Induction of primary antiphospholipid syndrome in mice by immunization with a human monoclonal anticardiolipin antibody (H-3)

Are animal models of vasculitis suitable tools?

Several rodent models have been proposed for various forms of systemic vasculitis. The MRL-lpr mouse has been studied extensively as a model for systemic lupus erythematosus. Backcross experiments in combination with genetic linkage studies have firmly established that the phenotype of autoimmune disease is dependent on the combination of various background genes. It has also become apparent that environmental factors, particularly infections, modulate the disease phenotype. Specific interventions, such as the treatment of Brown Norway rats with agents resulting in polyclonal B cell stimulation or immunization with human myeloperoxidase and subsequent localized perfusion with neutrophil lysosomal extract and H2O2, have provided substantial insights into the cellular and molecular mechanisms leading to the development of vasculitis and glomerulonephritis. Even though the existing models may not exactly mirror any specific human disease, they offer reproducible, highly controlled conditions to answer specific questions about pathogenesis and novel therapeutic approaches.

Characteristics and pathogenic role of anti-beta2-glycoprotein I single-chain Fv domains: induction of experimental antiphospholipid syndrome

Antiphospholipid syndrome is characterized by the presence of high titers of anti-beta(2)-glycoprotein I (beta(2)GPI) antibodies, lupus anticoagulant associated with thromboembolic phenomena, thrombocytopenia and recurrent fetal loss. Single-chain Fv (scFv) were prepared from four anti-beta(2)GPI mAb, CAM, CAL, CAR and 2C4C2, and one anti-ssDNA. All five scFv showed the same antigen binding properties as the original mAb. Replacement of the pathogenic CAM V(H) domain with the non-pathogenic CAL V(H) or anti-ssDNA V(H) decreased the binding affinity of the scFv to beta(2)GPI and completely abrogated the anticoagulant activity. Exchanging the CAM V(H) with anti-DNA V(H) resulted in a shift from anti-beta(2)GPI to anti-ssDNA binding of the scFv. Replacement of the CAM V(L) with CAL V(L) did not affect the binding and activity. BALB/c mice were immunized with the anti-beta(2)GPI scFv, and the scFv resulting from the substitution of the heavy (H) and light (L) chains. The mice which were immunized with CAM, 2C4C2 and CAR scFv developed clinical manifestations of experimental anti-phospholipid syndrome. Elevated titers of mouse anti-cardiolipin (aCL), anti-beta(2)GPI, associated with lupus anticoagulant activity, thrombocytopenia, prolonged activated partial thromboplastin time and a high percentage of fetal resorptions were detected, in the CAM scFv group and in the scFv composed of CAM V(H) groups. High titers of aCL, anti-beta(2)GPI, anti-ss/dsDNA and anti-histone associated with lupus findings were observed in the sera of the 2C4C2 scFv-immunized mice. Immunization with CAL scFv did not lead to any clinical findings. The current study shows that scFv of pathogenic antibodies are capable of inducing the same clinical manifestations as the whole antibody molecule upon active immunization. Replacement of H/L chains point to the importance of the V(H) domains in the pathogenic potential of anti-beta(2)GPI.

GDKV-Induced Antiphospholipid Antibodies Enhance Thrombosis and Activate Endothelial Cells In Vivo and In Vitro

Antiphospholipid (aPL) Abs are associated with thrombosis, pregnancy loss, and thrombocytopenia in patients with systemic lupus erythematosus or primary antiphospholipid syndrome (APS). β2-Glycoprotein I (β2GPI), a phospholipid-binding serum protein, is involved in aPL binding to phospholipids. aPL can be generated in mice by immunization with β2GPI, and these Abs are thrombogenic and cause pregnancy loss in mice. The objective of this study is to determine whether aPL induced by immunization with the phospholipid-binding site of β2GPI are thrombogenic and whether they activate endothelial cells (EC) in vivo and in vitro. Murine monoclonal aPL were generated from spleen cells of a mouse immunized with GDKV, a synthetic 15-aa peptide spanning Gly274–Cys288 in the fifth domain of human β2GPI, which represents the phospholipid-binding site of β2GPI. The Abs generated had aPL and anti-β2GPI activities. The effect of these Abs on thrombus formation and on EC activation in vivo was determined using a mouse model of thrombosis and microcirculation that enables examination of the adhesion of leukocyte to EC as an indication of EC activation as well as adhesion molecule expression using in vitro ELISA analysis. Mice injected with this monoclonal aPL showed a significant increase in leukocyte sticking and also produced larger thrombi that persisted longer. Exposure to GDKV-induced aPL for 4 h significantly increased surface Ag expression of E-selectin, ICAM-1, and VCAM-1. These data indicate that aPL induced by immunization with the phospholipid binding site of β2GPI are thrombogenic and activate endothelial cells.

Splenectomy for refractory thrombocytopenia in the antiphospholipid syndrome

OBJECTIVE

Thrombocytopenia, usually mild, is one of the clinical criteria of the antiphospholipid syndrome (APS). Rarely, this disorder requires treatment and, due to the shared characteristics with idiopathic thrombocytopenic purpura (ITP), similar rules are followed. We report our experience in patients who required splenectomy after being refractory to steroids and immunosuppressive therapy.

METHODS

Fifty-five APS patients with a platelet count of < 100 x 10(9)/l at least twice were analysed retrospectively. Therapeutic response or remission was considered when the platelet count was > 100 x 10(9)/l after 1 month and with no relapse on stopping or tapering the steroid dose. No response or refractory disease was defined as an absence of increase in platelet count, a total count that never exceeded 50 x 10(9)/l during treatment or when the dose requirements were such that the patient developed serious side-effects.

RESULTS

Fifty patients were classified as having secondary APS associated with systemic lupus erythematosus (SLE) and five were identified as primary APS (PAPS). Splenectomy was performed in 11 cases (20%), two PAPS and nine SLE-APS, with an average time of 28 +/- 9 months after the development of thrombocytopenia. Eight patients were initially characterized as ITP (six SLE-APS, two PAPS) with an average time of 4.4 +/- 1.1 yr until the APS diagnosis. All but two were responsive to splenectomy.

CONCLUSION

Splenectomy was required in 11 (20%) of the patients with APS-associated thrombocytopenia. There was a high rate of good and long-term response.

Anti-idiotype immunomodulation of experimental anti-phospholipid syndrome via effect on Th1/Th2 expression

Mice with experimental anti-phospholipid syndrome (APS), induced by active immunization with a human anti-cardiolipin MoAb (H-3), were treated with mouse anti-idiotypic MoAb (anti-H3, named S2.9) and with an irrelevant anti-idiotype. The immunized mice produced high titres of mouse anti-cardiolipin antibodies along with clinical manifestations of experimental APS: prolonged activated partial thromboplastin time (aPTT), thrombocytopenia and high rate of fetal loss. Treatment with the specific anti-Id (S2.9) as a whole molecule or F(ab)2 fraction, resulted in a decrease in serum levels of the anti-cardiolipin antibodies, rise in platelet count, shortened aPTT and reduced rate of fetal loss. The anti-Id effect was associated with a rise in the number of IL-2 and interferon-gamma (IFN-gamma)-secreting cells (Th1) and reduction in IL-4- and IL-6-secreting cells (Th2). The beneficial effect of the anti-Id treatment in mice with experimental APS induced by active immunization with an idiotype further supports the idiotypic aetiology of experimental APS and points to the role of Th1 cytokines in suppression of its manifestations.

Heterogeneity of anti-phospholipid and anti-endothelial cell antibodies

The role of the anti-phospholipid antibodies (APLA) and anti-endothelial cell antibodies (AECA) in the pathogenesis of anti-phospholipid syndrome (APS) is unclear. Differences in the reported involvement of APLA may be due, in part, to the polyclonal nature of these antibodies and the use of serum and serum fractions for analysis. To circumvent this issue, we generated monoclonal antibodies (MAB) from three patients with APS and two healthy controls. We then compared the antigen binding patterns and the heavy chain variable region (VH) DNA sequences of the MAB derived from patients with APS to those from healthy controls. The results of this study indicate that APLA and AECA comprise a highly heterogeneous population of antibodies with respect to the antigens they recognize, as well as VH gene usage. MAB derived from patients with APS do not differ from those derived from normal individuals based on either antigen recognition or VH gene usage. These results suggest the importance of additional predisposing factors in the pathogenesis of APS.

Lessons from experimental APS models

Several animal models for antiphospholipid syndrome (APS) have been reported in the literature. These experimental models have contributed significantly in resolving enigmas in this multisystemic disease. We, and others have previously shown the pathogenicity of anticardiolipin (aCL) antibodies in pregnancy outcome. We have expanded our studies to show the pathogenicity of aCL antibodies in renal dysfunction and neurological and behavioral impairments in animals with experimental APS. Animals immunized with aCL or with the cofactor beta2GPI developed clinical manifestations of APS, including fetal loss, thrombocytopenia and neurological and behavioral dysfunction, along with elevated levels of aPL antibodies. In another animal model, peripheral blood lymphocytes (PBLs) derived from APS patients could initiate APS manifestations with renal dysfunction in SCID mice. A unique in vivo model for thrombus formation was recently established to show the pathogenicity of aPL in thrombosis associated with APS. Histological evaluation of affected tissues derived from animals or from patients with APS have pointed to common mechanisms underlying APS, showing mainly thrombotic changes accompanied by mild inflammatory reaction.

Mechanism of action of beta2-glycoprotein I-dependent lupus anticoagulants

There is accumulating evidence showing that lupus anticoagulants (LA) are more strongly associated with thrombosis than anticardiolipin antibodies. In addition, indirect evidence has been presented indicating that beta2GPI-dependent LA are more strongly associated with thrombosis than prothrombin-dependent LA. From this, one may assume that anti-beta2GPI antibodies with LA activity are more pathogenic than anti-beta2GPI antibodies without LA activity. Therefore, it is of the utmost importance to understand the molecular basis on which some anti-beta2GPI antibodies behave as LA. In this presentation, the current knowledge on the interaction of beta2GPI with phospholipids and with anti-beta2GPI antibodies is reviewed and an integrated model for the anti-beta2GPI-dependent LA activity is proposed with implications for a pathogenic role of these particular antibodies.

Anti-phospholipid autoantibodies--do they have a pathogenic role in infertility?

Anti-phospholipid syndrome includes a variety of clinical manifestations, among which is recurrent pregnancy loss. Recently, it was suggested that anti-phospholipid antibodies might also have a role in infertility, mainly in unexplained infertility. Most of the studies report about an increased prevalence of these antibodies in infertile women; however, data regarding the implication of these antibodies on treatment outcome (mainly in in-vitro fertilization) and if there is a beneficial effect of treating these patients with aspirin, heparin and prednisone--remains still controversial. In this communication we review the literature reports of association of anti-phospholipid antibodies and infertility, and deal with the question whether they have a pathogenic role in these cases.

Current insights into the "antiphospholipid" syndrome: clinical, immunological, and molecular aspects

Advances in defining the target antigen(s) for the autoantibodies in the APS highlight the inadequacies of the current classification of these autoantibodies into anticardiolipin and LA antibodies. The discovery that beta 2GPI is the target antigen for the autoantibodies detected in solid-phase immunoassays has opened a number of areas of research linking these autoantibodies to atherogenesis and thrombus formation. Although the role of beta 2GPI in the regulation of blood coagulation in unclear, current evidence suggests that anti-beta 2GPI antibodies interfere with its "normal" role and appear to promote a procoagulant tendency. The expansion of research in this area and the diversity of the clinical manifestations of patients with APS have resulted in the inclusion of molecular biologists and pharmaceutical companies joining immunologists, hematologists, rheumatologists, obstetricians, neurologists, vascular surgeons, and protein and lipid biochemists in attempting to understand the pathophysiology of this condition. Although the published literature may result in conflicting results and introduce new controversies, developing standardized laboratory methods and extrapolation of in vitro experimental results to the vivo situation will advance our understanding of the regulation of the immune system and its interaction with normal hemostatic mechanisms. Since the authors' last review in 1991, the study and understanding of the pathophysiology of APS have evolved from lipid biochemistry to molecular techniques that may eventually provide specific therapies for the clinical manifestations of this condition. Although current treatment has improved the morbidity associated with this condition, especially in improving pregnancy outcomes, future therapies, as outlined in this review, may specifically address the biological abnormalities and have fewer side effects. Better diagnostic tools, such as magnetic resonance imaging with perfusion studies, will allow the study of the true incidence and prevalence of vascular flow changes/tissue ischemia and infarction associated with aPL antibodies and help determine treatment and prophylaxis for APS patients. APS is still the only hypercoagulable condition where both arterial and venous beds can be affected independently or in the same individual.

Effects of human monoclonal anticardiolipin antibodies on platelet function and on tissue factor expression on monocytes

OBJECTIVE

To investigate the effect of human monoclonal anticardiolipin antibodies (aCL) on platelet interaction with the subendothelium under flow conditions and on tissue factor (TF) expression on normal monocytes.

METHODS

Three monoclonal IgM aCL (TM1B3, GR1D5, and EY2C9) and 2 affinity-purified IgM aCL were studied. Immunoglobulins were added to normal blood and perfused through chambers containing denuded vascular segments. Platelet interactions were morphometrically evaluated by determining the percentage of total surface covered by platelets (PCS) or by large aggregates of thrombi platelets (TP). Expression of TF on monocytes was measured after immunoglobulin incubation with normal mononuclear cells.

RESULTS

Significant increases in the total PCS and expression of TF were observed using all aCL. Increased levels of TP were induced by all aCL except EY2C9 (obtained from a patient without thrombosis). Previous incubations of these aCL with subendothelial surfaces did not increase platelet interaction.

CONCLUSION

The effects of aCL on platelet function may help to explain the pathophysiology of thrombosis in the antiphospholipid syndrome.

Self-reactive antibodies (natural autoantibodies) in healthy individuals

Antibodies that are present in the serum of healthy individuals in the absence of deliberate immunization with any antigen, are refered to as natural antibodies. A vast majority of natural antibodies react with one or more self antigens and are termed as natural autoantibodies. The importance of natural autoantibodies in immune regulation has long been neglected, since tolerance to self was thought to be primarily dependent on the deletion of autoreactive clones, rather than on peripheral suppressive mechanisms. Clonal deletion and energy cannot account, however, for the prevalence of natural autoreactivity among healthy individuals. It is now well established that autoreactive antibodies and B cells, and autoreactive T cells, are present in healthy individuals, and in virtually all vertebrate species. Autoreactive repertoires are predominantly selected early in ontogeny. Questions pertaining to the role of natural antibodies in the regulation of the immune response and maintenance of immune homeostasis and to the distinction between natural autoreactivity and pathological autoimmunity have not been adequately addressed. Here, we focus on the current knowledge on the physicochemical and functional properties of NAA in man, and the use of NAA for therapeutic intervention. reserved.

Lipid interactions with human antiphospholipid antibody, beta 2-glycoprotein 1, and normal human IgG using the fluorescent probes NBD-PE and DPH

Recurrent venous thrombosis, arterial thrombosis and pregnancy losses are clinical manifestation associated with antiphospholipid antibody (aPL) that recognizes negatively charged phospholipid antigens. Enzyme-linked immunosorbent assays (ELISA) are generally used to determine the presence and specificity of aPL. In this paper, a fluorescence spectroscopy method has been applied, through monitoring the alteration of fluorescence intensity and anisotropy of a fluorophore that was incorporated in liposomes to explore the changes of molecular structure or configuration elicited by the binding aPL with phospholipid antigens. The bilayer surface was markedly ordered by aPL binding as indicated by the surface-sensitive probe NBD-PE. The binding of aPL on the bilayer surface is saturable. The saturation concentration of aPL is 40% (w/w, aPL/lipid) for cardiolipin membranes. The binding of aPL on cardiolipin took place in the absence of beta 2-GP1. The addition of beta 2-GP1 further increased the anisotropy and decreased the intensity of fluorescence. The binding of aPL is predominantly attributed to electrostatic interaction, but the configuration of the acyl chains of phospholipid also plays a role. It is found that the thermal history is important for aPL binding. The incubation at 37 degrees C is more favorable for aPL binding than ambient temperature. Normal human serine (IgG-NHS) did not elicit any distinct change of NBD-PE fluorescence, which indicates it does not interact with the lipid.

Increased prevalence of autoantibodies in celiac disease

Several features suggest an immune mechanism operates in celiac disease. Information on the autoantibody repertoire in this condition is lacking. The purpose of the study was to investigate the reactivity of celiac patients sera to various autoantigens widely distributed in the human intestine. Seventy children, celiacs and controls, were evaluated for serum autoantibodies using ELISA and immunofluorescence. Celiac patients had increased prevalence of serum anti-single-stranded DNA (14%), anti-double-stranded DNA (23%), anti-cardiolipin (14%), and anti-endomysial autoantibodies (63%). The relevance of this finding on the extraintestinal manifestations of celiac disease or the coexistence of autoimmune conditions and celiac disease remains to be determined.

Differential effects of anti-beta2-glycoprotein I antibodies on endothelial cells and on the manifestations of experimental antiphospholipid syndrome

BACKGROUND

The antiphospholipid syndrome (APS) entails a prothrombotic state associated with the presence of anticardiolipin antibodies (aCL). aCL were shown to promote endothelial cell and platelet activation and to induce an APS-like syndrome in mice when administered intravenously. Recent data suggest that aCL target the plasma cofactor beta2-glycoprotein I (beta2GPI) rather than negatively charged phospholipids. However, it has not been determined whether different epitope-specific anti-beta2GPI antibodies obtained from one patient possess pathogenic properties.

METHODS AND RESULTS

Three beta2GPI-binding IgM monoclonal antibodies (mAbs) (ILA-1, ILA-3, and ILA-4) were cloned from a patient with APS. The three antibodies were shown to bind beta2GPI immobilized on irradiated plates, yet only ILA-1 bound beta2GPI coated onto nonirradiated plates. Furthermore, when using the anti-beta2GPI enzyme-linked immunosorbent assay, ILA-1 was the only mAb inhibited by fluid phase beta2GPI. ILA-1 and ILA-3, but not ILA-4, induced adherence of U937 cells to endothelial cells in vitro (reflecting activation of endothelial cells). mAbs ILA-1 and ILA-3 as opposed to ILA-4 induced significant expression of adhesion molecules when preincubated with human umbilical vein endothelial cells. Passive administration of ILA-1 and ILA-3 to pregnant BALB/c mice induced clinical findings consistent with APS (increased fetal resorptions, reduced platelet counts, and prolonged activated partial thromboplastin time), whereas both ILA-4 and the control human IgM did not produce similar effects.

CONCLUSIONS

The results of the study demonstrate the differential effects of various populations of anti-beta2GPI antibodies on endothelial cell activation and on experimental APS.

Ciprofloxacin immunomodulation of experimental antiphospholipid syndrome associated with elevation of interleukin-3 and granulocyte-macrophage colony-stimulating factor expression

OBJECTIVE

To evaluate the immunomodulatory potential of ciprofloxacin in mice with experimental antiphospholipid syndrome (APS).

METHODS

Ciprofloxacin or ceftazidime (control antibiotic) was given to mice with experimentally induced APS. The titers of autoantibodies, levels of cytokines, and number of cytokine-producing cells were determined by enzyme-linked immunosorbent assay. Myeloid progenitor cells were determined by granulocyte-macrophage colony-forming unit, and interleukin-3 (IL-3) messenger RNA (mRNA) was tested by Northern analysis.

RESULTS

A decrease in the incidence of pregnancy loss and an improvement in the clinical manifestations of APS were noted in the mice treated with ciprofloxacin, compared with the mice given ceftazidime. The effect of ciprofloxacin was found to be associated with increased serum levels of IL-3 and with increased IL-3 mRNA transcription in the splenocytes. Expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) was documented by elevated titers in the sera and elevated numbers of colony-forming cells in the bone marrow.

CONCLUSION

Ciprofloxacin prevents the manifestations of experimental APS. This effect may be associated with increased IL-3 levels and GM-CSF expression.

Anti-DNA and antiphospholipid antibodies in IVIG preparations: in vivo study in naive mice

Intravenous immunoglobulins (IVIG) are therapeutic preparations of pooled normal polyspecific immunoglobulin G. We investigated the presence and the in vivo pathogenic potential of autoantibodies against phospholipids and DNA in several commercial IVIG preparations. The presence of autoantibodies and their antiidiotypic antibodies in the IVIG preparations was detected by ELISA. Naive mice were actively immunized with either IVIG preparations or pathogenic monoclonal antibodies (mAbs) against cardiolipin (CL) or DNA, in an attempt to induce autoimmune conditions. The mice were tested for the presence of mouse autoantibodies (auto-Abs) and for clinical parameters of autoimmune diseases. We found high levels of auto-Abs against a panel of phospholipids and DNA, as well as their antiidiotypic Abs, in all the IVIGs. Affinity studies pointed to a lower affinity of auto-Abs of IVIG origin to their respective antigens compared to pathogenic mAbs. Mice immunized with pathogenic anti-CL mAb had high levels of antiphospholipid auto-Abs, accompanied by thrombocytopenia, prolonged aPTT, and an increased fetal resorption rate. Mice immunized with pathogenic anti-DNA mAb had elevated anti-DNA and anti-CL auto-Abs, along with a high erythrocyte sedimentation rate, leukopenia, and significant proteinuria. Following immunization with IgGs from IVIG batches, mice developed high levels of auto-Abs against phospholipids and DNA, similar to mice immunized with pathogenic anti-DNA or anti-CL mAbs, but none of the mice expressed the clinical manifestations compatible with the presence of these autoantibodies. We conclude that commercial IVIG preparations contain high levels of antiphospholipid and anti-DNA auto-Abs, as well as their antiidiotypic Abs. Although these Abs induced the generation of mouse auto-Abs upon active immunization, following idiotypic manipulation they did not prove to be pathogenic in vivo.

Antiphospholipid antibodies or not? The role of beta 2 glycoprotein 1 in autoantibody-mediated pregnancy loss

Antiphospholipid antibodies are a family of autoantibodies including lupus anticoagulant and anticardiolipin antibodies that appear to react with negatively charged phospholipids. These antibodies induce thrombosis and pregnancy complications including recurrent stillbirth, recurrent miscarriage, pre-eclampsia and intra-uterine growth retardation. Recent evidence indicates that antiphospholipid antibodies do not bind directly to phospholipid but rather to phospholipid-binding proteins or to a combination of phospholipid and phospholipid-binding proteins. This opens the possibility that antiphospholipid antibodies may be pathogenic by disrupting the function of phospholipid-binding proteins rather than membrane phospholipid. The antigenic role of one phospholipid-binding protein, beta 2 glycoprotein, has been studied in the greatest detail and is reviewed. Despite being highly conserved and expressed at high levels, the physiological function of beta 2 glycoprotein 1 remains unknown. However, a number of putative roles have been proposed which allow speculation as to the mechanism by which antiphospholipid antibodies may disrupt haemostasis and pregnancy.

Antiphospholipid antibodies and cerebral lupus

Antiphospholipid antibodies probably play a minor role in cerebral lupus. They are associated primarily with stroke and transient ischemic attacks, which occur only in a minority of patients with central nervous system complications of SLE. However, ready demonstration of functional effects of antiphospholipid antibodies in the coagulation system as well as persuasive evidence that they can induce thrombosis and pregnancy loss in experimental mice lend credence to the belief that many autoantibodies play a direct role in disease pathogenesis. Hence the role of the many autoantibodies associated with CNS lupus is a legitimate field of inquiry. This review outlines the history of antiphospholipid antibodies, discusses the controversy concerning antiphospholipid antibody specificity, summarizes recent experimental data on their functional effects in the coagulation system, and describes animal models of the antiphospholipid syndrome in which antibodies with cardiolipin-binding activity have been shown to play a direct role in thrombosis and pregnancy loss.

Neurological dysfunction and hyperactive behavior associated with antiphospholipid antibodies. A mouse model

Antiphospholipid antibodies (aPL) have been associated with various neurological manifestations, but the underlying mechanism has not been elucidated. We assessed mice with induced experimental antiphospholipid syndrome (APS) for neurological and behavioral changes. After immunization with monoclonal human anticardiolipin antibody (H-3), female BALB/c mice developed elevated levels of circulating anti-negatively charged phospholipids (aPL), anti-beta2-glycoprotein I (abeta2GPI), and anti-endothelial cell antibodies (AECA), along with clinical manifestations of APS like thrombocytopenia and fetus resorption. APS mice were impaired neurologically and performed several reflexes less accurately compared to the controls, including placing reflex (P < 0.05), postural reflex (P < 0.05), and grip test (P = 0.05). The APS mice also exhibited hyperactive behavior in an open field, which tests spatial behavior (P < 0.03), and displayed impaired motor coordination on a rotating bar. aPL in combination with abeta2GPI and AECA is probably involved in the neurological and behavioral defects shown in mice with experimental APS.

Antiphospholipid antibody syndrome in pediatric patients

The antiphospholipid antibody syndrome is characterized by the association between recurrent arterial or venous thrombosis and the presence of circulating antiphospholipid antibodies. Antiphospholipid antibody-related thrombosis seems to constitute a significant proportion of childhood thromboses. About one third of children suffering a thrombotic event have circulating antiphospholipid antibodies, and more than two thirds of children with idiopathic cerebral ischemia meet the criteria for the diagnosis of antiphospholipid antibody syndrome. Because the other risk factors for thrombosis commonly found in adults have no impact on the pediatric patient, the risk for thrombosis and thrombotic recurrences and the optimal anticoagulation therapy may differ from adults.

Variable effects on murine pregnancy of immunoglobulin G fractions from women with antiphospholipid antibodies

OBJECTIVE

Initial studies showed that passive immunization with human immunoglobulin G fractions containing antiphospholipid antibodies can result in murine fetal loss. We intended to use the murine model to study mechanisms of fetal loss associated with antiphospholipid antibodies. However, we have since found variable effects of antiphospholipid antibodies on murine pregnancy. The objective of this study was to determine the consistency of murine pregnancy loss from antiphospholipid antibody containing immunoglobulin G fraction.

STUDY DESIGN

Pregnant C3H/HeN (mated with C57B1/6 males) and BALB/c (mated with BALB/c males) mice were passively immunized with antiphospholipid antibody containing human immunoglobulin G fraction from 20 women with antiphospholipid syndrome. The mice received either a single dose of 10 to 30 mg on day 12 of pregnancy or 10 mg per day on days 12 to 14 of gestation. Some mice receiving each dose of immunoglobulin G fraction were bled to confirm serum levels of anticardiolipin antibodies. Mice were killed on day 15 and the fetal status was determined.

RESULTS

Overall, passive immunization with individual antiphospholipid antibody containing immunoglobulin G fractions resulted in 801 live pups (75%), 232 fetal deaths (22%), and 38 resorptions (3%) in 131 mice. The effect of immunoglobulin G fractions from individual patients was highly variable. Immunoglobulin G fraction from eight women resulted in high rates of fetal loss. However, in spite of high levels of anticardiolipin antibodies, fetal outcome was normal in mice immunized with immunoglobulin G fraction from the majority of women. The rate of fetal death did not uniformly increase with increasing doses of immunoglobulin G fraction and was unrelated to the donor's medical history. Fetal outcome was similar for both C3H/HeN and BALB/c mice.

CONCLUSIONS

Human antiphospholipid antibodies have variable effects on murine pregnancy outcome. Characterization of antiphospholipid antibodies that do and do not cause murine fetal loss may provide insight into epitopes relevant to fetal loss associated with antiphospholipid syndrome.

Anti-beta2-glycoprotein I (beta2GPI) monoclonal antibodies with lupus anticoagulant-like activity enhance the beta2GPI binding to phospholipids

beta2-Glycoprotein I (beta2GPI), a plasma glycoprotein with phospholipid-binding property, is known to be the actual target antigen for autoimmune type anticardiolipin antibodies (aCLs). Certain groups of aCLs (anti-beta2GPI antibodies) exert lupus anticoagulant (LA) activity and perturb the function of vascular endothelial cells. This investigation aimed at highlighting some insights into the molecular basis by which aCLs exert their biological effects by using anti-beta2GPI mAbs with well-characterized epitopes from mice and from patients with antiphospholipid syndrome. Anti-beta2GPI mAbs directed against the third domain (Cof-20 and Cof-22) and fourth domain (Cof-21, EY1C8, and EY2C9) of beta2GPI inhibited the thrombin generation induced by Russell's viper venom in diluted plasma and that induced by the prothrombinase complex reconstituted with purified clotting factors. This anticoagulant activity was abrogated in the presence of an excess amount of phospholipids, thus resembling the LA activity. In stark contrast, anti-beta2GPI mAbs directed against the fifth domain and the carboxy-terminal region of the fourth domain showed no LA-like activity. These findings suggest that the LA activity of anti-beta2GPI antibodies depends on their epitope specificity. Experiments carried out to clarify the mechanism of the LA activity showed that anti-beta2GPI mAbs with LA-like activity, but not those without this effect, enhance the beta2GPI binding to phospholipids. In addition, the F(ab')2 fragment, but not the Fab' fragment, of the anti-beta2GPI mAbs was found to enhance the LA activity and the beta2GPI binding to phospholipids, suggesting that anti-beta2GPI antibodies induce formation of multiple complexes of beta2GPI on the surface of phospholipids because of their bivalent property. This clustering of beta2GPI molecules induced by anti-beta2GPI antibodies, probably because of their multivalent property and epitope specificity, might hinder the lateral mobility and activation of clotting factors on the surface of phospholipids and thus exert LA activity. Clustering of beta2GPI molecules may also explain the molecular mechanism by which anti-beta2GPI antibodies alter the function of leukocytes and endothelial cells. The well-documented heterogeneous LA activity of aCLs (anti-beta2GPI antibodies) may also be explained by their epitope specificity.

Thrombotic syndromes and autoimmune diseases

Maintenance of blood flow involves the dynamic interactions between the endothelium, circulating cellular components, coagulation factors, and factors involved in fibrinolysis. Autoantibodies, inflammatory cytokines and other undefined triggers in a genetically predisposed person may lead to an imbalance in the equilibrium between the various hemostatic pathways resulting in potentially catastrophic thrombotic events. This article reviews the clinical manifestations and treatment of selected, potentially life-threatening thrombotic syndromes that may occur in association with autoimmune diseases. Special mention is made of thrombotic events associated with Behçet's syndrome.

Autoantibodies to tyrosinase: the bridge between melanoma and vitiligo

BACKGROUND

Tyrosinase is an enzyme that participates in the process of melanin production in normal melanocytes and melanoma cells. Enzymes are known to be autoantigens in various autoimmune disorders; thus, after the detection of antityrosinase antibodies in patients with vitiligo and melanoma, tyrosinase was defined as an autoantigen in these conditions. In some patients with melanoma the disease is associated with the appearance of "vitiligo-like" white patches on the skin, called melanoma-associated hypopigmentation (MAH). In this article, the authors summarize the recent data related to antityrosinase antibodies and expand on their role in the pathogenesis of vitiligo, melanoma, and MAH. In addition, the beneficial clinical applications of antityrosinase antibodies are presented.

METHODS

An enzyme-linked immunoadsorbent assay to detect the antityrosinase antibodies in the serum of patients and healthy volunteers was established using mushroom tyrosinase. Employing this method, antityrosinase antibodies were analyzed in a diverse group of patients with melanoma and vitiligo and in mice immunized with tyrosinase.

RESULTS

In patients with melanoma, those with metastatic disease had a higher titer of antityrosinase antibodies compared with healthy subjects, whereas patients with MAH and those with no evidence of disease had similar titers to the control group. The titer of antityrosinase antibodies in patients with metastatic melanoma treated by vaccination with antiidiotypic antibodies mimicking the high molecular weight melanoma-associated antigen (HMW MAA) initially increased after the vaccination and then decreased. High titers of antityrosinase antibodies were detected in patients with diffuse vitiligo compared with patients with localized disease and with the healthy control group. Mice immunized with tyrosinase generated a high titer of antityrosinase antibodies and after the inoculation of melanoma cells developed a lower number of lung metastases compared with an unvaccinated control group.

CONCLUSIONS

The appearance of antityrosinase autoantibodies in the serum of patients with metastatic melanoma and diffuse vitiligo is characterized by these two pathologies. The changes in the serum level of these autoantibodies in patients with melanoma after immunization with another antigen (HMW MAA) may have diagnostic and therapeutic implications.

Placental pathology in systemic lupus erythematosus and phospholipid antibody syndrome

Fetal loss is increased in women who meet the Arthritis and Rheumatism Association criteria for systemic lupus erythematosus (SLE) and in women who have phospholipid antibody syndrome (APS). There are multiple causes for this fetal loss, and in patients with SLE, disease activity appears to be an important contributing factor. In APS patients, it appears that some individuals will experience recurrent fetal loss and will continuously fail to complete pregnancy naturally. Placental examination has helped to elucidate some of the pathology that may be contribute to this fetal loss and our studies have shown that the same pathology is repeated in subsequent pregnancies. Placental examination in SLE or APS patients with recurrent fetal loss is vital if we are going to be able to determine appropriate therapy to prevent fetal loss.

Animal models for antiphospholipid syndrome in pregnancy

Experimental models for antipospholipid syndrome (APS) have been established recently in lupus-prone mice and induced in naive mice. The induction of APS is performed by passive infusion or active immunization of antiphospholipid antibodies (aPL) or the cofactor beta 2GP-1. High levels of diverse aPL develop in the animals in conjunction with clinical manifestations similar to the human disease, entailing low fecundity rate, fetal resorptions, thrombocytopenia, prolonged activated partial thromboplastin time, and neurological and behavioral impairments. The pathogenicity of aPL was confirmed in an in vivo thrombosis model. Immunomodulation of APS manifestations and treatment regimens in the experimental models are discussed.

Antiphospholipid syndrome in pregnancy. Obstetric concerns and treatment

To be sure, antiphospholipid antibody syndrome is a protean disease with many manifestations, some of which are exacerbated during pregnancy, and some of which even lead to its initial diagnosis during pregnancy. Although the best treatment during pregnancy is uncertain at this point, and some of the treatments are even experimental, there does seem to be a benefit in at least identifying and probably treating those with risk factors. If treatment is not instituted with heparin, aspirin, or other medical management, at least monitoring for the known superimposed disease states, such as intrauterine growth retardation, preeclampsia, and fetal loss, should be judicious, with close antenatal surveillance.

New methods of treatment in an experimental murine model of systemic lupus erythematosus induced by idiotypic manipulation

In this article we have presented our experiences and those of others with various experimental and novel treatments in an experimental model of murine SLE, induced by immunisation with pathogenic anti-DNA antibody (fig 4). Many of the treatments (summarised in the table) were highly effective in ameliorating clinical, serological, and histological manifestations of the disease. According to our results, it seems that hormonal treatments--such as testosterone metabolites, anti-oestrogens, or bromocriptine--as well as immunomodulation with IVIG or anti-CD4 antibodies, hold the most promising potential for application in lupus patients. We believe, therefore, that these types of treatment should receive high priority in human trials. It should be emphasised, however, that the timing of treatment may be critical, since several treatments were effective when used before or during the induction of the disease. This limitation may pose difficulty for human application, since the aetiology of SLE is still obscure and is probably multifactorial38; therefore it is not yet possible to identify patients at risk of developing SLE. Nevertheless, those treatments which proved to be effective might be used early in the course of the disease in lupus patients and hence influence the outcome of the disease, or may even induce partial or complete remission.

Induction of experimental antiphospholipid antibody syndrome in PL/J mice following immunization with beta 2 GPI

PROBLEM

Immunization with beta 2-glycoprotein I (beta 2 GPI) induces antiphospholipid antibodies (aPL) in normal mice and rabbits. Recently we reported early onset of autoimmunity in MRL/(+2) mice following immunization with beta 2 GPI. There is a close association between aPL with thrombosis, recurrent fetal loss, and intrauterine growth retardation. In this study we evaluated the effect of beta 2 GPI-induced aPL on pregnancy outcomes in an inbred strain of mice (PL/J).

METHOD

Three groups of seven-week female PL/J mice (12 per group) were studied. Group A was immunized with beta 2 GPI and group B with ovalbumin; group C was not not immunized. After two booster injections, the mice were tested for aPL, anti-DNA by ELISA, and for ANA by indirect immunofluorescence. Platelet count and pregnancy outcomes were studied at the age of 14 weeks.

RESULTS

The aPL and anti-DNA levels were higher at 12 and 14 weeks in group A; the optical densities (OD) were 1.72 +/- 0.6 and 0.699 +/- 0.25 for group A, 0.09 +/- 0.040 and 0.230 +/- 0.47 for group B, and 0.0435 +/- 0.003 and 0.119 +/- 0.26 for group C (comparing group A with groups B and C combined, P < 0.001). ANA titers rose in groups A and B by age, but they were significantly higher at 14 weeks in group A. The mean titers were 1/286, 1/90, and 1/16 for A, B, and C, respectively (P < 0.001). The platelet counts were not significantly different among the three groups. The titer size was significantly smaller in group A, as evidenced by the numbers of viable fetuses among the mice that became pregnant in each group: 0.75, 2.45, and 5.5 in groups A, B, and C, respectively. Seven pregnant mice in group A had complete resorption, seven pregnant mice in group B showed focal (partial) resorption areas, by only one mouse in group C had complete resorption of the embryos, as shown by histopathological studies, although the fecundity rate was similar in the three groups.

CONCLUSION

Our data suggest a pathogenic role for beta 2 GPI-induced aPL in the development of experimental models of APS in PL/J mice.

Pathogenesis and treatment of the antiphospholipid antibody syndrome

Antiphospholipid antibody syndrome (APS) is one of the most important causes of thrombophilia, presenting most often as venous or arterial thrombosis, recurrent pregnancy loss, or thrombocytopenia. Both the lupus anticoagulant and anticardiolipin antibody are associated with APS. The mechanism of the prothrombotic state is not understood, but may involve beta-2 glycoprotein 1 (a naturally occurring anticoagulant), platelet aggregation, the protein C pathway, or endothelial cell function. The current treatment recommendation, after a venous or arterial thrombosis, is high-intensity, long-term warfarin therapy.

[Obstetrical complications of antiphospholipid syndrome]

Spontaneous miscarriages and fetal deaths take part of the definition of the antiphospholipid syndrome. Preeclampsia, fetal distress, preterm delivery, intrauterine growth retardation, mother's or newborn's vascular thrombosis are also included in the spectrum of clinical events linked to the antiphospholipid antibodies in pregnant women. The pathogenesis is not fully understood, but involves interactions between antibodies and phospholipidic molecules that are complexed to plasmatic proteins of the coagulation, or present on endothelial cell and platelet surfaces. The poor spontaneous prognosis of pregnancy in the context of the antiphospholipid syndrome is dramatically improved by preventive treatment. Therapeutic options are not codified and are various combinations of low-dose aspirin, heparin, steroids, intravenous immunoglobulins, and fish-oil derivatives. Excellent obstetrical care is mandatory in every case.

Isolation and purification of anticardiolipin antibody from plasma of a patient with antiphospholipid syndrome: induced generation of platelet thromboxane A2 synthesis

Antiphospholipid antibodies, particularly anticardiolipin antibodies (aCL) are autoantibodies frequently detected in the serum of patients with systemic lupus erythematosus (SLE) and the primary antiphospholipid antibody syndrome (PAPS). These patients commonly suffer from thrombosis, recurrent fetal loss and thrombocytopenia. Since platelet aggregation is pivotal in the genesis of thrombosis, we tested the hypothesis that perturbation of platelet membrane by aCL/beta 2-glycoprotein (aCL/beta 2GP) complex could trigger the biosynthesis of TXA2, a proaggregatory metabolite of AA. The preincubation of 14C-arachidonic acid (14C-AA)-labeled platelet pellets (14C-PP) from normal individuals with aCL alone followed by incubation with thrombin, resulted in a moderate increase in platelet thromboxane B2 (14C-TXB2) biosynthesis when compared to controls (without aCL). Similar incubations with beta 2GP-I alone resulted in negligible 14C-TXB2 biosynthesis. In contrast, the preincubations of normal 14C-PP with aCL/beta 2GP-I complex resulted in marked thrombin-induced TXB2 biosynthesis, underscoring the requirement of beta 2GP-I in aCL-induced platelet TXB2 biosynthesis. Taken together, these results are consistent with the view that aCL/beta 2GP-I platelet interactions do play a role, at least in part, in platelet hyperactivity and thrombosis in antiphospholipid antibody syndrome.

In vivo models of thrombosis for the antiphospholipid syndrome

Utilizing this unique animal model of thrombosis we demonstrated that human (IgG, IgM or IgA) polyclonal and monoclonal antiphospholipid antibodies derived from APS patients have a significant enhancing effect on thrombus formation. This effect is reversed by treatment of the mice with hydroxychloroquine (plaquenil). In addition murine polyclonal and monoclonal anticardiolipin antibodies induced by active immunization with human beta 2-GP1 or human anticardiolipin antibodies showed to have thrombogenic properties in CD1 mice. Antibodies with antihuman beta 2-GP1 activity alone did not seem to affect thrombus formation.

Immunomodulation of experimental APS: lessons from murine models

During the last few years several murine models for APS have been described. These include spontaneous occurring disease, or APS induced by immunization with pathogenic autoantibodies. Employing those models, several treatment modalities, in different stages of the disease, were studied. Treatments which showed promising potential for application in patients with APS include immunomodulation with specific anti-idiotypic or anti-CD4 antibodies, treatment with IL-3, high-dose intravenous immunoglobulins, ciprofloxacin or bromocriptine, as well as antithrombotic and anticoagulant treatments using aspirin and/or low-molecular-weight heparin. Bone-marrow transplantation was also found to improve clinical and serological manifestations of the disease. These studies might promote the handling of controlled clinical trials assessing their efficacy in APS patients.

Thrombogenic properties of murine anti-cardiolipin antibodies induced by beta 2 glycoprotein 1 and human immunoglobulin G antiphospholipid antibodies

BACKGROUND

Recurrent arterial thrombosis and venous thrombosis are frequent complications of the antiphospholipid syndrome (APS). Patients produce anti-cardiolipin antibodies, but the role of these antibodies in thrombus formation is uncertain. This study used a unique CD-1 mouse model of thrombosis to determine whether anti-cardiolipin and anti-beta 2 glycoprotein 1 (beta 2 GP1) antibodies induced immunologically in these animals are thrombogenic.

METHODS AND RESULTS

The CD-1 mouse model enables measurement of the kinetics of a thrombus induced in the femoral vein of the animal. Animals are first anesthetized, then one femoral vein is exposed and subjected to a standardized, nonpenetrating "pinch" injury that induces a thrombus. The vein is trans-illuminated, and the growing thrombus is visualized on a television screen. The rate of formation and disappearance of the thrombus as well as its area can be measured by a computer attached to the television. Three groups of CD-1 mice (each group comprising seven animals) were studied. Group 1 mice were actively immunized with beta 2GP1, resulting in production of anti-beta 2GP1 and anti-cardiolipin antibodies. Group 2 mice were actively immunized with human immunoglobulin G (IgG) anti-cardiolipin antibodies and produced anti-human IgG as well as anti-cardiolipin antibodies (the latter by an idiotype-anti-idiotype reaction). These animals did not produce anti-beta 2GP1 antibodies. Group 3 mice were immunized with human serum albumin (HSA) and produced anti-HSA but not anti-cardiolipin antibodies. The kinetics of thrombus formation induced in the femoral veins of the experimental mice were compared. Results showed that the mean thrombus area as well as mean time during which thrombi persisted were significantly greater in group 1 and group 2 mice compared with group 3. There was no statistical difference between group 1 or group 2.

CONCLUSIONS

Demonstration of a thrombogenic effect of murine anti-cardiolipin antibodies suggests that these antibodies may be pathogenic in humans with APS.

A monoclonal IgG anticardiolipin antibody from a patient with the antiphospholipid syndrome is thrombogenic in mice

Antiphospholipid antibodies, including anticardiolipin antibodies (ACA), are strongly associated with recurrent thrombosis in patients with the antiphospholipid syndrome (APS). To date, reports about the binding specificities of ACA and their role(s) in causing and/or sustaining thrombosis in APS are conflicting and controversial. The plasmas of patients with APS, usually containing a mixture of autoantibodies, vary in binding specificity for different phospholipids/cofactors and vary in in vitro lupus anticoagulant activity. Although in vivo assays that allow assessment of the pathogenic procoagulant activity of patient autoantibodies have recently been developed, the complex nature of the mixed species prevented determination of the particular species responsible for in vivo thrombosis. We have generated two human IgG monoclonal ACA from an APS patient with recurrent thrombosis. Both bound to cardiolipin in the presence of 10% bovine serum, but not in its absence, and both were reactive against phosphatidic acid, but were nonreactive against purified human beta-2 glycoprotein 1, DNA, heparan sulfate, or four other test antigens. Both monoclonal autoantibodies lacked lupus anticoagulant activity and did not inhibit prothrombinase activity. Remarkably, one of the monoclonal antibodies has thrombogenic properties when tested in an in vivo mouse model. This finding provides the first direct evidence that a particular antiphospholipid antibody specificity may contribute to in vivo thrombosis.

New therapeutic avenues in autoimmunity

During the last decade, much progress has been made in the understanding of processes that lead to autoimmunity. Cellular interactions mediated through cytokines and adhesion molecules were found to play a major role in the genesis of autoimmune conditions. During this period, we learned to recruit monoclonal antibodies to manipulate these delicate processes and to divert their outcome to a path we control better. Our comprehension of IVIG (intravenous immunoglobulin therapy) has broadened, and new indications for the implementation of this promising therapy have been pursued. In this review, we shed light on new therapeutic modalities that have been published since our previous report and discuss new data concerning the old modalities.

Antiphospholipid antibodies (aPL) increase the potential monocyte procoagulant activity in patients with systemic lupus erythematosus

Lupus anticoagulant (LA) and anticardiolipin antibodies (aCL) are frequently detected in sera from patients affected by systemic lupus erythematosus (SLE). However, the role of antiphospholipid antibodies (aPL) in thrombus formation has not been defined as yet. Twenty-two patients affected by SLE, all fulfilling the 1982 ARA revised criteria, and twenty healthy subjects were investigated for the presence of LA, aCL and other aPLs. Monocyte procoagulant activity-PCA (Tissue Factor production) was evaluated by one stage plasma recalcification time. In all patients the plasma levels of F1 + 2 and of plasminogen activator inhibitor (PAI) were also determined. Monocyte PCA was significantly higher in SLE patients with LA and/or aCL in comparison to SLE patients without LA and/or aCL (p < 0.01) and to controls (p < 0.05). However, no connection was observed between PCA expression by mononuclear cells and LA or aCL levels. No differences in F1 + 2 and PAI plasma levels were found between SLE patients with or without aPL and controls. In our SLE patients LA and/or aCL positivity appears strictly related to an increased monocyte activation that could play an important role in the occurrence of thrombotic events.

Libman-Sacks endocarditis in the antiphospholipid syndrome: immunopathologic findings in deformed heart valves

OBJECTIVE

To examine the potential immunologic mechanism and involvement of antiphospholipid antibodies in the pathogenesis of heart valve lesions in patients with the antiphospholipid syndrome (APS).

METHODS

Immunoperoxidase and immunofluorescence staining methods were used to evaluate 13 heart valve specimens derived from eight patients with the APS, either primary or secondary to systemic lupus erythematosus. Primary antibodies to human immunoglobulins, complement components, serum albumin and a monoclonal anti-idiotypic antibody to human anticardiolipin antibodies (aCL) were employed. Various tissue specimens from a patient with the APS as well as deformed and normal valves from subjects without the APS were used as controls.

RESULTS

Linear subendothelial deposition consisting of immunoglobulins with complement components but not of a non-specific serum protein was found in deformed valves from patients with the APS. None of the control valves or tissues disclosed similar deposition. The same pattern and location of staining was obtained by the anti-idiotypic antibody to aCL. A significant amount of IgG immunoglobulins that bound to cardiolipin was eluted from a valve of a patient with secondary APS.

CONCLUSION

Deposits of immunoglobulins including aCL, and of complement components, are common in affected valves of patients with primary and secondary APS. Such deposits may be involved in the pathogenesis of valvular lesions.

Heart valve involvement (Libman-Sacks endocarditis) in the antiphospholipid syndrome

The antiphospholipid syndrome (APS) is defined by the presence of anti-phospholipid antibodies (aPLs) and venous or arterial thrombosis, recurrent pregnancy loss, or thrombocytopenia. The syndrome can be either primary or secondary to an underlying condition, most commonly systemic lupus erythematosus (SLE). Echocardiographic studies have disclosed heart valve abnormalities in about a third of patients with primary APS. SLE patients with aPLs have a higher prevalence of valvular involvement than those without these antibodies. Valvular lesions associated with aPLs occur as valve masses (nonbacterial vegetations) or thickening. These two morphological alterations can be combined and are thought to reflect the same pathological process. Both can be associated with valve dysfunction, although such association is much more common with the latter alteration. The predominant functional abnormality is regurgitation; stenosis is rare. The mitral valve is mainly affected, followed by the aortic valve. Valvular involvement usually does not cause clinical valvular disease. The presence of aPLs seems to further increase the risk for thromboembolic complications, mainly cerebrovascular, posed by valve lesions. Superadded bacterial endocarditis is rare but may be difficult to distinguish from pseudoinfective endocarditis. The current therapeutic guidelines are those for APS in general. Secondary antithrombotic prevention with long-term, high-intensity oral anticoagulation is advised. The efficacy of aspirin, either alone or in combination, is yet to be assessed. Corticosteroids are not beneficial and may even facilitate valve damage. Immunosuppressive agents should only be used for the treatment of an underlying condition. Current data suggest a role for aPLs in the pathogenesis of valvular lesions. aPLs may promote the formation of valve thrombi. These antibodies may also act by another mechanism, as indicated by the finding of subendothelial deposits of immunoglobulins, including anticardiolipin antibodies, and of colocalized complement components in deformed valves from patients with APS.

Antiphospholipid syndrome manifested by ischemic stroke in a patient with Crohn's disease

Cerebrovascular accidents are rare but well documented in patients with Crohn's disease. Up to 10% of hypercoagulable state manifestations reported in association with inflammatory bowel disease are ischemic strokes. However, no clear mediating factor has thus far been suggested. A 44-year-old woman with Crohn's disease for 25 years developed a left temporal stroke associated with anticardiolipin antibody and lupus anticoagulant suggesting antiphospholipid syndrome. A thorough evaluation did not reveal any other risk factor for ischemic stroke. No possible sources of emboli were found in the carotids and heart, and no deficiencies of protein C and activated protein C, protein S, and anti-thrombin III leading to hypercoagulable state were present. There may be a possible association between antiphospholipid syndrome and hypercoagulable state in Crohn's disease.

The lupus anticoagulant/antiphospholipid syndrome

Lupus anticoagulants and anticardiolipin antibodies have been strongly associated with the risk of thrombosis, recurrent fetal loss, thrombocytopenia, and a number of other clinical manifestations that together have been referred to as the antiphospholipid syndrome. Despite growing evidence of the significance of this relationship, the pathogenetic mechanisms involved are largely unknown. Recent data suggest strongly that lupus anticoagulants (LACs) and anticardiolipin antibodies (ACAs) are antibodies to protein-phospholipid complexes rather than to phospholipids, as had originally been thought, and that other protein-phospholipid complexes, not recognized by standard assays for LACs or ACAs, may also exist in patients with the antiphospholipid syndrome. Although very recent experimental data may lead to new therapeutic approaches in this syndrome, at present we can only deal with the thrombotic risk by the use of long-term anticoagulation. This chapter reviews current methods of diagnosis, concepts of pathogenesis, and the basis for an approach to anticoagulation in patients at risk for thrombosis or other manifestations of the antiphospholipid syndrome.

Aspirin-interleukin-3 interrelationships in patients with anti-phospholipid syndrome

PROBLEM

Previously we reported on the generation of experimental anti-phospholipid syndrome (APS) in mice. These models were employed to evaluate the efficacy of various novel therapeutic modalities including interleukin-3 (IL-3) and low dose aspirin. The efficacy of the latter was found to be interrelated. Low dose aspirin is capable of inhibiting the activity of the enzyme cyclooxygenase which is responsible for the metabolism of arachidonic acid towards the production of prostaglandins. This shifts the metabolism of arachidonic acid to the other pathway and leads to an overproduction of leukotrienes. The leukotrienes act as stimulators of IL-3 production, a positive cytokine in pregnancy which enhances placental and fetal development. In the current study we evaluated the IL-3 levels in pregnant women with APS and expanded our knowledge on the interrelationships between aspirin, arachidonic acid metabolites and IL-3 in the human system.

METHODS

IL-3 levels were recorded in the serum of pregnant women with APS and compared to a control pregnant group. In addition peripheral blood mononuclear cells from healthy subjects were incubated with different concentrations of aspirin or with arachidonic acid metabolites (Leukotriene B4, C4 or PGE2), and IL-3 production in the culture fluids was evaluated.

RESULTS

Serum level of IL-3 in pregnant patients with primary APS, APS secondary to SLE and SLE was lower in comparison to the control group. The in vitro studies revealed that only low dose aspirin (10 mg/microliters) stimulated IL-3 production while higher doses of the drug failed to induce the cytokine generation. Leukotriene B4 and C4 were stimulatory whereas PGE2 acted as inhibitor of IL-3 production.

CONCLUSIONS

The serum level of IL-3 is decreased to pregnant women with primary or secondary APS. Low dose aspirin is capable of stimulating IL-3 production in vitro most probably through an elevation of leukotriene production, which may explain its beneficial activity in preventing the manifestations of APS.