Antiphospholipid antibodies--lobsters or red herrings?

Antiphospholipid antibodies can specifically target placental mitochondria and induce ROS production

Women with antiphospholipid antibodies (aPL) have increased risks of pregnancy complications, including a ten-fold increased risk of preeclampsia, which is potentially triggered by the release of placental toxins. Previously, aPL were shown to enter the outer layer of the placenta, the syncytiotrophoblast, associate with mitochondria, and alter mitochondrial function. We hypothesised that aPL may also increase mitochondrial reactive oxygen species (ROS) production, leading to cellular dysfunction and release of toxins. First trimester placental explants were incubated with monoclonal aPL, ID2 and IIC5 (25, 50, and 100 μg/mL), for 3 h at 37 °C and ROS production followed using CellROX Deep Red. In addition, the candidate treatment compounds chloroquine, melatonin, and Mito-Q were tested at therapeutic concentrations for their ability to prevent ROS production. Mitochondria isolated from term placentae were incubated with fluorescently-labelled ID2, IIC5, or control IgG antibodies (2.5, 5, 10, or 20 μg/mL) for 30 min, and mitochondria with bound antibodies were quantified using flow cytometry. In addition, respirometry coupled with fluorimetry was used to interrogate explant mitochondrial respiration and ROS production following incubation with 25, 50, or 100 μg/mL ID2, IIC5, or control IgG for 3 h at 37 °C. ID2 increased explant ROS production in a manner that was completely prevented by the endocytosis inhibitor chloroquine, and partially prevented by the antioxidants melatonin and Mito-Q. Both ID2 and IIC5 displayed a greater ability to bind isolated mitochondria than control antibodies, and increased ROS production attributable to the mitochondrial enzyme glycerol 3-phosphate dehydrogenase (mGPDH). Our evidence supports the hypothesis that aPL interact with syncytiotrophoblast mitochondria, likely via the binding of cardiolipin and β₂ glycoprotein I in mitochondrial membranes, and induce ROS production which contributes to overall oxidative stress and placental dysfunction.

Anti-phospholipid antibodies as a cause of recurrent pregnancy loss: a study in Calcutta, India

This prospective, observational study was carried out in a teaching hospital in Calcutta, India. The aim of the study was to evaluate the prevalence of anti-phospholipid syndrome (APS) among women with recurrent miscarriages/late pregnancy loss when no other apparent causes were identified, in the study population. The women were put through a variety of investigations to determine the cause of miscarriage/pregnancy loss. Only those women who had a normal result for all the investigation went for the anti-phospholipid antibodies (APLA) test. The expelled products of conception/placenta were also sent for histopathological confirmation. A total of 445 women were studied over a 4-year period. A total of 155 women were offered a screening for APLA antibodies. Out of them, 43 women (27.7%) tested positive for APLA. Histopathological evidence was present in all the specimens. Interestingly, one woman had histopathological evidence of thrombosis, but her blood tests for the antibody were negative.

Antiphospholipid antibodies in serum and follicular fluid--is there a correlation with IVF implantation failure?

BACKGROUND

Antiphospholipid antibodies (aPLs) are associated with infertility, but the mechanism underlying this statistical association is currently obscure. We aimed to investigate the finding that aPLs are concentrated in follicular fluid and to establish if this is associated with a poorer outcome from IVF.

METHODS AND RESULTS

In 19.2% of 99 women undergoing IVF, at least one aPL was detected in their serum and/or follicular fluids, but the antibody levels in follicular fluid were not higher than in serum. Women with aPLs had a lower implantation rate (14%) than women without these antibodies (24.1%), but this difference was not significant (P=0.127). There was also a non-significant reduction in the live birth rate for women with aPLs. In a parallel investigation, 10 sheep immunized with beta2 glycoprotein I (beta2GPI) or irrelevant control antigens showed strong immune responses, but there were no significant differences between the levels of antibodies in the follicular fluid or serum from beta2GPI or control immunized sheep.

CONCLUSION

aPLs do not appear to be selectively concentrated in follicular fluids and, when present, do not adversely affect the reproductive outcome of women undergoing IVF.

Anti-Phospholipid Antibodies against Phosphatidylinositol, and Phosphatidylserine are More Significant in Reproductive Failure than Antibodies against Cardiolipin only

PROBLEM

The humoral immune response to phospholipids was investigated in women with reproductive failure [1073 women after one in vitro fertilization (IVF), 853 women after two and more IVF, 627 women after three and more repeated spontaneous miscarriages or missed abortions, 412 women after diagnostic laparoscopy] and compared with that of 391 healthy fertile women.

METHOD OF STUDY

Sera from all women in the study were tested by enzyme-linked immunosorbent assay (ELISA) for the detection of IgG, IgA, and IgM isotypes of antibodies against seven phospholipids (aPLs), i.e. cardiolipin, L-phosphatidylserine, phosphatidylglycerol, phosphatidylinositol, phosphatidylethanolamine, phosphatidylacid as well as against beta2-glycoprotein I.

RESULTS

Patients after two and more IVF (48 and 50%, respectively), patients with three and more repeated spontaneous miscarriages (50 and 46.5%, respectively) are associated with significantly higher serum levels of aPLs against inositol, and L-serine (P < 0.01). A quarter of them were positive for three and more aPLs.

CONCLUSION

It seems that determination of aPLs only against cardiolipin in reproductive failure is not sufficient for obstetric-gynecology diagnosis as the primary anti-phospholipid syndrome. Our long-ranging study (from 1998 to 2003) shows the necessity to test for a complete aPLs profile. Sera from patients after two and more IVF procedures, and sera from women after three and more repeated abortions are immunologically more active than sera from women after one unsuccessful IVF and sera from women after diagnostic laparoscopy. This important result is very significant for future treatment.

Is previous aberrant reproductive outcome predictive of subsequently reduced fecundity?

BACKGROUND

Effect of past reproductive performance on subsequent fecundity is uncertain.

METHODS

A total of 2983 consecutive pregnant women self-completed questionnaires about time to pregnancy (TTP), pregnancy planning, previous pregnancies, contraceptive use, age, and individual/lifestyle variables. Outcome measures were: TTP, conception rates (CR) and, subfecundity odds ratio (OR; with 95% confidence intervals) before and after each outcome of last pregnancy.

RESULTS

After miscarriage, TTP was longer than before miscarriage [2.1 (1.4-3.0), P < 0.001] and than TTP after livebirth [OR = 2.1 (1.6-2.6), P < 0.001]. Also subfecundity OR after miscarriage increased [1.7 (1.2-2.4), 1.8 (1.2-2.5), P = 0.001, 0.002 respectively]. This effect was more evident in older and obese women. Compared with livebirth, time to ectopic pregnancy (EP) was longer [OR = 13.8 (1.8-108.5), P = 0.001] but TTP after EP was not significantly different. Subfecundity OR relative to livebirth were 12.8 (3.6-45.0) (P<0.001) before, and 3.9 (1.4-11.0) (P=0.01) after, EP. The CR after EP increased 3-fold (1.1-8.3) over those prior to EP. Time to the terminated pregnancies even without contraceptive failures was shorter than that to livebirth [OR = 0.5 (0.3-0.7), P = 0.001] and than TTP after termination [0.35 (0.1-0.8), P = 0.001]. Also subfecundity OR increased after termination [7.2 (1.8-29.7), P = 0.02].

CONCLUSIONS

Miscarriers should be counselled about short-term reduction in subsequent fecundity, and earlier investigations should be considered in those who have other potential risk factors for reduced fertility. Further studies are required to clarify the relatively favourable effect on fecundity following EP and the relative reduction in fecundity after termination of pregnancy.

Pregnancy outcome in women with antiphospholipid syndrome and alloimmunity: a case report

CONTEXT

Patients with antiphospholipid syndrome and alloimmunity have poor pregnancy outcomes. Several diagnostic and therapeutic options exist for these disorders, although there is no consensus as to the best treatment.

CASE REPORT

We present here the clinical course and treatment of a woman with a history of two miscarriages who joined our program 10 years ago and has been followed up ever since. After antiphospholipid syndrome and alloimmune failure were diagnosed, she was given preconceptional treatment using unfractionated heparin, aspirin, prednisone and lymphocyte immunizations. She delivered two premature babies in the following two pregnancies. At present both children are healthy and are attending school. The fifth pregnancy was unsuccessful, in spite of having undergone a similar but postconceptional therapeutic scheme. We discuss this case focusing on the pathogenic mechanisms and the therapeutic aspects of these disorders.

A randomized, double-blind, placebo-controlled trial of heparin and aspirin for women with in vitro fertilization implantation failure and antiphospholipid or antinuclear antibodies

OBJECTIVE

To investigate whether heparin and low-dose aspirin increase the pregnancy rate in antiphospholipid antibody or antinuclear antibody-seropositive women with IVF implantation failure.

DESIGN

A double-blind, randomized, transfer-by-transfer of fresh or cryopreserved embryos, crossover trial.A hospital infertility clinic and associated IVF service.

PATIENT(S)

Women seropositive for at least one antiphospholipid (APA), antinuclear (ANA), or beta(2) glycoprotein I autoantibody and >or=10 embryos transferred without achieving pregnancy (n = 143).

INTERVENTION(S)

Subcutaneous unfractionated heparin (5000 IU b.i.d.) and aspirin (100 mg daily) (158 transfers of 296 embryos) or placebo (142 transfers of 259 embryos) from the day of embryo transfer.

MAIN OUTCOME MEASURE(S)

Fetal heart per embryo transferred (implantation rate).

RESULT(S)

There was no significant difference in pregnancy rates or implantation rates between treated and placebo cycles; for example, fetal hearts per embryo transferred implantation rates were 6.8% (20/296) and 8.5% (22/259), respectively, and the generalized estimating equation covariate adjusted relative pregnancy rate was 0.65 (95% confidence interval, 0.33-1.28). The implantation rate for seropositive trial participants (42/555, 7.6%) compared favorably with that for IVF implantation-failure patients continuing treatment outside the trial (147/3237, 4.5%).

CONCLUSION(S)

Heparin and aspirin did not improve pregnancy or implantation rates for APA-positive or ANA-positive patients with IVF implantation failure.

Reflections on the management of reproductive failure in the antiphospholipid syndrome--the clinician's perspective

It is well known that women with systemic lupus erythematosus (SLE) who have antiphospholipid antibodies (aPL) are at increased risk for pregnancy loss. Additionally, other reproductive processes, such as unexplained infertility and implantation failure after in vitro fertilization and embryo transfer may be affected by aPL. Thus, clinical manifestations of the so-called 'gynaeco-obstetrical antiphospholipid syndrome' have been expanded into the concept of the 'reproductive autoimmune failure syndrome'. However, this is still a matter of debate with no general agreement with respect to both pathophysiological significance of the presence of aPL and patient management. This article analyses a number of controversies in the management of reproductive failure potentially associated with aPL in order to help clinicians dealing with such condition in daily clinical practice.

Low molecular weight heparin in immunological recurrent abortion--the incredible cure

The most compelling association between pregnancy loss and autoimmune phenomena has been with the presence of antiphospholipid antibodies (APA)--lupus anticoagulant and anticardiolipin antibody. The 'antiphospholipid antibody syndrome' has been described in women with a history of recurrent pregnancy loss or thrombosis with positive APA or lupus anticoagulant on two occasions. Although several treatments have been advocated, heparin and aspirin treatment is emerging as the treatment of choice for the APA syndrome associated with recurrent pregnancy loss. The rationale for prescribing aspirin in cases of recurrent reproductive failure associated with APA seropositivity is that aspirin may counter APA-mediated hypercoagulability in the choriodecidual space, a situation which if left unaddressed would traumatize the trophoblast and compromise feto-maternal exchange. Heparin on the other hand, through preventing APA from interfering with syncytialization of the early cytotrophoblast and by countering APA interference with phospholipid-decidual reactions that are vital to early implantation, might potentially promote both early implantation and subsequent placentation.

Epidemiology and the medical causes of miscarriage

Human reproduction is extraordinarily wasteful. The reasons for this have taxed all of the contributors to this book. As we move into the 21st century it is sobering to reflect on the fact that we have failed to harness the power of the evolving revolution in molecular medical biology to answer the fundamental question: why is the fate of a fertilized egg so hazardous and so unsuccessful? The following account summarizes our limited knowledge of the epidemiology of miscarriage and then moves on to consider some of the medical causes of miscarriage. The contribution of genetic abnormalities to the problem of pregnancy wastage is discussed elsewhere in this volume.

Pregnancy outcome is not affected by antiphospholipid antibody status in women referred for in vitro fertilization

OBJECTIVE

To determine the prevalence of antiphospholipid (aPL) and anti-beta 2 glycoprotein I (anti-beta2-GPI) antibodies in women referred for IVF and to prospectively evaluate the effect of these antibodies on IVF outcome.

DESIGN

Prospective observational study.

SETTING

A university hospital and IVF unit.

PATIENT(S)

Three hundred eighty consecutive women referred for IVF.

INTERVENTION(S)

Blood samples taken before commencement of IVF cycles were tested for the presence of aPL (lupus anticoagulant [LA], anticardiolipin [aCL], and antiphosphatidyl serine antibodies [aPS]) and anti-beta2-GPI antibodies.

MAIN OUTCOME MEASURE(S)

Antibody prevalence, pregnancy rates, and live birth rates.

RESULT(S)

Of the total 380 women, 89 tested persistently positive for aPL (23.4%). None of 176 women tested for IgG aPS antibodies had a positive titer. Only 3.3% (11 of 329) tested positive for anti-beta2-GPI antibodies. Pregnancy rate, live birth rate, gestational age at delivery, and birth weight were not affected by aPL status.

CONCLUSION(S)

Although women referred for IVF have a high prevalence of aPL, these antibodies do not affect the outcome of treatment. Screening women undergoing IVF for aPL is not justified.

Murine embryos as a direct target for some human autoantibodies in vitro

The involvement of one or another autoantibody in reproductive failure have long been thought to be through post-implantation thrombosis and/or peri-implantation trophoblast dysfunction and/or maternal hormonal imbalance. It can be postulated that the embryo may be a direct target for some autoantibodies prior to implantation. Mouse embryos have been labelled and cultured with affinity purified immunoglobulin (IgG) and IgA from positive for antiphospholipid antibody sera, as well as IgG from positive for antinuclear antibody sera and positive for antithyroid antibody sera. Intact IgG and IgA from healthy individuals were used as controls. All embryos cultured with purified antiphospholipid IgG or IgA, and anti-nuclear IgG exhibited strong immunofluorescence. No difference in fluorescent intensity was observed whether antiphospholipid or anti-nuclear antibodies were used, but the pattern of antibody distribution seemed to be different. Antiphospholipid IgG was more dominant on the zona pellucida, while antiphospholipid IgA and antinuclear IgG had predominant distribution on the embryonic cells. None of the embryos cultured with antithyroid IgG or with control immunoglobulins showed strong immunofluorescence. Embryos cultured with purified antiphospholipid and antinuclear immunoglobulins experienced significant growth impairment or death compared to those cultured with antithyroid or control immunoglobulins.

Heparin plus aspirin as a "single" therapy for recurrent spontaneous abortion associated with both allo- and autoimmunity

PROBLEM

The aim of this study was to contribute to the study of the pathogenesis and the treatment of recurrent spontaneous abortion (RSA) associated with immune alterations.

METHOD OF STUDY

This is a prospective clinical trial with 11 patients with RSA associated with allo- and autoimmunity not receiving lymphocyte immunizations but only heparin and aspirin preconceptionally and through pregnancy. A concurrent group of 8 patients receiving a complete therapy (lymphocyte immunizations, heparin, and aspirin) but not receiving heparin and aspirin preconceptionally is also included in this report.

RESULTS

The rate of pregnancy success in these patients was 90.9% (10/11), and the rate of success of the concurrent group was 75.0% (6/8).

CONCLUSIONS

The results are in agreement with the working hypothesis regarding the possible final common mechanism in the pathogenesis of abortion associated with allo- and autoimmunity. The "single" therapy with heparin and aspirin was effective, less costly, and logistically simpler to provide than a complete therapy including lymphocyte immunizations.

Correlation between beta 2-glycoprotein antibodies and antiphospholipid antibodies in patients with reproductive failure

PROBLEM

Antiphospholipid antibodies (APAs) are important in the etiology of reproductive failure. Studies have shown that binding proteins are necessary for the detection of APAs. One of these, beta 2-glycoprotein, has been shown to be necessary for detection of anticardiolipin antibodies. It is felt that some APAs may be directed to the binding protein itself, or to a combination of the binding protein and phospholipid.

METHOD OF STUDY

In this study, a comparison of APAs vs. anti beta 2-glycoprotein antibodies was performed on the sera of 123 women younger than 40 years of age with a history of reproductive failure. Antibodies to six phospholipid epitopes, cardiolipin, phosphatidyle-thanolamine, phosphatidylserine, phosphatidylinositol, phosphatidic acid, phosphatidylglycerol, and phosphatidylserine, were measured.

RESULTS

Of the 123 women tested, 33 had one or more positive immunoglobulin (Ig)G antibodies to phospholipids, of which 9 were to cardiolipin. However, only 1 of 123 women had IgG antibodies to beta 2-glycoprotein and she was APA negative. Thirty-eight of 123 women had one or more IgM antibodies to phospholipids, with none directed to cardiolipin IgM. In contrast, only 8 of the 123 women had IgM antibodies to beta 2-glycoprotein. Five of the eight patients had IgM APA; 4 of 5 had IgM antibodies to PE, 1 to PI.

CONCLUSIONS

There is no correlation between beta 2-glycoprotein antibodies and APA status in this population. To date, our most sensitive test for detecting phospholipid autoimmune-mediated in vitro fertilization failure still appears to be the ELISA assay for APA.

The selective use of heparin/aspirin therapy, alone or in combination with intravenous immunoglobulin G, in the management of antiphospholipid antibody-positive women undergoing in vitro fertilization

PROBLEM

The effect of mini-dose heparin/aspirin (H/A) alone vs. combined intravenous immunoglobulin G (IVIg) and H/A on in vitro fertilization (IVF) birthrates in women who test seropositive for antiphospholipid antibodies (APA+) was evaluated, as was the question of whether outcome is influenced by the gammaglobulin isotype(s) or the phospholipid (PL) epitope(s) to which the APAs are directed.

METHOD OF STUDY

A case-control study was conducted in three phases, spanning a 4-year period, in a multicenter clinical research environment. Six hundred eighty-seven APA+ women, who were younger than 40 years and who each, completed up to three consecutive IVF/embryo transfer cycles within a 12-month period, were given either H/A alone or H/A in combination with IVIg. Birthrates relative to the type of immunotherapy (i.e., H/A alone and H/A with IVIg) and APA profile were the main outcome measurements.

RESULTS

In phase I, 687 women who tested APA+ to one or more PL epitopes underwent two or fewer IVF attempts for a total of 1050 IVF cycles. Four hundred seventy-seven (46%) births occurred in 923 IVF cycles in which H/A alone was administered. Twenty-two (17%) births occurred after 127 IVF cycles in which H/A was not administered. In phase II, 322 of 687 women tested positive for a single APA subtype. These subjects underwent up to two consecutive IVF attempts for a total of 521 IVF cycles while receiving H/A alone. The birthrate was significantly lower for women whose APAs were directed toward phosphatidylethanolamine (PE) or phosphatidylserine (PS) involving IgG or IgM isotypes than for women who had any other APA (17% vs. 43%). In phase III, 121 women who did not achieve live births after two consecutive IVF attempts in which H/A alone was administered received IVIg in combination with H/A during their third consecutive IVF cycle. The birth rate was 41% after these IVF cycles when anti-PS or anti-PE involving IgG or IgM isotypes were present, as compared with 17% when H/A alone was administered. The IVF outcome did not improve when IVIg was administered in association with any other single APA.

CONCLUSIONS

The treatment of APA+ women with H/A alone improves IVF birthrates. This benefit is selective in that it does not apply in cases in which IgG- or IgM-related APAs are directed against PE or PS. In such cases, the addition of IVIg significantly improves the outcome.

High levels of anticardiolipin antibodies in patients with abnormal embryo morphology who attended an in vitro fertilization program

PROBLEM

Recently, it has been suggested that anticardiolipin antibodies (ACAs) may serve as possible markers for reproductive failure. The association between ACAs and embryo morphology in patients undergoing in vitro fertilization (IVF) was investigated.

METHOD OF STUDY

This prospective study comprised 117 patients with either tubal factor or unexplained infertility. Embryo morphology was blindly scored from I to IV according to blastomere regularity and the presence of fragments. Anticardiolipin antibodies (immunoglobulin [Ig] G and IgM) were detected.

RESULTS

Anticardiolipin antibodies were found in 26 (50%) of the 52 patients with abnormal morphology, compared with 13 (20%) of the 65 patients with normal embryo morphology (P = 0.001). No statistically significant differences were found between the prevalence of ACAs among patients with tubal factor and those with unexplained infertility (29.6% and 36.5%, respectively).

CONCLUSIONS

Our study shows an association between embryo morphology and the presence of ACAs. This association may explain the low implantation rate and early pregnancy loss in patients with ACAs.

The effect of sera from women with systemic lupus erythematosus and/or antiphospholipid syndrome on rat embryos in culture

Women with systemic lupus erythematosus (SLE) with or without antiphospholipid antibodies (APLA) suffer from a high rate of recurrent abortions perhaps as a result of specific antibodies that may damage the conceptus. We studied the effects of sera from women with SLE--with or without--APLA and recurrent abortions on 10.5-d-old rat embryos in culture. This was compared to the results of culture on sera from control women and on rat sera. In addition, we studied sera from women with SLE with or without APLA after treatment with low doses of aspirin and glucocorticosteroids. Seventy-three percent of embryos cultured in sera from women with SLE with or without APLA were malformed in comparison to only 10.2% in embryos cultured on control sera and 5.4% in embryos cultured on rat sera. The rate of anomalies was reduced to 37.5% in embryos cultured on sera from women with SLE with or without APLA after treatment, as in 6 of 13 sera, the treatment reduced or prevented the occurrence of embryonic anomalies. When sera were divided in to low- and high-risk sera, the effect of treatment was even more significant, as the average percentage of embryonic anomalies per serum was reduced from 81.7 to 44.7%. Specific ultrastructural changes were found in the yolk sacs of the embryos cultured on the sera from women with SLE with or without APLA by transmission electron microscopy and by scanning electron microscopy. It seems that the rat embryo culture system may be an important clinical diagnostic tool to identify women with recurrent abortions in whom the etiology may be immunologic rejection of the embryo and to assess the efficacy of various treatment modalities.

Autoantibody screening for infertility: explaining the unexplained?

Several laboratories currently offer panels of serum autoantibody assays to screen women with unexplained infertility and those undergoing in vitro fertilization (IVF). Offering these tests implies that they have predictive value for the outcome of proposed infertility treatments such that the results of the testing would alter clinical management. Because screening for antiphospholipid antibodies adds expense to already costly procedures, it is an appropriate time to review the justification for the use of these panels.

Prevalence and biological effects of anti-trophoblast and anti-endothelial cell antibodies in patients with recurrent spontaneous abortions

PROBLEM

Trophoblasts and endothelial cells represent a potential target for antibodies in women with recurrent spontaneous abortions. These antibodies have been shown to be associated with anti-phospholipid antibodies. Are they also present in women with unexplained pregnancy losses in the absence of anti-phospholipid antibodies?

METHOD OF STUDY

The anti-trophoblast antibodies were tested by an immunofluorescence assay on cells purified from pooled first-trimester placentae, whereas the anti-endothelial cell antibodies were measured by enzyme-linked immunoadsorbent assay (ELISA) on cells isolated from the umbilical vein and were cultured to confluence. The cytotoxicity of trophoblasts was evaluated in a homologous system. The expression of adhesion molecules on endothelial cells was quantitated by ELISA using specific monoclonal antibodies, and the expression of tissue factor was quantitated by a chromogenic assay measuring the formation of factor Xa.

RESULTS AND CONCLUSIONS

Complement-fixing antibodies to trophoblast represent a better marker to discriminate patients with recurrent spontaneous abortions from controls and are cytotoxic for the target cells. Anti-endothelial antibodies are also present in these patients and exhibit pro-inflammatory and pro-coagulant activities.

Midfollicular anticardiolipin and antiphosphatidylserine antibody titers do not correlate with in vitro fertilization outcome

OBJECTIVE

To determine the prevalence of anticardiolipin and antiphophatidylserine antibodies in an IVF population and to correlate their presence and specific isotype with IVF cycle outcome.

DESIGN

Retrospective clinical study using stored midfollicular sera for determination of antibody status.

SETTING

University hospital infertility clinic.

PATIENT(S)

Women who underwent IVF treatment in 1991.

INTERVENTION(S)

Midfollicular sera were used to assess antibody status during the time of stimulation for IVF.

MAIN OUTCOME MEASURE(S)

Anticardiolipin and antiphosphatidylserine antibody titers and biochemical or sonographic documentation of IVF cycle outcome.

RESULT(S)

The overall prevalence of anticardiolipin and antiphosphatidylserine antibodies in IVF patients was 7.0% and 11.2%, respectively. There was no statistically significant difference in the prevalence of these antibodies in the groups of patients with a biochemical pregnancy (0 for anticardiolipin and 2.8% for antiphosphatidylserine), spontaneous miscarriage (11.4% for anticardiolipin and 20% for antiphosphatidylserine), ongoing pregnancy (7.3% for anticardiolipin and 11.6% for antiphosphatidylserine), and patients who failed to conceive (7.2% for anticardiolipin and 10.8% for antiphosphatidylserine). There was no correlation between outcome and the antibody isotype expressed.

CONCLUSION(S)

Anticardiolipin and antiphosphatidylserine antibodies are poorly predictive of the IVF cycle outcome. Routine testing of IVF patients for the presence of these antibodies is of limited clinical utility.

Autoimmunity and reproduction

OBJECTIVE

To review the association between autoimmunity and reproductive failure.

DESIGN

A MEDLINE search done from 1965 to 1996. More than 300 original and review articles were evaluated, from which the most relevant were selected.

RESULT(S)

Autoimmune processes now are accepted widely as one of the possible mechanisms of many human diseases. The presence of autoimmune disorders has been associated repeatedly with reproductive failure. On the other hand, reproductive failure may be the first manifestation of autoimmune disorders.

CONCLUSION(S)

When abnormal autoantibody levels are present in women with reproductive failure, the reproductive failure alone should be considered as one of the possible clinical expressions of autoimmune disorders. Two relevant questions of whether these patients should be treated for autoimmunity remain unsolved. A prospective, placebo-controlled trial is necessary to evaluate the importance of any treatment.

Antiphospholipid antibodies in healthy pregnant women

This article discusses the prevalence and clinical significance of antiphospholipid antibodies (aPL) in the normal, healthy pregnant population. Although an increased risk for adverse fetal outcome has been shown in a small subset of this population, most pregnancies in aPL-positive mothers have successful outcomes. We review the variations in aPL levels during pregnancy and consider screening strategies and therapeutic interventions in healthy aPL-positive pregnant women.

Review: immunobiology of preeclampsia

Preeclampsia has been recognized clinically since the time of Hippocrates: however its etiology and pathophysiology remain enigmatic. This pregnancy-specific syndrome typically presents in late pregnancy as hypertension, edema, and proteinuria. Investigations over the past 15 years have revealed that preeclampsia is associated with abnormal placentation, reduced placental perfusion, endothelial cell dysfunction, and systemic vasospasm. Since it occurs more commonly in primigravidae and in women with underlying collagen-vascular diseases, an immunological component has long been suspected. Increased prevalence in high-order and molar pregnancies and those associated with increased placental mass suggests that trophoblastic volume and fetal antigen load are correlated with the syndrome. Epidemiological reports indicate that the prevalence of preeclampsia is decreased in women who received heterologous blood transfusions, practiced oral sex, or when a long period of cohabitation preceded an established pregnancy. Conversely, the use of condoms as a primary mode of contraception is associated with a higher risk of preeclampsia. These studies suggest that prior exposure to foreign or paternal antigens imparts a protection against the likelihood of developing preeclampsia. Clinical evidence of cellular and humoral immune dysfunction is associated with the syndrome. Fibrin and complement deposition and "foam" cells in atherosis lesions resemble the histopathology of renal allograft rejection. Relative T-cell, natural killer cell, and neutrophil activation have been reported in preeclampsia and circulating cytokines and antiphospholipid antibodies are more prevalent in preeclampsia than in normal pregnant women. These abnormalities are consistent with the systemic endothelial cell dysfunction that has been postulated as a pathophysiological feature of preeclampsia. While such associations do not prove causality, they suggest testable hypotheses for continued basic and clinical investigation of this major complication of human pregnancy.

Laboratory evaluation of women experiencing reproductive failure

Reproductive life table analysis indicates that the majority of reproductive failures result from post fertilization failures, whether before or after implantation. It is important to have a set of tests to clarify the diagnosis of the reproductive failure so that appropriate therapy can be instituted. To determine the frequency of abnormal immunologic tests among women experiencing reproductive failure, 108 patients were evaluated for the presence of antiphospholipid antibodies (APA); lupus anticoagulant (LA); thyroid-thyroglobulin and microsomal antibodies (TGT); embryotoxic factor (ETA); and systemic CD56+/CD16- cells. The frequency of abnormal results obtained from testing for APA, LA, TGT, ETA, and CD56+/CD16- cells among 108 patients with diagnoses of recurrent pregnancy loss (RPL)(n = 45), unexplained infertility (n = 45) including IVF failure (n = 10), endometriosis (n = 10), premature ovarian failure (n = 5), and polycystic ovaries (n = 3) were compared with 15 normal controls. Seventy of one hundred eight (65%) women experiencing reproductive failure had at least one positive test, compared to 1 of 15 (7%) controls (P = 0.0001). Presence of phospholipid antibodies was the most frequently abnormal result followed by elevated CD56+/CD 16 cells. The prevalence of a particular abnormal test varied among the diagnoses. The most frequent abnormal test among women with RPL was an increased percentage of CD56+/CD16- cells (40%), followed by APAs (29%), TGT (9%), and ETA (7%). The most frequent abnormal result among women with unexplained infertility was the presence of APAs (42%), followed by CD56+/CD16- cells (16%), ETA (16%), and TGT (9%). APA, CD56+/CD16- cells, ETA, and TGT are useful tools to assist in the diagnosis of reproductive failure.

Antiphospholipid antibody prevalence in patients with IVF failure

Antiphospholipid antibodies (APAs) have been associated with reproductive wastage. The purpose of this study was to establish the prevalence of APAs in women who have had at least 12 embryos transferred during several in vitro fertilization (IVF) cycles without ensuing pregnancy. Sera from 42 women with IVF failure and 42 women who successfully conceived after IVF were tested for the presence of APAs by ELISA. Successful post-IVF pregnancy was determined by obtaining two consecutive rising beta-hCG levels followed by an ultrasound to confirm a viable conceptus. The sera were tested for three isotypes of antibody: IgA, IgG, and IgM against seven phospholipids: cardiolipin (CL), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidic Acid (PA), phosphatidyl-glycerol (PG), phosphatidylcholine (PC), and phosphatidyl-serine (PS). From the IVF failure group, 11/42 (26.2%) were positive for APAs. From the control group, 2/42 (4.8%) were found positive only for IgA against PE. The difference between IVF failure and successful IVF groups was significant (P = 0.01). These results suggest that antiphospholipid antibodies should be considered an important marker for increased risk of IVF failure. Patients who are involved with an IVF program should be tested for the presence of APAs prior to initiation of an IVF cycle.

A model for the antiphospholipid antibody syndrome: monoclonal antiphosphatidylserine antibody induces intrauterine growth restriction in mice

OBJECTIVE

Antiphospholipid antibodies are associated with clinical intrauterine growth restriction. In this study we investigated whether immunoglobulin M monoclonal antibodies against phosphatidylserine or cardiolipin or cross-reactive with both phospholipids would induce intrauterine growth restriction in an experimental model of the antiphospholipid antibody syndrome.

STUDY DESIGN

Balb/c or CD-1 mice were injected intraperitoneally on day 8 of pregnancy with three immunoglobulin M monoclonal antibodies that differentiated between cardiolipin- and phosphatidylserine-dependent antigens or with control immunoglobulin M monoclonal antibodies against irrelevant antigens. The animals were killed on day 15 of pregnancy and placental and fetal weights were measured.

RESULTS

Monoclonal antibody 3SB9b, which reacted in enzyme-linked immunosorbent assays with phosphatidylserine but not cardiolipin, induced a significant reduction in both fetal and placental weights. Monoclonal antibodies BA3B5C4, which was cross-reactive with cardiolipin and phosphatidylserine, and D11A4, which reacted with cardiolipin, did not alter fetoplacental weights.

CONCLUSION

An antiphospholipid antibody that reacts with phosphatidylserine induces significant fetal and placental intrauterine growth restriction in a mouse model for the antiphospholipid antibody syndrome, but those that react with cardiolipin do not.

Longitudinal measurement of anticardiolipin antibodies during normal pregnancy: a prospective study

We have previously shown that elevation of anticardiolipin antibodies (aCL) at the first prenatal visit is associated with increased fetal loss in normal pregnancy. The variation in aCL levels during normal pregnancy has not been established. To examine this question we measured IgG, IgM and IgA aCL levels five times during pregnancy at weeks 5-15, 16-25, 26-35, 36-37 and at delivery. Data were analyzed to determine: (a) the within and between subject variability of aCL during pregnancy; (2) the temporal trend of aCL; and (3) the relation of serial measures of aCL with maternal complications of pregnancy. We divided our cohort of 354 subjects into two groups. Group A included those subjects with consistently normal levels of aCL and group B those subjects with at least one elevated level of aCL. In group A the within subject variability was relatively low (28-34%). In group B we found wide fluctuations in aCL levels and a within subject variability of 88-91%. Subjects in group B had no increase in maternal complications of pregnancy. The present data suggest that aCL may fluctuate significantly during normal pregnancy and there is little clinical value in measuring aCL on a serial basis during pregnancy.

Antiphospholipid antibody binding to bilayer-coated glass microspheres

Thrombosis, recurrent fetal loss, and thrombocytopenia are clinical manifestations associated with circulating antibodies that recognize cardiolipin (CL)- or phosphatidylserine (PS)-dependent antigens. Enzyme-linked immunosorbent assays (ELISAs) are generally used to determine the presence and specificity of antiphospholipid antibodies (aPLs). However, the presentation of the phospholipid antigen in the ELISA assay is unknown. In this study, we determined the specificity of three mouse monoclonal aPLs for phospholipid bilayer membranes. These monoclonal aPLs had been characterized by ELISA to have different specificities for CL and PS and were designated BA3B5C4 (CL+/PS+), 3SB9b (CL-/PS+), and D11A4 (CL+/PS-). Bilayers composed of 0-100% PS or CL in phosphatidylcholine (PC) were formed on the surface of 1.6 microns diameter glass microspheres to permit analysis by flow cytometry. BA3B5C4 and 3SB9b bound specifically to both PS- and CL-containing bilayers, and binding increased with increasing percentage of anionic phospholipid. The threshold for PS-dependent binding was 20 mol% PS for both BA3B5C4 and 3SB9b. For CL-dependent binding, the threshold was below 25 mol% CL for both of these antibodies. Binding to PS-containing bilayers was tested as a function of ionic strength for BA3B5C4 and 3SB9b. The ionic strength dependence of the binding suggested that the intermolecular attractive forces between anti-PS antibodies and PS-containing bilayers are predominantly multiple weak electrostatic bonds. D11A4 bound only to bilayers composed of 100% PS and 100% PC, and this antibody did not bind to CL-containing bilayers. The binding specificities of these aPLs to bilayer membranes suggest that, in this system, the conformation of the epitope involving CL, and perhaps PS, is different from that expressed in the routine clinical ELISA. Two of the monoclonal antibodies reacted in this model system at the low levels of PS typically externalized in the plasma membranes of activated platelets, apoptopic lymphocytes, and senescent red blood cells: thus, these surfaces are plausible candidates for the site of pathologically relevant antibody interactions.

Specific antiphospholipid antibodies (aPL) eluted from placentae of pregnant women with aPL-positive sera

The mechanism by which antiphospholipid antibodies (aPL) cause recurrent pregnancy loss remains unclear. It has however been reported that aPL may affect cytotrophoblasts in vitro and thus direct placental damage might occur. Therefore, we investigated whether aPL are bound directly to placental tissues in patients with immunoglobulin G (IgG)-aPL positive sera. The material investigated comprised the placentae of six patients with a history of recurrent pregnancy loss and subclinical autoimmune disorder and one with systemic lupus erythematosus, who were treated with a combination of prednisolone and aspirin. Normal controls consisted of placentae derived from six women, negative for serum aPL, with no medical or obstetrical complication during their pregnancy. Five kinds of IgG- and IgM-antiphospholipid (anti-PS, PI, PA, PG and CL) antibodies were eluted from the placentae of both patients and controls, which were measured by enzyme-linked immunosorbent assay. IgG-aPL were detected in the placental eluates of four of seven (57%) patients, whereas IgM-aPL were not found in any. With respect to the pregnancy outcome of the four patients with IgG-aPL-positive placental eluates, one experienced intrauterine fetal death (IUFD) at 23 weeks of gestation and three demonstrated intrauterine growth retardation (IUGR). In contrast, the remaining three patients, evaluated negative for IgG-aPL in placental eluates, gave birth to one baby with IUGR and two appropriate-for-date babies. The placentae of the four mothers with IgG-aPL-positive placental eluates pathologically showed severe thrombotic findings. These results suggest that IgG-aPL can directly bind to placental tissue and might cause pathologic damage resulting in IUFD or IUGR.

Monoclonal antiphosphatidylserine antibody reactivity against human first-trimester placental trophoblasts

OBJECTIVE

To investigate the binding of antibodies against negatively charged phospholipids (antiphospholipid antibodies) to human placenta, we tested the reactivity of three mouse monoclonal antiphospholipid antibodies against first-trimester human placenta.

STUDY DESIGN

Formalin-fixed and frozen sections of first-trimester placentas were stained by immunoperoxidase with three mouse monoclonal antibodies. Each monoclonal antibody reacted differently with cardiolipin and phosphatidylserine, 3SB9b reacted with phosphatidylserine, D11A4 reacted with cardiolipin, and BA3B5C4 reacted with both.

RESULTS

3SB9b reacted strongly with the syncytiotrophoblastic layer of both formalin-fixed and frozen placental tissue. Sporadic reactivity was observed against the cytotrophoblastic layer. BA3B5C4 reacted strongly and specifically with cytotrophoblastic cells. D11A4 reacted minimally or, more commonly, not at all.

CONCLUSION

The trophoblastic layer directly in contact with the maternal circulation is most reactive with antiphospholipid antibodies that react with phosphatidylserine rather than cardiolipin, suggesting that the trophoblasts may potentially be directly damaged by antiphospholipid antibodies through mechanisms unrelated to thrombosis. In addition, the differential reactivity of 3SB9b and BA3B5C4 suggests that the antigenic conformation involving phosphatidylserine on the cytotrophoblast is altered concurrent with fusion into the syncytium.

Placental thrombosis and fetal loss after passive transfer of mouse lupus monoclonal or human polyclonal anti-cardiolipin antibodies in pregnant naive BALB/c mice

In the present study we evaluated the effect of passive transfer of a mouse monoclonal (CAM) or a human polyclonal anti-cardiolipin IgG on pregnancy outcome in BALB/c mice. The mice were immunized through the tail vein immediately after mating with 10 micrograms of monoclonal or polyclonal anti-cardiolipin antibodies. Two other groups of mice were given a mouse irrelevant monoclonal antibody or normal human polyclonal IgG respectively, at the same dose. In mice immunized with monoclonal or polyclonal anti-cardiolipin antibody we observed a significant increase in the number of fetal resorptions and a significant reduction of the mean weights of the embryos and the placentas. In mice immunized with CAM we also found a significant decrease in the number of healthy pups, while mice infused with human aCL antibody expressed a significant reduction in the fecundity rate. The histological examination showed widespread thrombosis and necrosis in the placentas derived from the mice immunized with the anti-cardiolipin antibodies. The model supports a possible direct pathogenetic effect of anti-phospholipid antibodies in recurrent fetal loss and points out that thrombotic events at placental level can be instrumental in the pathogenesis of the obstetric complications.

Expression of phosphatidylserine-dependent antigens on the surface of differentiating BeWo human choriocarcinoma cells

PROBLEM

Antiphospholipid antibodies (aPLs) are associated with pregnancy loss, pregnancy-induced hypertension, and intrauterine growth retardation. We have previously reported that phosphatidylserine (PS)-dependent antigens are expressed in formalin-fixed cells concurrent with differentiation in a choriocarcinoma model (BeWo) of cytotrophoblast. That study, however, could not differentiate between cytoplasmic or surface antigen expression.

METHOD

Three monoclonal aPLs that differentiate between PS- and cardiolipin (CL)-dependent antigens were reacted with BeWo, with or without forskolin activation, before fixation, and antibody binding was evaluated by immunoperoxidase techniques.

RESULTS

Activation with forskolin induced a PS-dependent antigenic determinant on the surface on BeWo cells. CL-reactive monoclonal antibodies did not react with the cell surface, whether forskolin treated or not.

CONCLUSION

These observations demonstrate that a PS-dependent antigen is expressed on the surface of a model of differentiating cytotrophoblastic cells and should be accessible in vivo to circulating aPLs.

Monoclonal IgM antiphosphatidylserine antibody reacts against cytoskeleton-like structures in cultured human umbilical cord endothelial cells

PROBLEM

It has been proposed that antibodies against phospholipid-dependent antigens (aPLs), induce recurrent pregnancy loss and thrombosis through modulation of endothelial cell function, yet aPLs have not been conclusively shown to bind with endothelial cells.

METHOD

Using indirect immunofluorescence we investigated the anti-endothelial cell reactivity of three monoclonal antibodies that differentiate between the phospholipids cardiolipin (CL) and phosphatidylserine (PS): BA3B5C4 (CL+/PS+); 3SB9b (CL-/PS+); and D11A4 (CL+/PS-). Cultured umbilical cord endothelial cells were prepared without fixation or with cold acetone fixation.

RESULTS

None of the aPLs reacted with endothelial cells prepared without fixation. 3SB9B reacted strongly with cytoskeletal-like components in acetone-fixed cells, whereas BA3B5C4 and D11A4 were unreactive. The cytoskeletal-like binding of 3SB9b was completely blocked by a monoclonal antibody against vimentin, whereas antibodies against tubulin or actin were not inhibitory. Lipid extraction of the cells destroyed the 3SB9b reactive antigen without affecting the reactivity of anti-vimentin.

CONCLUSION

These results suggest that phospholipid-dependent antigenic determinants are not expressed on the surface of resting endothelial cells but that a PS-dependent antigenic determinant is associated with endothelial cell intermediate filaments.

Incidence of autoimmune antibodies in failed embryo transfer cycles

PROBLEM

The presence of antiphospholipid antibodies lupus anticoagulant (LAC), anticardiolipin antibody (ACA) as well as antinuclear antibody (ANA) has been associated with early spontaneous pregnancy loss and adverse pregnancy outcome. The purpose of this study was to investigate the possible role of autoimmune antibodies (LAC, ACA, and ANA) as a cause of implantation failure following embryo transfer (ET) after in vitro fertilization (IVF).

METHOD

Three groups were studied: Group I, 56 patients who failed to conceive following ET; group II, 14 patients who have conceived following IVF-ET and delivered or are carrying an uncomplicated ongoing pregnancy; and group III, 69 patients who were new candidates for IVF-ET.

RESULTS

Eighteen out of 56 (32.1%) of patients who failed to conceive following previous IVF-ET cycle (group I) tested positive for one or more of the autoimmune antibodies. None of the 14 patients of group II tested positive for autoimmune antibodies (P < .02). Seven out of the 69 patients (10%) of group III were found positive to one or more of the autoimmune factor. This rate is significantly lower than the rate of positive autoimmune antibodies detected in group I (P < .003). Fifteen patients of the 18 who tested positive for autoimmune antibodies and who had previously failed to conceive following ET underwent a subsequent IVF-ET cycle while being treated with prednisone and aspirin. Seven out of the 15 (46.6%) conceived and were able to sustain a clinical ongoing pregnancy.

CONCLUSIONS

Patients receiving ET are carrying viable embryos within the intrauterine environment. Therefore, in this unique group of patients, failure to demonstrate a positive pregnancy test represents an implantation failure or a very early postimplantation loss. The results of this study suggest that periimplantation events may be affected by autoimmune antibodies. Very early miscarriage or implantation failure may be related to the same pathophysiological mechanism that causes recurrent miscarriages and is diagnosed incorrectly as infertility.

Can tests for IgA, IgG, or IgM antibodies to cardiolipin or phosphatidylserine substitute for lupus anticoagulant assays in screening for antiphospholipid antibodies?

Antiphospholipid antibodies (APL) are detected by both ELISA and tests for lupus anticoagulants (LA). We evaluated ELISA tests for IgG, IgM, and IgA isotopes of antibodies binding cardiolipin (CL) and phosphatidylserine (PS) in samples from LA patients presenting with recurrent miscarriages. All values were expressed in multiples of the normal median (MOM). In 32% (11/34) of cases, not only were all ELISA values at or below 2.5 MOM, but the distribution of these ELISA MOM values within the normal range was similar to distribution of values from LA negative controls with the same history. Neither the use of PS as the antigen nor the addition of IgA assays improved the correlation of ELISA results with the presence of LA. ELISAs are inadequate as the sole screening test for these separate, but often associated, families of APL.

Modulation of phosphatidylserine epitope expression by BeWo cells during forskolin treatment

The adenylcyclase activator forskolin induces the human choriocarcinoma line, BeWo, to undergo differentiation and fusion within 48 to 72 h. Using three monoclonal antibodies that differentiate between the anionic phospholipids cardiolipin (CL) and phosphatidylserine (PS) and immunoperoxidase techniques we investigated the expression of PS by BeWo during 48 h of forskolin treatment. We observed that BeWo cells not exposed to forskolin express an epitope of pS that reacts strongly with monoclonal antibody BA3B5C4 (CL+/PS+), whereas following treatment with forskolin there is a decrease in reactivity with BA3B5C4 and a concurrent increased activity with a second PS-reactive monoclonal antibody, 3SB9b (CL-/PS+). A third monoclonal antibody, D11A4 (CL+/PS-), that reacted with all anionic phospholipids except PS did not bind to BeWo cells, whether forskolin treated or not. These observations support previous interpretations using human placenta that during cytotrophoblast differentiation two antigenic forms of PS are expressed. Based on the described relationship of PS with cellular fusion events in other systems and the association of naturally occurring antibodies against PS with pregnancy loss and intrauterine growth retardation in humans, we propose that altered expression of PS during normal placental development and in BeWo after exposure to forskolin may be critical in the cytotrophoblast differentiation process.

Specific antiphospholipid antibodies as a predictive variable in patients with recurrent pregnancy loss

PROBLEM

Antiphospholipid antibodies (APLs) consist of very heterogenous autoantibodies. It has not been fully explored what kind of specificities are most relevant to recurrent pregnancy loss. Thus, we investigated the effects of specific APLs on recurrent aborters.

METHOD

IgG and IgM antibodies against PE (treated with 1% acetic acid) and five negatively-charged phospholipids were measured by ELISA among 334 recurrent aborters without autoimmune disease. The relationships between APL specificities and subsequent pregnancy outcome were prospectively investigated in 38 recurrent aborters with positive APL who did not receive treatment with prednisolone and aspirin. Antibody levels exceeding the 99th percentile of 280 healthy women were considered positive.

RESULTS

Positive IgG and/or IgM APLs were detected in 14%, IgG APLs in 12%, and IgG antibodies against PA, PG, PI, PS, CL and PE, respectively, in 9%, 7%, 7%, 7%, 8%, and 8%. In a prospective study of the 38 untreated patients, fetal loss recurred in 82% of the 33 IgG APL-positive patients, but in 40% of the five patients positive for only IgM APLs. The incidence of fetal loss in the next pregnancy of patients with IgG specific APL-positive against PE, PI, PS, or Cl was even higher at 90% and over, and fetal loss recurred in all of 21 patients with two or more IgG APL-positive against PE, PI, PS, or CL.

CONCLUSION

These results suggest the possibility that two or more IgG APL-positive value against treated PE, PI, PS, or CL, may be more accurate as a predictive variable than that of only one IgG APL-positive in patients with recurrent pregnancy loss.

Monoclonal antiphospholipid antibody reactivity against human placental trophoblast

Naturally occurring antibodies against the negatively charged phospholipids cardiolipin (CL) and phosphatidylserine (PS) have been associated with recurrent pregnancy loss. One prevalent hypothesis proposes that antiphospholipid antibody (aPL) mediated pathophysiology is through increased placental thrombosis. In this study we investigated the reactivity of three mouse monoclonal aPLs with term and 26 week human placental preparations. Each monoclonal antibody reacted differently with CL and PS; 3SB9b reacted with PS (CL-/PS+), D11A4 reacted with CL (CL+/PS-) and BA3B5C4 reacted with both CL and PS (CL+/PS+). 3SB9b reacted strongly with the syncytiotrophoblastic layer of both formalin fixed and frozen placental tissue. Sporadic reactivity was observed against the cytotrophoblastic layer. BA3B5C4 reacted strongly and specifically with cytotrophoblastic cells. D11A4 had only weak reactivity in the subtrophoblastic stromal region of the placenta in frozen sections. aPL staining was also observed against extravillous cytotrophoblast. BA3B5C4 stained cytoplasmic structures, whereas 3SB9b stained the plasma membrane region with little cytoplasmic staining. These data suggest that the trophoblastic layer is reactive with aPLs and may potentially be directly damaged through mechanisms unrelated to thrombosis. In addition, the trophoblastic layer directly in contact with the maternal circulation is most reactive with aPLs that are PS+ rather than CL+. The differential reactivity of 3SB9b and BA3B5C4 suggests that the antigenic conformation involving PS on the cytotrophoblast is altered concurrent with fusion into the syncytium.