Stress-triggered abortion in mice prevented by alloimmunization

The role of CD4+ lymphocytes in the susceptibility of mice to stress-induced reactivation of experimental colitis

Idiopathic inflammatory bowel disease is a chronic relapsing condition. The role of stress in causing relapses of inflammatory bowel disease remains controversial. We now show that colitis induced in mice by dinitrobenzenesulfonic acid (DNBS) resolves by 6 weeks, but can subsequently be reactivated by stress plus a sub-threshold dose of DNBS, but not by DNBS alone. Stress reduced colonic mucin and increased colon permeability. Susceptibility to reactivation by stress required CD4+ lymphocytes and could be adoptively transferred. We conclude that stress reactivates experimental colitis by facilitating entry of luminal contents that activate previously sensitized CD4 cells in the colon.

The emerging role of immunoregulation of fibrinogen-related procoagulant Fgl2 in the success or spontaneous abortion of early pregnancy in mice and humans

PROBLEM

Abortion of chromosomally normal embryos in the CBA X DBA/2 mating combination is triggered by release of Th1 cytokines (tumor necrosis factor [TNF]-alpha, interferon [IFN]-gamma, and interleukin [IL]-1), which cause abortion via a novel prothrombinase, Fgl2, and polymorphonuclear leukocytes. The site of activation may be maternal vascular endothelium on arteries and veins nourishing the placenta. Activation of coagulation is also prominent in spontaneous abortion of chromosomally normal human embryos. We asked where is Fgl2 up-regulated in the uterus in murine abortions, and if similar Fgl2 expression occurs in human pregnancy failure.

METHODS

Control CBA X DBA/2 pregnant mice, or from mice injected with TNF-alpha + IFN-gamma on day 7.5 of gestation, were removed on day 8.5, fixed, sectioned, and subject to in situ hybridization for Fgl2. Sections were also stained for fibrin. Elective first trimester termination samples or biopsies taken early in the course of a recurrent miscarriage were similarly fixed, sectioned, and analyzed by in situ hybridization. Control and cytokine-treated mice were anticoagulated with heparin, an activator of antithrombin III, and/or the direct anti-thrombin inhibitor hirudin.

RESULTS

Low level Fgl2 expression localized to basal decidua remote from the embryo was noted in control mice; cytokine treatment, which causes greater than 80% of abortions, produced a striking up-regulation in this area as well as in a band at the junction of decidua and myometrium. Trophoblast also became strikingly positive. Fgl2 expression was associated with increased fibrin staining. Anticoagulation significantly protected against abortions, but doses were limited by the complication of retroplacental hemorrhage. In tissue from normal first trimester pregnancy, minimal Fgl2 positivity was seen in some villous syncytiotrophoblast, in villous stroma, cytotrophoblast, and in some cells in decidua. In spontaneous abortion of normal embryo, striking Fgl2 positivity was seen in syncytiotrophoblast and extravillous cytotrophoblast, in association with areas of thrombus formation.

CONCLUSIONS

Fgl2 appears to be physiologically expressed and may protect against the internal danger of maternal and/or fetal bleeding during pregnancy and at parturition; a role in inhibiting transplacental traffic is also possible. External dangers in the form of stress, endotoxin, and antigens eliciting Th1 cytokine responses upregulate Fgl2 prothrombinase in trophoblast as well as in decidua, which results in spontaneous abortion of immunogenetically "weaker" embryos.

Why did your mother reject you? Immunogenetic determinants of the response to environmental selective pressure expressed at the uterine level

PROBLEM

Maternal "rejection" of the implanted conceptus is considered to account for a significant proportion of miscarriages (abortions) in both humans and animals. Our understanding of mechanisms has been limited, and hence, explanations for nonrejection have remained largely speculative. Losses, when they occur, could represent either random accidental failure of protective mechanisms or a more purposeful discrimination.

METHOD OF STUDY

An analysis of the most recent data.

RESULTS AND CONCLUSIONS

The embryo is most akin to a parasite, and pregnancy is most akin to a host-parasite interaction. If one excludes chromosome abnormalities in the embryo as a cause of death, activation of coagulation mechanisms, leading to vasculitis affecting the maternal blood supply to the implanted embryo, appears to represent a major loss-causing mechanisms--a form of ischemic autoamputation. Proinflammatory T-helper (Th) 1-type cytokines trigger this process via upregulation of a novel prothrombinase, fgl2. Th2/3 cytokines, such as interleukin (IL)-4, IL-10, and transforming growth factor (TGF)-beta 2, may antagonize the processes involved. Cytokine balance is determined by the genetics of the mother, which regulate her response to stress; endotoxin (LPS); and paternal antigens, selectively expressed on the trophoblast of the embryo, via imprinting. Based on studies in abortion-prone mice, where immunity to paternal alloantigens prevents loss, three distinct gene products in the embryo are proposed to determine the cytokine response to maternal lymphomyeloid cells in the uterus.

TNF-alpha expression in embryos exposed to a teratogen

PROBLEM

The role of tumor necrosis factor (TNF)-alpha produced by embryonic cells in normal and abnormal development is poorly understood. To assess to what extent TNF-alpha may be involved in the process of induced dysmorphogenesis, the expression of TNF-alpha and TNF-alpha receptor (TNFRI) mRNA as well as TNF-alpha protein was evaluated in embryos responding to a cyclophosphamide (CP)-induced teratogenic insult. The effect of maternal immunostimulation increasing the embryo's tolerance to CP on TNF-alpha expression was also investigated.

METHOD OF STUDY

ICR female mice were treated intraperitoneally with 40 mg/kg CP on day 12 of pregnancy. The immunostimulator, xenogeneic rat splenocytes, was injected intrauterine 21 days before mating. Embryos were collected on days 13, 14, or 15 of pregnancy. TNF-alpha mRNA, TNFRI mRNA, and TNF-alpha protein expression were evaluated by in situ hybridization and immunostaining techniques in control, teratogen-treated, and immuno-stimulated teratogen-treated embryos.

RESULTS

CP-treated embryos showed severe external brain and craniofacial anomalies already visible on day 14 of pregnancy. TNF-alpha mRNA transcripts were detected in cells of the brain and the head of 13-day embryos, which preceded the occurrence of CP-induced external craniofacial anomalies. On day 15 of pregnancy, when severe craniofacial anomalies increased, a significant increase in the intensity of TNF-alpha, TNFR1 mRNA transcripts, and TNF-alpha protein expression were observed in cells of the malformed regions of the head and the brain. In other nonmalformed organs of CP-treated embryos such as the liver (not macroscopically different from controls), neither TNF-alpha nor TNFR1 transcripts were detected. Immunostimulation substantially diminished the severity of CP-induced brain and craniofacial anomalies, decreased the resorption rate, and was associated with decreased intensity of TNF-alpha mRNA transcripts detected on day 15 of pregnancy in the head and the brain of CP-treated embryos.

CONCLUSIONS

TNF-alpha expressed in the embryo may be one of the molecules promoting the formation of CP-induced brain and craniofacial anomalies. The decrease of TNF-alpha expression in embryos of immunostimulated females may be one of the mechanisms responsible for the increased tolerance to the teratogenic insult.

Murine T cell determination of pregnancy outcome: I. Effects of strain, alphabeta T cell receptor, gammadelta T cell receptor, and gammadelta T cell subsets

PROBLEM

T cells bearing alphabeta T cell receptor (TcR) and gammadelta TcR are present at the fetomaternal interface, and the latter, which express surface activation markers, can react with fetal trophoblast cell antigens. What is the role of these cells?

METHOD

Using stress-abortion-prone DBA/2-mated CBA/J and abortion-resistant C57/B16 mice, alphabeta, gammadelta, and CD8+/- T cell subsets were measured in spleen and uterine decidua. The effect of immunization against abortion and administration of anti-TcR antibody in vivo was examined. Cytokine synthesis was measured by intracellular staining of Brefeldin A-treated cells.

RESULTS

Abortion-prone matings showed an unexpected accumulation of gammadelta T cells beginning in the peri-implantation period and this was suppressed by immunization against abortion. The immunization deleted gammadelta T cells producing the abortogenic cytokines, TNF-alpha and gamma-interferon, and increased production of the anti-abortive cytokines, IL-10 and transforming growth factor-beta2 (TGF-beta2). Immunization also boosted the number of alphabeta T cells which were present in the decidua as early as 2 days after implantation. In vivo injection of GL4 (anti-delta) depleted gammadelta T cells producing Th1 cytokines in the peri-implantation period, and prevented abortions, whereas H57 (anti-beta) decreased the number of alphabeta T cells and led to 100% abortions. CD8+ T cells present in peri-implant decidua before onset of abortions were mostly alphabeta TcR+, although some were gammadelta+. Changes in gammadelta and alphabeta T cells in pregnancy were most dramatic in uterine tissue.

CONCLUSION

Although decidual gammadelta T cells after formation of a distinct placenta and fetus produce anti-abortive TGF-beta2-like molecules and IL-10, prior events can lead to abortion. High local production of TNF-alpha and gamma-interferon develop during the peri-implantation phase because of an excessive increase in the Th1 cytokine+ subset of gammadelta cells; these cytokines may be contributed by other tissues in decidua, and the contribution of bioactive factors by gammadelta T cells may augment the cytokine pool. In contrast, alphabeta T cells (which may be inactivated by stress that causes abortions) may mediate the anti-abortive effect of alloimmunization. Alloimmunization involves a shift from a Th1 to a Th2 pattern in the gammadelta T cells in decidua.

Soluble receptors neutralizing TNF-alpha and IL-1 block stress-triggered murine abortion

PROBLEM

In several models of abortion in rodents, the success or failure of the implanted embryos is determined by a balance between pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha), interleukin-2, interleukin-1 (IL-1), and gamma-interferon, and cytokines that counteract the former, such as interleukin-10 and transforming growth factor-beta 2 (TGF-beta 2)-related suppressor factor. Stress can trigger abortions in susceptible strains of mice and is thought to reflect the pathogenesis of some types of miscarriage in human pregnancy. In mice, stress increases levels of the abortogenic cytokine TNF-alpha and decreases the suppressive activity of TGF-beta 2-related factor via a neurotransmitter substance P (SP)-dependent pathway. Evidence for a role of pro-inflammatory cytokines in SP-mediated abortions in vivo is indirect.

METHODS

Direct evidence for a role of IL-1 and TNF-alpha in stress-triggered abortions was sought by injecting pregnant female mice with soluble receptors neutralizing TNF-alpha (rhuTNFR:Fc) or IL-1 (rmIL-IR) beginning 1 day after implantation and prior to stress.

RESULTS

The stress-triggered abortion rate was reduced by 68% when either TNF-alpha or IL-1 antagonists were injected. The stress-triggered decreased TGF-beta 2-like suppressive activity in the maternal uterine decidua was not restored by injection of either antagonist; indeed the soluble IL-1 receptor significantly reduced suppressive activity in unstressed control mice, and soluble TNF-alpha receptor had a lesser effect.

CONCLUSIONS

Both IL-1 and TNF-alpha play a role in the pathogenesis of stress-triggered abortions, and may induce a compensatory physiological increase in suppressive activity in normal pregnancy counteracting pro-inflammatory cytokines.

Regulation of abortion by gamma delta T cells

PROBLEM

T cells are present at the feto-maternal interface, but their function during pregnancy has not been fully elucidated. T cells bearing gamma delta T-cell receptor (TCR) may be particularly important, as some subsets can react to trophoblast cells by producing cytokines, such as interleukin-2 (IL-2).

METHOD

We depleted T cells bearing the gamma delta receptor by injecting monoclonal antibodies (mAb) into females of the abortion-prone animal model CBA x DBA/2. We investigated the percentage and number of gamma delta T-cell receptor positive (TCR)+ cells in decidua and spleen during pregnancy in control and gamma delta-depleted female mice. Pregnant females were also exposed to ultrasonic sound stress to boost the abortion rate.

RESULTS

Stress failed to increase the abortion rate in the gamma delta TCR-depleted mice. FACScan analysis show that the ratio of cells bearing the gamma delta TCR dramatically decreased after injection of mAB to the gamma delta TCR in spleen and decidua, these cells recovered six days after depletion, showing a change in cytokine pattern. Levels of TNF-alpha in decidual gamma delta T cells decreased; similar effects of decreasing Th1 cytokines could be observed in splenic gamma delta T cells. We further identified increased levels of intracellular TNF-alpha in the V delta 4 subset in the decidua, compared to spleen.

CONCLUSIONS

Trophoblast recognition by the V delta 4 T-cell subset in the decidua may cause the release of abortogenic cytokines such as TNF-alpha. Depletion of such gamma delta TCR T cells during early pregnancy may promote successful pregnancy outcome in normal pregnancy and prevent stress-induced abortions.

Stress triggered abortions are associated with alterations of granulated cells into the decidua

PROBLEM

Stress is known to be abortogenic in animals and humans. An increased decidual release of cytokines such as TNF-alpha and reduction in TGF-beta 2-related immunosuppressive activity has been proposed as the triggering mechanism. Substance P release by nerves in endometrium/decidua has been found to be the key neurotransmitter in this pathway. It is still unclear which cells are stimulated by substance P to produce the increased TNF-alpha level.

METHOD

As a measure of local activation, the granulation of granulated material gland (GMG) cells was measured by flow cytometry after sonic plus immobilization stress of mice or substance P treatment of GMG cells (both isolated GMG cells and GMG-cell containing decidua). TNF-alpha release from decidua and isolated GMG cells was investigated using a TNF-alpha bioassay. The degranulation of uterine mast cell, another potential source of TNF-alpha, was examined in situ by Toluidine blue staining.

RESULTS

We observed a striking increase in percentage of degranulated mast cells (8% -->24%) in the uteri of stressed animals, whereas the granularity of GMG cells was decreased by stress but increased with treatment with substance P in vitro. Isolated GMG cells appeared to release in vitro cytotoxins active in the TNF-alpha bioassay, but the magnitude of this activity was not increase by stress or by substance P treatment. In contrast, disaggregated decidual tissue which is known to release increased amounts of TNF-alpha after stress, did increase activity in response to substance P in vitro.

CONCLUSIONS

Uterine mast cells show activation as reflected by degranulation after stress exposure of pregnant mice and mast cells might be the cellular link between the neurotransmitter substance P and increase in decidual TNF-alpha release that leads to abortion.

Immunosuppressive properties of monoclonal antibodies and human polyclonal alloantibodies to the R80K protein of trophoblast

PROBLEM

The R80K protein on human trophoblast is antigenically polymorphic, and in all placentae of successful pregnancies, the protein is covered by maternal alloantibody. Alloantibody eluted from human placenta has been shown to inhibit killing by human NK cells. Do those antibodies to R80K that inhibit NK killing also affect the murine abortion models?

METHODS

We made three murine monoclonal antibodies to conserved epitopes, on human R80K, all of which also reacted with the homologous murine molecule. One antibody only, BA11, suppressed NK cytotoxicity to K562 and of mouse spleen NK cells to murine trophoblast. All three were tested in mouse models of abortion: the CBA x DBA/2 model with a high resorption rate of F1 embryos compared with the parental strains, an endotoxin induced abortion/resorption model and a third model in which the pregnant mouse is subject to sonic stress.

CONCLUSION

Those IgG antibodies eluted from microvesicles which bound to K562, and one of the three monoclonals, BA11, inhibited NK killing. The antibodies react with the murine molecule, and BA11 inhibited abortion in all three mouse abortion models. This reinforces the thesis that interference with NK killing can influence abortion/resorption in mice, and the BA11 antibody may effect similar results in analogous human situations.

Effect of chronic stress on estradiol action in the uterus of ovariectomized rats

The aim of this study was to investigate the development of estradiol (E2) effects in ovariectomized rat uterus under chronic stress. The chronically stressed rats (swimming and overcrowded cages) were treated with a single injection of E2 dipropionate (10 micrograms/ rat, i.m.) in olive oil (0.1 ml/rat). Control groups of ovariectomized rats included one group treated with the same dose of E2 but maintained in stress-free conditions, a second group subjected to the same procedure of chronic stress but injected with olive oil only, a third group treated with olive oil and maintained in stress-free conditions, and a final group which consisted of uninfluenced ovariectomized rats. E2 effects were determined by measuring activity of proliferation (mitotic index), cellular, nuclear, and nucleolar volumes (morphometry), DNA content (Feulgen's method) in luminal and glandular epithelia, stromal cells of endometrium at 24, 36 and 48 h after injection of E2 or olive oil. In chronically stressed rats treated with E2, at each time point almost all the parameters in all the structures were significantly (P < 0.05-0.001) higher, than in unstressed E2-treated rats. In E2-untreated rats, the stress did not influence uterine tissues. Thus, the chronic stress enhances strongly the E2-induced effects in the uterus of ovariectomized rats. It is likely mediated by the changes of some steps in the mechanism of estrogen action that leads to the increase in the sensitivity of uterine structures to estrogens.

Realization of estradiol effects in the uterus of ovariectomized rats under acute stress

The aim of this study was to examine the influence of acute stress on the realization of the effects of estrogens in the uterus of ovariectomized rats. The rats were immobilized for 6 h and given a single injection of estradiol dipropionate (E2; 10 micrograms/rat, i.m.). E2-only treated rats, olive oil injected and stressed rats, olive oil-only treated rats and untreated ovariectomized animals were used as controls. The effect of E2 was assessed by the volumes of cells, nuclei and nucleouli (morphometry), DNA content (Feulgen technique) and proliferative activity (mitotic index) in luminal epithelium, in glandular epithelium and in stromal cells of endometrium 24, 36 and 48 h after the injection of E2 or olive oil. All the effects of E2 were reduced in E2-treated rats subjected to stress in all the uterine structures. In olive oil treated rats, stress induced certain increase in the volume of cells and nuclei and slight increase in the DNA content in all the structures. It is suggested that the influence of stress on the uterus is mediated by impairment of some septs in the mechanism of action of estrogen on the uterus, which leads to a decrease in the sensitivity of the uterine structures to estrogens. Without estrogen stimulation the effect of stress on the uterus is realized via estrogen-independent pathways.

Stress-triggered abortion: inhibition of protective suppression and promotion of tumor necrosis factor-alpha (TNF-alpha) release as a mechanism triggering resorptions in mice

PROBLEM

Stress adversely affects pregnancy outcome and has been implicated as an abortogen in both animals and humans. However, the mechanisms whereby stress aborts are largely unknown. Alloimmunization can prevent stress-triggered abortion, and immunization is known to increase transforming growth factor-beta 2 (TGF-beta 2)-related suppressive activity.

METHOD

To investigate these mechanisms, DBA/2J males were mated to CBA/J or C3H/HeJ females, and the pregnant females were exposed to ultrasonic sound stress for a period of 24 h between day 4.5 to 8.5 of pregnancy.

RESULTS

Ultrasonic stress significantly elevated the resorption rate with a peak effect on day 5.5 in the CBA/J females and on day 4.5 in the LPS-resistant C3H/HeJ females. The tumor necrosis factor-alpha (TNF-alpha) release from the decidua was also elevated and the TGF-beta 2-mediated suppressive activity was significantly decreased. The resorption rate only increased when the TNF-alpha/TGF-beta 2 ratio was increased compared to the control.

CONCLUSION

These data suggest that stress may inhibit protective suppressor mechanisms and promote secretion of abortogenic cytokines such as TNF-alpha. Possible mechanisms are discussed.

Intralipid as treatment for recurrent unexplained abortion?

PROBLEM

Safe, effective, and inexpensive alternatives to partner leukocyte immunotherapy are being sought. Psychotherapy may be effective but it is uncertain what constitutes effective treatment and the form of treatment tested in cohort controlled trials is expensive. IVIG also appears effective, but is expensive.

METHOD

A published double blind randomized controlled trial in which Intralipid (Kabi Vitrum, Toronto, Ontario) was used as a control versus trophoblast membrane vesicles was reviewed. A prediction made from this data was then tested using the DBA/2-mated CBA/J mouse model of recurrent spontaneous abortion.

RESULTS

It can be hypothesized from the human clinical trial data that Intralipid even in small doses could be an effective antiabortion treatment. The number of patients in the published study is too small for the required degree of precision. Intralipid was highly effective in preventing abortion in mice, and protection was prolonged. This may be explained by previous data in the literature showing that Intralipid affects the reticuloendothelial system of the recipient.

CONCLUSIONS

The evidence suggests that Intralipid might be an effective treatment for human recurrent miscarriages, and injection into women who may become pregnant has been found ethically acceptable at one university center. Comparison of Intralipid to partner leukocyte immunotherapy or IVIG would be worthwhile. For adequate statistical power, this would require a large, multicenter, prognostically stratified randomized controlled trial and could be accomplished via the Recurrent Miscarriage Immunotherapy Trialists Group network.

The thymus in pregnancy: the interplay of neural, endocrine and immune influences

This article discusses the dramatic events that accompany thymic involution during pregnancy, and traces the possible immune, neural and endocrine interactions that may occur. Ann Clarke and Marion Kendall present accumulating evidence that activity, not inactivity, is a feature of the thymus at this time. Whilst the cortex shrinks, the medulla enlarges and rearranges to create a microenvironment containing increased numbers of mature thymocytes. It is suggested that these recently derived T cells may contribute to the unique populations of cells with suppressive function that appear during pregnancy, and thereby contribute to the immune suppression of the mother to paternal and fetal antigens. In addition, the pregnancy-associated cortical involution of the thymus may reflect the deletion of clones with potential reactivity to paternal and/or fetal antigens.