Is antipaternal cytotoxic antibody a valid marker in the management of recurrent abortion?

Regulatory T Cells in Pregnancy: It Is Not All About FoxP3

In pregnancy, the semi-allogeneic fetus needs to be tolerated by the mother's immune system. Regulatory T cells (Tregs) play a prominent role in this process. Novel technologies allow for in-depth phenotyping of previously unidentified immune cell subsets, which has resulted in the appreciation of a vast heterogeneity of Treg subsets. Similar to other immunological events, there appears to be great diversity within the Treg population during pregnancy, both at the maternal-fetal interface as in the peripheral blood. Different Treg subsets have distinct phenotypes and various ways of functioning. Furthermore, the frequency of individual Treg subsets varies throughout gestation and is altered in aberrant pregnancies. This suggests that distinct Treg subsets play a role at different time points of gestation and that their role in maintaining healthy pregnancy is crucial, as reflected for instance by their reduced frequency in women with recurrent pregnancy loss. Since pregnancy is essential for the existence of mankind, multiple immune regulatory mechanisms and cell types are likely at play to assure successful pregnancy. Therefore, it is important to understand the complete microenvironment of the decidua, preferably in the context of the whole immune cell repertoire of the pregnant woman. So far, most studies have focused on a single mechanism or cell type, which often is the FoxP3 positive regulatory T cell when studying immune regulation. In this review, we instead focus on the contribution of FoxP3 negative Treg subsets to the decidual microenvironment and their possible role in pregnancy complications. Their phenotype, function, and effect in pregnancy are discussed.

The optimal timing of immunotherapy may improve pregnancy outcome in women with unexplained recurrent pregnancy loss: A perspective follow-up study in northeastern China

PROBLEM

To determine whether patients with unexplained recurrent pregnancy loss (URPL) can benefit from pre-conception immunotherapy or on the early phase of the first trimester.

METHOD OF STUDY

The prospective follow-up study which involved pre-conception patients diagnosed with URPL following rigorous etiology screening in the medical center of recurrent pregnancy loss. In this study, pre-conception immunotherapy included lymphocyte immunotherapy (pre-LIT). Post-conception immunotherapy (post-IM) included LIT or intravenous immunoglobulin (IVIG). Patients were recommended to undergo post-IM immediately from human chorionic gonadotrophin (hCG) elevation. Autoimmune antibodies (AIA) and anti-paternal lymphocytotoxic antibodies (APLA) were tested before and after pre-LIT. Favorable outcome was defined as pregnancy over 14 weeks. Unfavorable outcomes included biochemical pregnancy loss (BPL) and pregnancy loss with clear implantation location (PLCIL).

RESULTS

In this study, URPL accounted for 12.9% of recurrent pregnancy loss (217/1682). Frequency of BPL was significantly lower in patients with post-IM than that without post-IM [2.8% vs 28.2%; adjusted relative risk (aRR), 0.06; 95% confidence interval (CI), 0.01-0.24]. There was a significant positive conversion in the AIA induced by pre-LIT (0.0% vs 31.0%). Frequency of PLCIL in patients with positive iatrogenic AIA conversion induced by pre-LIT was higher than that in patients without AIA conversion [30.4% vs 5.8%; aRR, 7.53; 95% CI, 1.31-43.34].

CONCLUSION

Pre-LIT of patients with URPL contributed to a positive iatrogenic AIA conversion, which was associated with an increased risk of PLCIL. Post-IM immediately initiated from the time of hCG elevation can reduce the incidence of BPL.

Infertility and miscarriage: common pathways in manifestation and management

The relationship between miscarriage and fertility is complex. While most healthcare settings treat miscarriage as a problem of subfertility in assisted reproduction units, others believe that miscarriage occurs in super-fertile women. Infertile women undergoing assisted reproduction are at a greater risk of having a miscarriage especially at an advanced age compared with women conceiving naturally. Aberrant expression of immunological factors and chromosomal abnormalities underlie both infertility and miscarriage. Common risk factors include increased maternal age, obesity, smoking, alcohol, pre-existing medical conditions and anatomical abnormalities of the reproductive system. Management pathways of both conditions may be similar with pre-implantation genetic testing and assisted reproductive technology used in both conditions. This paper discusses the synergies and differences between the two conditions in terms of their epidemiology, etiopathogenesis, risk factors and management strategies. The two conditions are related as degrees of severity of reproductive failure with common pathways in manifestation and management.

Factors influencing success rate of leukocyte immunization and anti-paternal antibodies in spontaneous recurrent miscarriage

PROBLEM

Paternal leukocyte immunotherapy has been used as treatment for spontaneous recurrent miscarriage; however, controversies have raged against the factors influencing its success.

METHODS

Five hundred and forty-nine women with three or more unexplained pregnancy losses were offered immunization. Two weeks after the second immunization, serum was tested for anti-paternal cytotoxic antibody (APCA) by cross matching and if revealed positive she was advised pregnancy. Meanwhile, decision trees have been developed by Waikato Environment for Knowledge Analysis package to predict factors influencing APCA production and pregnancy.

RESULTS

Of 549 subjects, 93 (16.9%) revealed to have positive APCA, among whom 49(52.7%) had clinically successful pregnancy (> or =28 weeks). Patient's age, consanguinity between couples and previous history of surgery, and infectious, endocrine, immunologic, uterine and cervix disorders were inversely associated with APCA production and clinically successful pregnancy, whilst, number of children was a potent positive predictor.

CONCLUSION

Leukocyte immunization could be borne in mind as a therapeutic approach in selected subjects. Younger females with negative past medical history who are not frequent aborters are more likely to take benefit from this therapeutic approach if they do not have any familial relationship with their spouse.

Immunological evaluation of patients with recurrent abortion

In a prospective study, we performed immunological tests in patients with recurrent abortion. Nine couples with two or more fetal losses of no apparent cause were selected as the patient group, and nine volunteer couples with at least two children and without a history of abortion were used as controls. The frequency of major histocompatibility complex (human leukocyte antigens, HLA) antigen sharing was determined by serological methods, antipaternal antibodies by microlymphocytotoxicity, lymphocyte phenotypes (CD4, CD8, CD19, CD16, CD56 and HLA-DR positive cells) by flow cytometry and natural killer (NK) cytotoxicity by (51)Cr release. NK activity was correlated to the degree of HLA-C sharing and to the percentage of CD16+ and CD56+ cells and to progesterone levels measured by radioimmunoassay. No difference in class I or class II HLA antigen sharing was detected between couples with and without recurrent abortion. Antipaternal antibodies were not found in the serum of any woman of the study. A higher absolute number of CD8+ cells (P=0.01) and a trend to increased CD19+ cells (P=0.05) were observed among patients. NK activity did not differ between the two groups when expressed as specific cytotoxicity and it was reduced among patients with recurrent abortion when expressed as lytic units/10(7) cells (P=0.04). There was correlation between NK activity and the percentage of CD16+ and CD56+ cells but not with progesterone levels in patients with recurrent abortion. Our data suggest that an increased NK activity may not play a role in the occurrence of repeated abortion. On the other hand, an increase in circulating CD8+ T cells was observed in patients suggesting that antifetal cytotoxicity in recurrent abortion may be mediated by T cells and not by NK cells.

The prognostic value of anti-paternal antibodies and leukocyte immunizations on the proportion of live births in couples with consecutive recurrent miscarriages

Anti-paternal antibodies directed towards paternal leukocytes have been used to predict the prognosis for the subsequent pregnancy in women with consecutive recurrent miscarriages (CRM) and also to determine if the patient has become immune after paternal leukocyte immunization. The predictive value is controversial, as these antibodies are not essential for pregnancy to develop, and only occur in a minority of parous women. This study tried to determine the predictive value of these antibodies when assessed separately for women with five or more abortions and compared to women with three or four abortions. The patients were assessed separately so that the higher live birth rate in the latter group would not obscure meaningful results in the former group with a poor prognosis. Antibody production, whether spontaneous, or induced by immunization, raised the live birth rate in primary and tertiary aborters with three, four, five or more abortions. Anti-paternal antibodies increased the proportion of live births from 18.5 to 53. 7% (P </= 0.01) and from 44.4 to 67.5% (P </= 0.001) in primary aborters with >/= 5 CRM and 3-4 CRM respectively. Both immunization with paternal leukocytes per se and the ability to express anti-paternal antibodies were associated with an increased proportion of live births in the next pregnancy. Multivariate analysis showed that that the odds ratio for a live birth was approximately four times greater in women who were immunized and produced anti-paternal antibodies than in control patients. The lack of anti-paternal antibodies at initial testing could serve as a marker for the benefit of immunization with paternal leukocytes; the subsequent presence as a prognostic marker for the subsequent pregnancy.

The Structure of the Human Placenta: Implications for Initiating and Defending Against Virus Infections

The architecture of the human placenta permits an extensive and intimate association between the maternal and fetal circulations. The fetal component consists of the elaborately branched villous tree, and this is bathed directly by maternal blood circulating within the intervillous space. Whilst this arrangement may favour metabolic exchange, it poses considerable risks for the vertical transmission of pathogens. Some features of placental structure can be considered potential impediments to transmission, such as the syncytial nature of the outer villous covering, the syncytiotrophoblast, and the ability of this tissue to secrete both nitric oxide and interferons. Other features may facilitate vertical transmission, including the lack of expression of MHC Class 1 antigens by the syncytiotrophoblast, and its vesicular and immunoglobulin transport pathways. More importantly, it is known that physical defects occur in the trophoblast layers at all stages in gestation. Whilst repair processes have been identified it must be assumed that pathogens or infected maternal white cells have access to the trophoblastic basement membrane, albeit transiently. The universal nature of these defects suggests that the trophoblast cannot be of paramount importance in the prevention of transmission. Rather, the defence mechanisms must lie either at the level of the basement membrane or within the villous core. There they may be represented by the resident macrophage population or the capillary endothelial cells and their junctional complexes. Consequently, the placenta should be viewed as an active rather than a passive barrier. Copyright 1997 by John Wiley & Sons, Ltd.

Immunogenetic and serological investigations in nonpregnant and in pregnant women with a history of recurrent spontaneous abortions. German RSA/IVIG Study Group

In the context of a controlled multicenter study on intravenous immunoglobulin (IVIG) treatment of patients with a history of unexplained recurrent spontaneous abortions (RSA), a number of controversial immunological parameters were evaluated prior to and during pregnancy with respect to their diagnostic and/or prognostic significance. A total of 390 serum samples from 52 patients were investigated. Sharing of 2 or more HLA (A, B, DR, DQ) antigens was significantly more frequent in RSA couples than in controls. The rate of cytotoxic or Fc-receptor (FcR)-blocking antibodies was not significantly lower in RSA patients than in individuals with normal pregnancies. Both tumor necrosis factor-alpha (TNF-alpha) levels and IgG anticardiolipin antibodies (IgG-ACA) were significantly increased in the patient group. While the occurrence of HLA sharing, cytotoxic/FcR-blocking antibodies and IgG-ACA did not correlate with the outcome of pregnancy, TNF-alpha levels were found to be significantly higher in patients with subsequent miscarriage than in those with successful pregnancy. IgG-ACA, if present, significantly decreased during the course of successful pregnancy but remained high in patients with subsequent abortion. It is concluded that the diagnostic and/or prognostic value of HLA sharing and cytotoxic/FcR-blocking antibodies has been overestimated while TNF-alpha and ACA levels are potential diagnostic markers and/or exhibit prognostic significance in subgroups of RSA patients.

Cytotoxic cells directed against placental cells detected in human habitual abortions by an in vitro terminal labeling assay

PROBLEM

From the clinical point of view, it has been proposed that an immunological imbalance between the mother and the fetus might exist in one of the mechanisms for human habitual abortion. However, in the definition of habitual abortion, we have no distinct immunological criteria for this clinical entity at the moment.

METHOD

We employed aborted placental cells as the target cells in an in vitro terminal labeling (IVTL) assay system, in which the cytotoxic activity of maternal peripheral blood mononuclear cells (PBMCs) against the placental cell was examined.

RESULTS

Our results showed that the cytotoxic activity of maternal PBMCs was significantly higher in the habitual aborters (the mean target cell destruction: %TCD = 34.9%, N = 14) than that in the women with a normal first trimester (the mean % TCD = 8.9%, N = 14, P < .01). The results from the IVTL assay did not correlate with other assays using paternal lymphocytes as the target cells. The surface marker analyses revealed that CD16+ cells, CD14+ cells, and CD5+ cells were involved in the cytotoxic response against the placental cells in various degrees among the cases.

CONCLUSIONS

The above evidence suggests that a variety of cytotoxic cells participate in the phenomenon of human habitual abortion.

Limiting dilution analysis of the allo-MHC anti-paternal cytotoxic T cell response. I: Normal primigravid and multiparous pregnancies

Anti-paternal cytotoxic T lymphocyte precursor frequencies (CTLpF) were determined by limiting dilution analysis (LDA) in the peripheral blood of eight primigravid and seven multiparous women during the three trimesters of pregnancy. In five of these women the responses to cord blood lymphocytes (CBL) and paternal lymphocytes were also determined at the time of delivery and at 6 weeks post delivery. As controls, CTLpF against unrelated third party donors were determined. A wide range of CTLpF against all three groups of targets was found in both the primigravid and multiparous women, reflecting the wide range of frequencies found in random populations. These frequencies remained fairly constant during and 6 weeks after the pregnancy. Splitwell analysis demonstrated that the responses generated in our culture system were specific to the stimulator. The LDA data conform to single-hit kinetics, indicating that only cytotoxic T cells were limiting in the assay. Proliferative responses of maternal lymphocytes to paternal, cord blood and third party MHC antigens also remained unchanged as determined by time-course mixed lymphocyte reactions (MLR). Our data suggest that there is no significant allo-stimulation or suppression of the maternal immune system during normal pregnancy. The mother remains immunocompetent and is capable of both cytotoxic and proliferative responses to paternally-derived fetal MHC antigens. Our findings confirm that in normal pregnancy the trophoblast, which is devoid of classical MHC antigens, forms an effective immune barrier which prevents interaction of the maternal and fetal immune systems.

Limiting dilution analysis of the allo-MHC anti-paternal cytotoxic T cell response. II: Recurrent spontaneous abortion and the effect of immunotherapy

Using limiting dilution analysis (LDA) we determined anti-paternal cytotoxic T lymphocyte precursor (CTLp) frequencies in the peripheral blood of 10 women with unexplained recurrent spontaneous abortion (RSA) before and after immunization with paternal lymphocytes. The women and their partners were HLA tissue-typed and none of the women had anti-paternal cytotoxic antibodies (APCA) before immunization. All other known causes of RSA were excluded. All 10 women were found to have high frequencies of specific anti-paternal cytotoxic T cells before immunization (range 1/1030 to 1/9574). Splitwell analysis showed that these cytotoxic cells were specific to paternal MHC antigens. These frequencies rose significantly following immunization (range 1/683 to 1/4652). The cytotoxic T lymphocyte frequencies against an HLA-mismatched third party varied from woman to woman, but were not affected by the immunization. The LDA data conformed to single-hit kinetics, indicating that only cytotoxic T cells were limiting in the assay. Our data are in sharp contrast to the previously held view that women with RSA may be hyporesponsive to paternal MHC antigens. Immunizing such women with paternal leucocytes further sensitizes them. These findings cannot be reconciled with a favourable outcome in the treatment of RSA with immunotherapy. We would argue that this treatment is at best of unproven value, and may even be harmful. That these women may sometimes have successful pregnancies following immunotherapy testifies to the effectiveness of the classical MHC antigen-deficient trophoblast as an immunological barrier between mother and fetus.

Characterization of antibodies induced by paternal lymphocyte immunization in couples with recurrent spontaneous abortion

This study was designed to identify and characterize the allo- and autoantibodies induced following successful paternal lymphocyte immunization to prevent recurrent spontaneous abortion. Firstly the titers of maternal anti-paternal antibodies in women with successful pregnancies as determined by the flow cytometry crossmatch (FCXM) were highly variable; however, in all cases, the initial pre-immunization titers were negative and the post-immunization titers were positive by the FCXM in successfully treated women. Secondly, the specificities of maternal alloantibodies to paternal HLA antigens (immunogen) were evaluated. No all predicted antibodies to mismatched paternal HLA antigens were found by microlymphocytotoxicity (MCX) assays and the specificities varied. Thirdly, antibodies in post- but not preimmunization sera reacted with two lymphoid cell lines, SupT1 and SB; in addition, the rise and fall of the titers of these sera with paternal cells seemed to be reflected with the cell lines by the FCXM. Fourthly, autoantibodies to activated lymphocytes were detected and seemed to correlate with successful immunization since women who had another abortion following immunotherapy lacked these autoantibodies. These findings suggest that the antibody response following successful immunotherapy is complex and needs to be studied further to understand the mechanism of this treatment.

Predictors for live birth after unexplained spontaneous abortions: correlations between immunologic test results, obstetric histories, and outcome of next pregnancy without treatment

Our objective was to determine whether results from tests for maternal serum antinuclear antibodies, cytotoxic antibodies to paternal lymphocytes, parental histocompatibility types, and blocking factors for maternal-paternal mixed lymphocyte reactions were predictive of pregnancy outcome without immunologic treatment. Pregnancy outcome data from 95 women with a history of unexplained recurrent spontaneous abortions who underwent immunologic tests at Jefferson Medical College were evaluated with multiple logistic regression analyses. The number of prior spontaneous abortions, history of another relevant diagnosis, parental sharing of one histocompatibility antigen, and maternal age were related to the outcome of the next pregnancy in women given no immunologic treatment (p = 0.05). No significant correlation was found between results from the immunologic tests or other history characteristics evaluated and outcome of the next pregnancy. The immunologic tests evaluated were not clinically useful predictors of pregnancy outcome.

The number of cells used for immunotherapy of repeated spontaneous abortion influences pregnancy outcome

One hundred and sixty-eight women were immunized on a single occasion with paternal mononuclear cells (MNC) for recurrent spontaneous abortion (RSA) and pregnancy outcomes were analysed with respect to the number of MNC given. The study was done in a prospective sequential fashion using all MNC recoverable from a unit of the spouse's blood and both patients and investigators were blinded as to the number of cells injected. Women receiving low and mid-range doses of MNC (58-305 x 10(6) and 308-567 x 10(6), respectively) had a significantly higher pregnancy success rate (57%) than those receiving the high (568-2677 x 10(6)) dose of MNC (41%). In 77 consecutive patients the diameter of the largest immediate skin flare reaction at the site of subcutaneous injection was recorded. No correlation was found between the skin flare response and the number of MNC injected. Our data suggest that a blinded trial of paternal MNC immunization comparing what appears to be optimum numbers of cells (100-550 million) to a low dose inoculum (e.g., 10 million), again noting the sizes of the skin flare reactions, might answer questions about efficacy and placebo effects of immunotherapy for RSA.

The normal fetomaternal immune relationship

The antigenic status of the preimplantation embryo is ill-defined and there are no clearly recognized maternal immune reactions against this early stage of development. Following implantation, the pregnant female shows evidence of immune recognition of her intrauterine allogeneic conceptus. In a proportion of pregnancies, particularly in multiparous women, there are maternal cytotoxic antibodies exhibiting specificity for the paternally inherited HLA antigens of the fetus. When these are undetectable there may be other antibodies that are non-complement fixing and non-cytotoxic or antibodies that are not present as free molecules and incapable of identification in conventional assays. Anti-HLA antibodies pose no threat to the fetus, principally owing to their absorption by the placenta and, very likely, the harmless binding of any that do reach the fetal circulation. No potentially deleterious cytotoxic T lymphocyte generation occurs in most pregnancies. The extent to which this is due to maternal immunoregulatory control processes is not yet established. The fetal trophoblast is able to act as a protective barrier by virtue of unique properties, including a lack of conventional class I and class II HLA molecules, that render it insusceptible to immune attack. The nature and significance of any maternal recognition of non-HLA antigens on trophoblast await elucidation. Maternal immune cell traffic across the placenta occurs only at a very low level, if at all, in normal pregnancy. This may take place to a greater degree in some of the rare instances of fetal graft-versus-host disease, but this is complicated by the associated fetal immunodeficiency. Maternal IgG antibodies are transmitted across the placental trophoblast by receptor-dependent mechanisms to provide immediate protection for the neonate against environmental pathogens. Leakage of fetal erythrocytes, leukocytes and platelets into the maternal circulation can elicit IgG isoantibodies that take advantage of the same mechanisms to gain access to the fetus, with pathological consequences. Autoantibodies in women with various disease states may similarly pass into the fetus but these normally produce only mild and transient effects. The development of the fetal immune system begins at an early stage of gestation. It is competent to respond to intrauterine infections from as early as 12 weeks and has full functional potential at birth. Maternally acquired IgG is available for up to 9 months of life until the infant's own immune system has been adequately primed and activated following first exposure to specific antigens. The normal fetomaternal immune relationship represents a remarkable harmonious association between two genetically disparate individuals.(ABSTRACT TRUNCATED AT 400 WORDS)

Complement regulatory proteins at the feto-maternal interface during human placental development: distribution of CD59 by comparison with membrane cofactor protein (CD46) and decay accelerating factor (CD55)

The complement (C) regulatory proteins decay-accelerating factor (DAF, CD55) and membrane cofactor protein (MCP, CD46), which control C3 convertases, together with CD59, an inhibitor of the membrane attack complex (MAC), were found to be present in the developing human placenta from at least 6 weeks of gestation until term. Immunostaining revealed differences in the distribution of these proteins on the fetally derived trophoblast epithelium, especially in early placentae which contain trophoblast populations of diverse proliferative potential and differentiation status. Expression of all three proteins occurred on the terminally differentiated syncytiotrophoblast epithelium covering chorionic villi and which is in direct contact with maternal blood. CD59 was also expressed on the underlying villous cytotrophoblast cells and on their extra-villous derivatives. These two populations showed differential expression of the C3 convertase regulators. Villous cytotrophoblast cells expressed MCP but were largely devoid of DAF. Proliferation of this population to generate extra-villous cytotrophoblast cell columns was associated with both an increase in DAF expression and a decrease in MCP expression. Throughout placental development, expression of DAF appeared to be lower than that of MCP and CD59 as assessed by solid-phase binding assays on isolated trophoblast membranes. Early placentae were also found to contain both DAF+ and DAF- chorionic villi. Conversely, expression of CD59 appeared comparatively high and transcripts for CD59 were found to be much more abundant than those for DAF in purified trophoblast cells. C regulatory proteins appear to play an important role throughout gestation in protecting the fetally derived human conceptus from maternal C. The differential expression patterns of the proteins on trophoblast may reflect differences in requirement for specific functional activities at different locations within the placenta.

The role of immunization treatment in preventing recurrent abortion

Published reports of controlled studies of immunization treatment in recurrent abortion have not shown any ability of either third-party cells or the husband's cells to prevent further abortions, whereas preliminary results of ongoing studies speak in favor of a beneficial effect of third-party cells. However, the lack of significant differences so far does not prove that immunotherapy in habitual abortion is ineffective, because all of these studies include too few patients in each group to give any conclusive results. Only a mega-trial could evaluate the efficacy and side effects of leukocyte immunotherapy. Such controlled studies are needed to clarify the true benefits, risks, and limitations of immunization treatment in recurrent abortion. Factors such as appropriate inclusion criteria, the time relationship between immunization and the next pregnancy, the number of immunizations required, the cell source and cell doses need to be established. Until this additional information is available this treatment should not be considered routinely indicated. This approach should be restricted to a few centers in order to provide maximal possibilities for collection and evaluation of the data.

Fc receptor blocking antibodies after active immunization for the treatment of recurrent spontaneous abortion

In a prospective study 140 couples who had at least three spontaneous abortions (RSA) were studied for the presence of Fc receptor blocking antibodies detected by the erythrocyte antibody rosette inhibition (EAI) assay, for anti-paternal cytotoxic antibodies (APCA), and for mixed lymphocyte culture inhibiting (MLCI) antibodies before and after active immunization with paternal lymphocytes. The comparative analysis revealed the EAI assay to possess a higher sensitivity than the APCA and/or MLCI tests in monitoring the specific immune response after active immunization. The success of pregnancy in EAI positive post-immunization patients was not influenced by the presence or absence of APCA or MLCI. In the light of a successful pregnancy outcome of 85.7% (n = 37) in this study we conclude that the monitoring of Fc receptor blocking antibodies is useful in active immunization protocols for RSA patients.

Selection of patients with habitual abortion for paternal leucocyte immunization

After potentiation of the immune response in habitual aborters 75-85% of subsequent pregnancies are claimed to result in healthy term infants. However, all publications to date have either been based on the authors concept of the immune processes involved or an attempt to demonstrate the efficacy of treatment either empirically or by matched trials. As immunization is coming into wider clinical use, it is necessary to determine which patients will benefit from this form of treatment. This paper presents our experience with paternal leucocyte immunization over the period 1985-1988. 207 patients were classified on a clinical basis and by immunological testing. 143 patients have been immunised, 129 pregnancies have occurred in 108 patients. The vast majority of our patients have recurrent missed abortions. Only six women habitually aborted live fetuses. Two had subsequent live births. Secondary aborters seem to do well in subsequent pregnancies, whether immunized or not. The patient most likely to benefit from immunization is the Primary missed aborter who does not possess antipaternal antibody (APCA), but is induced to produce APCA by immunization. Using these criteria, 75% success rates are observed in the subsequent pregnancy. This success rate is irrespective of HLA antigen sharing or in-vitro mixed lymphocyte reactivity.

Interpretation of blocking activity in maternal serum depends on the equation used for calculation of mixed lymphocyte culture results

Immunosuppressive blocking factors in maternal serum are usually determined by inhibition of mixed lymphocyte cultures (MLC), but reports on the importance of these factors for successful pregnancy are conflicting. Here we measured serum blocking activity in men, non-pregnant nulliparous women, non-pregnant multiparous women, women with normal pregnancies, and in women who had had recurrent spontaneous abortions and were treated with leucocyte immunizations. Three different equations were used for calculation of blocking activity: blocking effect index (BEI); stimulation index (SI); and blocking index (BI). By all three methods of calculation, significantly lower levels of blocking activity were noted for men and women compared with pregnant women and multiparae. In the patients with a history of recurrent spontaneous abortions blocking activity as determined by BEI and BI increased into the positive range after treatment with infusions of third-party donor leucocytes in a statistically significant number of women (P less than 0.05). However, blocking activity as determined by BEI had a higher predictive value for successful pregnancy than did that determined by BI or SI. Our data suggest that the equation used for calculating BEI is superior to other methods for the determination of blocking activity when monitoring the response to leucocyte immunization in women with recurrent spontaneous abortion. However, these results also cast doubt on the importance of blocking antibodies in histories of recurrent abortion, since pregnancies occurred in the absence and spontaneous abortions occurred in the presence of blocking activity.

The natural course of habitual abortion

In recurrent spontaneous abortion an immunological fetal-maternal imbalance has been postulated and successes of immunotherapy have been described. A prospective study on the reproductive performance of untreated women with three abortions of unknown etiology has not been performed. The benefit of therapy can only be estimated if the natural course of the disease is known. The aim of this study was to investigate prospectively the abortion rate in a well-defined group of women with a history of habitual abortion of unknown etiology and to test the hypothesis that immunologic factors are involved. Fourty-four couples were taken into study. The overall pregnancy rate in the first subsequent pregnancy was 62%. Neither significant increased sharing of Human Leucocyte Antigens (HLA) nor an aberrant mixed lymphocyte reactivity in this group was found when compared to control random matings. The presence or absence of antipaternal antibodies did not correlate with the outcome of the subsequent pregnancy. It is concluded that the prognosis of untreated patients with habitual abortion is favourable and that no aberrant immunologic reactivity could be demonstrated by means of up-to-date diagnostic procedures.

Association of HLA-DR5 with recurrent spontaneous abortion in women treated with paternal leukocytes. Possible subclinical autoimmune disease

The incidence of pregnancy loss is higher in patients with various autoimmune diseases than in the general population. The causes of recurrent spontaneous abortions (RSA) are unknown; however, the presence of antinuclear antibodies and other antibodies in some women with RSA who are otherwise healthy suggests the possibility of underlying autoimmune disease. Because autoimmune diseases are often associated with an increased incidence of certain histocompatibility antigens, we examined the occurrence of specific HLA antigens in patients who had been treated for RSA. We found HLA-DR5 to be significantly overrepresented in the patients with RSA who aborted again after treatment with paternal mononuclear cell immunotherapy, compared with the incidence of this phenotype in a control population. Neither antinuclear antibodies nor antilymphocyte antibodies segregated with DR5. However, DR5+ patients who developed antilymphocyte antibodies after immunotherapy were more likely than all other treated patients to experience subsequent abortion (P less than 0.01). Our findings suggest the possibility of an underlying autoimmune disease in these women.

[Immunologically-induced abortion--diagnosis and therapy]

As etiological factors responsible for repeated miscarriages disturbances of the maternal-fetal immunoregulation are involved. Diagnostic aspects of the immunobiology of abortion and the clinical management of habitual abortion by immunotherapy are discussed.

Pregnancy-maintaining antibodies: workshop report (Giessen, 1988)

To analyse the nature of antibodies which are purported to be essential for the maintenance of normal human pregnancy, six centers participated in a workshop of "blind" tests on 19 allosera. Fc-receptor dependent assays detected antibodies with specificity only for HLA. In addition to cytotoxic antibodies, the Fc-receptor dependent immune phagocytosis inhibition test revealed two non-cytotoxic alloantibodies with HLA specificity. These antibodies had high titers and may, therefore, be essentially non-cytotoxic. Murine monoclonal antibodies to HLA-A, B, C or DR (W6/32 and 2MC3) were used to evaluate the methods. These antibodies inhibited immune rosette formation as well as immune phagocytosis. Diluted to concentrations below the threshold of complement-dependent cytotoxicity, the monoclonal antibodies still inhibited the mixed lymphocyte reaction and the immune phagocytosis. A human monoclonal immunoglobulin M with specificity for monomorphic non-HLA lymphocyte antigens inhibited the mixed lymphocyte reaction. The immune rosette inhibition test exhibited several false positive reactions, e.g. three out of four with a serum that did not contain alloantibodies to blood cells. Non-cytotoxic antibodies were therefore rare in the selected sera of the workshop and they exhibited HLA specificity only. No participant was able to identify pregnancy-maintaining non-HLA-antibodies.

Treatment of recurrent spontaneous abortion by immunization with paternal lymphocytes: correlates with outcome

Previous observations have suggested that defective recognition of fetal alloantigens by the maternal immune system is associated with recurrent pregnancy failure and that this may be prevented by boosting the maternal immune system with paternal or pooled third-party leukocytes. The mechanism whereby this process achieves success is not clear, and accordingly to explore this we immunized 28 couples with recurrent fetal loss with 80 x 10(6) paternal peripheral blood mononuclear leukocytes (PBML) and followed various immunological parameters. The couples studied, in whom 55% achieved a successful pregnancy, showed no increase in sharing of human lymphocyte antigen (HLA)-A, -B, or -DR antigens and no consistent evidence of a decreased mixed leukocyte reaction (MLR) or MLR plasma-blocking factors compared with control couples. Immunization did not alter these parameters but did induce antipaternal lymphocytotoxins, although the presence of the latter did not correlate with pregnancy outcome. There was a correlation between rapid conception after immunization and a subsequent successful pregnancy. A successful pregnancy also correlated with sustained postimmunization, postconception maternal antipaternal allospecific CD-8+ suppressor T cells. Although these findings provide overall evidence that immunization produces changes in the way in which the maternal immune system interacts with the fetus, larger numbers of couples and a higher dose of paternal lymphocytes will be needed to establish clearly whether this therapy works and its mechanism of action.

Maternal immune responses to the fetus in early pregnancy and recurrent miscarriage

Direct evidence that maternal immune rejection of the fetus causes some unexplained recurrent spontaneous abortions was sought in 18 women with this condition. Tests of maternal cell-mediated immunity to fetal (paternal) antigens were done before conception, in early pregnancy, and at miscarriage, and were compared with those in 10 controls in their first pregnancies. Maternal cytotoxic alloantibody production and the blocking effect of maternal sera on maternal lymphocyte activation were also evaluated. There was no evidence for maternal cell-mediated reactivity to paternal antigens in normal early pregnancy or in most women who aborted, but circulating cytotoxic cells were found at miscarriage in a third of affected women. There was no correlation between the production of cytotoxic antibodies and serum blocking activity, and the success of the pregnancy. These data provide evidence that cell-mediated immune reactivity may be changed in some women who abort recurrently but show that circulating immunological blocking factors are not relevant to the success of pregnancy. Their induction by maternal immunisation with paternal leucocytes does not explain why this procedure prevents recurrent spontaneous abortions.

Immunological studies in recurrent spontaneous abortion: effects of immunization of women with paternal mononuclear cells on lymphocytotoxic and mixed lymphocyte reaction blocking antibodies and correlation with sharing of HLA and pregnancy outcome

The occurrence of maternal antipaternal lymphocytotoxic antibody (LCTA), mixed lymphocyte reaction blocking factors (MLRBF) and human leukocyte antigen (HLA) antigen sharing was studied in 115 couples with unexplained repeated spontaneous abortions (RSA). Comparisons were made to the same studies done on 41 couples with explained repeated miscarriages. We found no significant difference between the patient and control group with respect to the percent of couples sharing none, one, or two or more HLA-A,-B, or -DR antigens. Examination of the occurrence of LCTA and MLRBF likewise did not reveal differences between the groups, nor did the occurrence of these antibodies on initial testing correlate with HLA disparity between couples. Women with three or more spontaneous abortions were immunized with paternal mononuclear cells (MNC) if they met at least two of the following three criteria: they shared two or more HLA antigens; their serum was negative for paternal MNC-directed LCTA; their serum did not contain maternal versus paternal MLR blocking factors. Complete HLA, LCTA and MLRBF data pre- and post-treatment are available on 60 women. Sixty-three percent of women converted to LCTA positive 6 +/- 1 weeks after immunization, and 35% of women converted from negative to positive for MLR blocking after immunization. Fifty-eight women who had all three tests done prior to immunization became pregnant after immunization. Only 50% of this selected group have experienced successful pregnancy as judged by delivery of a live-born infant. In the patients presented, successful pregnancy outcome did not correlate with HLA antigen disparity, but successful patients were more likely than aborters to have either LCTA or MLRBF prior to pregnancy (28 vs. 7%). Post-immunization conversion to LCTA positive was more prevalent in the women who aborted after immunization (74%) compared to those who had successful pregnancy (48%) while MLR blocking antibody conversion from negative to positive was the same in both groups. The data indicate that neither HLA antigen sharing nor conversion to LCTA or MLR blocking positive after paternal WBC immunization are predictors for successful pregnancy outcome. Results so far suggest that conversion to LCTA positive after immunization may have a negative influence on pregnancy outcome.