand, some recent reports have suggested that APS is a "pro-inflammatory state." This article is focused on the importance of TNF-alpha and annexin A2 (anxA2) for patients with vascular (thrombotic) manifestations of the primary APS. The classic antithrombotic and antiplatelet therapy does not protect APS patients from the development of recurrent thrombosis. Therefore, an urgent need for the introduction of new therapeutic approaches in the treatment of APS patients is obvious. This review provides a rationale for the necessity for the use of immunomodulatory medications that could interfere with β2gpI binding to its receptor(s), such as anxA2, and/or inhibit TNF-alpha activity.

Proinflammatory proteins in female and male patients with primary antiphospholipid syndrome: preliminary data

The latest classification criteria for the diagnosis of the antiphospholipid syndrome (APS, an autoimmune disease characterized by thromboses, miscarriages and presence of antiphospholipid antibodies (Abs)) emphasized that thrombotic manifestations of APS should be without any signs of an inflammatory process. However, atherosclerosis (a chronic inflammatory response to the accumulation of lipoproteins in the walls of arteries) and APS are characterized by some similar features. We evaluated whether proinflammatory proteins were associated with the features of the primary APS (PAPS). PAPS patients without obstetric complications and with impaired lipid profile were included in the study. Antiphospholipid antibodies, TNF-alpha, and apo(a) were determined by ELISA. Complement components and hsCRP were measured by immunonephelometry. Decreased C3c was observed in female patients with increased titers of IgG anti-β2gpI (χ(2) = 3.939, P = 0.047) and in male patients with increased IgM anticardiolipin Abs (χ(2) = 4.286, P = 0.038). Pulmonary emboli were associated with interleukin (IL)-6 in male (χ(2) = 6.519, P = 0.011) and in female (χ(2) = 10.405, P = 0.001) patients. Cerebrovascular insults were associated with LDL-cholesterol (P = 0.05, 95 % CI: 1.003 - 12.739) in female and with apo(a) (P = 0.016, 95 % CI: 0.000-0.003) in male patients. Older female patients had increased LDL-cholesterol levels and frequency of myocardial infarctions. Proinflammatory proteins were associated with features of primary APS. No real gender differences in regard to proinflammatory protein levels were observed. Premenopausal state of female PAPS patients confers lower cardiovascular risk.

Complement levels and anti-C1q autoantibodies in patients with neuropsychiatric systemic lupus erythematosus

Objective

The objective of this paper is to analyse serum levels of anti-C1q, C1q circulating immune complexes (CIC), complement activation and complement components in systemic lupus erythematosus (SLE) patients during the first central nervous system neuropsychiatric (NP) event and to define the possible association between these results and clinical and laboratory characteristics.

Methods

A total of 280 patients suspected of having NP involvement due to SLE were recruited in the Leiden NPSLE-clinic. All SLE patients were classified according to the ACR 1982 revised criteria for the classification of SLE. The clinical disease activity was measured by the SLE Disease Activity Index 2000 (SLEDAI-2K) and NP diagnoses were classified according to the 1999 ACR case definitions for NPSLE. We measured in serum of all patients anti-C1q and C1q CIC levels, the activation capacity of complement (CH50 and AP50) and different complement components (C1q, C3, C4).

Results

In 92 patients the symptoms were attributed to SLE. NPSLE patients consisted of 63 patients with focal NPSLE and 34 patients with diffuse NPSLE. Anti-C1q antibodies were significantly higher and CH50, AP50 and C3 were significantly lower in NPSLE patients compared with SLE patients without NPSLE. This association was specially marked for diffuse NPSLE while no differences were found for focal NPSLE. After using potential predictors, decreased C4 remained significantly associated with focal NPSLE, but only when antiphospholipid antibodies (aPL) were included in the model. C3 and AP50 were independently associated with diffuse NPSLE. When SLEDAI-2K was included in the model these two associations were lost. When individual NPSLE syndromes were analysed, psychosis and cognitive dysfunction showed significantly lower values of complement activation capacity and all complement components. No significant associations were seen for other individual NPSLE syndromes.

Conclusion

The associations between diffuse NPSLE and anti-C1q, C3/AP50 and focal NPSLE and C4 may be explained by disease activity and the presence of aPL, respectively. The role of complement activation and complement components in lupus psychosis and cognitive dysfunction merits further research.

Autoantibodies against a complement component 1 q subcomponent contribute to complement activation and recurrent thrombosis/pregnancy morbidity in anti-phospholipid syndrome

OBJECTIVE

To investigate the prevalence and significance of the autoantibodies against complement component 1 q subcomponent (C1q) in patients with APS.

METHODS

In all, 40 consecutive primary APS patients, 42 patients with non-SLE CTDs and 20 SLE patients negative for aPL were enrolled in this retrospective analysis. Refractory APS was defined as a clinical status of recurring thrombosis or pregnancy morbidity during adequate secondary prophylaxis. An ELISA was used to measure serum levels of anti-C1q antibodies and anaphylatoxins (C3a, C4a).

RESULTS

Anti-C1q antibodies were found in 36% (15/42) and 2.5% (1/40) of primary APS patients and controls, respectively. Among primary APS patients, anti-C1q antibody titres were significantly correlated with serum C4a levels (P = 0.013). Neither the prevalence nor the titre of anti-C1q antibodies was associated with any specific clinical manifestations of APS, nor titres of aPL. Refractory APS patients (n = 10) had a higher prevalence of anti-C1q antibodies (9/10 vs 6/32, P = 0.01) than APS patients without recurrence (n = 32).

CONCLUSION

Anti-C1q antibodies are associated with complement activation in APS and may contribute to the pathogenesis, particularly in refractory cases.

Circulating Immune Complexes of IgA Bound to Beta 2 Glycoprotein are Strongly Associated with the Occurrence of Acute Thrombotic Events

Aim: Antiphospholipid syndrome (APS) is characterized by recurrent thrombosis and/or gestational morbidity in patients with antiphospholipid autoantibodies (aPL). Over recent years, IgA anti-beta2-glycoprotein I (B2GPI) antibodies (IgA aB2GPI) have reached similar clinical relevance as IgG or IgM isotypes. We recently described the presence of immune complexes of IgA bounded to B2GPI (B2A-CIC) in the blood of patients with antecedents of APS symptomalology. However, B2A-CIC's clinical associations with thrombotic events (TEV) have not been described yet.

Methods: A total of 145 individuals who were isolate positive for IgA aB2GPI were studied: 50 controls without any APS antecedent, 22 patients with recent TEV (Group-1), and 73 patients with antecedents of old TEV (Group-2).

Results: Mean B2A-CIC levels and prevalence in Group-1 were 29.6 ± 4.1 AU and 81.8%, respectively, and were significantly higher than those of Group-2 and controls (p < 0.001). In a multivariable analysis, positivity of B2A-CIC was an independent variable for acute thrombosis with a 22.7 odd ratio (confidence interval 5.1 –101.6, 95%, p < 0.001). Levels of B2A-CIC dropped significantly two months after the TEV. B2A-CIC positive patients had lower platelet levels than B2A-CIC-negative patients (p < 0.001) and more prevalence of thrombocytopenia (p < 0.019). Group-1 had no significant differences in C3 and C4 levels compared with other groups.

Conclusion: B2A-CIC is strongly associated with acute TEV. Patients who did not develop thrombosis and were B2A-CIC positive had lower platelet levels, which suggest a hypercoagulable state. This mechanism is unrelated to complement-fixing aPL. B2A-CIC could potentially select IgA aB2GPI-positive patients at risk of developing a thrombotic event.

Early Components of the Complement Classical Activation Pathway in Human Systemic Autoimmune Diseases

The complement system consists of effector proteins, regulators, and receptors that participate in host defense against pathogens. Activation of the complement system, via the classical pathway (CP), has long been recognized in immune complex-mediated tissue injury, most notably systemic lupus erythematosus (SLE). Paradoxically, a complete deficiency of an early component of the CP, as evidenced by homozygous genetic deficiencies reported in human, are strongly associated with the risk of developing SLE or a lupus-like disease. Similarly, isotype deficiency attributable to a gene copy-number (GCN) variation and/or the presence of autoantibodies directed against a CP component or a regulatory protein that result in an acquired deficiency are relatively common in SLE patients. Applying accurate assay methodologies with rigorous data validations, low GCNs of total C4, and heterozygous and homozygous deficiencies of C4A have been shown as medium to large effect size risk factors, while high copy numbers of total C4 or C4A as prevalent protective factors, of European and East-Asian SLE. Here, we summarize the current knowledge related to genetic deficiency and insufficiency, and acquired protein deficiencies for C1q, C1r, C1s, C4A/C4B, and C2 in disease pathogenesis and prognosis of SLE, and, briefly, for other systemic autoimmune diseases. As the complement system is increasingly found to be associated with autoimmune diseases and immune-mediated diseases, it has become an attractive therapeutic target. We highlight the recent developments and offer a balanced perspective concerning future investigations and therapeutic applications with a focus on early components of the CP in human systemic autoimmune diseases.

Delineating the deranged immune system in the antiphospholipid syndrome

The antiphospholipid syndrome (APS) is a systemic autoimmune disease that is characterized serologically by the presence of antiphospholipid antibodies (aPL) and clinically by vascular thrombosis and obstetric complications. The protein β2 glycoprotein I (β2GPI) is identified as the most important autoantigen in this syndrome. Activation of endothelial cells, thrombocytes and placental tissue by anti-β2GPI antibodies relates to the clinical manifestations of APS. This review describes genetic and environmental factors in relation to APS and summarizes the current knowledge on abnormalities in components of both the innate and adaptive immune system in APS. The role of dendritic cells, T-cells, B-cells, monocytes, neutrophils and NK-cells as well as the complement system in APS are discussed. Several gaps in our knowledge on the pathophysiology of APS are identified and a plea is made for future extensive immune cell profiling by a systems medicine approach in order to better unravel the pathogenesis of APS, to gain more insight in the role of the immune system in APS as well as having the potential to reveal biomarkers or novel therapeutic targets.

Factor H Autoantibodies in Patients with Antiphospholipid Syndrome and Thrombosis

OBJECTIVE

Autoantibodies to complement factor H (FH) are associated with atypical hemolytic uremic syndrome, but can also be detected in patients with rheumatoid arthritis and in patients positive for lupus anticoagulants and thus potentially antiphospholipid syndrome (APS). To our knowledge, no data are available on the association between the presence of FH autoantibodies in APS and clinical manifestations.

METHODS

We determined FH autoantibody levels using ELISA in 2 cohorts of patients with primary (PAPS) and secondary APS (SAPS) from Serbia and Italy, and an additional cohort including patients with venous thromboembolism (VTE) from Sweden.

RESULTS

FH autoantibodies were detected in 13.7% of patients (n = 73) with PAPS and 30.3% of patients (n = 33) with SAPS in the Serbian cohort. FH autoantibody frequency in the Italian cohort was 33.3% (n = 15) and 36% (n = 25) in PAPS and SAPS, respectively. Both FH autoantibody levels and frequencies observed in both APS cohorts were significantly higher than in matched healthy controls (5%). Further, patients with PAPS with venous thrombosis in the Serbian cohort had significantly higher levels of FH autoantibodies. Therefore, we analyzed a dedicated Swedish thrombosis cohort and found that patients with FH autoantibody positivity had higher risk of VTE recurrence (HR 2.0, 95% CI 1.2-3.3, p = 0.011) compared with the reference group of FH autoantibody-negative patients.

CONCLUSION

Overall, the data indicate that in patients with APS and recurrent venous thrombosis, there are increased levels of FH autoantibodies, a finding associated with poor clinical outcome.

Evasion and interactions of the humoral innate immune response in pathogen invasion, autoimmune disease, and cancer

The humoral innate immune system is composed of three major branches, complement, coagulation, and natural antibodies. To persist in the host, pathogens, such as bacteria, viruses, and cancers must evade parts of the innate humoral immune system. Disruptions in the humoral innate immune system also play a role in the development of autoimmune diseases. This review will examine how Gram positive bacteria, viruses, cancer, and the autoimmune conditions systemic lupus erythematosus and anti-phospholipid syndrome, interact with these immune system components. Through examining evasion techniques it becomes clear that an interplay between these three systems exists. By exploring the interplay and the evasion/disruption of the humoral innate immune system, we can develop a better understanding of pathogenic infections, cancer, and autoimmune disease development.