Immunological mechanisms of pregnancy maintenance and failure: a critique of theories and therapy

Specific innate immune cells uptake fetal antigen and display homeostatic phenotypes in the maternal circulation

Pregnancy represents a period when the mother undergoes significant immunological changes to promote tolerance of the fetal semi-allograft. Such tolerance results from the exposure of the maternal immune system to fetal antigens (Ags), a process that has been widely investigated at the maternal-fetal interface and in the adjacent draining lymph nodes. However, the peripheral mechanisms of maternal-fetal crosstalk are poorly understood. Herein, we hypothesized that specific innate immune cells interact with fetal Ags in the maternal circulation. To test this hypothesis, a mouse model was utilized in which transgenic male mice expressing the chicken ovalbumin (OVA) Ag under the beta-actin promoter were allogeneically mated with wild-type females to allow for tracking of the fetal Ag. Fetal Ag-carrying Ly6G+ and F4/80+ cells were identified in the maternal circulation, where they were more abundant in the second half of pregnancy. Such innate immune cells displayed unique phenotypes: while Ly6G+ cells expressed high levels of MHC-II and CD80 together with low levels of pro-inflammatory cytokines, F4/80+ cells up-regulated the expression of CD86 as well as the anti-inflammatory cytokines IL-10 and TGF-β. In vitro studies using allogeneic GFP+ placental particles revealed that maternal peripheral Ly6G+ and F4/80+ cells phagocytose fetal Ags in mid and late murine pregnancy. Importantly, cytotrophoblast-derived particles were also engulfed in vitro by CD15+ and CD14+ cells from women in the second and third trimester, providing translational evidence that this process also occurs in humans. Collectively, this study demonstrates novel interactions between specific maternal circulating innate immune cells and fetal Ags, thereby shedding light on the systemic mechanisms of maternal-fetal crosstalk.

Antinuclear antibodies positivity is a risk factor of recurrent pregnancy loss: A meta-analysis

OBJECTIVE

Immunologic mechanisms have been proposed as part of the pathogenesis mechanisms involved in recurrent pregnancy loss (RPL). Presence of positive antinuclear antibodies (ANA) is regarded as a typical feature of autoimmunity. Many studies had tried to clarify the association of ANA with RPL, but the conclusions were controversial. The aim of this meta-analysis was to assess whether ANA was positively associated with increased RPL risk.

METHODS

We searched PubMed and Embase databases for relevant literatures on the association between ANA positivity and RPL. The odds ratios (OR) with 95% confidence intervals (95%CI) were pooled using meta-analysis, and either fixed-effect or random-effect model was used based on heterogeneity across the included studies.

RESULTS

Twenty-one studies with 5038 participants (including 2683 RPL patients and 2355 controls) met the inclusion criteria were included. The total positive rate of ANA was 22.0% (591/2683) in RPL group, and 8.3% (196/2355) in the control group. RPL patients had a significantly higher ANA positive rate than controls (OR = 2.97, 95%CI 1.91-4.64, P<0.00001; I² = 75%), and a significant association between positive ANA and unexplained RPL was also observed (OR = 3.27, 95%CI 2.01-5.31, P<0.00001; I² = 70%). ANA positivity was also significantly associated with increased risk of RPL in women without defined autoimmune diseases (OR = 2.23, 95%CI 1.40-3.55, P=0.0007). Subgroup analysis demonstrated low titers of ANA (1:40≤ANA≤1: 80) were not associated with RPL (OR = 2.44, 95%CI 0.42-14.06, P=0.32), while higher ANA titer (≥1:160) had a significant association with RPL (OR = 45.89, 95%CI 8.44-249.45, P<0.00001). A higher rate of homogenous pattern in RPL patients was observed (OR = 4.89, 95%CI 2.20-10.87, P<0.001), and no significant difference in speckled pattern or nucleolar pattern was found.

CONCLUSIONS

This study demonstrated that ANA positivity was positively associated with increased RPL risk. ANA positivity is an important risk factor for RPL which needed to be screened among women with RPL.

The role of immunotherapy in in vitro fertilization: a guideline

Adjuvant immunotherapy treatments in in vitro fertilization (IVF) aim to improve the outcome of assisted reproductive technology (ART) in both the general ART population as well as subgroups such as patients with recurrent miscarriage or implantation failure. The purpose of this guideline is to evaluate the role of immunomodulating therapy in ART. Unfortunately, many of the evaluated therapies lack robust evidence from well-designed adequately powered randomized controlled trials to support their use. Immunotherapies reviewed in the present document are either not associated with improved live-birth outcome in IVF or have been insufficiently studied to make definitive recommendations.

Does the presence of autoantibodies without autoimmune diseases and hereditary thrombophilia have an effect on recurrent pregnancy loss?

OBJECTIVE

To assess whether the presence of autoantibodies has any effect on recurrent pregnancy loss (RPL) and obstetric complications in women who do not have autoimmune diseases and hereditary thrombophilia.

METHODS

Retrospectively, 515 patients who underwent antibody investigation with anti-nuclear antibody, extractable nuclear antigen, anti-double stranded DNA, anti-parietal cell, anti-smooth muscle, anti-mitochondrial (AMA), anti-thyroid peroxidase, anti-thyroglobulin (anti-TG) and anti-phospholipid (aPL) at Hacettepe University were included. Of those patients, 212 had one or more autoantibodies whereas the remaining 303 were negative for all autoantibodies. RPL was the primary outcome and was defined as ≥2 pregnancy losses (n = 119).

RESULTS

The frequency of RPL was significantly higher in the autoantibody positive group than controls (28.3% versus 14.5%, p<0.001). Anti-TG (21.2% versus 7.8%, p < 0.001), aPL (18.3% versus 5.6%, p < 0.001) and AMA (4.8% versus 0.5%, p = 0.001) antibodies were more common in patients with RPL. For the view of obstetric complications, oligohydramniosis (3.8% versus 0.7%, p = 0.03) and stillbirth (17.0% versus 10.6%, p = 0.002) were significantly higher in the autoantibody-positive group.

CONCLUSIONS

Even in women without autoimmune disease or hereditary thrombophilia, autoantibodies per se might directly increase the risk of RPL and obstetric complications. The screening anti-TG and aPL autoantibodies in the first step might be considered in patients with RPL.

Immunotherapy for recurrent miscarriage

BACKGROUND

Because immunological aberrations might be the cause of miscarriage in some women, several immunotherapies have been used to treat women with otherwise unexplained recurrent pregnancy loss.

OBJECTIVES

The objective of this review was to assess the effects of any immunotherapy, including paternal leukocyte immunization and intravenous immunoglobulin on the live birth rate in women with previous unexplained recurrent miscarriages.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (11 February 2014) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomized trials of immunotherapies used to treat women with three or more prior miscarriages and no more than one live birth after, in whom all recognized non-immunologic causes of recurrent miscarriage had been ruled out and no simultaneous treatment was given.

DATA COLLECTION AND ANALYSIS

The review author and the two co-authors independently extracted data and assessed study quality for all studies considered for this review.

MAIN RESULTS

Twenty trials of high quality were included. The various forms of immunotherapy did not show significant differences between treatment and control groups in terms of subsequent live births: paternal cell immunization (12 trials, 641 women), Peto odds ratio (Peto OR) 1.23, 95% confidence interval (CI) 0.89 to 1.70; third-party donor cell immunization (three trials, 156 women), Peto OR 1.39, 95% CI 0.68 to 2.82; trophoblast membrane infusion (one trial, 37 women), Peto OR 0.40, 95% CI 0.11 to 1.45; or intravenous immunoglobulin, (eight trials, 303 women), Peto OR 0.98, 95% CI 0.61 to 1.58.

AUTHORS' CONCLUSIONS

Paternal cell immunization, third-party donor leukocytes, trophoblast membranes, and intravenous immunoglobulin provide no significant beneficial effect over placebo in improving the live birth rate.

Peri-implantation glucocorticoid administration for assisted reproductive technology cycles

BACKGROUND

In order to improve embryo implantation for in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) cycles the use of glucocorticoids has been advocated. It has been proposed that glucocorticoids may improve the intrauterine environment by acting as immunomodulators to reduce the uterine natural killer (NK) cell count and normalise the cytokine expression profile in the endometrium and by suppression of endometrial inflammation.

OBJECTIVES

To investigate whether the administration of glucocorticoids around the time of implantation improved clinical outcomes in subfertile women undergoing IVF or ICSI when compared to no glucocorticoid administration.

SEARCH METHODS

The Cochrane Menstrual Disorders and Subfertility Group Trials Register (September 2011), the Cochrane Central Register of Controlled Trials (CENTRAL) (September 2011), MEDLINE (1966 to September 2011), EMBASE (1976 to September 2011), CINAHL (1982 to September 2011) and Science Direct (1966 to September 2011) were searched. Reference lists of relevant articles and relevant conference proceedings were handsearched.

SELECTION CRITERIA

All randomised controlled trials (RCTs) addressing the research question were included.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed eligibility and quality of trials and extracted relevant data.

MAIN RESULTS

Fourteen studies (involving 1879 couples) were included. Three studies reported live birth rate and these did not identify a significant difference after pooling the (preliminary) results (OR 1.21, 95% CI 0.67 to 2.19). With regard to pregnancy rates, there was also no evidence that glucocorticoids improved clinical outcome (13 RCTs; OR 1.16, 95% CI 0.94 to 1.44). However, a subgroup analysis of 650 women undergoing IVF (6 RCTs) revealed a significantly higher pregnancy rate for women using glucocorticoids (OR 1.50, 95% CI 1.05 to 2.13). There were no significant differences in adverse events, but these were poorly and inconsistently reported.

AUTHORS' CONCLUSIONS

Overall, there was no clear evidence that administration of peri-implantation glucocorticoids in ART cycles significantly improved the clinical outcome. The use of glucocorticoids in a subgroup of women undergoing IVF (rather than ICSI) was associated with an improvement in pregnancy rates of borderline statistical significance and should be interpreted with care. These findings were limited to the routine use of glucocorticoids and cannot be extrapolated to women with autoantibodies, unexplained infertility or recurrent implantation failure. Further well designed randomised studies are required to elucidate the possible role of this therapy in well defined patient groups.

Pregnancy immunology

Immunology is a fast developing and intriguing biomedical science, which can give rise to specific considerations about the physiological process of both successful and unsuccessful vivparous pregnancy. It is normal in clinical organ transplantation for unmatched foreign tissues (allografts) to provoke immunological rejection by the host, unless there has been prior tissue matching (histocompatibility antigen tissue typing) or immunosuppressive therapy. Thus, it is still not fully clear how, after ‘random’ mating, haplo-nonidentical fetal tissue is able to survive in the potentially hostile immunocompetent maternal environment. The majority of pregnancies survive uninterrupted and there has now been much speculation and research regarding the immunological success of pregnancy (i.e. nature’s transplant). Medawar orginally offered four nonexclusive hypotheses to explain the enigmatic immunological survival of normal pregnancy:

1) the conceptus is not immunogenic and therefore does not evoke an immunological response;

2) pregnancy alters the maternal immune response;

3) the uterus is an immunologically privileged site;

4) the placenta is an immunological barrier between the mother and the as yet immunologically incompetent fetus.

Before discussing these, as well as some of the clinical immunological problems that may arise during pregnancy, it is necessary to outline some of the basic components of the normal immune system. This will lead to a description of current understanding of immunological events at the fetomaternal interface as well as the maternal immune response in human pregnancy.

Peri-implantation glucocorticoid administration for assisted reproductive technology cycles

BACKGROUND

In order to improve embryo implantation in in-vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) cycles, the use of glucocorticoids has been advocated. It has been proposed that glucocorticoids may improve the intra-uterine environment by acting as immuno modulators to reduce the uterine NK cell count, normalise the cytokine expression profile in the endometrium and by suppression of endometrial inflammation.

OBJECTIVES

To investigate whether the administration of glucocorticoids around the time of implantation improves clinical outcomes in subfertile women undergoing IVF or ICSI, compared to no glucocorticoid administration.

SEARCH STRATEGY

The Cochrane Menstrual Disorders and Subfertility Group's trials register (February 2006), the Cochrane Central Register of Controlled Trials (Cochrane Library Issue 2, 2006), MEDLINE (1966 to June 2006), EMBASE (1976 to June 2006), CINAHL (1982 to June 2006) and Science Direct (1966 to June 2006) were searched. Reference lists of relevant articles and relevant conference proceedings were also hand searched.

SELECTION CRITERIA

All randomised controlled trials (RCTs) addressing the research question were included.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed eligibility and quality of trials and extracted relevant data.

MAIN RESULTS

Thirteen studies (1759 couples) were included. Three studies reported live birth rate and these did not identify a significant difference after pooling the (preliminary) results (OR 1.21, 95% CI 0.67 to 2.19). With regard to pregnancy rates, there was also no evidence that glucocorticoids improved clinical outcome (13 RCTs; OR 1.16, 95% CI 0.94 to 1.44). However, a subgroup analysis of 650 women undergoing IVF (6 RCTs) revealed a significantly higher pregnancy rate for women using glucocorticoids (OR 1.50, 95% CI 1.05 to 2.13). There were no significant differences in adverse events, but these were poorly and inconsistently reported.

AUTHORS' CONCLUSIONS

Overall, there is no clear evidence that administration of peri-implantation glucocorticoids in ART cycles significantly improves clinical outcome. The use of glucocorticoids in women undergoing IVF (rather than ICSI) was associated with an improvement in pregnancy rates of borderline statistical significance. These findings are limited to the routine use of glucocorticoids and cannot be extrapolated to women with auto-antibodies, unexplained infertility or recurrent implantation failure. Further well designed randomised studies are required to elucidate the possible role of this therapy in well defined patient groups.

Autoantibodies in Argentine women with recurrent pregnancy loss

PROBLEM

To determine the presence or absence of subclinical autoimmunity in Caucasian Argentine healthy women with first trimester recurrent pregnancy loss (RPL), the sera of 118 healthy women with a history of three or more consecutive abortions and 125 fertile control women without abortions and two children were analyzed for the presence of autoantibodies: immunoglobulin (Ig)G and IgM anticardiolipin, antinuclear (ANA), antismooth muscle (ASMA), antimitocondrial (AMA), antiliver-kidney-microsomal fraction (LKM), antigastric parietal cells (GPC), antineutrophil cytoplasmatic (ANCA) and antibodies antigliadin type IgA and IgG and IgA antitransglutaminase related with celiac disease (CD).

METHOD OF STUDY

ANA, ASMA, AMA, anti-LKM, antibodies to GPC and ANCA were determined by indirect immunofluorescence (IFI) and anticardiolipin, antigliadina and antitransglutaminase antibodies were measured by enzyme-linked immunosorbent assays (ELISA).

RESULTS

There was no significant difference between controls and patients with ANA, ASMA, AMA, LKM, ANCA and GPC. The prevalence of anticardiolipin antibodies in RPL was significantly higher than controls (P < 0,01) and the prevalence of positive antibodies for antigliadina type IgA and IgG and IgA antitransglutaminase in RPL was significantly higher than controls (P < 0.04).

CONCLUSION

We show that Caucasian Argentine women with RPL showed significantly higher incidence of anticardiolipin antibodies than normal controls and finally we recommended the screening of IgA and IgG antigliadina and IgA antitransglutaminase antibodies in pregnancy, because of the high prevalence of subclinical CD in RPL and the chance of reversibility through consumption of a gluten free diet.

Immunotherapy for recurrent miscarriage

BACKGROUND

Because immunological aberrations might be the cause of miscarriage in some women, several immunotherapies have been used to treat women with otherwise unexplained recurrent pregnancy loss.

OBJECTIVES

The objective of this review was to assess the effects of any immunotherapy, including paternal leukocyte immunization and intravenous immune globulin on the live birth rate in women with previous unexplained recurrent miscarriages.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group Trials Register (December 2005), the Cochrane Central Register of Controlled Trials (The Cochrane Library 2004, Issue 3), MEDLINE (1966 to September 2004) and EMBASE (1980 to September 2004).

SELECTION CRITERIA

Randomized trials of immunotherapies used to treat women with three or more prior miscarriages and no more than one live birth after, in whom all recognised non-immunologic causes of recurrent miscarriage had been ruled out and no simultaneous treatment was given.

DATA COLLECTION AND ANALYSIS

The review author and the two co-authors independently extracted data and assessed study quality for all studies considered for this review.

MAIN RESULTS

Twenty trials of high quality were included. The various forms of immunotherapy did not show significant differences between treatment and control groups in terms of subsequent live births: paternal cell immunization (12 trials, 641 women), Peto odds ratio (Peto OR) 1.23, 95% confidence interval (CI) 0.89 to 1.70; third party donor cell immunization (three trials, 156 women), Peto OR 1.39, 95% CI 0.68 to 2.82; trophoblast membrane infusion (one trial, 37 women), Peto OR 0.40, 95% CI 0.11 to 1.45; intravenous immune globulin, Peto OR 0.98, 95% CI 0.61 to 1.58.

AUTHORS' CONCLUSIONS

Paternal cell immunization, third party donor leukocytes, trophoblast membranes, and intravenous immune globulin provide no significant beneficial effect over placebo in improving the live birth rate.

Evidence-based care of recurrent miscarriage

Between 0.5 and 1.0% of couples experience recurrent pregnancy loss (RPL), which is defined as three or more consecutive miscarriages. Losses are classified as pre-embryonic (<5 weeks), embryonic (5-10 weeks) or fetal (>10 weeks). Genetic abnormalities are responsible for RPL in 2-4% of these couples. Inadequate progesterone production has been proposed a cause of RPL and progesterone is given to prevent miscarriage, despite a lack of supportive evidence. The factor V Leiden and prothrombin G20210A mutations are common inherited thrombophilias also associated with RPL. Antenatal thromboprophylaxis is sometimes recommended although no data exist regarding efficacy. Antiphospholipid syndrome is known to cause RPL and antenatal thromboprophylaxis reduces the risk of miscarriage. Uterine abnormalities might also result in RPL. About 50% of cases of RPL have no identifiable cause. Alloimmune incompatibility has been proposed as a cause for RPL in these women. The concept of alloimmune-related RPL has not been scientifically validated.

Placental glycosylation in peccary species and its relation to that of swine and dromedary

Comparison has been made between glycans at the fetomaternal interface of two Tayassu species (New World peccaries or wild pigs) and those of swine (true pigs) and dromedary, which have similar epitheliochorial placentae. Plastic sections of near-term fetomaternal interface from Tayassu tajacu (120 days gestation) and Tayassu pecari (140 days gestation) were stained with 20 lectins and compared with those of swine (109 days) and dromedary (375 days). Both Tayassu species showed similar staining characteristics, which differed only slightly from those of the swine. Most differences were quantitative rather than qualitative, except for binding of Arachis hypogaea lectin to terminal beta-galactose which was absent in swine uterine epithelium though present in both Tayassu species, and binding of Sambucus nigra lectin to sialic acid which was absent in swine epithelium and trophoblast though present in Tayassu. Glycosylation of the dromedary fetomaternal interface showed, in contrast, significant differences compared to Tayassu and swine, particularly regarding fucosyl, sialyl and terminal galactosyl residues. Despite a divergence of between 33 million and 37 million years between true pigs and peccaries, glycosylation of the fetomaternal interface has remained similar, with most of the observed changes affecting terminal structures. The dromedary has an epitheliochorial placenta with a similar architecture, but different glycan expression, suggesting modification of glycosyl transferases with evolution. These data contain clues to changes of glycosyl transferase activity that accompany speciation.

Female multiple mating behaviour, early reproductive failure and litter size variation in mammals

Female promiscuity is widespread among mammals, although its function is poorly understood. Recently, much interest has been generated by the hypothesis that female promiscuity, combined with post-copulatory paternity-biasing mechanisms, may function to reduce the costs of reproductive failure resulting from genetic incompatibility. Here, a comparative approach is used to determine if average rates of reproductive failure differ for polytocous mammal species with contrasting levels of female multiple-mating behaviour. After control for phylogeny, promiscuous species were found to have significantly lower rates of early reproductive failure than monogamous and polygynous species, in which females are relatively monandrous. Monandrous females appear to compensate for higher early reproductive failure with increased ova production, and thus produce comparable average litter sizes to those of more promiscuous females. However, there is significantly more variation around the average litter sizes produced by relatively monandrous females. These findings are broadly consistent with predictions of the genetic incompatibility avoidance hypothesis, although it is emphasized that alternative explanations cannot be ruled out on the basis of the comparative evidence presented. Further studies are needed to explore ecological correlates of multiple-mating behaviour, to investigate potential post-copulatory paternity-biasing mechanisms, and to identify the causes of reproductive failure in natural mammal populations.

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.

Immunotherapy for recurrent miscarriage

BACKGROUND

Immunologic aberrations might be the cause of recurrent early pregnancy loss in some women.

OBJECTIVES

The objective of this review was to assess the effects of leukocyte immunisation or other immunologic treatments such as intravenous immune globulin (IVIG) on the live birth rate in women with previous unexplained recurrent miscarriages.

SEARCH STRATEGY

The Cochrane Pregnancy and Childbirth Group trials register was searched (September 2002). Individual patient data were obtained from the American Society for Reproductive Immunology.

SELECTION CRITERIA

Randomised trials of immunotherapy in women with three or more prior miscarriages and no more than one live birth; all recognised non-immunologic causes ruled out and no simultaneous treatment intervention.

DATA COLLECTION AND ANALYSIS

Eligibility and trial quality were assessed by one reviewer.

MAIN RESULTS

Nineteen trials of high quality were included. The various forms of immunotherapy did not show significant differences between treatment and control groups in terms of subsequent live births: paternal cell immunisation (11 trials, 596 women), odds ratio (OR) 1.05, 95% confidence intervals (CI) 0.75 to 1.47; third party donor cell immunization (3 trials, 156 women), OR 1.39, 95% CI 0.68 to 2.82; trophoblast membrane infusion (1 trial, 37 women), OR 0.40, 95% CI 0.11 to 1.45; intravenous immune globulin (IVIG), OR 0.98, 95% CI 0.61 to 1.58.

REVIEWER'S CONCLUSIONS

Paternal cell immunization, third party donor leukocytes, trophoblast membranes, and intravenous immune globulin provide no significant beneficial effect over placebo in preventing further miscarriages.

Low dose prednisolone administration in routine ICSI patients does not improve pregnancy and implantation rates

BACKGROUND

Glucocorticoids have been used in conjunction with zona dissection to improve pregnancy and implantation rates in IVF patients. The aim of this prospective randomized study was to evaluate the effect of low-dose prednisolone in addition to the standard protocol, on pregnancy and implantation rates in routine ICSI patients before and after embryo replacement.

METHODS

A total of 313 patients in 360 consecutive cycles (patients <39 years old and with three or less than three ICSI attempts) performed at our centre were randomly assigned by computer-generated list to receive either prednisolone (10 mg/day in two divided doses), starting on the first day of ovarian stimulation and continuing for 4 weeks (group A), or no treatment (group B).

RESULTS

The mean age, number of previously failed IVF attempts, basal FSH levels and the mean rank of trials were comparable between groups A and B. The mean (+/- SD) number of metaphase II oocytes retrieved (11.9 +/- 5.5 versus 12.0 +/- 5.1), 2-pronuclei fertilization rate (67.2 versus 65.8%), the pregnancy and the implantation rates were not different between the study and control groups (49.0 and 23.6% versus 50.0 and 23.3% respectively).

CONCLUSION

Low-dose prednisolone treatment in addition to the standard protocol before and after embryo replacement does not appear to have a significant effect on pregnancy or implantation rates.

Cytokine production by maternal lymphocytes during normal human pregnancy and in unexplained recurrent spontaneous abortion

It has been proposed that successful pregnancy is a T helper 2-type phenomenon, and that T helper (Th)1-type reactivity is deleterious to pregnancy. The objective of this study was to compare the concentrations of Th1 and Th2 cytokines produced by peripheral blood mononuclear cells from women undergoing unexplained recurrent spontaneous abortion (RSA) with those produced during normal pregnancy at a similar gestational stage. The control group consisted of 24 women with a history of successful pregnancies and the abortion group comprised of 23 women with a history of unexplained RSA. Blood from the control group was obtained at the end of the first trimester as gestational age controls for the abortion group from whom blood was collected at the time of abortion. Phytohaemagglutinin-stimulated peripheral blood cell culture supernatants were analysed for concentrations of cytokines. Significantly higher concentrations of Th2 cytokines were produced by the first trimester normal group than by the RSA group, while significantly higher concentrations of Th1 cytokines were produced by the abortion group as compared to first trimester normal pregnancy, indicating a distinct Th2-bias in normal pregnancy and a Th1-bias in unexplained RSA.

Paradoxical behavior of asymmetric IgG antibodies

Changes in the quantity and quality of antibodies occur in the course of an immune response. This review describes the physicochemical and biological properties of asymmetric antibodies as well as their functions, beneficial or harmful to the host, according to the nature of the antigen and the particular situation in which they act. Asymmetric antibodies have two paratopes, one of high affinity, with K0 similar to that of symmetric antibodies, and the other one with an affinity for the antigen 100 times lower. Functional univalence is due to steric hindrance present in one of the paratopes by the carbohydrate moiety attached to the Fd fragment of the Fab region, so these antibodies are unable to form large antibody-antigen complexes and cannot trigger reactions, such as complement fixation, phagocytic activity and antigen clearance. When asymmetric IgG antibodies are specific for self-antigens, they prove beneficial for the host by exerting regulatory functions. In allergic manifestations, in autoimmune diseases and especially during pregnancy, despite the fact that the antigens responsible for the process are foreign to the host, they also perform beneficial activity. During pregnancy, the placenta secretes molecules or factors that regulate the synthesis of these antibodies, thus favoring fetal protection.

Proliferative responses to recall antigens are associated with pregnancy outcome in women with a history of recurrent spontaneous abortion

Maternal tolerance of the fetal hemiallograft suggests that immunomodulation occurs during gestation. Therefore, recurrent spontaneous abortion (RSA) may represent a failure of the immune changes that maintain pregnancy. We hypothesized that fertile women but not women with RSA may lose their immune responses to recall antigens when pregnant. This phenomenon has been seen in immunosuppressed transplant recipients and is associated with graft survival. Therefore, we evaluated proliferative responses to recall antigens in four groups of women: group 1, nonpregnant fertile women with no history of pregnancy loss and at least one prior healthy pregnancy, n = 13; group 2, nonpregnant women with a history of three or more spontaneous abortions, n = 28; group 3, healthy pregnant women between 6 and 9 wk of gestation without a history of prior pregnancy loss, n = 15; and group 4, pregnant women between 6 and 9 wk of gestation, with a history of RSA, n = 22. Proliferative responses of peripheral blood leukocytes to the recall antigens influenza and tetanus, alloantigens, and phytohemagglutinin were determined prospectively. Positive responses (stimulation index > 3) to recall antigens (a response to either influenza or tetanus was considered positive) were as follows: group 1 (nonpregnant fertile women), 11/13 (85%); group 2 (nonpregnant RSA women), 24/28 (86%); group 3 (pregnant fertile women), 4/15 (27%) (P </= 0.007); and group 4 (pregnant RSA women), 13/22 (59%) (P = 0.032) [corrected]. In group 4, there was 100% fetal survival in the nine women who lost responsiveness to recall antigens; however, in the 13/22 patients who responded to recall antigens, 9/13 (69%) had a repeat spontaneous abortion. These findings suggest that immunosuppression, indirectly measured by proliferation to recall antigens, is necessary for early pregnancy maintenance. Furthermore, this approach may be useful for predicting pregnancy outcome for women with RSA and may provide a useful means for designing and monitoring therapies.

Suppressed cell-mediated immunity and monocyte and natural killer cell activity following allogeneic immunization of women with spontaneous recurrent abortion

Spontaneous recurrent abortion (SRA) has been treated by means of immunization with paternal or third-party white blood cells, yet the immunological basis for SRA and for the role of immunization protocols in pregnancy outcome remains controversial. To elucidate this question, nine women with SRA were immunized with paternal mononuclear cells and studied before and 2 weeks after immunization. Seven women who became pregnant gave birth to live newborns. Secretion of the T helper 1 cytokines IL-2 and interferon-gamma by patients, mononuclear cells decreased, while production of IL-10 increased. The levels of natural killer and lymphokine-activated killer cell-mediated cytotoxicity were markedly decreased. Monocyte functions such as secretion of IL-1 alpha, tumor necrosis factor alpha, IL-6, and cytotoxic activity decreased concurrently with elevations in IL-10 and transforming growth factor beta secretion. Production of IL-12, a pivotal regulatory cytokine, decreased. Furthermore, B7/1 expression on patients' mononuclear cells was downregulated. This resulted in a decrease in monocyte costimulatory activity of purified T cells with soluble anti-CD3, paralleled by a decline in allogeneic proliferative responses. These results suggest that the improved pregnancy success rate in women with SRA following immunization may be partly related to suppression of cell-mediated immunity and monocyte and natural killer cell activity.

Inhibitory serum factor of lymphoproliferative response to allogeneic cells in pregnancy

INTRODUCTION

An inhibitory serum factor of mixed lymphocyte culture (MLC) has been associated with successful pregnancy after lymphocyte transfusion in women with unexplained recurrent spontaneous abortions (RSA).

OBJECTIVE

Investigate whether the inhibitory serum factor of MLC is essential for a successful pregnancy.

METHOD

Sera from 33 healthy pregnant women and from 40 women with RSA were assessed by a one-way MLC in which the woman's lymphocytes were stimulated with her partner's lymphocytes or with third party lymphocytes.

RESULTS

An inhibitory serum effect (inhibition > 50% as compared to normal serum) was detected in 45% of the pregnant women who had at least 1 previous parity, in 8% of the primigravidea, in 29% of those with one abortion and in 58% of those with more than one abortion.

CONCLUSION

MLC inhibitory serum factor does not seem to be an essential factor for pregnancy development. Therefore, it should not be considered as a parameter for the assessment of RSA patients.

Localisation of glycans in the placenta: a comparative study of epitheliochorial, endotheliochorial, and haemomonochorial placentation

Specimens of mid-term (horse), near-term (pig, cow, sheep, mink) and term (human) placentae and associated tissues have been examined with a panel of 15 biotinylated lectins combined with an avidin-peroxidase revealing system. The aim of this study has been to analyse the expression of glycans at the materno-fetal interface in order to establish whether the morphological diversity exhibited by these six species is reflected by accompanying biochemical diversity, or whether similar types of glycan are expressed in tissues performing similar functions. Lectin staining intensity was scored in the following elements of the interhaemal placental barrier: maternal capillaries, maternal uterine epithelium, the materno-fetal interdigitating microvillous membrane (brush border in the human), trophoblast, and fetal capillaries. A high degree of biochemical diversity was found in the glycan expression of the various placental components within and among placental types. Each layer showed widely differing patterns of lectin binding between species, with only a few findings in common: 1) the relative lack of simple fucosyl termini, 2) the presence of non-bisected bi/tri-antennary N-glycan in most layers, 3) an abundance of terminal N-acetyl galactosamine, and 4) the restriction of high mannose glycans to intracellular granules. This diversity may be a mechanism to avoid hybridisation, although glycan patterns may change between conception and placental development, or it may have evolved as a consequence of morphological changes. It is possible that it may also be part of the cause, rather than the result, of the structural diversity that is so characteristic of mammalian placentation.

Parental MHC antigen sharing and pregnancy wastage in captive pigtailed macaques

Among some human populations, immunogenetic similarity between mates is associated with increased risk of pregnancy loss. To investigate the relationship between histocompatibility and reproductive performance in non-human primates, 128 pigtailed macaque couples were classified as 'reproductively successful' or 'unsuccessful' according to previous breeding performance. These couples were arranged into 64 triads composed of individual females, and a 'successful' and 'unsuccessful' mate. Individuals were typed for class I MHC antigens using a microcytotoxicity technique and species-specific alloantisera. Matched-pair analysis revealed that significantly more 'unsuccessful' couples shared MnLA-A antigens than did the matched 'successful' couples. Conditional matched-pair logistic regression analysis further revealed that parental sharing of MnLA-A antigens is an even more significant predictor of pregnancy wastage than is advanced maternal age. In our study population, sharing of MnLA-A antigens predicted 72% of pregnancy loss among 'unsuccessful' couples (P < 0.009). Identification of histocompatibility-associated factors influencing pregnancy success could have profound clinical implications for chronic spontaneous abortion, intra-uterine growth retardation and birth defects in humans. Among captive primates, identification of MHC or MHC-linked genes affecting reproductive outcome could lead to more efficient colony management strategies as well as development of a model for understanding human immunologically-mediated reproductive failure.

Enhancement of the expression of progesterone receptor on progesterone-treated lymphocytes after immunotherapy in unexplained recurrent spontaneous abortion

PROBLEM

The immunological mechanism of an effective immunotherapy with paternal lymphocytes for unexplained recurrent spontaneous abortion (RSA) is not yet clear. Previous studies revealed that progesterone plays an important role in maintaining normal pregnancy and lower expression of progesterone receptor (PGR) on lymphocytes was found in RSA. Therefore, it was of interest to investigate whether immunotherapy for RSA would be able to enhance the expression of PGR on lymphocytes of RSA.

METHOD

PGR expression on lymphocytes was analyzed with indirect immunofluorescence using flow cytometry.

RESULTS

There was no change of PGR expression on PBL of RSA between pre- and post-immunotherapy (P > 0.05), while in the presence of 10.0 micrograms/ml progesterone for 24 h, PGR expressed on PBL on post-immunotherapy was increased significantly as compared with that of pre-immunotherapy in successful cases (P < 0.05) and decreased in abortive cases (P < 0.05). Most PGR was expressed on both CD4+ and CD8+ lymphocyte subsets. In successful cases, CD8+PGR+ subset of post-immunotherapy was found to be increased significantly (P < 0.05) in comparison with that of pre-immunotherapy.

CONCLUSION

The data in the present study suggest that immunotherapy for RSA induced a higher expression of PGR on progesterone-treated lymphocytes, which may be involved in successful pregnancy.

Placental interferons

Trophectoderm of ruminant conceptuses (embryo and associated membranes) secrete tau interferons (IFN tau) as the pregnancy recognition signal. Secretion of IFN tau on gestational days 12-13 for sheep and gestation days 14-17 for cows and goats is critical for pregnancy recognition. IFN tau acts on uterine epithelium to suppress estrogen receptor and oxytocin receptor gene expression, which prevents uterine release of luteolytic pulses of prostaglandin F2 alpha (PGF). Expression of the progesterone receptor (PR) gene in uterine endometrium is not affected by oIFN tau. Maintenance of progesterone secretion by the corpus luteum (CL) ensures establishment of pregnancy. Pig conceptuses secrete both IFN alpha and IFN gamma between days 15-21 of gestation, but their role(s) in early pregnancy is unknown. Estrogen secreted by pig trophoblast between gestational days 11-13 and 15-25 increases endometrial receptors for prolactin and causes exocrine secretion of PGF into the uterine lumen to prevent luteolysis. Shared cell-signaling mechanisms by IFNs and lactogenic hormones through Janus kinases (JAK) 1 and 2 may provide a common pathway to abrogate luteolytic mechanisms to ensure establishment of pregnancy. The role(s) of IFNs produced by human and rodent placentae is not known.

Human pregnancy serum suppresses the proliferative response of lymphocytes to autologous PHA-activated T lymphoblasts

PROBLEM

We have previously demonstrated that human serum can suppress the proliferative response in autologous mixed lymphocyte reaction (AMLR) in which phytohemagglutinin (PHA)-activated T lymphoblasts act as stimulators (T-TPHA AMLR). The aim of the present work was to determine whether pregnancy serum (PS) possesses an inhibitory capacity similar or different in magnitude.

METHODS

Sixteen PS were added to T-TPHA AMLR cultures and the proliferative response was compared with that in the presence of human serum. The effect of PS on the IL-2 dependent proliferation of PHA-activated T Lymphoblasts was examined as well.

RESULTS

PS induced a significantly more pronounced suppression of T-TPHA AMLR than human serum (P < 0.05). One PS tested was not inhibitory but rather stimulatory. This PS was obtained from a woman who subsequently had IUGR. The inhibition is related to the existence of a serum inhibitory factor and not to the lack of a serum supporting factor. PS inhibited not only T-TPHA AMLR of the same woman but also T-TPHA AMLR of other individuals as well, implying that the inhibitor is a non-MHC restricted factor. IL-2 dependent cell proliferation was not inhibited by PS, implying that the inhibitor detected in T-TPHA AMLR is not a general cell proliferation inhibitor.

CONCLUSIONS

These results suggest that a non-MHC restricted inhibitory factor present in PS may play an important biological role in regulating local immune responses in the fetal-placental unit mediated by autoreactive T cells restricted to autologous activated T lymphocytes.

Cellular immune responses in the pig uterus during pregnancy

In pigs, little is known about the role of the uterine immune system during pregnancy. Immunohistochemical studies were conducted using a panel of monoclonal antibodies to pig leukocytes on uterine tissues taken from gilts after fertile mating and at different stages of pregnancy. Acute inflammation in the endometrium in response to fertile mating which included marked changes in the tissue and immune cell components of the endometrium was observed. Throughout pregnancy the pig uterus contained a substantial population of leukocytes. MHC class II staining was prominent in the endometrium at all stages examined and included macrophages, dendritic and fibroblast-like cells, lymphocytes and the endothelial lining of many uterine blood vessels. The majority of lymphoid cells were CD2+, indicating the prevalence of T cells. In early pregnancy specific changes were seen in the tissue distribution of uterine immune cells. Following placentation distinct cellular changes in the local immune cell environment of the uterus were also observed despite the non-invasive nature of the pig placenta. There appears to be suppression and activation of various immune cell components in the uteri of pregnant pigs. This phenomenon is presumably in response to foetal or trophoblast antigens, suggesting that the local immune system is involved in the uterine response to pregnancy.

Low-dose glucocorticoids after in vitro fertilization and embryo transfer have no significant effect on pregnancy rate

OBJECTIVE

To determine the effect on pregnancy rate (PR) of low-dose glucocorticoid treatment in cycles without micromanipulation.

DESIGN

Randomized, prospective, double-blinded, placebo-controlled trial.

SETTING

One university-based tertiary infertility center and two private infertility centers.

PATIENTS

All patients receiving standard stimulation IVF-ET or transfer of cryopreserved embryos at the participating facilities from January to September 1993 were asked to participate in this study. Patients having micromanipulation were excluded from this study.

INTERVENTIONS

Participating patients were randomized to either 16 mg oral 6-alpha-methylprednisolone for four evenings starting the evening of retrieval or the evening before thawing cryopreserved embryos or to placebo administered in an identical fashion. Both groups were treated with 250 mg oral tetracycline four times per day starting with initiation of the study medication and continuing for 4 days. Cryopreservation and stimulation cycles were managed according to pre-established protocols for all patients. A clinical pregnancy was confirmed by an appropriately rising hCG titer and a gestational sac on ultrasound.

RESULTS

A total of 206 stimulation patients and 61 cryopreservation patients were randomized and had an ET. Patient characteristics were similar between groups. The clinical pregnancy and implantation rates between placebo and glucocorticoid groups were 35.9% versus 40.8% and 12.8% versus 11.7% for stimulation cycles and 30.3% versus 25% and 9.9% versus 7.4% for cryopreservation cycles, respectively. None of these differences were statistically significant.

CONCLUSIONS

Glucocorticoid plus antibiotic treatment at these doses for transfers of nonmicromanipulated embryos does not appear to have a significant effect on pregnancy or implantation rates.

Immune dysfunction in patients with unexplained repeated abortions

OBJECTIVES

To examine the immunological profiles by antiphospholipid antibodies IgG, IgM, IgA immunoglobulins ACA, as well as C3, C4 complement component levels.

METHODS

A group of 44 women with a history of three or more consecutive pregnancy losses was compared with 34 normal women.

RESULTS

Our results showed lower levels of IgG immunoglobulins for the patient group (P < 0.001) while the C3, C4 complement component levels remained unaltered. Anticardiolipin antibodies were positive in ten patients for IgG or IgM isotypes or for both presenting a prevalence of 22.7% while none of the control subjects had ACA positive titers. The lupus anticoagulant was not detected in either group. Ten patients (22.7%) presented positive autoantibody tests as compared with only 3 (8.8%) of the control group. No statistical differences were found between the two groups when the frequency of each autoantibody's positive tests were examined separately.

CONCLUSIONS

An inconsistent immune derangement seems to be present in recurrent aborters with the presence of anticardiolipin antibodies as the stronger representative marker of immune alteration.

Functions of macrophages in human decidual tissue in early pregnancy

PROBLEM

Roles of decidual macrophages (DMs) in the maintenance of early pregnancy was determined by comparing three of their functions, antigen presentation, immunoregulation, and lymphokine production, with those of peripheral monocytes (PMos) isolated from the same subjects.

METHOD

The antigen-presenting capacity of DMs was examined by the one-way mixed lymphocyte reaction (MLR) in which accessory cell-depleted mononuclear cells isolated from pregnant women were used as responders. The effect of DMs on cellular immunity was investigated by inhibition tests of either one-way MLR or phytohemagglutinin stimulation. The production of interleukin-1 (IL-1) and prostaglandin E2 (PGE2) by DMs following lipopolysaccharide stimulation was examined.

RESULTS

Addition of increasing concentrations of DMs to the culture resulted in a concentration-dependent proliferative response, as well as with PMos. In both assays, a stronger suppression was observed in the presence of DMs from normal pregnant women compared with PMos from the same subjects. DMs were found to secrete significantly lower levels of IL-1 alpha and IL-1 beta than PMos. No difference in PGE2 production was observed between DMs and PMos.

CONCLUSIONS

These findings suggest that DMs present in human early decidual tissue have a capacity for allo-antigen presentation, a higher suppressive activity, and a lower capacity to produce IL-1 than their peripheral counterparts.

Clinical evaluation of immunotherapy in early pregnancy with x-irradiated paternal mononuclear cells for primary recurrent aborters

OBJECTIVE

The purpose of this study was to evaluate the beneficial effect of immunotherapy for the treatment of recurrent abortion.

STUDY DESIGN

We immunized 106 primary recurrent aborters, twice at around 5 and 7 weeks of gestation, with intradermal injection of approximately 100 to 200 million x-irradiated (50 Gy) paternal mononuclear cells. We injected another 38 primary recurrent aborters in the same manner with only 1 million such paternal cells, to examine the relationship between the paternal cell dose used for immunization and pregnancy outcome.

RESULTS

The pregnancy success rate (83.0%) in patients immunized with a large number of cells was significantly higher than that (55.3%) in those immunized with a small number of cells (p < 0.001). Furthermore, the frequency of twins in the former group was high (5.7%, five of 88).

CONCLUSION

This positive relationship between the paternal cell dose used for immunization in early pregnancy and the pregnancy outcome reflects the efficacy of this mode of immunotherapy for recurrent aborters.

Recurrent spontaneous abortion: histocompatibility between partners, response to immune therapy, and subsequent reproductive performance

PROBLEM

Immunological factors may account for previously unexplained cases of recurrent abortion.

METHOD

After screening 76 couples for causes of recurrent spontaneous abortion and measuring maternal antipaternal immunity, 23 primary spontaneous recurrent aborters were immunized once with their husbands' leukocytes. Testing for antipaternal cytotoxicity was repeated in 21 couples. Seroconversion was significantly less frequent in couples who shared more than one human leukocyte antigen [one of five (20%) versus 13 of 16 (81%), P < .02].

RESULTS

Twelve of 16 women (75%) who became pregnant had live children and five of those have had a second live child. All 12 women who achieved successful pregnancies had become antipaternal cytotoxic antibody-positive after immunization, whereas all four patients who had repeat abortions had failed to seroconvert (P < .001). However, this relationship is not necessarily causative, as the successful group also tended to have fewer previous abortions and less human lymphocyte antigen sharing.

CONCLUSION

Except for transient illness after immunization, one moderately small for gestational age baby and one premature labor at 32 wk, no complications were observed after immunization.

Polycystic ovaries and levels of gonadotrophins and androgens in recurrent miscarriage: prospective study in 50 women

OBJECTIVE

To compare the serum levels of gonadotrophins and androgens, as well as ovarian morphology, in 50 women with a history of recurrent miscarriage and in 20 healthy controls.

DESIGN

Prospective study on women with a history of at least three consecutive miscarriages in Department I and II of Obstetrics and Gynecology, University Central Hospital of Helsinki, Finland.

RESULTS

The recurrent miscarriage group as a whole exhibited gonadotrophin and androgen levels comparable to those seen in the controls. Ultrasound examination revealed polycystic ovaries (PCO) in 22 patients (44%) and in four control women (20%, P = 0.06) but no differences in the levels of gonadotrophins and androgens emerged between the patients with or without PCO. During follow up, 33 (66%) women with a history of recurrent miscarriage who became pregnant; 16 miscarried again (48.5%), whereas 17 (51.5%) succeeded. The presence of PCO did not predict miscarriage, but the patients who miscarried had higher levels of total testosterone, free testosterone and dehydroepiandrosterone sulphate than RSA women with continuing pregnancies.

CONCLUSIONS

PCO and hyperandrogenism may be associated with repeated miscarriage.

Treatment of recurrent spontaneous abortion by immunization with paternal lymphocytes: results of a controlled trial

PROBLEM

It remains unclear whether maternal immunization with paternal lymphocytes prior to conception improves the reproductive outcome in women with recurrent abortion in whom all secondary causes have been excluded.

METHOD

A double-blind placebo controlled trial was instituted in women with unexplained recurrent spontaneous abortion, comparing immunization with 400 million paternal to 400 million maternal (autologous) lymphocytes. The groups were compared in a paired sequential trials chart, by logistic regression, and, in addition, a meta-analysis of this and other published trials was carried out.

RESULTS

The live birth rate among pregnancies in paired couples with paternal lymphocyte immunization was 68% compared to 47% in the women who received their own cells. The results bordered on, but did not achieve, statistical significance. The women in each group were thoroughly investigated to exclude known causes of recurrent pregnancy loss and appeared to have been well matched in all variables. Women with lymphocytotoxic antibodies against paternal lymphocytes were excluded. Unlike our previous study there was not association between the time to conception and the chance of a successful outcome. Indeed, the time to conception was relatively short, 12 wk in all groups. The meta-analysis supported an overall modest favorable experience with paternal cells.

CONCLUSION

The study is consistent with a general trend favoring paternal over maternal lymphocyte immunization but reinforces the need for larger multicenter controlled trials as well as more detailed biological study in humans to understand the nature of the maternal-fetal interface and its breakdown.

Soluble interleukin-2 receptors in recurrent miscarriage and the effect of leukocyte immunotherapy

The relationship between soluble interleukin-2 receptors (IL-2R) and pregnancy outcome was investigated in women with a history of miscarriage, some of whom were treated with partner-specific leukocyte immunotherapy. IL-2R were significantly elevated in patients with a poor obstetric history possessing cardiolipin antibodies, and higher levels were also found in recurrent aborters without cardiolipin antibodies who had particularly bad histories. Furthermore, values obtained during early pregnancy were lower in patients who subsequently had successful pregnancies than in those who aborted again. Eight out of 35 patients immunised with their partners' lymphocytes, but none of 16 patients immunised with their own cells, showed a marked decrease in IL-2R levels a month later. It is possible that the minority who respond to immunotherapy with a marked drop in IL-2R may be the same minority who may derive benefit from this treatment.

Cytokines considered critical in pregnancy

Cytokines considered critical in pregnancy include interleukin-1 (IL-1), tumor necrosis factor alpha (TNF-alpha), interferon gamma (IFN-gamma, granulocyte-macrophage colony stimulating factor (GM-CSF), and colony stimulating factor (CSF-1). They affect blastocyst attachment, trophoblast outgrowth, implantation, proliferation of cells isolated from placentas, proliferation of trophoblast cell lines, and percent fetal resorption in spontaneously aborting mice. Cytokines also affect chorionic gonadotrophin and progesterone production by trophoblast. Cytokine effects vary with concentration, route of administration, and timing of secretion.

Immune recognition at the maternal-fetal interface: overview

Trophoblast antigens at the maternal-fetal interface that are capable of stimulating maternal immune responses have been studied. Candidates are blood group I and P, HLA, Fc gamma-receptors, TLX, and phospholipids. Antigens I and P on trophoblast have been implicated in pregnancy loss but incompatible i,p mothers are rare. HLA-G is expressed on cytotrophoblast; however, no evidence for HLA-G allotypy or maternal responses to these molecules exists, although HLA-G has been implicated in recruitment of suppressor T cells. Receptors for IgG (Fc gamma-RI, Fc gamma-RII and Fc gamma-III) are present on trophoblast but allotypy is limited to the NA1-NA2 antigen system associated with Fc gamma-RIII on neutrophils. Maternal Fc-gamma R blocking antibodies have been linked to pregnancy success. The TLX alloantigen system was described by using xenogeneic antisera. Idiotype-antiidiotype regulated maternal responses to TLX are proposed as necessary for successful pregnancy. Several putative TLX monoclonal antibodies (Mab) recognize a regulator of complement activation called MCP (membrane cofactor protein, or CD46). Mab to MCP do not exhibit allotypy. Syncytial and cytotrophoblastic membranes are rich sources of MCP. Preliminary data suggest that a conformational site induced by C3b (iC3) binding to MCP may be responsible for TLX allotypy. Certain pregnancy loss patients produce antiphospholipid antibodies (aPA). Some investigators believe that aPA recognize a plasma protein cofactor, beta 2 GPI and not phospholipid per se. We produced three Mab specific for beta 2 GPI, one of which fails to recognize beta 2 GPI bound to phospholipid [corrected].(ABSTRACT TRUNCATED AT 250 WORDS)

Preferential synthesis of asymmetric antibodies in rats immunized with paternal particulate antigens. Effect on pregnancy

The effect of immunization of female Fischer rats with particulate (spleen cells) (group I) or soluble (supernatant of disintegrated spleen cells) (group II) paternal antigens previous to mating with Buffalo rats was investigated. The percentage of asymmetric IgG molecules in the serum of rats inoculated with particulate antigens was 38% while in those injected with soluble antigens it was 29% and 28% in non-immunized animals. These percentages further increased during pregnancy to 45%, 38% and 37%, respectively. The antipaternal antibody titres, as determined by indirect immunofluorescence (IIF), was much higher in the animals immunized with particulate antigens but the effector activity, judged by complement fixation, was similar in both groups. The same values were observed at the time of mating (after 3 months of immunization) and at day 17 of pregnancy. Fetus and placenta weights and offspring survival were equally greater in group I than in group II or non-immunized rats (group III). The results obtained indicate the preferential synthesis of antipaternal IgG asymmetric antibodies in rats injected with particulate antigens previous to mating and suggests a beneficial effect of these antibodies in pregnancy.