Intracellular signaling triggered by antiphospholipid antibodies in platelets and endothelial cells: a pathway to targeted therapies

Understanding the intracellular events triggered by antiphospholipid (aPL) antibodies in platelets and endothelial cells (ECs) is important in designing new modalities of targeted therapies for the treatment of thrombosis in Antiphospholipid Syndrome (APS). A recent study showed a significant increase in the expression of GPIIb/IIIa on platelets treated with aPL antibodies and a thrombin receptor peptide agonist (TRAP), and these effects were abrogated by hydroxychloroquine (HQ). Hydroxychloroquine has also been shown to reduce in vivo aPL-induced thrombus formation. Furthermore, aPL-enhanced thrombosis in vivo can be abrogated by infusions of a GPIIb/IIIa antagonist (1B5) monoclonal antibody, and aPL-mediated thrombophilia is not observed in GPIIb/IIIa-deficient mice. Treatment of platelets with aPL antibodies has resulted in a significant increase in p38 mitogen-activated protein kinase (p38MAPK) phosphorylation and aPL-induced platelet aggregation and thromboxane B2 (TXB2) production was abrogated by SB203580 (a p38MAPK inhibitor). aPL antibodies induce increased expression, function and transcription of tissue factor (TF) on EC. Activation of ECs and thrombogenicity of aPL in vivo can be reversed by treatment of the animals with statins. Upregulation of TF on ECs can also be abrogated by treatment of the cells with fluvastatin. There is also indication of activation of nuclear factor kappa B (NFkappaB), increase in phosphorylation of p38MAPK in ECs by aPL antibodies that can be reversed by specific inhibitors MG132 and SB203580, respectively. The data open the possibility to new treatment modalities that may include the use of hydroxychloroquine, statins, specific antagonists of GPIIb/IIIa (such as abciximab or equivalent) and specific p38MAPK inhibitors, after the completion of well-designed clinical studies.

Coronary and valvular syndromes and antiphospholipid antibodies

Since the recognition of the antiphospholipid syndrome (APS), a large number of cardiac manifestations have been reported in association with these antibodies, including coronary artery and valvular disease, cardiomyopathy, and intracardiac thrombosis. Most of these manifestations are explicable on the basis of thrombotic lesions either in the coronary circulation or on the valves and may mimic other similar conditions, such as rheumatic fever or infectious endocarditis. The APS coagulopathy in these patients requires the careful and judicious use of appropriate antiaggregant and anticoagulant therapy. In this review article, the focus will be on the main cardiac features related to the presence of antiphospholipid antibodies (aPLs), which may be of interest to clinicians.

[Levels of antiphospholipid antibodies in the serum and aqueous humor of glaucoma patients]

PURPOSE

Evaluation of antiphospholipid antibodies in the serum and aqueous humor in patients with glaucoma.

MATERIAL AND METHODS

48 persons (38 women and 17 men), aged 30-86 (mean age 70), suffering from glaucoma was examined. There were 19 with POAG, 18 with PACG and 11 with PEXG. All patients have undergone trabeculectomia. The group of 20 operated, because of age-related cataracta patients (7 men and 13 women), aged 47-82 (mean age 65) constituted a control group. All patients agreed to samples collection. In plasma and anterior chamber fluid the level of antiphospholipids antibodies classes IgM and IgG were measured, using ELISA method (commercial kits produced by Euroimmun) according to producent's instruction. Statistical analysis was performed using U Mann-Whitney test.

RESULTS

The mean values of antiphospholipids in both group are put in the table. The significant differences between glaucoma and no-glaucoma patients were observed in levels of IgG in serum (p=0.014) and in levels of IgM antibodies in aqueous humor (p=0.013).

CONCLUSIONS

The presence of elevated levels of antiphospholipid antibodies in aqueous humor and serum may be a risk factor in progression of glaucomatous neuropathy.

Sulfatides: targets for anti-phospholipid antibodies

BACKGROUND

Sulfatides are sulfated glycosphingolipids expressed on the surface of erythrocytes, leukocytes, and platelets. Sulfatides interact with several cell adhesion molecules involved in hemostasis. Beta2-glycoprotein I is an anionic phospholipid-binding plasma protein, and the phospholipid-bound form is the target for most anti-phospholipid antibodies that are associated with recurrent thrombosis, miscarriages, and neurological symptoms. In this study, we examined whether beta2-glycoprotein I forms a complex with sulfatides and thereby becomes a target for anti-phospholipid antibodies.

METHODS AND RESULTS

Beta2-glycoprotein I binds to surface-bound sulfatides but not to other glycolipids, such as ceramide, cerebrosides, sphingomyelin, or ganglioside. At a sulfatide coating density of 1 microg/well, beta2-glycoprotein I reaches half-maximal binding at 2.5 microg/mL, and the binding is saturated at 10 microg/mL. The binding of beta2-glycoprotein I also depends on the coating density of sulfatides in the well. At a constant beta2-glycoprotein I concentration of 5 microg/mL, maximal binding of beta2-glycoprotein I is observed at a coating density of 1 mug/well. The serum from 14 patients with anti-cardiolipin antibodies, a subset of anti-phospholipid antibodies, bound to sulfatide-bound beta2-glycoprotein I and previous absorption on cardiolipin-coated surfaces decreased the immunoreactivity toward sulfatide-beta2-glycoprotein I complex by >50% in 12 of 14 patients. Furthermore, immunoaffinity-purified anti-cardiolipin antibodies from 4 of 5 patients reacted with sulfatide-bound beta2-glycoprotein I.

CONCLUSIONS

These results show that not only anionic phospholipids, as commonly known, but also sulfatides are targets for most anti-phospholipid antibodies. We therefore postulate that interactions of these antibodies with sulfatides may contribute to some of the clinical symptoms of the anti-phospholipid antibody syndrome.

Antiphospholipid antibodies as a risk factor for atherosclerotic events in renal transplant recipients

BACKGROUND

Epidemiologic studies reported that antiphospholipid antibodies (APAs) were independent predictors of atherosclerotic events. We recently reported a high prevalence of APAs in renal transplant recipients. Nevertheless, the role of APAs on atherosclerotic events has not been prospectively studied in this high-risk population.

METHODS

Participants in the study were 324 consecutive renal transplant recipients. Patients were enrolled between January 1996 and May 1998 and followed up until June 2002.

RESULTS

The patients were followed for a mean duration of 62 +/- 26 months. Eighty seven (26.8%) patients exhibited APAs. We found a slight, but significant, correlation between total plasma homocysteine (tHcy) concentration and anticardiolipin (ACA) titers (r = 0.26; P = 0.036). Fifty six athersclerotic events (17.2%) occurred in 54 patients. Atherosclerotic events occurred more frequently in patients with APAs (33% vs. 9%; P = 0.0003) and ACAs levels were higher in patients who experienced atherosclerotic events (23.7 +/- 13.1 IU vs. 13.9 +/- 9.4 IU; P = 0.003). APAs were associated with an increased risk of atherosclerotic events (RR, 2.82; 95% CI, 1.17 to 5.31). Cox regression analysis also revealed that age above the median (RR, 5.21; 95% CI, 1.67 to 17.13), a previous history of cardiovascular disease (RR, 3.54; 95% CI, 1.57 to 10.43), hyperhomocysteinemia (RR, 4.01; 95% CI, 1.22 to 14.61), and current smoking (RR, 2.17; 95% CI, 1.01 to 6.72) were risk factors for atherosclerotic events.

CONCLUSION

The presence of APAs is an independent cardiovascular risk factor in renal transplant recipients. Prevention trials are necessary to assess the efficacy and safety of anticoagulation therapy in transplant patients with APAs.

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

INTRODUCTION

Previous studies have suggested the importance of somatic mutations and arginine, asparagine and lysine residues in the complementarity determining regions (CDRs) of antiphospholipid antibodies (aPL) implicated in the pathogenesis of the antiphospholipid antibody syndrome. The relative contributions of the heavy and light chains of aPL in binding to cardiolipin (CL) were assessed by pairing the heavy and light chains of two IgG, beta(2)GPI dependent aPL (IS4 and CL24) with different partner chains from other IgG, beta(2)GPI independent aPL (UK4) and anti-DNA antibodies (B3 and 33H11).

METHODS

Four heavy (V(H)) and five light (V(L)) chain variable sequences from three aPL and two anti-DNA antibodies were cloned into expression vectors containing appropriate gamma(1), lambda or kappa constant region cDNA. Paired combinations of heavy and light chain expression plasmids were transfected into COS-7 cells allowing transient expression of whole IgG molecules, which were harvested and tested for the ability to bind CL and DNA by enzyme-linked immunosorbant assay (ELISA).

RESULTS

Whole IgG was produced from 19 heavy/light chain combinations. IS4V(H) was dominant in conferring the ability to bind CL with four of the five V(L) tested. The identity of the V(L) region paired with IS4V(H) was important in determining the strength of binding to CL. IS4V(H) contains multiple arginine residues in CDR3, which may have accumulated due to antigen driven selection. It is likely that these arginine residues may interact with CL. The combination B3V(H)/B3V(L) also bound CL, but none of the other 14 combinations showed any binding in this assay.

CONCLUSION

Whole IgG molecules capable of binding CL were produced by in vitro expression in COS-7 cells. Arginine residues play important roles in binding to CL and double-stranded DNA. However, different patterns of mutation to arginine are associated with binding to each of these antigens.

[Catastrophic antiphospholipid syndrome in the immediate puerperium]

We describe a female previously diagnosed of primary antiphospholipid antibody syndrome who presented a preclampsia in the second pregnancy. An urgent caesaria was made because of a worsening high blood pressure and oliguria. In the immediated puerperium she showed low platelets and persistent high blood pressure. Afterwards acute renal failure and neurological signs with a severe aortic valvulopathy were diagnosed. An haemolytic anemia was also detected. Definitive diagnosis was made by kidney biopsy with the result of a thrombotic microangiopathy. Treatment with low weight heparin and aspirin and systemic corticosteroids was started in the immediate puerperium and fresh frozen plasma was then added with a good response to treatment. Actually she is still with high blood pressure, aortic valvulopathy. Renal function is normal one year later.

Apolipoprotein H variant modifies plasma triglyceride phenotype in familial hypercholesterolemia: a molecular study in an eight-generation hyperlipidemic family

In the course of investigating familial coronary artery disease in Utah, we studied 196 members of an eight-generation extended family of familial hypercholesterolemia (FH), in which 73 members were affected with type IIa hyperlipoproteinemia (HLPIIa; high plasma cholesterol) and 11 members with type IIb hyperlipoproteinemia (HLPIIb; high plasma cholesterol as well as plasma triglyceride). A splice-site mutation of the LDL receptor (LDLR) gene (IVS14 + G > A) co-segregated with elevated plasma cholesterol among all the members, but not with the elevated plasma triglyceride and VLDL cholesterol levels seen in HLPIIb patients. The apolipoprotein H (apoH) gene plays a role in plasma triglyceride removal and lipoprotein lipase enhancement. Intra-familial correlation analysis of the modifier effect of Val247Leu substitution in the apoH gene was carried out among 84 LDLR-mutation carriers and 112 non-carriers. When plasma triglyceride levels in the LDLR-mutation carriers were compared, the values were lowest among V/V homozygotes (mean +/- SD = 145 +/- 53 mg/dl), highest in L/L homozygotes (277 +/- 177 mg/dl), and intermediate among V/L heterozygotes (191 +/- 102 mg/dl) (p = 0.0015). All eleven patients who presented with HLPIIb had inherited both the defective LDLR allele and an apoH 247Leu allele, whereas all 45 carriers of the defective LDLR allele not carrying the apoH Leu allele presented with HLPIIa but not HLPIIb (p = 0.0001). These results indicate a significant modification of the phenotype of FH with a defective LDLR allele, by apoH Leu variation in our studied family.

Prothrombin and beta 2-glycoprotein I frequently contribute to antiphospholipid antibody interactions with phospholipids and the generation of abnormal waveform profiles in coagulation assays

Transmittance waveforms are generated during clot formation on photo-optical coagulation analyzers. We previously showed that 61.5% of patients with antiphospholipid antibodies (APLA) exhibited a negative deflection in the pre-coagulation phase of the prothrombin time (PT slope 1). The current studies investigated the 'molecular basis' of this abnormal parameter. We found that the negative PT slope 1 is IgG-mediated and is not dependent on the presence of fibrinogen or thrombin activity. We also found that IgG from most of the patients required a specific thromboplastin and the presence of prothrombin or beta(2)-glycoprotein I beta(2) GPI) to produce an abnormal IgG wave-form assay. In addition, the abnormal IgG waveform required cofactor binding to phospholipids when beta(2) GPI was the cofactor, and annexin V could partially block this interaction. In conclusion, these results showed that the interactions of IgG with phospholipids via beta(2) GPI or prothrombin constitute the core mechanisms of the abnormal waveforms.

Antiphospholipid syndrome: an overview

Antiphospholipid antibodies are a heterogeneous group of autoantibodies that are detected by immunoassays and functional coagulation tests. The antigenic targets are negatively charged phospholipids and serum phospholipid-binding proteins. The latter antibodies are frequently associated with thrombosis, fetal loss and other clinical manifestations of the antiphospholipid syndrome. These antibodies are felt to be etiologically important in the syndrome, although the precise pathogenic mechanisms are still being determined. Proposed mechanisms include antibody-mediated interference with coagulation homeostasis, activation of platelets and endothelial cells and a T-cell immune response to serum phospholipid-binding proteins. The mainstay of therapy is anticoagulation, whereas immunosuppression is ineffective.

The autoreactivity of anti-phosphorylcholine antibodies for atherosclerosis-associated neo-antigens and apoptotic cells

Abs specific for phosphorylcholine (PC) are known to contribute to the immune defense against a variety of microbial infections. To assess for other types of binding interactions, we performed surveys of anti-PC Abs of diverse biologic origins and structural diversity and demonstrated a common autoreactivity for oxidatively modified low density lipoprotein and other oxidation-specific structures containing PC-Ags. We also found that cells undergoing apoptosis sequentially express a range of oxidation-specific neo-self PC determinants. Whereas natural Abs to PC recognized cells at early stages of apoptosis, by contrast, an IgG anti-PC Ab, representative of a T cell-dependent response, recognized PC determinants primarily associated with late stages of apoptosis. Cumulatively, these results demonstrate a fundamental paradigm in which Abs from both the innate and the T cell-dependent tiers of the B cell compartment recognize a minimal molecular motif arrayed both on microbes and as neo-self Ags linked to atherosclerosis and autoimmune disease.

[The importance of antiphospholipid antibodies in strokes]

INTRODUCTION AND METHOD

The study of antiphospholipid antibodies has aroused a great deal of interest among researchers, as some of them are related to neurological diseases and in particular with cerebral ischemia. Cases of strokes in which the aetiology is unknown have been reported in young patients. Until now anticardiolipin antibodies and lupus anticoagulant have received the most attention in studies, but recently descriptions have been published of anticardiolipin antibodies with other particularities that can act as more specific immunity markers for strokes of undetermined origin in young adults. Recent research has been directed towards gaining an understanding of the mechanisms that allow these antibodies to play a direct role in the physiopathology of thrombosis and how certain risk factors smoking, high blood pressure, lipid disorders can exert an influence on the expression of phospholipids in the cerebral endothelium. Several authors have described different pathological mechanisms that help to understand the heterogeneous clinical manifestations of antiphospholipid syndrome.

CONCLUSION

There is a need to study the different possible antigens of the antiphospholipid antibodies, as well as their specificities and pathological mechanisms, in greater depth in order to obtain a phospholipid immunity marker that is useful in the diagnosis of young stroke patients who are positive for these antibodies.

Regulation of anti-phosphatidylserine antibodies

The degree of heavy chain (H) editing, the types of Vkappa editors, and the pattern of Jkappa usage are correlated with a range of the affinity of anti-DNA. This range was determined by the number and location of arginine (R) residues in the VH. We, here, changed a key arginine residue in the VH of anti-DNA transgene to glycine, which sharply reduces the affinity for dsDNA. However, complete reversion of this anti-DNA to germline enhances the affinity for phosphatidylserine (PS). The B cells of this low-affinity anti-DNA and anti-PS transgenic mouse are tightly regulated by receptor editing. Thus, anti-PS B cells are another example of a constitutive self-antigen regulated in the bone marrow.

[Antiphospholipid antibodies in patients with vestibular manifestations. A study of 16 cases]

INTRODUCTION

Antiphospholipid antibodies lupus anticoagulant (LA) and anticardiolipin antibodies (aCL) play a role in promoting arterial and venous thrombosis in several vascular territories. Acute vestibular syndromes are a common complaint in general and neurology practice. Approximately 9% of cases are due to central nervous system vestibular areas lesions, often associated with vascular disorders.

OBJECTIVE

Define the potential relationship between these antibodies and central or peripheral vestibular failure.

PATIENTS AND METHODS

We report the presence of antiphospholipid antibodies in 16 patients with central vestibular symptoms. All patients were seen in the Neuro otology and Vascular Neurology clinics at the Institute for Neurological Research in Buenos Aires. Magnetic resonance imaging (MRI) and ancillary neuro otologic tests were used to determine the etiology of vestibular manifestations. Determinations of LA and aCL were done using standard criteria.

RESULTS

We evaluated 16 patients (13 women and 3 men), aged 44 4 years (21 65). Thirteen patients did not have stroke risk factors. MRI lesions were found in 11 subjects (1 cerebellar infarct, 3 pontine ischemic changes, and 9 white matter abnormalities). All patients had signs consistent with dysfunction of vestibulo cerebellar structures or the vestibular nuclei. All patients had positive LA and 4 of them had also elevated aCL.

CONCLUSION

Our findings suggest a potential association between the presence of a prothrombotic state and central vestibular dysfunction of vascular etiology. To the best of our knowledge, this is the first report of such an association in the absence of clinically evident autoimmune disease.

Use of single point mutations in domain I of beta 2-glycoprotein I to determine fine antigenic specificity of antiphospholipid autoantibodies

Autoantibodies against beta(2)-glycoprotein I (beta(2)GPI) appear to be a critical feature of the antiphospholipid syndrome (APS). As determined using domain deletion mutants, human autoantibodies bind to the first of five domains present in beta(2)GPI. In this study the fine detail of the domain I epitope has been examined using 10 selected mutants of whole beta(2)GPI containing single point mutations in the first domain. The binding to beta(2)GPI was significantly affected by a number of single point mutations in domain I, particularly by mutations in the region of aa 40-43. Molecular modeling predicted these mutations to affect the surface shape and electrostatic charge of a facet of domain I. Mutation K19E also had an effect, albeit one less severe and involving fewer patients. Similar results were obtained in two different laboratories using affinity-purified anti-beta(2)GPI in a competitive inhibition ELISA and with whole serum in a direct binding ELISA. This study confirms that anti-beta(2)GPI autoantibodies bind to domain I, and that the charged surface patch defined by residues 40-43 contributes to a dominant target epitope.

Kinetics of prothrombin-mediated binding of lupus anticoagulant antibodies to phosphatidylserine-containing phospholipid membranes: an ellipsometric study

Antiphospholipid antibodies interact with phospholipid membranes via lipid binding plasma proteins, mostly, prothrombin and beta(2)-glycoprotein I. Using ellipsometry, we characterized prothrombin-mediated binding of lupus anticoagulant (LA) positive IgG, isolated from patients with antiphospholipid syndrome, to phosphatidylserine (PS)-containing membranes. LA IgG did not bind to membranes in the absence of prothrombin, but addition of prothrombin resulted in high-affinity binding of prothrombin-LA IgG complexes; half-maximal binding was attained at IgG and prothrombin concentrations of 10 microg/mL and 4 nM, respectively. Adsorption to membranes containing 10-40 mol % PS revealed that membrane-bound rather than solution-phase prothrombin determines the adsorption kinetics. Depletion of prothrombin and LA IgG from the solution results in rapid desorption which is strongly inhibited by addition of prothrombin but not of LA IgG. Prothrombin-mediated adsorption of monovalent Fab1 fragments prepared from patient LA IgG was negligible, indicating that monovalent interaction between prothrombin and LA IgG is weak. The kinetics of adsorption and desorption indicate that divalent binding of LA IgG to prothrombin at the lipid membrane occurs.

Autoantibody-mediated atherosclerosis

Beta2-glycoprotein I (beta2-GPI) is a major antigen for antiphospholipid antibodies (aPL) present in patients with antiphospholipid syndrome (APS). Oxidized low-density lipoprotein (oxLDL) is subsequently targeted by beta2-GPI and anti-beta2-GPI autoantibodies. Ligands specific for beta2-GPI derived from oxLDL have been characterized as oxidized forms of cholesteryl linoleate, such as 7-ketocholesterol-9-carboxynonanoate, i.e. 9-oxo-9-(7-ketocholest-5-en-3beta-yloxy) nonanoic acid, (namely oxLig-1). The in vitro phenomenon that it is significantly increased in binding of oxLig-1 containing liposomes to macrophages via an interaction with beta2-GPI and an anti-beta2-GPI autoantibody (via the Fcgamma receptor) may propose a novel mechanism on 'autoantibody-mediated atherosclerosis'. Furthermore, autoantibodies against a complex of beta2-GPI and oxLig-1 are detected in sera of APS patients and appearance of the antibodies is associated with episodes of thrombosis, especially, arterial thrombosis. Thus, autoimmune atherogenesis linked to beta2-GPI interaction with oxLDL and autoantibodies may be present in APS.

Antiphospholipid antibodies: biological basis and prospects for treatment

Antiphospholipid antibodies (aPL) are autoantibodies that are associated with recurrent reproductive failure and thrombotic disease. There are two well-characterised aPL, lupus anticoagulant and anticardiolipin antibodies. aPL were originally thought to bind to negatively-charged phospholipids but it is now clear that the title aPL is a misnomer and that the antigens for these autoantibodies are actually phospholipid-binding proteins. Chief amongst these phospholipid-binding proteins are prothrombin and beta(2) glycoprotein I. This review concentrates on the role of beta(2) glycoprotein I in the reproductive failure caused by aPL. Exactly how aPL cause reproductive failure remains unknown but there is emerging evidence that the antibodies may have several different adverse effects on trophoblasts. There is also evidence questioning the traditional hypothesis that fetal demise is secondary to thrombosis of the utero-placental circulation. Heparin is commonly used to treat pregnant women with aPL but if these antibodies do not cause fetal demise primarily by a thrombotic mechanism a question must be raised over the role of heparin. However, heparin binds to many proteins including beta(2) glycoprotein I and it is possible that the reported beneficial effects of heparin in aPL-affected pregnancies may be due to the ability of heparin to prevent the interaction of aPL and beta(2) glycoprotein I.

[Prevention of recurrent ischemic stroke: recent clinical trial results]

Clinical trials are providing new insights into long-existing clinical biases for the treatment of acute ischemic stroke and prevention of recurrence. The structure and completeness of the data sets available for some of the published studies have raised controversies about the generality of some of the findings. Among these controversies for acute ischemic stroke are whether the benefits of so-called low-dose unfractionated heparin exceed or are negated by hemorrhagic complications and whether results with heparinoids can be considered a surrogate for unfractionated heparin. For prevention of recurrent ischemic stroke, a double-blind study showed no statically-significant differences for serious hemorrhagic complications nor for prevention of recurrence in non-cardioembolic stroke for aspirin 325 mg daily against adjusted-dose warfarin with an INR 1.4-2.8, the INR value which showed clinical benefit in prevention of first stroke with atrial fibrillation. In this study, patent cardiac foramen ovale and antiphospholipid antibody status did not predict stroke recurrence. Other platelet antiaggregants show varying degrees of reduction in recurrent ischemic stroke compared with placebo or aspirin but the recurrent events rates make it difficult to compare directly through meta-analysis the results against warfarin. More work on these important management issues is justifiable.

Endometriosis in reproductive immunology

PROBLEM

Endometriosis is suggested to represent an autoimmune disorder, but what is the prevalence of autoantibodies to antigens relevant to reproduction?

METHOD OF STUDY

The humoral immune response to the women with endometriosis (stage I-II: 261 women; stage III-IV: 62 women) in serum and in peritoneal fluid was investigated compared with 101 healthy women. Enzyme-linked immunosorbent assay (ELISA) was used in all the women for the detection of seven antiphospholipid antibodies [antiphospholipid antibodies (aPLs) against cardiolipin, L-phosphatidyl (ph)-serine, ph-glycerol, ph-inositol, ph-ethanolamine, phosphatidic (ph)-acid and against beta2-glycoprotein I] of class IgG, IgA, and IgM. A passive haemmagglutination method and ELISA (BioGen) was used for assessment of antizona pellucida antibodies (aZP), tray agglutination test (TAT) and indirect mixed anti-imunoglobulin reaction test (MAR-test) for the determination of sperm antibody levels.

RESULTS

Endometriosis I-II were associated with higher serum and peritoneal fluid levels of aPLs against inositol, cardiolipin, ethanolamine, and beta2-glycoprotein I. Forty percent of patients were positive for aZPA.

CONCLUSIONS

Patients with lesions of endometriosis stage I-II had more autoantibodies than those with stage III-IV, and may be immunologically more active. This result may be significant for future treatments such as in vitro fertilization and embryo transfer.

The immunological "Wars of the Roses": disagreements amongst reproductive immunologists

The relevance of abnormal autoimmune function to reproductive function in the female has over recent years become an increasingly controversial and contentious issue. Opposing views have led to a polarization of opinions which, at times, resulted in publications of rather vocal opinions by individuals as well as societal committees. This communication is an attempt to reconcile these, at times diametrically opposing opinions, in a concept of (auto)immune-driven reproduction failure, which could explain and unify these opposing opinions and, thus, hopefully end the ongoing "immunological wars of the roses".

[Von Willebrand factor-cleaving protease activity in patients of collagen disease with antiphospholipid antibodies]

Acquired thrombotic thrombocytopenic purpura (TTP), characterized by widespread thrombus formation in the microcirculation, is a ponderous complication of antiphospholipid syndrome. Recently, von Willebrand factor-cleaving protease (VWF-CPase) activity has been reported as a possible determinant for the occurrence of TTP. To clarify the role of VWF-CPase in the thrombus formation associated with antiphospholipid syndrome, we investigated plasma VWF-CPase activity in patients of collagen diseases with lupus anticoagulant (LA). Decreased plasma VWF-CPase activity less than 50% of the normal activity was observed in 25.7% (n = 18) in 70 patients with collagen diseases and 7 (10%) cases of them showed more lower VWF-CPase activity less than 25%. The IgG fractions obtained from 2 patients with the low VWF-CPase activity strongly inhibited the proteolytic reaction of normal VWF-CPase. There was no significant relationship between LA and plasma VWF-CPase activity. Thrombotic episodes, especially arterial thrombosis, were more frequently observed in LA-positive patients with low VWF-CPase activity. These results suggest that decreased activity of VWF-CPase, partly due to IgG type inhibitor to the enzyme activity may be an additional risk factor for arterial thrombosis in collagen disease patients with antiphospholipid antibodies.

Certain autoantibodies to phosphatidylethanolamine (aPE) recognize factor XI and prekallikrein independently or in addition to the kininogens

Recent evidence shows that many antiphospholipid antibodies (aPL) to negatively-charged phospholipid (PL) do not target anionic PL per se, but are specific for anionic PL-binding plasma proteins, for example, beta(2)-glycoprotein I (beta(2)-GPI) and prothrombin. We also reported that certain antiphosphatidylethanolamine antibodies (aPE) are not specific for phosphatidylethanolamine (PE) per se, but are directed to PE-binding plasma proteins, high molecular weight kininogen (HK), and low molecular weight kininogen (LK). Additional studies have shown that certain aPE failed to recognize purified kininogens but continued to produce aPE ELISA reactivity in the presence of semipurified HK preparations containing the HK binding proteins, factor XI (FXI) and prekallikrein (PK). We therefore investigated if certain of these aPE recognized FXI and/or PK. In this study we observed that aPE can recognize contact proteins FXI and PK independently or in combination with HK. Since contact proteins such as HK, PK and factor XII (FXII) have anti-coagulant and profibrinolytic functions, the pathophysiological role of aPE has yet to be elucidated. We propose that aPE of different specificities may initiate or promote characteristics pathological conditions in patients with thrombosis or recurrent pregnancy losses.

Increased lipid peroxidation correlates with platelet activation but not with markers of endothelial cell and blood coagulation activation in patients with antiphospholipid antibodies

Recent studies have shown that patients with antiphospholipid antibodies (aPL) have increased lipid peroxidation. We evaluated the urinary excretion of 11-dehydro thromboxane B2 (11-DH-TXB(2) and isoprostane F(2alpha)III (IPF(2alpha)III), reflecting platelet activation and lipid peroxidation in vivo, and plasma soluble markers of endothelial cell, platelet and blood coagulation activation: soluble vascular cell adhesion molecule-1 (sVCAM-1), P- and E-selectin (sPsel and sEsel), F1 + 2 fragment of prothrombin (F1 + 2), thrombin-antithrombin complexes (TAT) and D-Dimer (DD). We studied 79 patients with aPL (47 with previous thrombosis), 45 healthy volunteers (normal controls, NC), 12 patients with systemic lupus erythematosus (SLE) without aPL and a thrombosis control group (TCG) without thrombophilia (n = 16). Urinary levels (mean, range) of eicosanoids and isoeicosanoids were significantly increased in 39 patients with aPL compared with 25 NC, 11-DH-TXB(2) 164.0 ng/mmol creatinine (9.5-1162.8) versus 43.4 ng/mmol creatinine (4.2-87.6), P < 0.001; IPF(2alpha)III 56.9 pg/mg creatinine (5.5-388.7) versus 27.0 pg/mg creatinine (4.6-87.6), P = 0.03. Both metabolites were significantly correlated (rho = 0.49, P = 0.014), but none correlated with any clinical manifestation or antibody profile. The aPL group presented increased levels of sPsel, sEsel, sVCAM-1, TAT, F1 + 2 and DD, but any soluble marker correlated with IPF2alphaIII. Urinary 11-DH-TXB(2) correlated with sPsel (rho = 0.39, P = 0.04). Compared with SLE controls, the SLE group with aPL had higher levels of F1 + 2. Plasma levels of F1 + 2 and DD were significantly increased and a trend to higher sPsel was found in aPL patients with thrombosis compared with the TCG. Platelet activation, lipid peroxidation and blood coagulation activation seem to be important in the pathophysiology of antiphospholipid syndrome.

Antiphospholipid syndrome, antiphospholipid antibodies, and atherosclerosis

The antiphospholipid syndrome is characterized by arterial and venous thrombosis, as well as pregnancy morbidity, in the presence of elevated levels of antiphospholipid antibodies. These autoantibodies have procoagulant activity, as they affect platelets, humoral coagulation factors, and endothelial cells. In addition, they are proatherogenic, as demonstrated by animal models and by the increased prevalence of cardiovascular diseases in patients with systemic lupus erythematosus and antiphospholipid syndrome. Moreover, antiphospholipid antibodies, including anticardiolipin, anti-b2-glycoprotein-I, and anti-oxidized low-density lipoprotein, are associated with atherosclerosis and its consequences in the general population as well. This autoimmune aspect of atherosclerosis in the presence or absence of an autoimmune disease suggests benefit from development of immunomodulating therapies.

Thrombogenic effects of antiphospholipid antibodies are mediated by intercellular cell adhesion molecule-1, vascular cell adhesion molecule-1, and P-selectin

Recent studies have shown that antiphospholipid (aPL) enhances expression of intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin on endothelial cells (ECs) and that these effects are correlated with increased adhesion of leukocytes to endothelium in cremaster muscle in vivo and with thrombosis in a mouse model. Activation of ECs by aPL may create a hypercoagulable state that precedes and contributes to thrombosis in patients with aPL syndrome (APS). This study proposed to examine whether this in vivo activation of ECs and enhanced thrombosis by aPL are mediated by ICAM-1, P-selectin, or VCAM-1. The dynamics of thrombus formation and the number of adhering leukocytes were studied in ICAM-1-deficient (ICAM-1(-/-)) mice or ICAM-1-/P-selectin-deficient (ICAM-1(-/-)/P-selectin(-/-)) mice treated with affinity-purified aPL antibodies (ap IgG-APS) or with control IgG and compared with wild-type mice treated in a similar fashion. In another set of experiments, the adhesion of leukocytes to cremaster muscle and the dynamics of thrombus formation were studied in CD1 mice treated with aPL or control IgG before and 30 minutes after intravenous infusion with 100 microg monoclonal antibody anti-VCAM-1. The results indicate that the enhanced adhesion of leukocytes to endothelium in wild-type mice was significantly reduced in ICAM-1(-/-) and completely abrogated in ICAM-1(-/-)/P-selectin(-/-) mice treated with ap IgG-APS compared with wild-type mice treated with ap IgG-APS (6.9+/-2.3, 0.4+/-0.4 versus 35+/-12, respectively). More importantly, this correlated with a significant reduction in thrombus size compared with wild-type mice treated with ap IgG-APS (895+/-259 microm(2), 859+/-243 microm(2) versus 3816+/-672 microm(2), respectively). Infusion of the mice with anti-VCAM-1 antibodies significantly reversed the enhanced adhesion of leukocytes (14.9+/-3 to 11.3+/-2.1) and thrombus size 3830+/-1008 microm(2) versus 876+/-548 microm(2)) in mice treated with ap IgG-APS. The data indicate that ICAM-1, P-selectin, and VCAM-1 expression are important in thrombotic complications by aPL antibodies and may provide novel targets for therapy in patients with APS.

Recurrent miscarriage--an aspirin a day?

Recurrent miscarriage and later pregnancy complications are in some cases associated with placental thrombosis and infarction. The aim of this study was to assess the value of low dose aspirin (75 mg daily) in improving the subsequent livebirth rate amongst women with either unexplained recurrent early miscarriage (<13 weeks gestation; n = 805) or unexplained late pregnancy loss (n = 250). Amongst women with recurrent early miscarriages, there was no significant difference in the livebirth rate between those who took aspirin (251/367; 68.4%) compared with those who did not take aspirin [278/438; 63.5%; odds ratio (OR) 1.24; 95% confidence interval (CI) 0.93-1.67]. This relationship was independent of the number of previous early miscarriages. In contrast, women with a previous late miscarriage who took aspirin had a significantly higher livebirth rate (122/189; 64.6%) compared with those who did not take aspirin (30/61; 49.2%: OR 1.88; 95% CI 1.04-3.37). The empirical use of low dose aspirin amongst women with unexplained recurrent early miscarriage is not justified. We are currently investigating the role of incremental doses of aspirin in the treatment of women both with early miscarriages associated with thrombophilic abnormalities and in those with late pregnancy losses.

Antiphospholipid antibodies are related to portal vein thrombosis in patients with liver cirrhosis

The pathogenesis of portal vein thrombosis (PVT) in cirrhotic liver patients is not known. PVT has been related to liver dysfunction, neoplasm, hemodynamic factors, and hypercoagulability states. PVT has been reported in patients with antiphospholipid syndrome without liver cirrhosis. Our aim was to find the role of antiphospholipid antibodies (APAs) and coagulation inhibitors in PVT in patients with liver cirrhosis. We present a case-controlled study, matched by age, liver function, and etiology, to discover the role of APAs and anticoagulant protein activity in PVT in cirrhotic patients. We studied 30 cirrhotic patients: 6 of 10 (60%) patients with PVT were APA-positive, whereas only 2 of 20 (10%) in the cirrhotic control group were APA-positive (p < 0.005). Low serum levels of protein C, protein S antithrombin III, and plasminogen were found in cirrhotic patients; and, no differences were found between patients with and without PVT. Significantly lower protein S and antithrombin III levels were found in patients with Child-Pugh class C. Therefore, APAs were related to PVT in cirrhotic patients; but, a lower concentration of coagulation inhibitors was associated with liver dysfunction alone.

Epitope studies with anti-beta 2-glycoprotein I antibodies from autoantibody and immunized sources

This paper examines the methodology of anti-beta(2)-glycoprotein I (beta(2)-GPI) epitope determination and provides further epitope studies using human sera containing anti-beta(2)-GPI autoantibodies. Studies in this field may be misleading as the antigen coating density using mutant forms of beta(2)-GPI may be below the threshold required for monogamous divalent binding by low affinity anti-beta(2)-GPI autoantibodies, while being easily detected by high affinity anti-beta(2)-GPI from immunized animals. The antigen density threshold effect is found in anti-beta(2)-GPI autoantibodies from humans and from monoclonal anti-beta(2)-GPI derived from mice with models of autoimmune disease. Anti-beta(2)-GPI from an autoimmune mouse and from 18/21 human sera did not bind above background levels to a domain-I-deleted mutant. In addition, single point mutations in domain I result in dramatic changes in the binding of many human sera containing anti-beta(2)-GPI. These findings support a conclusion that domain I of beta(2)-GPI contains significant epitopes for the anti-beta(2)-GPI antibodies found in the antiphospholipid syndrome.

How accelerated atherosclerosis in SLE has changed our management of the disorder

Basic science insights along with the assessment of risk factors so clearly documented by the Canadian and Hopkins cohorts in earlier papers of this special issue have clearly led to a change in the way rheumatologists manage SLE. This review will highlight specific ways it should alter our day to day treatment of lupus patients.

Autoimmunity in atherosclerosis: lessons from experimental models

The modern view of atherosclerosis is of a chronic inflammatory disorder. In accord with this paradigm, the process of uninhibited influx of fat to the vessel wall results from an 'adequate' response to various forms of injury (i.e. turbulence, infections, modified lipoproteins). This idea has been further extended by several groups, to assume that the atherosclerotic lesion can be the target of an autoimmune mediated attack. According to this hypothesis, the site of initiation of the plaque should bear/express the target autoantigen, whereas concomitantly a respective immune response is generated in the periphery. The examples illuminating this notion are beta2GPI as a target autoantigen, HSP60/65 an oxidized-LDL. Herein we present evidence to support the involvement of autoimmune mechanisms in atherogenesis based on the experience from experimental models and human studies.

Antibodies to oxidised LDL

In prospective studies antibodies to oxidised LDL (low density lipoprotein) have been shown to predict myocardial infarction and progression of carotid atherosclerosis in non-autoimmune subjects. The antibodies to oxidised LDL are crossreactive with antiphospholipid antibodies most likely due to their binding to oxidised phospholipids. The frequent occurrence of these antibodies and their association with arterial thrombosis in patients with SLE and antiphospholipid syndrome suggest their involvement in the development of accelerated atherosclerosis in these patients. Some in vitro studies suggest that antibodies to oxidised LDL may have an atherogenic effect by enhancing the lipid accumulation into macrophages in the atherosclerotic vessels. These antibodies can be considered as markers of the pathogenic determinants of atherosclerosis, such as enhanced lipid oxidation, proinflammatory stage and impaired vasodilatation.

Immunological responses to oxidized LDL

Considerable evidence now points to an important role for the immune system in experimental models of atherosclerosis. We have reviewed the growing body of evidence that oxidation of LDL generates a wide variety of neoself determinants that lead to cellular and humoral immune responses. In particular, we have demonstrated that at least some of the oxidation-specific epitopes generated on the oxidized LDL particle, such as oxidized phospholipid epitopes, are also generated on apoptotic cells and are also present on the surface of some bacteria. Many of these same epitopes serve as important ligands mediating the binding and clearance of oxidatively damaged lipoprotein particles and apoptotic cells, and the innate immune response to these epitopes can be seen as a concerted response to effect their removal. In addition, other epitopes of OxLDL also undoubtedly play a role in the immune activation that characterizes the progressive atherosclerotic plaque. It will be of great importance to define the importance of the role of these responses and to understand which are beneficial and which deleterious. Such information could lead one day to novel therapeutic approaches to inhibit atherogenesis that take advantage of the ability to manipulate the immune response.

Antiphospholipid antibodies and the endothelium

This article reviews current understanding of the relationship between antiphospholipid antibodies and the endothelium. In vitro antiphospholipid antibodies produce endothelial cell activation. Clinical data in this area are scanty and worthy of future research, which could lead to new therapies in the management of antiphospholipid syndrome.

Ultrastructural localization of monoclonal antiphospholipid antibody binding to rat brain

Antiphospholipid antibodies (aPL), in the presence or absence of systemic lupus erythematosus, are associated with a number of neurologic complications. However, the role aPL play in pathology is unclear. A thrombotic etiology seems likely for many associated disorders, but not for others. Here we describe aPL-reactive sites in the central nervous system (CNS). Previously, using light microscopy, we showed direct binding of two monoclonal phosphatidylserine-reactive antibodies (aPS) to ependyma and myelin of fixed cat brain. In this study we determined the ultrastructural localization of their binding sites in rat CNS using immunogold electron microscopy techniques. Both monoclonal antibodies reacted strongly with myelin, preferentially with the major dense line formed by the cytoplasmic apposition of the oligodendrocyte plasma membrane. Both monoclonal antibodies also reacted with an antigen that appears associated with the axoneme in cilia of ependymal and choroid plexus epithelium. One monoclonal aPS also showed some reactivity with brain vascular endothelium and reacted slightly with mitochondria, while the other aPS did not react with these structures. While the etiology of aPL-associated neurologic disorders remains unclear, our data suggest possible target sites within the CNS with which aPL can react.

Monovalent binding of autoantibodies to beta2-glycoprotein I, detected using surface plasmon resonance at low antigen density

The precise mechanism of interaction between autoantibodies and beta2-glycoprotein I (beta2GPI) and the experimental conditions to be used for their detection are still under debate. Until now, these interactions have been studied under static conditions. We have investigated the interactions of purified IgG from 25 lupus anticoagulant-positive patients with immobilized beta2GPI under flow conditions by real-time analysis based on surface plasmon resonance technology. Sensor chips were coated with purified human beta2GPI coupled to dextran via amino groups at low densities (1.4, 1.8 or 2. 4 ng beta2GPI/mm2). Four patients' IgG displayed efficient binding and had the highest so-called antiphospholipid IgG levels by enzyme-linked immunosorbent assay (ELISA) and the highest absorbance values in an anti- beta2GPI ELISA at a beta2GPI density reported to be around 12 ng/mm2. Binding of antibodies to the beta2GPI sensor chips proved to be dependent upon the IgG concentration and beta2GPI density and was inhibited by a rabbit antibody against beta2GPI. Similar association and dissociation profiles were observed for the four efficient binders. The fast rate of dissociation limited the binding of autoantibodies to beta2GPI and was highly suggestive of a monovalent association, confirmed by binding of Fab fragments under similar experimental conditions. In conclusion, monovalent binding of low-affinity antibodies to beta2GPI immobilized at a density as low as 1.8 ng/mm2 could be detected using surface plasmon resonance.

The influence of different types of antibodies on in vitro fertilization results

PROBLEM

The influence of anti-sperm (ASA), anti-phospholipid (APA), and antizonal (AZA) antibodies on in vitro fertilization (IVF) results and the need for intracytoplasmic sperm injection (ICSI) were assessed.

METHOD OF STUDY

Forty-four couples with infertility of immunologic origin were investigated. ASA in serum and ovulatory mucus were studied by a tray agglutination test (TAT) and indirect mixed anti-globulin reaction test (MAR) test, AZA were studied by passive hemagglutination and commercial enzyme-linked immunosorbent assay (ELISA; BioGen, Germany), and APA were tested by ELISAs in immunoglobulin isotypes IgG and IgM.

RESULTS

Because of failed or very low fertilization after standard IVF in the previous cycle, ICSI had to be used in five out of 15 cases with ASA (33.3%), in 16 out of 18 couples with AZA (89.4%), and in only one case if APA were present (9%). Clinical pregnancy rate was 60% in cases with ASA, 38.5% with AZA, and 27.3% per embryo transfer (ET) if APA were detected.

CONCLUSIONS

Immunologic infertility can be treated by IVF with very good results. The most important group are women with AZA, in whom IVF ICSI without any delay is recommended.

High levels of antiphospholipid antibodies are associated with cytomegalovirus infection in unrelated bone marrow and cord blood allogeneic stem cell transplantation

Antiphospholipid antibodies (APA) are a family of autoimmune and alloimmune immunoglobulins recognizing protein-phospholipid complexes in in vitro laboratory test systems. These antibodies have been associated with several conditions (malignancies, autoimmune diseases, infections, use of drugs); moreover, a syndrome capable of inducing thromboembolic disease has recently been associated with the presence of these antibodies. The aim of this prospective study was to investigate the levels of APA in subjects affected by haematological malignancies undergoing allogeneic haematopoietic stem cell transplantation (ASCT). Between March 1996 and December 1997, 32 patients undergoing ASCT were studied prospectively until day +180 from transplant. The mean values of IgG and IgM anticardiolipin antibodies (ACA) increased in recipients of stem cells from anunrelated donor, and a statistically significant difference inACA IgG mean value between unrelated and related transplanted patients was demonstrated between days +95 and +180. All of the subjects who received stem cells from an unrelated donor had APA levels higher than the mean normal value +3 SD vs. 35% of those receiving stem cells from a related donor (P < 0.01). The reason for such a difference may be a result of the different incidence in documented cytomegalovirus (CMV) infection in the two groups (83% vs. 23%; P < 0.01), as indicated by the significant correlation between APA positivity and CMV infection (P < 0.05). No relationship was found between APA, conditioning regimen and acute or chronic graft vs. host disease (GVHD). Moreover, we did not observe any thromboembolic disorder or veno occlusive disease (VOD).

Binding properties of antibodies to prothrombin and beta2-glycoprotein I (beta2-GPI) assayed by ELISA and dot blot

Most anti-phospholipid antibodies (aPL) associated with the anti-phospholipid syndrome are autoantibodies with specificity towards beta2-GPI (anti-beta2-GPI) or prothrombin (anti-II). They are mainly screened by ELISA using polyoxygenated plates. However, some authors have claimed that immunoblotting can also be used. Exposure of cryptic epitopes or increase of antigen density on its binding to either phospholipids or suitable plastic surfaces are the two hypotheses proposed for the interaction of beta2-GPI or prothrombin with their antibodies. Forty-five patients with aPL were studied: 25 with lupus anti-coagulant (LA) and anti-cardiolipin antibodies (aCL), 10 with LA alone and 10 with aCL but negative LA. All patients with LA and aCL were positive for anti-beta2-GPI by ELISA and dot blot, while 15/25 had anti-IIELISA and 14 of them also had anti-II by dot blot assay. No patient with LA alone tested positive for anti-beta2-GPI by ELISA or dot blot, whereas 6/10 had anti-IIELISA (five of them were also positive by dot blot). Four out of 10 aCL-positive patients had anti-beta2-GPI by ELISA and dot blot, while none of this group had anti-II by ELISA or dot blot. Antibody binding to beta2-GPI or prothrombin in both ELISA and dot blot was significantly reduced by phospholipid liposomes mixed together with beta2-GPI or prothrombin, whereas liposomal eluants retained it in both assays. Parallel fluid-phase inhibition experiments using increasing concentrations (up to 200 microg/ml) of beta2-GPI or prothrombin demonstrated that antibody binding reduction was more evident on dot blot than on ELISA. It was almost completely abolished on dot blot, while on ELISA a moderate inhibition was achieved even at the highest protein concentration. However, antibody binding on ELISA was virtually abolished when diluted sera were incubated with high protein concentrations applied to nitrocellulose membranes. We could infer that ELISA and dot blot detect antibodies with some differences in avidity but directed against native epitopes on beta2-GPI and prothrombin.