Complement activation as a mediator of antiphospholipid antibody induced pregnancy loss and thrombosis

Thrombocytopenia in primary antiphospholipid syndrome: association with prognosis and clinical implications

OBJECTIVES

Thrombocytopenia, a frequent clinical manifestation in patients with APS, could be an independent predictor of recurrent thrombotic, obstetric and severe extracriteria events.

METHODS

This single-centre prospective study enrolled 218 consecutive patients diagnosed with primary APS between 2010 and 2021. Thrombocytopenia was defined as a platelet count less than 100 × 109/L.

RESULTS

Our cohort included 74 (33.94%) patients with thrombocytopenia and 144 patients with a continuous normal platelet count. Comparison of baseline characteristics indicated that patients with thrombocytopenia had more visceral venous thromboses [10 (13.51%) vs 5(3.47%); P = 0.009] and extracriteria manifestations [mainly haemolytic anaemia; 20 (27.03%) vs 17 (11.81%); P = 0.007]. Hypocomplementemia was more likely among patients with thrombocytopenia [19 (25.68%) vs 16 (11.11%); P = 0.01]. The presence of aCL-IgG/IgM, anti-β2-glycoprotein I and lupus anticoagulant were more frequently detected in patients with thrombocytopenia. In survival analysis, thrombotic, obstetric and severe extracriteria survival rates were significantly worse in patients with thrombocytopenia. In multivariate Cox regression, thrombocytopenia was an independent risk factor for all endpoint events, including thrombotic events [hazard ratio (HR) 2.93 (95% CI 1.31, 6.56), P = 0.009], pregnancy morbidity [HR 8.00 (95% CI 2.43, 26.37), P = 0.0006] and severe extracriteria events [HR 15.27 (95% CI 1.85, 125.98), P = 0.01].

CONCLUSION

Thrombocytopenia could identify primary APS patients at high risk of developing thrombotic events, pregnancy morbidity and severe extracriteria events.

16th International Congress on Antiphospholipid Antibodies Task Force Report on Antiphospholipid Syndrome Treatment Trends

Antiphospholipid syndrome (APS), an acquired autoimmune thrombophilia, is characterised by thrombosis and/or pregnancy morbidity in association with persistent antiphospholipid antibodies. The 16th International Congress on Antiphospholipid Antibodies Task Force on APS Treatment Trends reviewed the current status with regard to existing and novel treatment trends for APS, which is the focus of this Task Force report. The report addresses current treatments and developments since the last report, on the use of direct oral anticoagulants in patients with APS, antiplatelet agents, adjunctive therapies (hydroxychloroquine, statins and vitamin D), targeted treatment including rituximab, belimumab, and anti-TNF agents, complement inhibition and drugs based on peptides of beta-2-glycoprotein I. In addition, the report summarises potential new players, including coenzyme Q10, adenosine receptor agonists and adenosine potentiation. In each case, the report provides recommendations for clinicians, based on the current state of the art, and suggests a clinical research agenda. The initiation and development of appropriate clinical studies requires a focus on devising suitable outcome measures, including a disease activity index, an optimal damage index, and a specific quality of life index.

Plasma glycated CD59 (gCD59), a novel biomarker for the diagnosis, management and follow up of women with Gestational Diabetes (GDM) - protocol for prospective cohort study

BACKGROUND

The prevalence of Gestational Diabetes (GDM) is rising and with it the number of mothers and children at risk of adverse outcomes. As treatment has been shown to reduce adverse events, it is imperative that we identify all at-risk pregnant women. In Ireland, the national standard of care is selective screening with a 2-hour 75 g oral glucose tolerance test (OGTT). Aiming for universal screening is of utmost importance but this is difficult given the length, the unfeasibility and impracticability of the OGTT. We aim to assess if the novel biomarker glycated CD59 (gCD59) is a suitable contender for the OGTT in identifying women with GDM.

METHODS

In this prospective cohort study, the study participants will be consecutive pregnant women at Galway University Hospital, Galway, Ireland. Samples for the plasma gCD59 biomarker will be taken together with routine bloods at the first antenatal visit, at weeks 24-28 at the time of routine 75 g OGTT, in trimester 3- and 12-weeks post-partum for women with GDM while having their routine post-partum 75 g OGTT. The constructed database will contain baseline information on each study participant, baseline laboratory data, follow-up laboratory data and pregnancy related outcomes. We aim to recruit a total of 2,000 participants over the project period and with a national GDM prevalence of 12-13%, we will have 240-260 subjects who meet OGTT criteria for GDM. Following regional prevalence, we expect to have 34-37 women who will develop either diabetes or pre-diabetes in the early post-partum period. The sensitivity and specificity of plasma gCD59 to predict the results of the OGTT will be assessed using nonparametric estimates of the receiver operating characteristic (ROC) curves and respective area under the ROC curve (AUROC).

DISCUSSION

A body of clinical and experimental evidence supports a link between the complement system, complement regulatory proteins, and the pathogenesis of diabetes complications. Building on this research, our study plans to look at the plasma gCD59 capacity to classify pregnant women with normal or abnormal glucose tolerance but also to assess if plasma gCD59 can be used as an early predictor for GDM, for adverse pregnancy outcomes and/or post-partum glucose intolerance.

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.

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.

Serum C3 and uterine artery Doppler indices at 14-20 weeks gestation for preeclampsia screening in low-risk primigravidas: A prospective observational study

PROBLEM

Preeclampsia affects 2-10% of human pregnancies with poor screening tests. In order to intervene preventively, high risk population should be identified before the 20th week of pregnancy and by a method not subjected to operator efficiency.

METHODOLOGY

Prospective observational study recruiting 825 low risk primigravidas. Serum C3 and uterine artery Doppler indices were measured at 14-20 weeks.

RESULTS

Serum C3 levels at 14-20 weeks of gestation had a sensitivity 83.3%, specificity 100%, PPV 100% and NPV 98.3% when the cut-off value was 53.1mg/. For the mean RI, the best cut off value found was 0.72 with 100% sensitivity, 99.1% specificity, 92.3% PPV and 100% NPV. For the mean PI the best cut off value was 1.35 with 100% sensitivity, 94.1% specificity, 63.2% PPV and 100% NPV. The combination of serum C3 level and mean uterine artery PI showed 100% sensitivity, 97.4% specificity, 80% PPV and 100% NPV in prediction of PE.

CONCLUSION

Serum C3 levels at 14-20 weeks can be used for prediction of PE with comparable results to uterine artery Doppler indices but has the superiority of being operator independent.

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.

Complement Activation in Arterial and Venous Thrombosis is Mediated by Plasmin

Thrombus formation leading to vaso-occlusive events is a major cause of death, and involves complex interactions between coagulation, fibrinolytic and innate immune systems. Leukocyte recruitment is a key step, mediated partly by chemotactic complement activation factors C3a and C5a. However, mechanisms mediating C3a/C5a generation during thrombosis have not been studied. In a murine venous thrombosis model, levels of thrombin–antithrombin complexes poorly correlated with C3a and C5a, excluding a central role for thrombin in C3a/C5a production. However, clot weight strongly correlated with C5a, suggesting processes triggered during thrombosis promote C5a generation. Since thrombosis elicits fibrinolysis, we hypothesized that plasmin activates C5 during thrombosis. In vitro, the catalytic efficiency of plasmin-mediated C5a generation greatly exceeded that of thrombin or factor Xa, but was similar to the recognized complement C5 convertases. Plasmin-activated C5 yielded a functional membrane attack complex (MAC). In an arterial thrombosis model, plasminogen activator administration increased C5a levels. Overall, these findings suggest plasmin bridges thrombosis and the immune response by liberating C5a and inducing MAC assembly. These new insights may lead to the development of strategies to limit thrombus formation and/or enhance resolution.

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Thrombin is not a major direct contributor to C5a generation during venous thrombosis in mice.

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Plasmin, a protease generated in response to thrombin generation and fibrin deposition, efficiently cleaves C5 to C5a.

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In an arterial thrombosis model, administration of a plasminogen activator augments C5a plasma levels.

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Plasmin participates in immunothrombosis, liberating chemotactic C5a and inducing assembly of the procoagulant C5b-9.

Venous and arterial thrombosis are major causes of death and morbidity. Leukocytes are early and active participants in thrombus formation, recruited partly by complement factor C5a. We examined how C5a is generated in the setting of thrombosis. In venous thrombosis in mice, we show that thrombin, a key clot-promoting enzyme, is not a major contributor to C5a generation. Rather, plasmin, a fibrinolytic enzyme formed in response to thrombin generation and clot formation, efficiently generates C5a. The findings were validated in an arterial thrombosis model in mice. These insights may be valuable in developing therapeutic strategies to limit thrombus formation.

Experimental Malaria in Pregnancy Induces Neurocognitive Injury in Uninfected Offspring via a C5a-C5a Receptor Dependent Pathway

The in utero environment profoundly impacts childhood neurodevelopment and behaviour. A substantial proportion of pregnancies in Africa are at risk of malaria in pregnancy (MIP) however the impact of in utero exposure to MIP on fetal neurodevelopment is unknown. Complement activation, in particular C5a, may contribute to neuropathology and adverse outcomes during MIP. We used an experimental model of MIP and standardized neurocognitive testing, MRI, micro-CT and HPLC analysis of neurotransmitter levels, to test the hypothesis that in utero exposure to malaria alters neurodevelopment through a C5a-C5aR dependent pathway. We show that malaria-exposed offspring have persistent neurocognitive deficits in memory and affective-like behaviour compared to unexposed controls. These deficits were associated with reduced regional brain levels of major biogenic amines and BDNF that were rescued by disruption of C5a-C5aR signaling using genetic and functional approaches. Our results demonstrate that experimental MIP induces neurocognitive deficits in offspring and suggest novel targets for intervention.

A growing body of evidence has established the importance of the in utero environment on neurodevelopment and long-term cognitive and behavioral outcomes. These data suggest factors that disrupt the tightly regulated in utero environment can modify normal neurodevelopmental processes. Approximately 125 million pregnancies worldwide are at risk of malaria infection every year. However the impact of in utero exposure to MIP on fetal neurodevelopment is unknown. Here we use a mouse model of malaria in pregnancy to examine the impact of maternal malaria exposure on neurocognitive outcomes in offspring. We observed impaired learning and memory and depressive-like behavior in malaria-exposed offspring that were neither congenitally infected nor low birth weight. These neurocognitive impairments were associated with decreased tissue levels of neurotransmitters in regions of the brain linked to the observed deficits. Disruption of maternal C5a complement receptor signaling restored the levels of neurotransmitters and rescued the associated cognitive phenotype observed in malaria-exposed offspring. This study provides the first evidence implicating a causal link between pre-natal exposure to malaria, complement signaling and subsequent neurocognitive impairment in offspring.

Human IgG Antinuclear Antibodies Induce Pregnancy Loss in Mice by Increasing Immune Complex Deposition in Placental Tissue: In Vivo Study

PROBLEM

A threefold higher prevalence of antinuclear antibodies (ANA) has been reported in patients with recurrent pregnancy loss (RPL). Nevertheless, the role of ANA in reproductive failure is still unclear. The aim of this study was to investigate the role of ANA during early pregnancy in vivo.

METHOD OF STUDY

We used pregnant mice treated with immunoglobulin G (IgG) obtained from normal healthy subjects (NHS); ANA(+) sera of patients with RPL; and ANA(+) sera from women with uncomplicated pregnancies (HW). Placental immunohistochemical/immunofluorescence staining was performed to detect complement and immune complex deposition. ELISA was performed to evaluate complement levels.

RESULTS

ANA(+) IgG from RPL women significantly increased embryo resorption rate, reduced C3, and increased C3a serum levels compared to NHS IgG or ANA(+) -HW IgG. Increased C3 deposition and increased immune complex staining in placental tissues from mice treated with ANA(+) -RPL IgG fraction compared to NHS- and ANA(+) -HW-IgG-treated mice were found.

CONCLUSION

ANA(+) IgG injection in mice is able to induce fetal resorption and complement activation. The presence on placental tissues of immune complexes and complement fragments suggests the complement activation as a possible mechanism of placental damage.

Early elevations of the complement activation fragment C3a and adverse pregnancy outcomes

OBJECTIVE

To estimate whether elevations of complement C3a early in pregnancy are predictive of the subsequent development of adverse pregnancy outcomes.

METHODS

A plasma sample was obtained from each enrolled pregnant woman before 20 weeks of gestation. The cohort (n=1,002) was evaluated for the development of adverse pregnancy outcomes defined as hypertensive diseases of pregnancy (gestational hypertension or preeclampsia), preterm birth (before 37 weeks of gestation), premature rupture of the membranes, pregnancy loss (during the embryonic and fetal period), intrauterine growth restriction, and the composite outcome of any adverse outcome.

RESULTS

One or more adverse pregnancy outcomes occurred in 211 (21%) of the cohort. The mean levels (ng/mL) of C3a in early pregnancy were significantly (P=<.001) higher among women with one or more adverse outcomes (858±435) compared with women with an uncomplicated pregnancy (741±407). Adjusted for parity and prepregnancy body mass index, women with levels of C3a in the upper quartile in early pregnancy were three times more likely to have an adverse outcome later in pregnancy compared with women in the lowest quartile (95% confidence interval, 1.8-4.8; P<.001). The link between early elevated C3a levels and adverse pregnancy outcomes was driven primarily by individual significant (P<.05) associations of C3a with hypertensive diseases of pregnancy, preterm birth, and premature rupture of the membranes.

CONCLUSION

Elevated C3a as early as the first trimester of pregnancy is an independent predictive factor for adverse pregnancy outcomes, suggesting that complement-related inflammatory events in pregnancy contribute to the subsequent development of poor outcomes at later stages of pregnancy.

LEVEL OF EVIDENCE

II.

Revisiting the molecular mechanism of neurological manifestations in antiphospholipid syndrome: beyond vascular damage

Antiphospholipid syndrome (APS) is a multiorgan disease often affecting the central nervous system (CNS). Typically, neurological manifestations of APS include thrombosis of cerebral vessels leading to stroke and requiring prompt initiation of treatment with antiplatelet drugs or anticoagulant therapy. In these cases, alterations of the coagulation system at various levels caused by multiple effects of antiphospholipid antibodies (aPL) have been postulated to explain the vascular damage to the CNS in APS. However, several nonvascular neurological manifestations of APS have progressively emerged over the past years. Nonthrombotic, immune-mediated mechanisms altering physiological basal ganglia function have been recently suggested to play a central role in the pathogenesis of these manifestations that include, among others, movement disorders such as chorea and behavioral and cognitive alterations. Similar clinical manifestations have been described in other autoimmune CNS diseases such as anti-NMDAR and anti-VGCK encephalitis, suggesting that the spectrum of immune-mediated basal ganglia disorders is expanding, possibly sharing some pathophysiological mechanisms. In this review, we will focus on thrombotic and nonthrombotic neurological manifestations of APS with particular attention to immune-mediated actions of aPL on the vascular system and the basal ganglia.

Maternal and fetal alternative complement pathway activation in early severe preeclampsia

PROBLEM

We sought to determine whether alternative complement activation fragment Bb (Bb) levels are elevated in the maternal, fetal, and placental blood in cases of severe preeclampsia (PE) compared with normotensive controls.

METHOD OF STUDY

This was a cross-sectional study of women admitted at ≥24 weeks gestation with or without severe PE. Maternal plasma was collected at the time of enrollment. Umbilical venous cord and intervillous space blood were collected at delivery. Plasma Bb levels were assessed using ELISA. Bb levels were compared between cases and controls.

RESULTS

Median Bb levels were higher in the maternal plasma of severe PE subjects (n = 24) than in controls (n = 20), 1.45 ± 1.03 versus 0.65 ± 0.23 μg/mL, P < 0.001. In umbilical venous plasma, Bb levels were higher in severe PE subjects (n = 15) compared with controls (n = 15), 2.48 ± 1.40 versus 1.01 ± 0.57 μg/mL, P = 0.01.

CONCLUSION

Activation fragment Bb is increased in the maternal and umbilical venous blood of cases of severe PE when compared with normotensive controls. These data provide support for alternative complement pathway involvement in the pathogenesis of severe PE and demonstrate that alternative complement activation occurs not only in the maternal but also in the fetal compartment.

Receptors involved in cell activation by antiphospholipid antibodies

The antiphospholipid syndrome (APS) is an autoimmune disease associated with arterial or venous thrombosis and/or recurrent fetal loss and is caused by pathogenic antiphospholipid antibodies (aPLA). The plasma protein β2-glycoprotein 1 (β2GP1) has been identified as a major target of aPLA associated with APS. Cell activation by aPLA appears to be a major pathogenic cause in the pathogenesis of APS. Receptors, co-receptors and accessory molecules are known to assist the pathogenic effects of aPLA. Members of the TLR family and the platelet receptor apolipoprotein E receptor 2' (apoER2'), a receptor belonging to the low-density lipoprotein receptor (LDL-R) family, as well as GPIbα, were identified as putative candidates for aPLA recognition. CD14, a co-receptor for TLR2 and TLR4, and annexin A2, a ubiquitous Ca2+ -binding protein that is essential for actin-dependent vesicle transport, could serve as important accessory molecules in mediating the pathogenic effects of aPLA. Finally, complement activation has been reported in association with the pathogenicity of APS. The relative contribution of these different mechanisms in the pathogenesis of APS is controversial. Here, we review the various in vivo and in vitro models that have been used to investigate the pathogenic mechanisms of aPLA in APS.

Duration of anticoagulation treatment for thrombosis in APS: is it ever safe to stop?

Antiphospholipid syndrome (APS) is an auto-immune thrombophilia for which anti-thrombotic medication is necessary for long-term management to reduce thrombotic risk or pregnancy morbidity. Choosing the type of pharmacological treatment, i.e. the intensity and duration of anticoagulation, depends on the severity of an individual's APS and the risk of bleeding. This article reviews the current literature on anticoagulation therapy, provides recommendations on when to initiate therapy, and suggests possible alternatives for optimisation of management.

Antithrombotic therapy for pregnancy loss

BACKGROUND Although an association between thrombophilia and pregnancy loss has been observed in many studies, little is known about the pathophysiological mechanisms behind this association. Considering the association between thrombophilia and pregnancy loss, the efficacy of antithrombotic therapy for women with pregnancy loss (with or without thrombophilia) has been studied for the past 30 years. METHODS We performed a comprehensive review of the literature on the strength of the association between thrombophilia and pregnancy loss, the pathophysiological mechanisms and the efficacy of antithrombotic therapy to increase the chance of live birth. RESULTS The association between pregnancy loss and thrombophilia varies according to the type of thrombophilia (e.g. antiphospholipid syndrome versus forms of inherited thrombophilia) and according to the type of pregnancy loss (single versus recurrent pregnancy loss and early versus late pregnancy loss). Thrombophilia may induce thrombosis in decidual vessels or impair placentation through hypercoagulability and inflammation, but these hypotheses need further verification. For women with antiphospholipid syndrome, evidence from small-sized trials suggests a beneficial effect of antithrombotic therapy but additional randomized controlled trials are essential to confirm this. Whether antithrombotic therapy increases the chance of live birth in women with inherited thrombophilia is unknown. Recent randomized controlled trials have consistently shown that antithrombotic therapy does not increase the chance of live birth in women with unexplained recurrent miscarriage. CONCLUSIONS There are large gaps in knowledge and a lack of evidence for treatment of women with pregnancy loss with thrombophilia. To provide a solid base for clinical practice, further studies on the role of coagulation in reproduction, as well as international collaborations in randomized controlled trials of antithrombotic therapy in women with pregnancy loss, and antiphospholipid syndrome or inherited thrombophilia are urgently needed.

Positive C4d immunostaining of placental villous syncytiotrophoblasts supports host-versus-graft rejection in villitis of unknown etiology

ABSTRACT Chronic villitis of unknown etiology (VUE) occurs in 5% of placentas submitted to pathology and is characterized by lymphohistiocytic infiltration of chorionic villi. VUE is associated with fetal growth restriction, preterm birth, and recurrent pregnancy loss. Accumulating evidence indicates that VUE may represent a host-versus-graft reaction analogous to transplant rejection. Pathologists routinely screen for antibody-mediated rejection in transplant biopsies by immunostaining for C4d, which highlights the recognition of donor cells by the host immune system. Since the hemochorial placenta is bathed in maternal blood, we hypothesized that cases of VUE may show C4d deposition onto villous syncytiotrophoblasts (STB). Chronic villitis was diagnosed in 82 of 1986 (4%) singleton placentas submitted to our department from 2007 through 2011. Forty randomly selected cases were gestational age-matched with 40 negative controls. Patient charts were reviewed and representative placental sections were immunostained for C4d. A positive C4d result was defined as circumferential immunostaining of the STB around at least one villous, or strong staining of fetal endothelial cells in the chorionic plate or stem villi. Our data indicate that VUE usually occurs in the 3rd trimester (37 ± 0.5 weeks) and is associated with significantly reduced placental weight (P  =  0.006). Positive C4d staining of STB was more common in VUE (35/40, 88%) compared with negative controls (2/40, 5%) (P < 0.0001). It was also more common in multiparous (35/66, 53%) than primiparous (2/14, 14%) women (P < 0.01). Although the precise mechanism remains to be determined, our data support the hypothesis that VUE may represent host-versus-graft rejection by the mother.

Organ specific complement proteins inhibition can reduce the risk of antiphospholipid antibodies mediated fetal loss

Antiphospholipid syndrome is a pregnancy related, systemic autoimmune disorder in which antibodies directed against cell membrane phospholipids with multiple venous/arterial thromboses. Though the etiology of antiphospholipid syndrome has not been identified exactly, experimental evidences suggest the possible mechanisms involved in the pathogenicity of this syndrome. Antiphospholipid antibodies mediate deposition of complement proteins in placenta and over expression of tissue factor on the surface of neutrophils which are reported to be the prominent cause of prothrombotic phenotype. The activation complement components C3 and C5 by antiphospholipid antibodies would eventually activates blood coagulation pathway that leads to thrombosis. Inhibition of activated complement components C3a and C5a by anticomplement agents protects from antiphospholipid antibody mediated fetal loss. Since the interference of complement pathway may lead to deleterious effects, we hypothesis that local inhibition of complement proteins C3a and C5a at placenta would reduce the risk of antiphospholipid antibody mediated placental thrombosis and pregnancy complications.

C6 knock-out mice are protected from thrombophilia mediated by antiphospholipid antibodies

BACKGROUND

Complement activation plays a role in pathogenesis of the antiphospholipid syndrome (APS), but the involvement of the C5b-9 membrane attack complex (MAC) is unknown. Here we studied the effects of human polyclonal antiphospholipid (aPL) antibodies on thrombosis and tissue factor (TF) up-regulation in C6 deficient (C6(-/-)) mice.

METHODS

C6(-/-) mice or the wild-type C3H/HeJ (C6(+/+)) mice were injected twice with IgG-APS (n = 2) or IgM-APS (n = 1) isolated from APS patients or with the corresponding control immunoglobulins (Igs) of normal human serum, (NHS) (IgG-NHS or IgM-NHS). Then, the sizes of induced thrombi in the femoral vein were determined 72 hours after the first injection. Tissue factor was determined in homogenates of carotid arteries and in peritoneal macrophages.

RESULTS

Thrombus sizes were significantly larger in C6(+/+) treated with IgG-APS1 or with IgG-APS2 or with IgM-APS when compared with C6(+/+) mice treated with IgG-NHS or with IgM-NHS, respectively. The sizes of thrombi were significantly smaller in the C6(-/-) mice injected with IgG-APS1, IgG-APS2 or IgM-APS (p < 0.001), compared to their C6(+/+) counterparts showing an important abrogation of thrombus formation in mice lacking C6. The TF expression and activity in the C6(-/-) mice treated with IgG-APS or IgM-APS were diminished when compared to C3H/HeJ (C6(+/+)) mice treated with the same Igs. All mice injected with IgG-APS and IgM-APS had medium-high titers of anticardiolipin (aCL) and anti-β(2)glycoprotein I (aβ(2)GPI) antibodies.

CONCLUSIONS

These data indicate that the C6 component of the complement system mediates aPL-thrombogenic effects, underscoring an important pathogenic mechanism and indicating the possibility of inhibiting complement to ameliorate APS-related manifestations.

Complement and the antiphospholipid syndrome

PURPOSE OF REVIEW

The antiphospholipid antibody syndrome (APS) is characterized by arterial or venous thrombosis or pregnancy morbidity in patients with persistent antiphospholipid antibodies (aPL). Experimental data supporting activation of the complement cascade has provided critical insight into the underlying pathophysiology of aPL-induced pregnancy loss and thrombosis.

RECENT FINDINGS

Although the mechanism by which pregnancy loss and thrombosis is incompletely elucidated, studies using mice deficient in complement components and specific inhibitors to complement have demonstrated that activation of complement contributes to fetal loss, growth restriction and thrombosis. Inhibition of complement activation can prevent these complications. Use of a specific complement inhibitor to C5 has been used successfully in a patient with catastrophic APS undergoing renal transplantation.

SUMMARY

Activation of complement plays an important role in the pathogenesis of aPL-induced pregnancy morbidity and thrombosis. This understanding has been advanced primarily using mouse models of APS and clinical studies in patients with APS are needed. Although there is currently no specific complement-targeted therapy approved for APS, developing and evaluating complement-targeted therapies in patients with APS are warranted. Complement inhibition may provide a novel upstream treatment option for patients with APS compared with the current standard treatment of anticoagulation.

Engraftment of peripheral blood mononuclear cells from systemic lupus erythematosus and antiphospholipid syndrome patient donors into BALB-RAG-2-/- IL-2Rγ-/- mice: a promising model for studying human disease

OBJECTIVE

To construct a humanized mouse model of systemic lupus erythematosus (SLE) that resembles the human disease in order to define the pathophysiology and targets for treatments.

METHODS

We infused peripheral blood mononuclear cells (PBMCs) from SLE patients into BALB- RAG-2-/- IL-2Rγ-/- double-knockout (DKO) mice, which lack T cells, B cells, and natural killer cells. PBMCs from 5 SLE patients and 4 normal donors were infused intravenously/intraperitoneally at a density of 3-5×10(6) cells per animal into nonirradiated 4-5-week-old mice. We evaluated the engraftment of human CD45+ cells and monitored the plasma levels of human IgG, anti-double-stranded DNA (anti-dsDNA) antibody, and anticardiolipin antibody (aCL), as well as proteinuria and kidney histology.

RESULTS

There was 100% successful engraftment in 40 DKO mice infused with human PBMCs. In the PBMC fraction from SLE PBMC-infused DKO (SLE-DKO) mice and normal donor PBMC-infused DKO (ND-DKO) mice, an average of 41% and 53% human CD45+ cells, respectively, were observed at 4 weeks postengraftment, with 70-90% CD3+ cells. There were fewer CD3+CD4+ cells (mean±SEM 5.5±2.1%) and more CD3+CD8+ cells (79.4±3.6%) in the SLE-DKO mice as in the SLE patients from which the PBMCs were derived. CD19+ B cells and CD11c+ monocytic cells were found in the spleen, lung, liver, and bone marrow. There was no significant difference in plasma levels of human IgG and anti-dsDNA antibodies between SLE-DKO and ND-DKO mice. Levels of aCL were significantly higher in all SLE-DKO mice infused with PBMCs from an SLE patient who had high titers of aCL. SLE-DKO mice had proteinuria, human IgG deposits in the kidneys, and a shorter life span. In SLE-DKO mice engrafted with PBMCs from the aCL-positive patient, we found microthrombi and infiltration of CD3+, CD8+, and CD19+ cells in the glomeruli, recapitulating the human antiphospholipid syndrome in these mice.

CONCLUSION

We established a novel humanized SLE-DKO mouse exhibiting many of the immunologic and clinical features of human SLE.

[Pathogenic mechanisms of the anti-phospholipid antibodies]

The antiphospolipid syndrome (APS) is an autoimmune disease characterized by recurrent fetal loss, thrombotic events (arterial or venous) and hemocytopenic disorders associated to high titers of circulating aPL. Two variants of the APS have been described. Primary APS is a clinical entity without evidence of any other autoimmune disease and secondary APS is a clinical disorder mainly associated with Systemic Lupus Erithematosus (SLE). aPL are a widely group of immunoglobulins directed against different components or proteins factors. In 1990 three groups of researchers identified that β(2)GP-I is the mainly antigenic target of aPL in APS patients. There are evidences that show that more than one pathogenic mechanism is involved in the development of the APS. The best documented clinical manifestations associated with the APS are recurrent fetal loss and thrombotic disorders. The latter is based on observations in vivo in animal models and in vitro on the effects caused by aβ(2)GP-I antibodies from patients with APS or from animals which cause experimental APS. The objective of the present paper is to show the pathogenic mechanisms that participate in the development of the APS. We also presented evidence that shows that aβ(2)GP-I induces pro-inflammatory, pro-adhesive and pro-coagulant disorder.

Anti-fibrillin-1 autoantibodies in normal pregnancy and recurrent pregnancy loss

PROBLEM

The aim of this study was to investigate anti-fibrillin-1 autoantibody in patients with a history of recurrent pregnancy loss (RPL) and during normal pregnancy.

METHOD OF STUDY

Anti-fibrillin-1 IgG and IgM antibodies were measured by a home made ELISA in serum samples of 48 medically and obstetrically normal pregnant women, classified to three trimester groups, 15 female patients with RPL and 26 healthy non-pregnant women classified to two control subgroups: (a) women who had already had at least one previous successful pregnancy and (b) women who had never been pregnant. Differences in anti-fibrillin-1 autoantibodies between the groups were analyzed for statistical significance (P<0.05) with one-way analysis of variance (ANOVA) and multiple comparison test - Post Hoc test, Least Significant Difference method.

RESULTS

Anti-fibrillin-1 IgM autoantibodies were significantly decreased in the second and third trimester pregnant women compared to the nulligravida controls. RPL patients had significantly increased anti-fibrillin-1 IgM antibody compared to control group (a).

CONCLUSION

Fibrillin-1 degradation seems to be decreased during the second and third trimester of normal pregnancy. Increased anti-fibrillin-1 IgM antibodies in RPL patients may be a secondary phenomenon of increased fibrillin-1 degradation and contribute to the pathogenesis of pregnancy losses.

Preeclampsia and pregnancies with small-for-gestational age neonates have different profiles of complement split products

OBJECTIVE

The activation of the complement system results in the generation of split products with pro-inflammatory properties. The objective of this study was to determine whether preeclampsia and small-for-gestational age (SGA) are associated with changes in the maternal plasma concentrations of anaphylatoxins C3a, C4a and C5a.

METHODS

A cross-sectional study was conducted in the following groups: (a) normal pregnant women (n = 134); (b) women who delivered an SGA neonate (n = 53); (c) preeclampsia with (n = 52) and without SGA (n = 54). Maternal plasma anaphylatoxin concentrations were determined by enzyme-linked immunoassay.

RESULTS

(1) Women with preeclampsia with or without SGA had a significantly higher median plasma C5a concentration than that of normal pregnant women and those with SGA alone (all P < 0.01); (2) women with SGA alone did not have an increase in plasma C5a concentration; (3) in contrast, the median maternal plasma concentration of C4a was lower in women with preeclampsia and SGA than that of those with a normal pregnancy (P = 0.001); (4) no changes in C3a were observed among the study groups.

CONCLUSION

Preeclampsia is associated with increased plasma concentration of C5a, regardless of the presence or absence of an SGA fetus. In contrast, there was no difference in the plasma C3a, C4a and C5a concentration in patients with SGA.

Dysregulated complement activation as a common pathway of injury in preeclampsia and other pregnancy complications

The complement system protects the host against invading organisms, initiates inflammation and dispose of immune complexes and the products of inflammatory injury. The complement system provides an important link between the innate and adaptive immune systems. Experimental observations suggest that increased complement activation causes and/or perpetuates inflammation during pregnancy. Recent studies suggest a link between complement activation and preeclampsia. Excessive activation or insufficient regulation of complement recruits leukocytes and unleashes potent inflammatory and anti-angiogenic mediators associated with placental insufficiency and maternal endothelial dysfunction characteristic of preeclampsia. We review the animal and human studies that link complement activation and pathogenic events in preeclampsia, present evidence that activation of the complement system is associated with the development of preeclampsia and provides new targets to prevent its complications.

Antiphospholipid syndrome treatment beyond anticoagulation: are we there yet?

Persistently positive antiphospholipid antibodies in association with thromboses and/or pregnancy morbidity is the hallmark of the antiphospholipid syndrome. The management of antiphospholipid antibody-positive patients has been focused on utilizing anti-thrombotic medications such as heparin or warfarin. Given that our understanding of the molecular mechanisms of antiphospholipid antibody-mediated thrombosis has been growing, it is highly likely that the current ‘anti-thrombotic’ approach to these patients will be replaced by an ‘immunomodulatory’ approach in the near future. This review article will address the experimental and/or clinical evidence behind some of these potential ‘immunomodulatory’ approaches (tissue factor inhibition, P38 mitogen-activated protein kinase inhibition, nuclear factor-κB inhibition, platelet glycoprotein receptor inhibition, hydroxychloroquine, statins, inhibition of β2GPI and/or anti-β2GPI binding to target cells, complement inhibition, and B cell inhibition) in antiphospholipid syndrome.

The interrelationship of complement-activation fragments and angiogenesis-related factors in early pregnancy and their association with pre-eclampsia

OBJECTIVE

To determine the interrelationships during early pregnancy of complement-activation fragments Bb, C3a and sC5b-9, and angiogenesis-related factors placental growth factor (PiGF), soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng), and their associations with pre-eclampsia.

DESIGN

Prospective cohort study.

SETTING

Denver complement study (June 2005-June 2008).

POPULATION

A total of 668 pregnant women with singleton gestations, recruited between 10 and 15 weeks of gestation.

METHODS

Using univariable and multivariable logistic regression analysis, concentrations of complement-activation fragments and angiogenesis-related factors were compared between 10 and 15 weeks of gestation in women who subsequently did or did not develop pre-eclampsia. Interrelationships between these variables were tested using the non-parametric Spearman rank correlation coefficient.

MAIN OUTCOME MEASURE

Pre-eclampsia. The association of complement-activation fragments and angiogenesis-related factors with obesity was also examined.

RESULTS

The mean (+/-SD) levels of complement Bb in early pregnancy among women who did and did not develop pre-eclampsia were 0.84 (+/-0.26) microg/ml and 0.69 (+/-0.2) microg/ml, respectively (P = 0.001). Concentrations of PiGF were significantly (P = 0.01) lower (31 +/- 12 pg/ml) in early pregnancy in the pre-eclamptic group of women, as compared with the normotensive group (39 +/- 32 pg/ml). The adjusted odds ratio (AOR) of Bb and PiGF were 2.1 (CI = 1.4-3.1, P < 0.0003) and 0.2 (CI = 0.07-0.7, P = 0.01), respectively. There was no significant difference in the levels of C3a, sC5b-9, sFlt-1 and sEng in early pregnancy among women who developed pre-eclampsia, compared with women who remained normotensive during pregnancy. Higher levels of Bb (P = 0.0001) and C3a (P = 0.03), and lower levels of sFlt-1 (P = 0.0002) and sEng (P = 0.0001) were found among women with obesity, compared with non-obese controls. No meaningful relationships were found between the complement-activation fragments and the angiogenesis-related factors.

CONCLUSIONS

In this cohort during early pregnancy, increased concentrations of complement-activation factor Bb and lower concentrations of PiGF were associated with the development of pre-eclampsia later in pregnancy.

Molecular markers of preterm labor in the choriodecidua

Because relevant biochemical changes are known to begin at the choriodecidual interface some weeks before actual clinical onset of labor, we hypothesized that the preterm choriodecidua may display gene and protein expression patterns specific to preterm labor. Transcriptomic (microarray) and proteomic (2-dimensional gel electrophoresis [2DGE]) profiling methodologies were used to compare changes in choriodecidual tissue collected from women who delivered before 35 weeks of gestation following spontaneous preterm labor (n = 12) and gestation-matched nonlaboring controls (n = 7). Additionally, 2DGE was used to compare differences in protein expression during term and preterm labor and to construct a choriodecidual proteome map. Overall, expressed transcripts and proteins indicated active tissue remodeling independent of labor status and an association with inflammatory processes during labor. Spontaneous, infection-induced and abruption-associated preterm deliveries were each defined by distinct transcriptional profiles. Proteins osteoglycin and progesterone receptor component 2 (PGRMC2) were upregulated during term and preterm labor while galectin 1, annexin 3, annexin 5, and protein disulfide isomerase (PDI) were upregulated only during preterm labor, suggesting a probable association with the underlying pathology. Together, these results represent novel data that warrant further investigations to elucidate plausible causal relationships of these molecules with spontaneous preterm delivery.

Evidence for complement activation in the amniotic fluid of women with spontaneous preterm labor and intra-amniotic infection

OBJECTIVE

The complement system plays an important role in host defense against infection. Concentrations of complement split products or anaphylatoxins (C3a, C4a, and C5a) in biological fluids are considered to reflect complement activation. The purpose of this study was to determine if term and preterm parturition are associated with evidence of complement activation in the amniotic fluid.

STUDY DESIGN

Amniotic fluid (AF) samples were collected from 270 women in the following groups: (1) normal pregnant women in midtrimester (n = 70), (2) term not in labor (n = 23), (3) term in labor (n = 48), and (4) preterm labor (PTL) (n = 129). PTL was categorized into: (a) PTL without microbial invasion of the amniotic cavity (MIAC) who delivered at term (n = 42), (b) PTL who delivered preterm without MIAC (n = 57), and (c) PTL with MIAC (n = 30). C5a, C4a, and C3a concentrations in amniotic fluid were determined by ELISA. Nonparametric tests were used for statistical analysis.

RESULTS

(1) The median AF C5a concentration was higher in women at term than that of those in the midtrimester (p = 0.02); (2) Spontaneous labor at term was not associated with changes in AF concentrations of anaphylatoxins C3a, C4a, and C5a (all p > 0.05); (3) Among patients with PTL who delivered preterm, those with MIAC had higher AF C4a and C5a concentrations than those without infection (p < 0.01); and (4) AF C3a, C4a, and C5a concentrations were higher in patients with PTL with MIAC than in those with PTL without MIAC who delivered at term.

CONCLUSION

Patients with spontaneous preterm labor and intact membranes with microbial invasion of the amniotic cavity had higher median amniotic fluid concentration of complement split products C3a, C4a, and C5a than patients without intra-amniotic infection. These findings suggest that preterm labor in the context of infection is associated with activation of the complement system.

Use of Heparin in Women With Early and Late Miscarriages With and Without Thrombophilia

Objective: In women with a history of recurrent miscarriage, the risk of miscarriage in a subsequent pregnancy is about 30% to 40%. In patients with thrombophilia, the risk is even higher. Placental thrombosis has been found in women with unexplained recurrent miscarriage independent of thrombophilia. In addition, proinflammatory changes, for example, altered Th1 to Th2 cytokine ratio and complement activation, have been repeatedly demonstrated in these women. Because of the fact that heparin has both anticoagulative and anti-inflammatory effects, the current study evaluated the efficacy of low-molecular-weight heparin (LMWH) in unexplained abortions. Study Design: A total of 164 women with unexplained early and late miscarriages presented in our hemostaseological clinic for thrombophilia screening. For these 164 women, 82 subsequent pregnancies in 79 patients were treated with subcutaneous LMWH independently of thrombophilia. In 54/82 unselected pregnancies, 100 mg aspirin was administered in addition to LMWH. Two patients were excluded due to termination of pregnancy. Results: Overall, 83.8% (67/80) of pregnancies resulted in live births. In 22/79 women (27.8%), thrombophilia markers were positive. Most noteworthy, patients with thrombophilia markers had live births at a similar frequency as patients without those parameters. No severe side effects of LMWH were seen. Conclusions: Our data support the notion that LMWH is efficacious in patients with recurrent abortions and thrombophilia. We demonstrated the same effect of LMWH in women with unexplained abortions without thrombophilia. The potential mechanism of action of LMWH in early and late abortions warrants further study.

Complement activation fragment Bb in early pregnancy and spontaneous preterm birth

OBJECTIVE

The objective of this study was to determine whether an elevated level of the complement activation fragment Bb in early pregnancy was associated with spontaneous preterm birth (SPTB) at less than 34 weeks' gestation or SPTB between 34 and 37 weeks' gestation (late SPTB).

STUDY DESIGN

This was a prospective study of 784 women enrolled at less than 20 weeks' gestation.

RESULTS

Following exclusions, 13 women (1.7%) had a SPTB at less than 34 weeks' gestation and 25 (3.2%) a SPTB between 34 and 37 weeks' gestation. Women with Bb in the top quartile were 4.7 times more likely to have an SPTB less than 34 weeks' gestation as compared with women who had levels of Bb in the lower 3 quartiles (95% confidence interval [CI] 1.5-14, P = .003). There was no association between Bb and late SPTB (relative risk 0.8, 95% CI 0.3-2).

CONCLUSION

A significant relationship was found between an elevated Bb in early pregnancy and SPTB less than 34 weeks' gestation. These results suggest that inflammatory events in early pregnancy are part of the pathogenic mechanisms of this condition.

Alternative complement pathway activation fragment Bb in early pregnancy as a predictor of preeclampsia

OBJECTIVE

Preeclampsia is a multisystem disease classically defined on the basis of hypertension and proteinuria. As shown in animal studies, complement activation is associated with inflammation in the placenta and adverse pregnancy outcomes. The association between complement activation in humans and adverse pregnancy outcomes is unclear. The purpose of this study was to determine whether elevated levels of the activation fragment Bb in early pregnancy are predictive of preeclampsia.

STUDY DESIGN

This prospective study of 701 women was conducted in Denver, CO. A single plasma sample was obtained from each woman before 20 weeks' gestation. The cohort was followed up throughout pregnancy for the development of preeclampsia. Analysis included multivariate logistic regression to adjust for established risk factors for preeclampsia.

RESULTS

Preeclampsia developed in 4.6% of the cohort. Women with elevated Bb (90th or greater percentile) were substantially more likely to develop preeclampsia than women who had levels less than the 90th percentile (unadjusted relative risk [RR], 3.3, 95% confidence interval [CI] 1.6 to 7, P = .0009). Other significant risk factors for preeclampsia included nulliparity (RR, 2.1, 95% CI, 1-4), a high body mass index (P = .006 for trend), and maternal medical (preexisting maternal hypertension, type 1 diabetes, systemic lupus erythematosus) disease (RR, 4.4, 95% CI, 2-10). Significant risk factors among multiparous women included a history of hypertension in a previous pregnancy (RR, 5, 95% CI, 1.6 to 16) and a change of paternity (RR, 5.1, 95% CI, 1.6 to 15). Adjustment for risk factors did not attenuate the association between an elevated Bb and preeclampsia (adjusted odds ratio [OR], 3.8, 95% CI, 1.6 to 9, P = .002) in the cohort. After removing women with plasma obtained before 10 weeks, the adjusted OR of Bb in the top decile for preeclampsia was 6.1 (95% CI 2.2, 17, P = .0005).

CONCLUSION

The complement activation product Bb in early pregnancy is a biomarker for elevated risk of preeclampsia. This observation suggests that events linked to activation of complement in early pregnancy are associated with the pathogenesis of preeclampsia.

Novel therapies for the antiphospholipid syndrome

Antiphospholipid antibodies (aPL Abs) are associated with thrombosis in patients with the antiphospholipid syndrome (APS). There is strong evidence that aPL Abs are pathogenic in vivo from studies in animal models. Furthermore, there are now convincing data indicating that activation of complement is involved in those processes. This report addresses current modalities of treatment, as well as recent findings with respect to molecular events triggered by aPL Abs on endothelial cells, platelets, monocytes and complement activation. A separate section addresses recent findings with regard to the putative receptor(s) recognized by aPL Abs on target cells. Based on experimental evidence using in vitro and in vivo models, new targeted therapies for treatment and/or prevention of thrombosis in APS are proposed and discussed.

New targeted therapies for treatment of thrombosis in antiphospholipid syndrome

Antiphospholipid (aPL) antibodies (Abs) are associated with thrombosis and pregnancy loss in antiphospholipid syndrome (APS), a disorder initially characterised in patients with systemic lupus erythematosus (SLE) but now known to occur in the absence of other autoimmune disease. There is strong evidence that aPL Abs are pathogenic in vivo, from studies of animal models of thrombosis, endothelial cell activation and pregnancy loss. In recent years, progress has been made in characterising the molecular basis of this pathogenicity, which includes direct effects on platelets, endothelial cells and monocytes as well as activation of complement. This review summarises the clinical manifestations of APS and current modalities of treatment, and explains recent advances in understanding the molecular events triggered by aPL Abs on target cells in coagulation pathways as well as effects of aPL Abs on complement activation. Based on this information and on additional scientific evidence using in vitro and in vivo models, new potential targeted therapies for treatment and/or prevention of thrombosis in APS are proposed and discussed.

The Role of Anti-Phospholipid Auto Antibodies Syndrome in Cerebrovascular Diseases

Objectives: The aims of the study are to determine the role of anti-phospholipid autoantibodies (APLAs) among patients with stroke and/or transient ischaemic attacks (TIAs), to identify the types and effective isotype of some important APLAs which are lupus anticoagulant (LA), anticardiolipin (aCL), anti∼fi2 glycoprotein I dependent (afi2-GPI), and anti-phosphatidyl serine (aPS). Also, to find out any concomitant effect of non-APLAparameters not specific to antiphospholipid syndrome (APS).

Subjects and Methods: This study was carried out on 50 patients attending mainly the Teaching and General Hospitals in Mosul, Duhok, and Erbil Cities, Iraq during the period between 1st March 2004 and 1st March 2005. The studied cases were under 50 years of age, and had no recognizable risk factors. The activated partial thromboplastin time (APTT) was used for LA estimation and ELISA assay was used to test for IgG& IgM isotypes ofaCL, aJ32-GPI, and aPS. The ANA, RF, VDRL, CRP, and C4 complement were tested by different immuoserological methods. The thrombocytopenic (TP) status was diagnosed by estimation of platelets counts.

Results: The strokes and!or TIAs related to APS were diagnosed in 22/50 (44%) of patients and a significant correlation was reported among patients with IgG plus IgM aCL (p <  0.05), IgG afi2-GPI (p <  0.05), and IgG aPS (p <  0.05). In APLAs positive patients, raised CRP concentrations were reported in 36.4%, TP status in 22.7%, ANA in 22.7%, RF positive in 13.6%, and low C4 levels in l3.6%. Finally,the FP-VDRL test was found in 50 % of APLAs positive cases.

Conclusions: The aCL, afi2- GPI, and aPS antibodies were shown to play a significant role in the development of stroke and!or TIAs among the studied cases.

Neurological manifestations of the antiphospholipid syndrome: risk assessments and evidence-based medicine

The antiphospholipid syndrome (APS) is a systemic autoimmune disorder characterised by autoantibody production and vascular thrombosis or pregnancy morbidity. Autoantibodies generated against phospholipid and phospholipid-binding proteins often impair phospholipid-dependent clotting assays (lupus anticoagulants). These autoantibodies activate endothelial cells, platelets and biochemical cascades and can exist in autoimmune disorders such as lupus. Consistently positive antibodies may worsen the severity of thrombo-occlusive disease. The most common neurological manifestations of APS include stroke and transient ischaemic attacks due to arterial thromboses. Antiphospholipid antibodies may cause additional neurological impairments through both vascular and immune mechanisms. Antiaggregant or anticoagulant therapies are indicated for APS-related ischaemic strokes. Treatment regimens for asymptomatic antibody-positive patients and those with refractory disease remain controversial. There is scant literature on neurological APS manifestations in paediatric patients. Assessment of traditional cardiovascular and inherited thrombophilia risk factors is essential in patients with APS. Modifiable risk factors and valvular heart disease may worsen thrombotic and cerebrovascular outcomes. Alternative therapies such as statins, anti-malarials, angiotensin-converting enzyme inhibitors and thrombin inhibitors warrant further research.

Role of complement in antiphospholipid antibody-mediated thrombosis

The mechanisms by which an antibody that reacts with phospholipids (universal components of mammalian membranes) causes thrombosis are not immediately obvious. The development of an animal model of antiphospholipid antibody syndrome has moved the field forward in dissecting the pathogenesis of antiphospholipid antibody syndrome and has implicated the complement system in the mechanism of disease. Understanding complement's role in promoting thrombosis will be important in designing safer, more effective approaches to the treatment of patients with antiphospholipid antibodies, and may shed light on which patients are at greatest risk for thrombosis, perhaps permitting primary prophylaxis before irreversible tissue and organ damage occur.

Mechanisms of aPL-mediated thrombosis: effects of aPL on endothelium and platelets

Antiphospholipid antibodies (aPL) are associated with thrombosis and pregnancy loss in patients with systemic lupus erythematosus and antiphospholipid syndrome. Strong evidence demonstrates that aPL are pathogenic in vivo from studies that utilized animal models of thrombosis, endothelial cell activation, and pregnancy loss. However, the mechanisms by which aPL mediate disease are only partially understood, and our knowledge is limited by the polyspecificity of the antibodies, the multiple potential end-organ targets, and the variability of the clinical context in which the disease may present. This review discusses and summarizes the most current data available on molecular interactions and pathogenic mechanisms in antiphospholipid syndrome.

C5a Receptor-Deficient Mice Are Protected from Thrombophilia and Endothelial Cell Activation Induced by Some Antiphospholipid Antibodies

Recent findings indicate that complement activation--involving specifically C3 and C5--contributes to antiphospholipid (aPL)-mediated thrombosis. Two complement effector pathways are initiated by the cleavage of C5, C5a and C5b, which leads to the formation of the C5b-9 membrane attack complex. To delineate and distinguish the role of C5a from the C5b-9 membrane attack complex seeded by C5b, we examined the in vivo effects (thrombosis) of aPL on C5a receptor-deficient (C5aR-/-) mice. C5aR-/- and C5aR+/+ mice were injected with IgM or with IgG from two different patients with APS (IgM-APS or IgG-APS) or with control IgM or IgG (IgM-NHS or IgG-NHS) twice. Complement fixing activity of the Ig fractions and anticardiolipin activity in the sera of the mice were determined by enzyme-linked immunosorbent assay. Surgical procedures to study thrombus dynamics were performed. IgM-APS but not IgG-APS fixed C1q to cardiolipin-coated plates. IgM-APS significantly enhanced thrombus size in C5aR+/+ mice compared to C5aR+/+ mice treated with IgM-NHS (3198 +/- 2361 microm2 versus 585 +/- 460 microm2). C5aR-/- mice treated with IgM-APS showed a significant reduction in thrombi size as compared with C5aR+/+ mice (676 +/- 690 microm2 versus 3198 +/- 2361 microm2; P = 0.001). IgG-APS enhanced thrombus formation significantly in C5aR+/+ when compared to IgG-NHS-treated mice (3507 +/- 965 microm2 versus 1321 +/- 798 microm2), and these effects were not altered in C5aR-/- mice (3400 +/- 1681 microm2). The data indicate that C5aR-/- mice are protected from the thrombogenic effects of some aPL antibodies.

Excessive complement activation is associated with placental injury in patients with antiphospholipid antibodies

OBJECTIVE

Studies that use a murine model of antiphospholipid syndrome have demonstrated a critical role for complement activation that leads to fetal and placental injury in the presence of antiphospholipid antibodies (APAs). We examined the placentas of patients with APAs to demonstrate a similar association with tissue injury in humans.

STUDY DESIGN

Immunohistochemical analyses with the use of antibodies to the complement products C4d, C3b, and C5b-9 were performed on paraffin-embedded tissue sections of placentas from 47 patients with APAs and 23 normal control patients.

RESULTS

We found evidence of increased complement deposition in the trophoblast cytoplasm (C4d and C3b), trophoblastic cell and basement membrane (C4d), and extravillous trophoblasts (C4d) of patients with APAs, compared with control patients. We report a correlation between placental pathologic features and complement deposition (C4d) in the trophoblastic cytoplasm, cell membrane, and basement membrane.

CONCLUSION

These findings are consistent with murine studies that implicate complement as a critical factor in the fetal tissue injury observed in antiphospholipid syndrome.