Early embryo loss is associated with local production of nitric oxide by decidual mononuclear cells

Specific Localization of Macrophages in Pregnant Bovine Caruncles

The objective of this study was to evaluate the distribution and phagocytotic function of macrophages in bovine caruncles during pregnancy. Pregnant Holstein caruncles obtained at a slaughterhouse and by Caesarean section just before the onset of parturition were used. Macrophages in these caruncles were observed immunohistochemically and histochemically. Macrophages were present in the parenchyma of caruncles throughout pregnancy. The macrophages were irregular in shape, and exhibited thin, long processes along the main and intermediate septa of caruncles. Macrophages increased as the gestation period progressed. Acid phosphatase activity of the macrophages appeared at 5-6 months of gestation and remained until the end of gestation period. In particular, macrophages showed strong acid phosphatase activity at the peripheral region of the caruncles just facing the chorionic villi. In addition, they were conglomerated in the hyperplastic prominences of caruncles. These results indicate that caruncle macrophages maintain the appropriate size and shape of each caruncle during pregnancy.

TH1/TH2 paradigm in pregnancy: paradigm lost? Cytokines in pregnancy/early abortion: reexamining the TH1/TH2 paradigm

In this paper, we briefly survey the history of concepts in reproductive immunology from antibody-mediated tolerance to the "fetal allograft" to the current concept of an embryo "bathing in a sea of cytokines". We then review the paradigm that "allopregnancy is a Th2 phenomenon" and some of the evidence gained in animals and humans supporting it. We continue by discussing the light it sheds on immunologically caused recurrent abortion, and the present status of the concepts. We next show the limits of the Th1/Th2 paradigm by reviewing the role of "inflammatory" cytokines in implantation (as first seen with leukemia inhibitory factor). We go on to discuss recent data showing that interferon-gamma is not solely a "bad guy", e.g. abortifacient as the paradigm would predict, but is needed at low doses for the vascular development and transformation of uterine spiral arteries required for implantation and successful pregnancy. We conclude by discussing the emerging role of NK and IL-12, IL-15, IL-18 tripods and other cytokines in local angiogenesis and tissue remodelling, a series of new data bringing us well beyond the Th1/Th2 paradigm in pregnancy which, in this context, appears now obsolete and an oversimplification, although it has indeed been useful at first. Rather, step-specific events have to be considered and a key role is seen in local tissue remodelling, in which immune cytokines play an important role while not always being secreted by immune cells.

Systemic and placental productions of tumor necrosis factor contribute to induce fetal mortality in mice acutely infected with Trypanosoma cruzi

Blood levels and placental productions of IFN-gamma and TNF, known to be harmful for pregnancy, were determined in pregnant mice acutely infected with Trypanosoma cruzi and suffering massive fetal losses without congenital infection. INF-gamma was detected mainly at day 9 and TNF at days 17 and 19 of pregnancy in plasma of infected mice. TNF levels were significantly correlated to the percentages of dead fetuses. Placental cells produced TNF but not IFN-gamma, and addition of T. cruzi lysate to such cells strongly stimulated TNF production. Treatment of infected mice with pentoxifylline, known to decrease IFN-gamma production and to inhibit the TNF-alpha gene transcription, reduced the placental production of TNF, and the fetal mortality in comparison to control animals. Altogether these result suggest that TNF produced at systemic and placental levels plays a role in the fetal mortality induced in mice acutely infected with T. cruzi.

Expression of allograft inflammatory factor-1 in mouse uterus and poly(I:C)-induced fetal resorption

PROBLEM

To investigate whether the allograft inflammatory factor-1 (AIF-1) is expressed and plays a role in the reproductive system.

METHOD OF STUDY

AIF-1 expression was examined in uteri of non-pregnant and pregnant mice by Northern blot analysis, RT-PCR and immunohistochemistry.

RESULTS

The expression of AIF-1 varied during the estrous cycle with a peak at estrus. After the insemination, the expression of AIF-1 mRNA diminished gradually and again increased in the pre-implantation or implantation period in allogeneic or syngeneic pregnancy, respectively. Enhanced expressions of AIF-1, tumor necrosis factor-alpha (TNF-alpha) and nitric oxide synthase 2 (NOS2) mRNA were observed in the embryos of resorption-prone pregnancy injected with poly(I:C).

CONCLUSIONS

This study demonstrated for the first time that AIF-1 was expressed in uterus. The expression level was associated with the population size of macrophage and varied during the estrous cycle and the pregnancy period. The augmented expression of AIF-I with concomitant expressions of TNF-alpha and NOS2 mRNA in poly(I:C)-injected mice suggests a correlation between AIF-1 production and fetal resorption.

IL-10 inhibits nitric oxide synthesis in murine uterus

OBJECTIVES

Recent reports point to a role for the nitric oxide/nitric oxide synthase (NO/NOS) system in implantation. It has been suggested that inducible NOS expressed at peri-implantation would lead to enhanced NO production, which could promote the attachment of the blastocyst. Short-term administration of NO donors during the pre-implantation period reduced the pregnancy rate in a dose-dependent manner. Thus, it is thought that optimal levels of NO are critical for embryo implantation, so regulation of NOS must be crucial. Taking this into consideration, interleukin-10 (IL-10), synthesized and secreted by the embryo, could be modulating NOS during implantation. In this study we have investigated the in vitro effect of IL-10 on NOS in the uterus.

METHODS

To determine the effect of IL-10, slices of uterus from estrogenized mice were pre-incubated for 60 min with different concentrations of IL-10 and NOS activity was measured.

RESULTS

IL-10 (50 and 100 ng/ml in vitro) diminished NOS activity. The in vivo administration of lipopolysaccharide (LPS; 8 mg/kg) significantly increased the conversion of arginine into citrulline. This effect was abolished after 60 min of preincubation with IL-10 (100 ng/ml). The stimulatory effect of LPS and estrogen on NOS activity is exerted on the Ca-independent isoform and IL-10 in vitro abolished this increase. We observed that the uterus of pregnant mice on day 5 of gestation synthesized NO. This production was significantly inhibited by preincubation with IL-10 (100 ng/ml).

CONCLUSIONS

This report demonstrates that IL-10 is capable of inhibiting NO synthesis in estrogenized, LPS-treated and pregnant rat uterus.

Anti-abortive effect of Radix scutellariae and Rhizoma atractylodis in mice

The objective of this study is to investigate the significance of natural killer (NK) cells and interleukin-2 in uterus in the early embryo loss (or resorption), and to elucidate the immunological modulation of maternal-fetal interface with Chinese herbal medicine Radix scutellariae (huang qin) and Rhizoma atractylodis (bai zhu). Lipopolysaccharide (LPS) was given via the tail vein to induce abortion in mice at day 7 of gestation. Uterine NK cells and IL-2 contents were analyzed by immunohistochemistry and enzyme linked immunosorbent assay (ELISA), respectively. The number of NK cells was found to be much higher (mean = 180 +/- 39) in the decidua of LPS-treated abortion mice. But when the Chinese herbal medicine was used to prevent LPS-induced abortion, less NK cells (mean = 11 +/- 4) were counted (p < 0.01). The mean value of IL-2 in LPS-treated mice was 5.25 +/- 2.5938 pg/mg protein, higher than (p < 0.05) that of the herb prevention group, which was only 1.86 +/- 0.9789 pg/mg protein. The results therefore indicate that the increase of NK cells in the decidua and IL-2 contents in the uterus in LPS-treated mice is closely related to the embryo loss, and that the Chinese herbal medicine prescription composed of Radix scutellariae and Rhizoma atractylodis has an anti-abortive effect through inhibition of maternal-fetal interface immunity.

Reduced phagocytotic activity of macrophages in the bovine retained placenta

This study was carried out to investigate the distribution of immune cells in the bovine placenta during the postpartum period and to compare these cells between normal and retained placenta. Within 1 h after normal calving, biopsy samples of placentomes were collected from 10 cows. The occurrence of retention of fetal membranes was monitored for more than 8 h post-calving, and the samples obtained were divided into two groups: normally discharged and retained placenta (n = 5 each). Immunohistochemical procedures were utilized to detect macrophages and T lymphocytes. Numerous CD14-positive macrophages were found in the stroma of both normal placenta and retained placenta whereas only a few CD3-positive T lymphocytes were found in both cases. However, histochemical staining for acid phosphatase, a predominant lysozomal enzyme, revealed that almost all macrophages showed strong enzyme activity in the normally discharged placentas, whereas in retained placenta the activity of acid phosphatase was conspicuously decreased in intensity. These results indicate that there are functional differences in placental macrophages between normal and retained placenta.

Inducible nitric oxide synthase expression by peritoneal macrophages in endometriosis-associated infertility

OBJECTIVE

Determine whether peritoneal macrophages from women with endometriosis-associated infertility express more inducible nitric oxide synthase (NOS2) and produce more NO than fertile controls.

DESIGN

Unblinded clinical study.

PATIENT(S)

Nine infertile women with endometriosis and nine normal fertile women undergoing laparoscopy.

INTERVENTION(S)

Peritoneal fluid and macrophages were collected. Cells were also cultured with the NOS2 inducers interferon-alpha (IFN-alpha) or IFN-gamma plus lipopolysaccharide (LPS).

MAIN OUTCOME MEASURE(S)

Peritoneal fluid NO levels, peritoneal macrophage NOS activity, and peritoneal macrophage NOS2 protein expression.

RESULT(S)

NOS enzyme activity was higher in peritoneal macrophages from endometriosis patients. Immunoblots demonstrated NOS2 protein only in peritoneal macrophages from women with endometriosis. Peritoneal fluid NO concentration was similar in the two groups, but total peritoneal fluid NO content was higher in endometriosis patients. After 3 days' culture, peritoneal macrophages from women with endometriosis produced more NO in response to IFN-alpha or IFN-gamma plus LPS than controls.

CONCLUSION(S)

Peritoneal macrophages from women with endometriosis-associated infertility express higher levels of NOS2, have higher NOS enzyme activity, and produce more NO in response to immune stimulation in vitro. As high levels of NO adversely affect sperm, embryos, implantation, and oviductal function, reducing peritoneal fluid NO production or blocking NO effects may improve fertility in women with endometriosis.

Nitric oxide as a regulator in preimplantation embryo development and apoptosis

OBJECTIVE

To investigate the mechanisms of nitric oxide (NO) in the development and apoptosis of preimplantation mouse embryos.

DESIGN

Prospective, controlled study.

SETTING

Medical college laboratory.

SUBJECT(S)

Two-cell embryos from outbred ICR mice.

INTERVENTION(S)

Hyperstimulation protocol, two-cell embryos were collected, then treated with or without an NO synthase inhibitor (L-NAME) or an NO donor (SNP) and combined with a cGMP analogue (8-Br-cGMP) or a selective inhibitor of NO-sensitive soluble guanylyl cyclase (ODQ).

MAIN OUTCOME MEASURE(S)

The development of ICR mouse embryo from two cells to blastocyst stages in vitro.

RESULT(S)

The development of blastocyst was inhibited by L-NAME in a concentration-dependent manner (0.1-10 microM) and 0.1 microM SNP reversed this effect (80.5% of control). Annexin-V/propidium iodide and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling techniques demonstrated that excessive NO (> or =10 microM) might induce apoptosis in the mouse embryos. 8-Br-cGMP reversed the inhibitory effect of L-NAME and rescued the embryo growth. ODQ inhibited the embryo development in a dose-responsive fashion (0.1--100 microM) but had no effect in the NO-induced embryo apoptosis. P53 and Bax were found to be up-regulated during the embryo fragmentation.

CONCLUSION(S)

These results indicate that the cGMP pathway might be involved in the NO-regulated embryonic development, but not in NO-induced apoptosis, for which P53/Bax pathway might be involved.

Does nitric oxide play a role in the aetiology of pre-eclampsia?

Although progress has been made toward our understanding of the pathophysiology of pre-eclampsia, the precise aetiology of this disease still remains an enigma. One of the hallmarks of pre-eclampsia is a failure of the extravillous cytotrophoblast cells to invade and remodel the uterine spiral arterioles during the first trimester of pregnancy. Moreover, studies suggest that the cause of this disorder may be immunological in nature. Evidence is provided here suggesting that impaired trophoblastic invasion of the spiral arterioles may be linked to the altered immunological response associated with pre-eclampsia. Previous studies by Reister et al., 1999 demonstrated a direct relationship between macrophage infiltration of the myometrial segments of spiral arterioles and reduced trophoblastic invasion in pre-eclampsia. Also, it is well established that activated macrophages produce large amounts of nitric oxide (NO). Our present findings reveal that low concentrations of NO-mimetic drugs (glyceryl trinitrate and sodium nitroprusside) inhibit the ability of trophoblast cells to penetrate through reconstituted extracellular matrix (Matrigel). This inhibition is accompanied by a reduced expression of the cell surface urokinase receptor, a molecule important for invasion. These results suggest a possible mechanistic link between the aberrant macrophage infiltration associated with pre-eclampsia, and the maladapted uteroplacental arterioles that characterize the disease.

NADPH-diaphorase activity and nitric oxide synthase isoforms in the trophoblast of Calomys callosus

The pattern of expression of a variety of placental nitric oxide synthase isoforms has contributed to elucidating the regulatory mechanisms of nitric oxide (NO) synthesis during gestation. The maintenance of vascular tone, attenuation of vasoconstriction, prevention of platelet and leukocyte adhesion to the trophoblast surface, and possible participation in uterine blood flow seem to be the main functions of NO generated at the fetal-maternal interface in humans and mice. Extending this knowledge to other rodent species commonly used as laboratory animals, in this study we focus on NADPH-diaphorase activity and the distribution of nitric oxide synthase isoforms (NOS) in the trophoblast cells of Calomys callosus during different phases of pregnancy. NADPH-diaphorase activity was evaluated cytochemically and the presence of NOS isoforms detected by immunohistochemistry. These techniques were performed on pre- and postimplantation embryos in situ and in vitro, as well as in placentae on d 14 and 18 of pregnancy. Neither NADPH-diaphorase activity nor inducible or endothelial NOS isoforms were found in pre-implanting embryos except after culturing for at least 48 h, when some of the embryonic cells were positive for the diaphorase reaction. On d 6.5 of pregnancy, trophoblast cells showed intense diaphorase activity both in situ and under in vitro conditions. A positive reaction was also found in the different placental trophoblast cells on d 14 and 18 of pregnancy. The inducible NOS (iNOS) isoform, but not the endothelial isoform, was immunodetected in trophoblast cells from the placenta and from postimplantation embryos in situ and under in vitro conditions. These results strongly suggest the production of NO by the iNOS isoform in the trophoblast of Calomys callosus after embryo implantation. The data also emphasise a possible role for the trophoblast in producing and releasing cytotoxic molecules at the fetal-maternal interface.

Lipopolysaccharide (LPS)-induced intra-uterine fetal death (IUFD) in mice is principally due to maternal cause but not fetal sensitivity to LPS

The present study deals with whether lipopolysaccharide (LPS)-induced intra-uterine fetal death (IUFD) is related to LPS-susceptibility of either mother or fetus and how LPS or LPS-induced TNF causes IUFD. LPS-susceptible C3H/HeN or -hypo-susceptible C3H/HeJ pregnant mice and the mice mated reciprocally with these mice were used on days 14 to 16 of gestation for experiments. All of fetuses in pregnant C3H/HeN mice mated with either C3H/HeN males [HeN(HeN)] or C3H/HeJ males [HeN(HeJ)] were killed within 24 hr when injected intravenously (i.v.) with 50 or 100 microg of LPS. On the other hand, the majority of fetuses in C3H/HeJ females mated with either C3H/HeJ males [HeJ(HeJ)] or C3H/HeN males [HeJ(HeN)] survived when injected i.v. with even 400 microg of LPS. These findings indicate that LPS-induced IUFD depends on the maternal LPS-responsiveness. LPS injected into mothers could pass through placenta to fetuses, since an injection with 125I-labeled LPS or IgG into pregnant mice resulted in considerable levels of radioactivity in fetuses as well as placenta. Cultured peritoneal macrophages derived from F1 mice of HeJ(HeN) or HeN(HeJ) mice, produced nitric oxide (NO) and tumor necrosis factor (TNF) in response to LPS, although the levels of NO and TNF were lower in comparison with those of C3H/HeN macrophage cultures, suggesting a possibility that the fetus as well as F1 cells might be responsible to LPS. LPS-induced IUFD was not blocked by treatment with anti-TNF antibody which inhibited LPS-induced TNF production in pregnant females, although an injection of recombinant TNFalpha instead of LPS could induce IUFD, suggesting that the cause of IUFD cannot be attributed to mother-derived TNF alone. The roles of LPS passed through placenta and LPS-induced mediators on IUFD were discussed.

Lack of interferon-γ confers impaired neutrophil granulocyte function and imparts prolonged survival of adult filarial worms in murine filariasis

We investigated the role of IFN-gamma in host defense during murine filariasis. Using the fully permissive infection of BALB/c mice with the rodent filaria Litomosoides sigmodontis, we show that interferon (IFN)-gamma is essential for encapsulation of adult filarial worms in inflammatory nodules and for normal worm clearance. IFN-gamma knockout (KO) mice had only one third of the nodules of wild-type mice but displayed a more than twofold increase in worm burden and increased microfilaremia. Neutrophil granulocytes, but not macrophages or eosinophils, appear to directly control worm load and nodule formation. Neutrophils, which we showed earlier to be essential for the encapsulation process in the thoracic cavity, where the worms reside, were diminished at this location in IFN-gamma KO compared to wild-type mice; they also displayed strongly reduced chemotactic and phagocytic activity compared to neutrophils of controls. This argues for a distinct defect in neutrophil activation accounting for the low formation of inflammatory nodules. Tumor necrosis factor-alpha, a major neutrophil-activating cytokine expressed by macrophages in the thoracic cavity around the worms, was highly induced in wild-type but absent in KO mice. Diminished activation of neutrophils seems to be a general hallmark of IFN-gamma KO mice, since neutrophils from uninfected KO mice also showed a reduction in chemotactic and phagocytic activity when induced by casein. In conclusion, these data are the first to define an IFN-gamma-dependent immune effector mechanism in murine filarial infection, i.e. neutrophil-mediated control of the adult worm load.

Prostaglandins and nitric oxide as molecular targets for anti-inflammatory therapy

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most used drugs worldwide, in spite of their renal and gastric side effects. Medicinal plants may represent a useful source of new effective therapeutic agents, particularly considering the new findings concerning the mediators of inflammation, such as prostaglandins and nitric oxide. In fact, the discovery of two isoforms of the enzyme cyclooxygenase, which catalyzes the conversion of arachidonic acid to prostaglandins, has opened new interesting perspectives in the treatment of inflammatory diseases. As cyclooxygenase, also nitric oxide synthase, the enzyme which converts L-arginine to nitric oxide, exists in two isoforms. It appears that the constitutive isoforms of both enzymes (cyclooxygenase-1 and constitutive nitric oxide synthase) have a regulatory-physiological role, whereas the inducible isoforms (cyclooxygenase-2 and inducible nitric oxide synthase) are involved in inflammation. A number of medicinal plants have been screened for their ability to inhibit cyclooxygenase-2 and/or inducible nitric oxide synthase activity and/or expression.

Immunology at the maternal-fetal interface: lessons for T cell tolerance and suppression

Mammalian reproduction poses an immunological paradox because fetal alloantigens encoded by genes inherited from the father should provoke responses by maternal T cells leading to fetal loss. Current understanding of T cell immunobiology and the critical role of inflammatory processes during pregnancy is reviewed and discussed. Lessons derived from studies on the regulation of T cell responsiveness during mammalian gestation are considered in the wider context of T cell tolerance toward some microbial infections and tumors, avoidance of autoimmunity, and tissue allograft rejection.

Evidence of a T(H) 1 type response associated with recurrent miscarriage

OBJECTIVE

To determine whether the T(H) 1 cytokine interferon (IFN)-gamma is associated with miscarriage whereas the T(H) 2 cytokine interleukin (IL)-10 is associated with successful pregnancy.

DESIGN

Controlled clinical study.

SETTING

Healthy volunteers in an academic setting.

PATIENT(S)

Group 1 comprised 10 nonpregnant women; group 2, 10 first-trimester primigravid women; group 3, 10 first-trimester primigravid women suffering spontaneous abortion; and group 4, 10 first-trimester pregnant women with a history of miscarriage. All women were pregnant at the time of sampling, but 5 miscarried later in the first trimester.

INTERVENTION(S)

None of the patients received any medication.

MAIN OUTCOME MEASURE(S)

Serum levels of IL-10 and IFN-gamma.

RESULT(S)

Levels of IL-10 were significantly raised in normal pregnancy. Levels of IFN-gamma were raised in the recurrent-miscarriage group as compared with normal pregnancy. When patients in group 4 were divided into those whose pregnancies went to term and those who miscarried, we found that successful pregnancy was associated with a statistically significant increase in IL-10, whereas miscarriage was associated with significantly increased levels of IFN-gamma.

CONCLUSION(S)

These results support the view that miscarriage is associated with a T(H) 1 type response.

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.

Mitogen-induced cytokine responses of maternal peripheral blood lymphocytes indicate a differential Th-type bias in normal pregnancy and pregnancy failure

PROBLEM

Profiles of Th1- and Th2-type cytokines were studied in women with a history of successful pregnancy and in women with a history of unexplained recurrent spontaneous abortions (RSA) with the objective of elucidating Th1- and Th2-type bias in normal pregnancy and pregnancy failure.

METHOD OF STUDY

Peripheral blood mononuclear cells (PBMCs) from 54 women with a history of normal pregnancy and 23 women with a history of unexplained RSA, obtained at delivery or on the day of abortion, respectively, were stimulated with phytohemagglutinin (PHA), followed by the estimation of four Th2 cytokines and four Th1 cytokines.

RESULTS

Significantly greater levels of Th2 cytokines were produced by the normal group than by the RSA group. On the other hand, significantly higher levels of Th1 cytokines were produced by the RSA group than by the normal pregnancy group.

CONCLUSIONS

These data support the concept that unexplained recurrent spontaneous abortion is associated with an increase in Th1-type reactivity, while Th2 dominance is a feature of successful pregnancy.

Development of bovine IVF oocytes cultured in medium supplemented with a nitric oxide scavenger or inhibitor in a co-culture system

Bovine IVF oocytes were cultured in modified bovine embryo culture medium (mBECM) supplemented with either a nitric oxide (NO) scavenger, hemoglobin (Hb, 1 microg/mL) and/or a NO synthesis inhibitor, L(omega)-nitro-L-arginine methyl ester (L-NAME, 1 or 1000 nM) in a cumulus-granulosa cell co-culture system. In Experiment 1, a total of 1,675 cumulus-oocytes complexes was collected for 7 mo and cultured to the blastocyst stage in mBECM with or without Hb after IVM and IVF. There were significant (P<0.0024) model effects of Hb addition and month of oocyte collection on embryo development. A significant (P<0.0023) monthly variation was detected in all developmental stages. However, addition of Hb to mBECM consistently enhanced embryo development to the blastocyst stage over all months. No statistical differences were found in the interaction between Hb addition and month except for the cleavage rate. Overall, a greater percentage of oocytes developed to the 8-cell (P<0.0459), 16-cell (P<0.001), morula (P<0.0013) and blastocyst (P<0.0024) stages after the addition of Hb. In Experiment 2, addition of L-NAME to mBECM supplemented with Hb did not further stimulate prehatched development. In conclusion, the promoting effect of Hb on in vitro development of embryos is highly repeatable over an extended period of time.

Pregnancy Ameliorates Induction and Expression of Experimental Autoimmune Uveitis

Female patients suffering from autoimmune uveitis are reported to experience a temporary remission during pregnancy. Experimental autoimmune uveitis (EAU) is a model for human uveitis. Here we examine the effect of pregnancy on the development of EAU and its associated immunological responses. Susceptible C57BL/6 mice were immunized with interphotoreceptor retinoid-binding protein (IRBP). EAU scores and Ag-specific responses were evaluated 21 days later. Mice immunized during pregnancy developed significantly less EAU than nonpregnant controls. Their lymph node cells and splenocytes produced a distinct pattern of cytokines in response to IRBP: reduced IFN-γ and IL-12 p40, but unchanged levels of TNF-α, IL-4, IL-5, and IL-10. Anti-IRBP Ab isotypes revealed an up-regulation of IgG1, indicating a possible Th2 bias at the humoral level. Ag-specific proliferation and delayed hypersensitivity, as well as mitogen-induced IFN-γ production, remained undiminished, arguing against an overall immune deficit. Interestingly, pregnant mice that received an infusion of IRBP-primed lymphoid cells from nonpregnant donors also developed reduced EAU, suggesting that pregnancy suppresses not only the generation, but also the function of mature uveitogenic effector T cells. Pregnant mice at the time of immunization exhibited elevated levels of TGF-β, but not of IL-10, in the serum. We suggest that protection from EAU during pregnancy is due primarily to a selective reduction of Ag-specific Th1 responses with only marginal enhancement of Th2 function, and that these effects may in part be secondary to elevated systemic levels of TGF-β.

From the decidual cell internet: trophoblast-recognizing T cells

The mammalian fetus has been perceived, paradoxically, as a successful allograft, a successful tumor, and a successful parasite. Success depends on fetal trophoblast cells, which form the interface with the mother. The maternal immune system is involved in the success of pregnancy and in its failure. The discovery that maternal gammadelta T cells may recognize and react to the fetal trophoblast and the definition of a vascular mechanism whereby their Th1 and Th2/3-type cytokines may abort embryos replaces confusion and debate with a new and simple clarity that enables further research.

Docosahexaenoic acid, a constituent of fetal and neonatal serum, inhibits nitric oxide production by murine macrophages stimulated by IFN gamma plus LPS, or by IFN gamma plus Listeria monocytogenes

Murine macrophage activation is deficient in the fetus and the neonate, and in areas of the placenta perfused by the fetal circulation. Fetal and neonatal serum concentrations of docosahexaenoic acid (DHA) are 150 microM, or approximately 50-fold higher than in the adult. We previously showed that DHA inhibits activation of the gene for inducible nitric oxide synthase (iNOS) in murine macrophages stimulated in vitro with interferon gamma (IFN gamma) plus lipopolysaccharide (LPS). We have now pursued these observations in greater depth. An assay system was developed which separated the stimulation of macrophages by IFN gamma plus LPS, and the actual production of nitric oxide (NO). It was found that macrophages do not produce NO until they have been stimulated by IFN gamma plus LPS for a period of 10 h. NO is produced during the subsequent 10 h, even though IFN gamma plus LPS are not longer present. DHA, if present, inhibited only during the initial 10 h stimulation; DHA did not inhibit the production of NO by macrophages which had previously been stimulated by IFN gamma plus LPS, and were already producing NO. It was also found that DHA was less inhibitory if given prior to the IFN gamma plus LPS stimulation. In a dose-responsive manner, DHA inhibited the increased abundance of iNOS mRNA by macrophages stimulated by IFN gamma plus LPS. NO contributes to the host defense against Listeria monocytogenes and other intracellular pathogens. We therefore investigated the ability of DHA to inhibit NO production by macrophages stimulated by IFN gamma plus Listeria monocytogenes in vitro; DHA inhibited transcription of the iNOS gene and also the listeriocidal activity of activated macrophages. Inhibition of NO production by DHA may contribute to the increased susceptibility of the fetoplacental unit and neonate to intracellular infections.

Tumor necrosis factor-alpha mRNA-positive cells in spontaneous resorption in rodents

PROBLEM

It has been proposed that high rates of resorption/spontaneous abortion may result from interaction in the decidua of gamma-interferon-producing natural killer (NK) cells and tumor necrosis factor (TNF)-alpha-producing macrophages. An increased release of TNF-alpha from placental tissue of resorptions has been reported, but macrophages producing TNF-alpha have so far not been demonstrated at the feto-maternal interface. Therefore, we have sought to identify TNF-alpha-producing cells by in situ hybridization at the feto-maternal interface in two inbred, well-characterized, and stable strains of laboratory rodents with high and low resorption rates.

METHOD OF STUDY

Pregnant DBA/2-mated CBA/J mice with a resorption rate of 20% to 30% (dependent on NK cells and macrophages) and diabetes-resistant Bio-Breeding/Edinburgh (DR-BB/E) rats with low resorption rates (presumed to result from chromosomal abnormalities) were studied. AsialoGM1+ cells were detected by immunohistochemistry, and TNF-alpha mRNA+ cells were detected by in situ hybridization.

RESULTS

TNF-alpha mRNA+ cells were detected in DBA/2-mated CBA/J mice at the time of resorption but only at the trophoblast-decidual junction. AsialoGM1+ cells were present in decidua, as assessed by immunohistochemistry, but few if any gave a positive signal for TNF-alpha. In rat resorptions, TNF-alpha mRNA-positive cells were present within the yolk sac and in contact with the trophoblast, but not at the trophoblast-decidual junction. In neither species did a significant accumulation of detectable TNF-alpha mRNA+ cells occur before the usual time of onset of resorption.

CONCLUSIONS

In the DBA/2-mated CBA/J mouse, the removal of the placenta is associated with removal of a thin rim of adherent decidua similar to the location of the TNF-alpha mRNA+ cells detected in this study. Our data suggest that increased TNF-alpha in tissues associated with failing feto-placental units may arise from infiltration/activation of scavenger cells from decidua that are likely to be macrophages. Local TNF-alpha production in decidua, which occurs as a prelude to resorption in the CBA x DBA/2 model, could not be detected due to the insensitivity of the TNF-alpha probe we used; the release of TNF-alpha from decidual tissue left after the removal of the placenta does not differ between resorbing and healthy implant sites. AsialoGM1+ cells did not seem to be major producers of TNF-alpha. TNF-alpha mRNA+ cells in a low rate of resorption (rat) model were only found on the fetal side of the trophoblast, and they may also represent a macrophage response (to dying embryo tissue) derived from a nondecidual source. The location of TNF-alpha mRNA+ cells may identify distinct and different mechanisms of resorption in rodents.

Granulated metrial gland cells contain nitric oxide synthases during pregnancy in the rat

Nitric oxide synthase (NOS) enzyme activity is present in rat decidua and metrial gland, and the activity decreases near the end of pregnancy. In this study, inducible and endothelial NOS isoforms were immunolocalized to rat granulated metrial gland (GMG) cells using anti-NOS antibodies proven to be isoform specific. These NOS-positive GMG cells are of the natural killer cell lineage as they stained positively for NKR-P1 cell surface receptor, and for perforin. The number of NOS-positive GMG cells corresponded with the level of decidual and metrial gland NOS enzyme activity. NOS activity declined when GMG cells containing NOS decreased in number. Uterine arteriolar vascular smooth muscle also stained positively for inducible NOS and the staining did not change with advancing gestation. Only a minority of uterine myocytes stained positively for inducible NOS and these were subjacent to the placental attachment site. Neuronal NOS immunostaining was not present in the decidua and the metrial gland.

Modification of macrophage response to lipopolysaccharide by fetuin

The physiological role(s) of fetuin, a protein present in plasma and many tissues of developing animals at levels much higher than in the adult, is unknown. Here we show that fetuin can modify the responses of macrophages to lipopolysaccharide (LPS) stimulation. At concentrations of fetuin in the medium, corresponding to fetal levels of this protein in plasma, the production and secretion of interleukin 1beta (IL-1beta) and nitric oxide (NO) is almost abolished, tumour necrosis factor-alpha (TNF-alpha) reduced, while that of IL-6 is not affected. On the other hand, concentrations of fetuin corresponding to adult plasma levels (i.e. 40-60 mg/100 ml) were without much effect on macrophage synthesis and secretion of these cytokines.

Altered interleukin 12 and nitric oxide levels in recurrent miscarriage

The causes of recurrent miscarriage are not fully understood. Recent studies have suggested that whilst a TH 2 type immune response may be associated with a healthy pregnancy, miscarriage may be associated with a TH 1 type response. Serum levels of nitric oxide (NO) and Interleukin 12 (IL 12) were measured in; healthy non-pregnant women; healthy pregnant women; women suffering spontaneous abortion; pregnant women with a history of recurrent miscarriage; non-pregnant women with a history of recurrent miscarriage. Normal pregnancy was associated with a significant decrease in serum levels of nitrite (13.0 vs. 22.0 P < 0.0001). In women admitted with spontaneous abortion there was a significant increase in the levels of nitrite (16.0 vs. 13.0 P < 0.05), but no change in IL 12 compared to normal pregnant women. In pregnant women with a history of recurrent miscarriage levels of nitrite (16.0 vs. 13.0 P < 0.05) and IL 12 (10.0 vs. 6.0 P < 0.0006) were significantly elevated compared to normal pregnancy. When these women were sampled prior to becoming pregnant the levels of NO were found to be significantly lower than those in the non-pregnant control group (13.1 vs. 22.0 P < 0.05) although levels of IL 12 were unchanged. No correlation was found between serum nitrite and IL 12 levels. This report further supports the idea that polarisation of the immune response during pregnancy may predispose to recurrent miscarriage.

Female steroid hormones regulate production of pro-inflammatory molecules in uterine leukocytes

Estrogens and progesterone could be among the environmental signals that govern uterine immune cell synthesis of pro-inflammatory substances. In order to investigate this possibility, we first mapped expression of the inducible nitric oxide synthase (iNOS) and tumor necrosis factor-alpha (TNF-alpha) genes in the leukocytes of cycling and pregnant mouse uteri, then tested the ability of estradiol-17 beta (E2) and progesterone to influence gene expression. Immunohistochemistry, in situ hybridization, and other experimental approaches, revealed that the iNOS and TNF-alpha genes are expressed in mouse uterine mast cells, macrophages and natural killer cells (uNK). Gene expression in each cell type was noted to be dependent upon stage of the cycle or stage of gestation, implying potential relationships with levels of female hormones and state of cell differentiation or activation. Further in vivo and in vitro experiments showed that individual hormones have cell type-specific effects on synthesis of iNOS and TNF-alpha that are exerted at the level of transcription. In uterine mast cells, iNOS and TNF-alpha are promoted by E2 whereas preliminary studies in macrophages suggest that transcription and translation of the two genes are unaffected by E2 but are inhibited by progesterone. Uterine NK cell production of iNOS and TNF-alpha is strongly related to cell differentiation, which is initiated and sustained by progesterone. Collectively, the results indicate that regulation of synthesis of pro-inflammatory molecules by hematopoietic cells in cycling and pregnant uterus comprises a new and potentially critical role for female steroid hormones.

Role of interferon-gamma in the priming of decidual macrophages for nitric oxide production and early pregnancy loss

We have previously shown that both priming and triggering signals were needed for nitric oxide production by decidual macrophages and that nitric oxide was responsible for embryo wastage. In this study, we investigated the role of IFN-gamma as the primary signal for macrophage activation in early embryo loss. IFN-gamma-deficient (GKO) and heterozygous F1 control mice were injected with lipopolysaccharide (LPS) at day 7 of gestation. The results showed that the GKO mice were more resistant to LPS-induced embryo loss than the wild type. This suggested that IFN-gamma was needed for LPS-induced embryo resorption and that decidual macrophages from pregnant GKO mice were not primed and could not be activated when given LPS. Further, the results showed that IFN-gamma mRNA was simultaneously expressed in the same embryos that also expressed mRNA markers for macrophage activation (TNF-alpha and iNOS), indicating that macrophage activation could be a consequence of IFN-gamma production. Similarly, we investigated the role of IL-12 as a switch cytokine capable of eliciting TH1-associated cytokine production including IFN-gamma. The results showed that IL-12 mRNA expression was correlated with IFN-gamma expression and macrophage activation. In this in vivo study, we showed for the first time that spontaneously increased decidual IFN-gamma expression is detrimental to embryo survival.

Low serum M-CSF levels are associated with unexplained recurrent abortion

PROBLEM

The purpose of this study was to determine whether the serum macrophage-colony stimulating factor (M-CSF) level is associated with early pregnancy loss in unexplained recurrent spontaneous abortion (RSA) patients.

METHOD

We therefore compared preconceptional serum M-CSF levels between unexplained RSA patients and controls. The former comprised 44 bed-rest therapy patients and 43 intradermal immunization (IDI) patients receiving paternal lymphocyte therapy, who had experienced two and three or more consecutive first-trimester pregnancy losses, respectively. The controls were 46 healthy non-pregnant women. We also prospectively studied the association between M-CSF levels during pregnancy and adverse pregnancy outcomes. Sera from a total of 31 pregnant women, including 16 of the bed-rest therapy group and 15 of the IDI therapy group, were collected at the 4th, 6th, and 8th gestational weeks and were measured for M-CSF levels, using the enzyme-linked immunoadsorbent assay (ELISA) method established by Hanamura et al.

RESULTS

Serum M-CSF levels were significantly lower in the non-pregnant RSA patients (460.0 +/- 185.6 U/ml; mean +/- SD) than in the control group (726.5 +/- 134.0 U/ml) and also were lower at the 8th, but not the 4th or 6th gestational week in those patients of both the bed-rest and IDI therapy groups whose outcome was pregnancy failure.

CONCLUSION

Thus a low level of serum M-CSF was found to be associated with unexplained recurrent pregnancy loss in both the preconceptional and conceptional phases. These results raise the possibility that M-CSF may play an important role in the maintenance of pregnancy and that it can be used as a parameter for determining individuals at risk.

Maternal anti-placental cell-mediated reactivity and spontaneous abortions

PROBLEM

Does Th1/Th2 balance determine pregnancy outcome, and if so, what determines Th1/Th2 balance in pregnancy?

METHOD

Review and synthesis of existing data.

RESULTS

A bias toward Th1 is strongly correlated with pregnancy failure in mice and humans. Pregnancy usually shifts the balance toward Th2 and placental factors/progesterone and progesterone-stimulated CD8+ T cell production of suppressor factor; TGFbeta2 and IL4/10 may be responsible. The bias toward a Th1 response may result from intracellular parasitic infection and other as yet undefined factors.

CONCLUSION

The Th1/Th2 balance thesis appears to be valid.

Decidual infiltration and activation of macrophages leads to early embryo loss

PROBLEM

There is considerable controversy concerning the root cause and mechanisms of early embryo loss. It has been suggested that most pregnancy losses occur due to morphogenetic anomalies of the embryo. It has also been suggested that the maternal specific immune system rejects the embryo.

METHODS

Existing data on the cell and molecular biology of early embryo loss in murine experimental models is reviewed.

RESULTS

Using the CBA(female) x DBA/2(male) model of early embryo loss, it has been established that maternal inflammatory cells infiltrate the decidua basalis of all implantation sites within 48 hr after implantation. For most embryos, the relatively low numbers of macrophages (Mphi) and natural killer-like (NK-like) cells of maternal origin remain relatively constant after day 8, whereas 20-30% of the embryos show a significant increase in inflammatory cells in the maternal decidua, corresponding to the incidence of early embryo resorption visible at day 12. Evidence will be reviewed to suggest that decidual NK-like cells are not cytolytic but may be producing the Mphi-activating cytokine interferon gamma (IFN-gamma), which activates decidual Mphi and other cells. Furthermore, embryo loss is ameliorated by in vivo treatment with anti-IFNgamma or anti-NK antisera, indicating that NK-like cells and/or IFNgamma are required for embryo loss, but not for embryo survival. In resorbing embryos, the inflammatory Mphi show evidence of having been primed during early pregnancy, in that in vitro incubation with lipopolysaccharide induced the production of tumor necrosis factor alpha and nitric oxide.

CONCLUSION

These findings support the concept that early embryo loss is a nonspecific event mediated by the triggering of cytotoxin production by primed decidual macrophages.

The antiabortive effect of progesterone-induced blocking factor in mice is manifested by modulating NK activity

Immunologic effects of progesterone are mediated by a protein named the progesterone-induced blocking factor (PIBF), which inhibits NK activity and displays an antiabortive effect in mice. Our previous data provide indirect evidence for the importance of PIBF in the maintenance of normal gestation. This study was aimed at investigating whether neutralization of endogenous PIBF production influences pregnancy outcome and if so, what are the mechanisms that participate in this process. Syngeneically pregnant Balb/c mice on Day 8.5 of pregnancy were injected ip with 0.3 mg/kg of RU 486 or with 0.5 mg of rabbit anti-PIBF IgG alone, or together with anti-NK monoclonal antibodies. Mice treated with the same amount of normal rabbit serum or untreated mice of similar gestational age were used as controls. On Day 10.5 the ratio of living and resorbed embryos and NK activity of the spleen cells were determined. In mice treated with anti-PIBF the ratio of resorbed fetuses was significantly higher than that in untreated controls. In RU 486-treated mice we also observed significantly increased resorption rate, which was associated with the inability of spleen cells to produce PIBF. Both anti-PIBF treatment and that with progesterone receptor blocker resulted in increased splenic NK activity. There was a positive relationship between NK activity and the rate of resorptions. All the above effects were corrected by simultaneous treatment with anti-NK or anti-NC (natural cytotoxic) antibodies. These data allow the conclusion that PIBF contributes to normal gestation in mice and that the effect of PIBF is manifested via blocking NK and/or NC activity.