Activation of maternal killer cells in the pregnant uterus with chronic indomethacin therapy, IL-2 therapy, or a combination therapy is associated with embryonic demise

Racial differences in risk of spontaneous abortions associated with periconceptional over-the-counter nonsteroidal anti-inflammatory drug exposure

PURPOSE

Nonsteroidal anti-inflammatory drugs (NSAIDs) are one of the most common medications reported in pregnancy. NSAIDs directly impact prostaglandin pathways and have been proposed as potential risk factors for spontaneous abortions (SABs, gestation <20 weeks). SAB risk and drug response across several medications differ by race; therefore, we evaluated whether associations between NSAIDs and SAB risk differ by race.

METHODS

Women were enrolled in the Right from the Start (2004-2010) prospective cohort. Data regarding over-the-counter NSAIDs up to the sixth week of pregnancy were obtained from interviews. Race was self-reported. Cox proportional hazards regression models were used to estimate the association between NSAID exposure and SAB, adjusted for confounders.

RESULTS

Among 2493 pregnancies, 12% were African American and 88% were Caucasian. NSAID exposure was reported by 40% (n = 124) of African Americans and 43% (n = 945) of Caucasians. Race-stratified analyses showed protection from SAB among African Americans (adjusted hazard ratio [aHR], 0.84; 95% confidence interval [CI], 0.73-0.96) but no effect in Caucasians (aHR, 1.01; 95% CI 0.88-1.16).

CONCLUSIONS

Our findings suggest that risk for SAB due to over-the-counter NSAIDs in early pregnancy is modified by race. Further investigation of dose, timing in gestation, and indication may help to further reconcile the relationship between race, NSAIDs, and SAB.

Periconceptional over-the-counter nonsteroidal anti-inflammatory drug exposure and risk for spontaneous abortion

OBJECTIVE

To estimate the association between over-the-counter nonsteroidal anti-inflammatory drug (NSAID) exposure during the early first trimester and risk for spontaneous abortion (gestation before 20 weeks of gestation) in a prospective cohort.

METHODS

Women were enrolled in the Right from the Start study (2004-2010). Exposure data regarding over-the-counter NSAID use from the last menstrual period (LMP) through the sixth week of pregnancy were obtained from intake and first-trimester interviews. Pregnancy outcomes were self-reported and verified by medical records. Gestational age was determined from the LMP. Stage of development before loss was determined from study ultrasonography. Cox proportional hazards regression models were used to estimate the association between NSAID exposure and pregnancy outcome taking into account candidate confounders.

RESULTS

Among 2,780 pregnancies, 367 women (13%) experienced a spontaneous abortion. NSAID exposure was reported by 1,185 (43%) women. NSAID exposure was not associated with spontaneous abortion risk in unadjusted models (hazard ratio [HR] 1.01, 95% confidence interval [CI] 0.82-1.24) or models adjusted for maternal age (adjusted HR 1.00, 95% CI 0.81-1.23).

CONCLUSION

Our findings suggest that use of nonprescription over-the-counter NSAIDs in early pregnancy does not put women at increased risk of spontaneous abortion.

Cytokines: Important for implantation?

PROBLEM

Cytokines are obviously very important in an established pregnancy, but what about human embryo implantation?

METHODS

Literature review.

RESULTS

We first discuss the necessity and limits of animal models, and then review the few cytokines which have been demonstrated by knock-out methods to be absolutely necessary for embryo implantation using in animal models. We then review what is known or discussed about the role of other cytokines as deduced from quantitative and/or qualitative dysregulation in animals and in humans.

CONCLUSIONS

Cytokines are indeed involved in implantation as they are in ongoing pregnancy and delivery. Relevance to infertility and recurrent pregnancy loss is discussed.

Immunology of normal pregnancy

Since Medawar's initial contemplations in 1953 on the mechanisms of immune evasion allowing for the survival of the allogeneic conceptus in an immunologically competent mother, physicians and immunologists alike have struggled to understand the immunological paradox of pregnancy. Ultimately, our attempts to define the immunology of normal pregnancy have broadened our appreciation of the myriad mechanisms at play that enable the promotion of implantation and maintenance of pregnancy. In this review, we summarise what is known regarding the immunology of normal pregnancy, with special emphasis on the relation to common disorders of pregnancy.

Regulation of chemokine production in response to pro-inflammatory cytokines in first trimester decidual cells

OBJECTIVE

Chemokines initiate the immune response by controlling leukocyte migration and lymphocyte development. Macrophage infiltration of the decidua has been implicated in the genesis of recurrent miscarriage and preeclampsia. Therefore, we determined whether cultured human decidual cells produce monocyte/macrophage-recruiting chemokines in response to a potent pro-inflammatory cytokine, interleukin-1beta (IL-1beta), and whether decidual cell-conditioned medium contains monocyte- and macrophage-chemoattractant activity.

METHODS

Leukocyte-free first trimester decidual cells were treated for 6h with estradiol (E(2)) and medroxyprogesterone acetate (MPA) to mimic the steroidal milieu of pregnancy, or E(2) and MPA and IL-1beta (1 ng/ml) to mimic inflamed decidua. Total RNA was used for cDNA synthesis. Biotinylated cRNAs were generated and chemically fragmented for hybridization on Affymetrix HG_U133 Plus 2.0 chips followed by fluorescence labeling and optical scanning. Raw data generated from Affymetrix GCOS 1.2 (GeneChip Operating Software) were analyzed by GeneSpring 7.2 software. Subsequently microarray results were validated by real time RT-PCR and Western blotting. A functional study of monocyte migration was carried out also using conditioned media from culture.

RESULTS

Five chemokines responsible for monocyte/macrophage chemoattraction and activation, including C-C motif ligand 2 (CCL2), CCL5, C-X-C motif ligand 2 (CXCL2), CXCL3 and CXCL8, were markedly elevated from 29- to 975-fold after exposure to IL-1beta in cultured first trimester decidual cells. The results of real-time RT-PCR (up-regulation from 43- to 3069-fold) and Western blotting (up-regulation from 15- to 300-fold) confirmed the microarray findings. Monocyte migration was significantly induced by the conditioned medium from IL-1beta-treated decidual cells.

CONCLUSIONS

Treatment of first trimester decidual cells with IL-1beta induces secretion of monocyte/macrophage recruiting-chemokines and promotes monocyte migration. Extrapolation of these in vitro results to the milieu of implantation site suggests a mechanism whereby IL-1beta could mediate excessive macrophage infiltration of the decidua.

Dietary Echinacea purpurea during murine pregnancy: effect on maternal hemopoiesis and fetal growth

BACKGROUND

The medicinal benefits of Echinacea sp. plants in several disease conditions, including insect bites, respiratory ailments, and even cancer and AIDS, have been touted for decades. Echinacea sp.-based phytoceuticals are among the top selling herbals in the Western marketplace today. However, evidence is very scant concerning the effects of using Echinacea species herbals during pregnancy. While available data indicates that fetal malformations do not occur during pregnancy in humans consuming this herb, there are no formal studies aimed at assessing the possibility that consuming Echinacea herbals may promote spontaneous abortions, thereby reducing the number of live births upon which to assess the presence or absence of malformations.

OBJECTIVES

We undertook a study in which pregnant mice were fed daily Echinacea purpurea from pregnancy onset until gestational days 10, 11, 12, 13, and 14.

METHODS

Maternal spleen and bone marrow were taken for enumeration of cells in each of five separate hemopoietic lineages/organ, and fetal status was recorded.

RESULTS

The data indicate that the significant, pregnancy-induced elevation in splenic lymphocytes and nucleated erythroid cells was all but eliminated in those females which consumed E. purpurea daily throughout their pregnancy. Moreover, consuming E. purpurea during pregnancy reduced the number of viable fetuses.

CONCLUSIONS

The data may be extrapolated to suggest that in humans, abstention from consuming Echinacea products during the early/mid stages of pregnancy, may be prudent.

Perforin improves the morphogenesis of mouse placenta disturbed by IL-2 treatment

The pore-forming protein (perforin) produced by lymphocytes can induce apoptosis in target cells. In mouse placenta, although a large amount of perforin is produced by the uterine natural killer (uNK) cells, its role in the reproductive process is still not clear. Since the cytotoxicity of uNK cells can be enhanced by interleukin (IL)-2, we studied the role of perforin in the placenta of wild-type and perforin-knockout mice treated with IL-2 during days 10-14 of pregnancy. Immunohistochemistry of the wild-type mice showed that the perforin was positive in the membrane of trophoblast glycogen cells as well as the cytoplasm of uNK cells, and there was an increase in the expression level following IL-2 treatment as revealed by RT-PCR analysis, although no change was identified in fertility. In the IL-2-treated perforin-knockout mice, however, the number of live fetuses was decreased, accompanied by an increase in the weight of placentae. Examination of these placentae showed an abnormally enlarged junctional zone, occupied by a large number of the trophoblast glycogen cells and significantly few of the apoptotic cells. These findings indicate that perforin can contribute to a successful pregnancy by inhibiting the excessive growth of the junctional zone induced by IL-2.

Leukocyte Subpopulations in the Uteri of Leukemia Inhibitory Factor Knockout Mice During Early Pregnancy1

Leukemia inhibitory factor (LIF) is transiently expressed on Day (D) 1 of pregnancy by the uterine epithelium and on D4 specifically by the glandular epithelium. The Lif knockout female mice are infertile because of uterine defects that affect embryo implantation, but pregnancy can be rescued in these mice by injections of LIF on D4 of pregnancy. Many of the specific actions of LIF in the uterus are unknown, especially with regard to uterine cell biology. Leukocytes, such as macrophages, natural killer (NK) cells, and eosinophils, are present in the pregnant uterus and are thought to be beneficial, because alterations in their proportions can adversely affect pregnancy. Immunocytochemistry and cell counting were used to compare the distributions and dynamics of leukocyte subpopulations in wild-type and Lif knockout mice. The percentage of macrophages was reduced by more than half in the Lif knockout mice on D3 of pregnancy, and their distribution was disrupted, suggesting that LIF is a chemokine for these cells. The NK cells were detected as early as D3 of pregnancy, but the Lif knockout mice had double the percentage of NK cells compared to wild-type mice at this time, indicating that LIF restricts the migration of NK cells to the uterus. The Lif knockout mice also had significantly higher percentages of eosinophils in the outer stroma on D3, and in the midstroma on D4, of pregnancy, suggesting that LIF also may restrict eosinophil migration to the uterus. These alterations of the uterine leukocyte subpopulations in Lif knockout mice may disrupt pregnancy and contribute to failure of implantation.

Decidualization of the human endometrial stromal cell: an enigmatic transformation

Changes in human endometrium are essential to allow the establishment of pregnancy. These changes are induced in vivo by progesterone, and include appearance within the tissue of a specific uterine natural killer cell, characterized by an abundant expression of CD56. Changes also occur in the stromal cells, which undergo a characteristic decidualization reaction. Decidualized stromal cells are derived from the fibroblast-like cells within the endometrium, which maintain their progesterone receptors in the presence of progesterone. Prolonged exposure to progesterone induces a rounded cell characterized by release of prolactin and insulin-like growth factor binding protein-1 (IGFBP-1), and expression of tissue factor. Additional changes include the secretion of interleukin (IL)-15, vascular endothelial growth factor, and surface expression of zinc dependent metalloproteinases such as CD10 and CD13. In vitro, elevated intracellular cAMP as well as progesterone is necessary for decidualization. In vivo, these conditions may be provided by progesterone from the corpus luteum, by prostaglandin E, a stimulator of adenyl cyclase, and relaxin, which has recently been shown to be a phosphodiesterase inhibitor. Given the co-distribution of uterine natural killer cells and decidualized stromal cells, a mutual interaction might provide the correct regulatory environment for successful implantation, and penetration of the maternal blood vessels by trophoblastic cells.

Prolactin-like protein-A is a functional modulator of natural killer cells at the maternal-fetal interface

Natural killer (NK) cells are the predominant lymphocytes present in healthy rodent and human implantation sites. In the rat, the expansion, differentiation and subsequent migration of NK cells away from the developing chorioallantoic placenta coincide with the expression of a novel pregnancy- and trophoblast cell-specific cytokine, prolactin (PRL)-like protein A (PLP-A). PLP-A specifically binds to uterine NK cells but does not appear to utilize receptor systems for PRL. In the present report, we show that PLP-A interactions with NK cells are not mediated by receptors utilized by known modulators of NK cell function, including interleukin-2, interleukin-7, interleukin-12, and interleukin-15 (IL-15). Uterine NK cells respond to PLP-A or IL-15 with an increase in intracellular calcium mobilization. In contrast, PLP-A, unlike IL-15, effectively suppresses the ability of NK cells to produce interferon-gamma (IFNgamma), a key mediator of NK cell function. Placental PLP-A expression is reciprocal to mesometrial decidua expression of IFNgamma. Increased expression of PLP-A by the placenta coincides with the decline of IFNgamma content in the mesometrial decidua adjacent to the placenta. In summary, trophoblast cell-derived PLP-A contributes to the regulation of NK cells at the maternal-fetal interface to ensure appropriate embryonic growth and development.

Cyclooxygenase is involved in the effects of progesterone-induced blocking factor on the production of interleukin 12

OBJECTIVE

Immunologic effects of progesterone are mediated by the progesterone-induced blocking factor. Progesterone-induced blocking factor inhibits natural killer cytotoxic activity and arachidonic acid release from mononuclear cells. The relationship between increased prostaglandin synthesis and increased cytotoxic activity of the lymphocytes is still unclear; therefore we investigated the effect of progesterone-induced blocking factor-neutralizing antibody, as well as simultaneous indomethacin treatment, on interleukin 12 production.

STUDY DESIGN

Pregnancy lymphocytes were treated with anti-progesterone-induced blocking factor antibody or lipopolysaccharide as a positive control in the presence or absence of indomethacin. Interleukin 12 production by peripheral blood mononuclear cells was detected by immunocytochemical examination. The 2-tailed Student t test was used for statistical evaluation.

RESULTS

Neutralization of progesterone-induced blocking factor, as well as lipopolysaccharide treatment, resulted in an increased expression of interleukin 12 that was corrected by simultaneous indomethacin treatment.

CONCLUSION

Progesterone-induced blocking factor reduces the expression of interleukin 12 via the inhibition of arachidonic acid metabolism. This results in lowered cytotoxic natural killer activity, which favors a normal pregnancy outcome.

Uterine natural killer cells are targets for a trophoblast cell-specific cytokine, prolactin-like protein A

PRL-like protein A (PLP-A) is a member of the PRL family expressed in trophoblast cells coincident with establishment of the chorioallantoic placenta. The purpose of this investigation was to identify targets for PLP-A. Using an alkaline phosphatase-tagging strategy, we show that PLP-A specifically interacts with a population of natural killer (NK) lymphocytes within the mesometrial compartment of decidua from pregnant and pseudopregnant rats. These observations are supported by the codistribution of PLP-A targets with cells expressing the rat NK cell surface marker, gp42, the absence of PLP-A binding in conceptuses from NK cell-deficient tg epsilon26 mice, and the specific interaction of PLP-A with a rat NK cell line, RNK-16. We have further demonstrated that PLP-A effectively suppresses RNK-16 cell cytolytic activities. Our results provide evidence for a new paradigm of embryonic-maternal communication involving a PLP-A signaling pathway between trophoblast cells and uterine NK lymphocytes.

Lymphocyte subsets and mitogen stimulation of blood lymphocytes in preeclampsia

PROBLEM

The question of whether there are differences in systemic immune reactivity in severe preeclampsia compared with normal pregnancy was addressed.

METHOD OF STUDY

During the third trimester, blood samples were taken from 12 pregnant women with severe preeclampsia. Five of the preeclamptic pregnancies were analyzed separately because they were treated with dexamethasone before the blood samples were taken. The seven dexamethasone-treated preeclamptic pregnant women were analyzed and compared with six uncomplicated pregnancies. A control group consisted of 15 nonpregnant females. Lymphocyte subsets were identified by flow cytometry. The function of peripheral blood mononuclear cells (PBMCs) was studied as proliferative responses to mitogens alone and in combination with immunomodulating drugs.

RESULTS

An increased number of B lymphocytes (CD19+) (P < 0.05) and natural killer (NK) cells (P < 0.05) was noticed in severe preeclampsia compared with normal pregnancy. The proliferative response of PBMCs in phytohemagglutinin (PHA)-stimulated cultures in autologous serum from patients with severe preeclampsia was reduced (P < 0.05) compared with normal pregnancy. The addition of indomethacin and cimetidine significantly stimulated (P < 0.05) the proliferative responses. The enhancing effect of cimetidine was not found in dexamethasone-treated preeclamptic patients.

CONCLUSIONS

The presence of systemic immunosuppression in severe preeclampsia is demonstrated as a reduced proliferative response of PBMCs to PHA, which could be partly restituted by indomethacin or cimetidine, indicating immunosuppressor activity that is mediated by prostaglandin and histamine. Increased levels of B lymphocytes and NK cells were also noticed.

In vitro response to oxytocin and interferon-Tau in bovine endometrial cells from caruncular and inter-caruncular areas

Caruncules are differentiated sites of the endometrium in which placentation occurs in ruminants. We investigated whether the response to agents involved at the time of recognition of pregnancy differed in the caruncular (CAR) and inter-caruncular (ICAR) areas of the endometrium in vitro. The specialization in prostaglandin (PG) production previously described in cells from whole endometrium was reproduced in the CAR and ICAR areas: PGF2alpha and PGE2 were produced in greater proportions, respectively, in epithelial and stromal cells. The relative production of PGE2 was equivalent in epithelial cells from CAR and ICAR regions, but the production of PGF2alpha was higher (p < 0.05) in the ICAR region (2.2 +/- 0.5 vs. 4.0 +/- 0.2 ng/ microg DNA, respectively). In stromal cells, the ICAR area produced more PGE2 than did the CAR area (3.4 +/- 0.4 vs. 2.1 +/- 0.4 ng/ microg DNA, p < 0.05), and the respective PGE2:PGF2alpha ratio was significantly higher in the ICAR area (p < 0.05). The production of PGs was measured first in response to oxytocin (OT, 10(-9) to 10(-5) M) and then to recombinant ovine interferon-tau (roIFN-tau, 0.02 to 20 microg/ml) in a separate set of experiments. In epithelial cells, OT stimulated the production of PGF2alpha 6.3-fold in the CAR area and more than 33.0-fold in the ICAR area (7.1 +/- 3.2 vs. 36.3 +/- 9.8 ng/ microg DNA, respectively, p < 0.05). Production of PGE2 was also increased in both regions and reached a plateau at 4.1 +/- 0.4 ng/ microg DNA. In epithelial cells from the ICAR but not the CAR region, the PGE2:PGF2alpha ratio was decreased in the presence of OT (p < 0.05). In separate experiments, addition of roIFN-tau stimulated PGE2 production significantly (p < 0.05), and no difference (p > 0.8) was observed between CAR and ICAR regions. An increase in PGE2:PGF2alpha ratio was observed in epithelial cells from both CAR and ICAR regions, but it was significant only in the CAR region (p < 0.05). In stromal cells, roIFN-tau stimulated PGE2 production significantly in cells from the CAR and ICAR regions (35.6 +/- 2.9 vs. 24.1 +/- 3.8 ng/ microg DNA, respectively, p < 0.05). In summary, the ICAR region seems to be the privileged site for regulation of PGF2alpha production by OT, but the caruncules may be a preferred site for recognition of the embryonic IFN-tau signal. Endometrial cells from the CAR and ICAR areas appear to exhibit specialized responses, with cells from the ICAR region more responsive to OT and those from the CAR region more sensitive to roIFN-tau.

TGF-beta 2 and PGE2 in rabbit blastocoelic fluid can modulate GM-CSF production by human lymphocytes

PROBLEM

During normal pregnancy, major changes occur in the production of Th2/Th1 cytokines at the feto-maternal interface. Th2 cytokines such as interleukin-4 (IL-4) or interleukin-10 (IL-10) are predominantly produced locally in the uterine and placental tissues, whereas the production of Th1 cytokines such as tumor necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) are decreased. Because these modulation might be induced by the embryo, the current study was carried out to test the effect of rabbit blastocoelic fluid on the production of Th2/Th1 cytokines by lymphocytes, and to investigate the possible implication of transforming growth factor beta 2 (TGF-beta 2) prostaglandin E2 (PGE2) as modulators of the production of these cytokines.

METHOD OF STUDY

Human peripheral blood lymphocytes (PBL) were cultured along with ConcanavalinA(Con A), and rabbit blastocoelic fluid was collected on day 12 of gestation (BF d-12). Concentrations of cytokines in culture media were determined by enzyme-linked immunoadsorbent assay (ELISA).

RESULTS

Addition of BF d-12 in the culture medium induced a strong inhibition of IL-2, TNF-alpha, IL-10, and granulocyte-macrophage colony-stimulating factor (GM-CSF) production. However, an initial pretreatment of the lymphocytes with BF d-12, followed by a Con A stimulation, led to a marked increase in GM-CSF production, whereas IL-2, TNF-alpha, and IL-10 secretions were inhibited. It was also demonstrated, for the first time, that a pretreatment of the lymphocytes with TGF-beta 2 and PGE2 increased GM-CSF production to the same level reached after the addition of BF d-12. Furthermore, removal of TGF-beta 2 and PGE2 from BF d-12 by affinity chromatography reduced the effect of BF d-12 on GM-CSF production.

CONCLUSIONS

Taken together, these findings suggest that the embryo, in modulating harmful and beneficial cytokine production locally, plays an active role in its protection against maternal immune cellular assault. These results also emphasize the importance of growth factors for successfully maintaining pregnancy.

PGE2, but not TGF beta 2, in rabbit blastocoelic fluid regulates the cytotoxic activities of NK and LAK cells

Spontaneous and induced fetal resorptions have been associated with the infiltration and activation of GM1-positive natural killer (NK)-like cells. Predominance of these cells in the decidua and their reduced lytic activity suggest that regulation of their killing activity could be important for the survival of the fetus. It has therefore been hypothesized that the embryo was regulating NK lytic activity. To test this hypothesis, human and rabbit lymphocytes were cultured with various concentrations of interleukin-2. Their ability to kill 51Cr-labelled NK and lymphokine-activated killer (LAK)-sensitive targets was assessed in the presence of rabbit blastocoelic fluid taken at day-12 of pregnancy (BF D-12). BF D-12 dramatically suppressed the killing activity of NK and LAK cells. This effect was observed on K562 (NK-sensitive targets), P815 cells (LAK-sensitive targets), and freshly isolated cells in rabbit trophoblastic cell preparation. Elimination of prostaglandin E2 (PGE2), but not transforming growth factor beta 2 (TGF beta 2) or 6 keto prostaglandin F1 alpha (6KPGF 1 alpha), by affinity chromatography, completely abolished BF biological activity. These findings clearly suggest that PGE2 in BF regulates the killing activity of NK and LAK cells, and that the semiallograft embryo plays an active role in its own protection. To our knowledge, it is the first demonstration that PGE2 from the embryo inhibits NK and LAK cell lytic activity.

Interleukin-2-induced mortality during the metamorphosis of Xenopus laevis

In anuran metamorphosis, histoincompatible adult cells arise within an immunocompetent larval body. However, the larvae are unresponsive to these altered-self cells. The basis for this tolerance is an issue of considerable interest. While a loss of tolerance in mammalian pregnancy may initiate localized abortion, since the entire metamorphic amphibian is involved, there is the potential for total body self-destruction. Metamorphosing Xenopus laevis, the South African clawed toad, produce an internal corticosterone environment that induces T-cell anergy. This impairment may save the animal from immune self-destruction. Here we examine the capacity of recombinant gene produced human interleukin 2 (IL-2) to substitute for, or restore the level of autologous IL-2, as a further test of whether the altered-self tolerance found during metamorphosis may rely on corticosteroid-induced anergy. We find that the capacity of rIL-2 to break this tolerance and stimulate mortality is low, unless it is accompanied by antigenic co-stimulation. A study of sections of experimental and control animals revealed lymphocyte and mast cell increases within the kidney, particularly in the region of the coelomoduct, perhaps reflecting autoimmune reactivity responsible for the mortality.

Sequence of interleukin-2 isolated from human placental poly A+ RNA: possible role in maintenance of fetal allograft

There are several cell types within the placenta that produce cytokines which can contribute to the regulatory mechanisms that ensure normal pregnancy. The immunological milieu at the maternofetal interface is considered to be crucial for survival of the fetus. Interleukin-2 (IL-2) is expressed by the syncytiotrophoblast, the cell layer between the mother and the fetus. IL-2 appears to be a key factor in maintenance of pregnancy. Therefore, it was important to determine the sequence of human placental interleukin-2. Direct sequencing of human placental IL-2 cDNA was determined for the coding region. Subclone sequencing was carried out for the 5'- and 3'-untranslated regions (5'-UTR and 3'-UTR). The 5'-UTR for human placental IL-2 cDNA is 294 bp, which is 247 nucleotides longer than that reported for cDNA IL-2 derived from T cells. The sequence of the coding region is identical to that reported for T cell IL-2, while sequence analysis of the polymerase chain reaction (PCR) product showed that the cDNA from the 3' end was the same as that reported for cDNA from T cells. Human placental IL-2 cDNA is 1,028 base pairs (excluding the poly A tail), which is 247 bp longer at the 5' end than that reported for IL-2 T cell cDNA. Therefore, the extended 5'-UTR of the placental IL-2 cDNA may be a consequence of alternative promoter utilization in the placenta.

Up-regulated expression of CD56+, CD56+/CD16+, and CD19+ cells in peripheral blood lymphocytes in pregnant women with recurrent pregnancy losses

PROBLEM

To analyze immunophenotypic profiles of peripheral blood and humoral autoimmune responses in women with a history of recurrent spontaneous abortions (RSA).

METHOD

Peripheral blood lymphocyte subsets by flow cytometry and autoantibodies to phospholipids and nuclear components by ELISA were measured in nonpregnant and pregnant women with RSA of unknown etiology. Thirty-five pregnant and eighty-one nonpregnant women with RSA were studied. Seventeen nonpregnant and twenty-two pregnant normal controls were included.

RESULTS

Natural killer (NK) cells (CD56+) were significantly elevated in nonpregnant women with RSA as compared with nonpregnant controls. Pregnant women with RSA demonstrated significantly increased NK (CD56+, CD56+/CD16+) and B cells (CD19+) as compared with pregnant controls. Women who miscarried the index pregnancy demonstrated significantly lower CD3+ cells in comparison with normal controls. Women with RSA and antiphospholipid antibodies showed significantly elevated NK cells when compared with women without antiphospholipid antibodies. Women with autoantibodies to nuclear components demonstrated significantly elevated CD19+/CD5+ cells when compared to women without autoantibodies to nuclear components.

CONCLUSIONS

Women with RSA demonstrate an abnormal cellular immune response by increasing peripheral natural killer cells and B cells as compared with normal controls.

Presence of activated macrophages in a murine model of early embryo loss

PROBLEM

Even though our knowledge of the phenomenon at play at the fetoplacental interface has greatly advanced during the past years, a complete understanding of the reasons why the developing embryo is not rejected by maternal immune effector cells remains largely unknown.

METHODS

We have used immunohistochemistry with the macrophage-specific markers F4/80 and MHC II to study the relationship between decidual infiltration and resorption in murine models of embryo loss between days 6 and 10 of gestation.

RESULTS

Analysis of day 8 CBA/J x DBA/2 pregnancies has revealed 2 distinct populations of embryos. The majority (69.4%) expressed low levels of F4/80+ cells, but a minority (30.6%) expressed much higher level of the macrophage marker. In FBA/J x BALB/c, most embryos (91.7%) expressed low numbers of F4/80+ cells. As earlier experiments established that products of activated macrophages (TNF-alpha and nitric oxide) were implicated in embryo loss in this model, the activation status of the F4/80+ macrophages was assessed through the cell surface expression of MHC II. Again, a similar association was established: 30.6% of the CBA/J x DBA/2 embryos were infiltrated by significantly more MHC II+ cells than the control CBA/J x BALB/c mating. Finally, when coordinate expression of F4/80, MHC II and CD11b was assessed, it was found that an embryo significantly infiltrated by cells bearing one of the 3 markers was also heavily infiltrated by cells bearing the 2 other markers.

CONCLUSIONS

This study has shown that the augmented infiltration of the deciduum with maternal macrophages is an early event which precedes spontaneous abortion of the early embryo.

Possible role and mechanism of inactivation of decidual NK cells in pregnancy

Decidual NK cells are present in murine decidua in early pregnancy, but they decline by midpregnancy. The participation of these cells in rapid rejection of abnormal fetuses and possible cytolitic activity of these cells to trophoblasts seems unlikely. But, their production of cytokines (like CSF-1, which promote differentiation and growth of trophoblasts cells) may be the primary role of decidual NK cells in time of establishment of fetal-maternal connection. Later, inactivation of decidual NK cells by prostaglandins prevents damage of embryos.

Natural killer and natural cytotoxic cells are present at the maternal-fetal interface during murine pregnancy

NK cell activity has been detected in the early murine decidua, and hypothesized to be mediated by granulated metrial gland (GMG) cells. The possibility that natural cytotoxic (NC) cells are also present in the decidua has not been investigated. In this study mAb to NK cells (anti-NK-1.1) and NC cells (anti-NC-1.1) were used to characterize the decidual cells of days 8-14 pregnant (CBA x C57BL/6) F1 mice. Flow cytometric and immunohistological analyses showed predominantly NK-1.1+ and NC-1.1+ large and granular single nucleated decidual cells with abundant cytoplasm. A 'bright' and a 'dim' subset were identified for both NK-1.1+ and NC-1.1+ cells. The NC-1.1dim and NK-1.1dim cells increased in number and size as pregnancy progressed. When tested in 51Cr-release assays, the decidual cells showed significant levels of both NK and NC activities which increased with progression of pregnancy. The NK and NC activities were partially inhibited (47 and 34%) by preincubation of the decidual cells with anti-NC-1.1 and complement (C'), or anti-NC-1.1 alone. Results indicate that natural cell-mediated cytotoxicity in the decidua is in part, at least, mediated by NK-1.1+ and NC-1.1+ cells, and that the NK-1.1dim and NC-1.1dim cells are very likely to be GMG cells. This is the first report of NC cells in the mouse uterus.

Actions of interleukin-2 on amnion prostaglandin biosynthesis

Preterm labor is associated with increased intrauterine prostaglandin (PG) production. Intrauterine infections are frequently associated with preterm labor and increased cytokine production. The cytokine interleukin-2 (IL-2) is a potent T-cell growth factor necessary for effective cell-mediated immunity. In this study we evaluated the effects of IL-2 on PGE2 biosynthesis by human amnion cells. IL-2 alone modestly but significantly inhibited amnion PGE2 production. Moreover, IL-2 also attenuated, in a concentration-related fashion, the stimulatory actions of IL-1 beta on PGE2 production by amnion cells. These data suggest that IL-2 could potentially represent a negative regulatory element in the mechanisms of preterm labor in association with intrauterine infection.

Actions of interleukin-2 on chorio-decidual prostaglandin biosynthesis

The onset of preterm labor requires increased intrauterine prostaglandin production. Intrauterine infections are frequently associated with preterm labor and increased cytokine production. The cytokine interleukin-2 (IL-2) is a potent T-cell growth factor necessary for effective cell-mediated immunity. In this study we evaluated the effect IL-2 has on prostaglandin E2 (PGE2) biosynthesis by human chorion and decidual cells. IL-2 alone significantly stimulated decidual and chorion PGE2 production. IL-2 enhanced the stimulatory actions of interleukin-1 (IL-1), epidermal growth factor (EGF), ionomycin, and phorbol 12-myristate 13-acetate (PMA) on PGE2 production by decidual cells. Similarly, IL-2 enhanced the stimulatory actions of EGF and PMA, but not IL-1 or ionomycin, on PGE2 production by chorion cells. These data suggest that IL-2 could potentially participate in the mechanisms of preterm labor in association with intrauterine infection.

Effect of prostaglandin synthesis inhibitors on spontaneous and endotoxin-induced abortion in mice

The putative role of prostaglandin E2 (PGE2) in suppressing rejection of the 'fetal allograft' (resorption) in C3H/HeJ and CBA/J allopregnant mice was tested by administration of the prostaglandin synthesis inhibitors indomethacin (INDO) and acetylsalicylic acid (ASA). When the resorption rate was low, INDO fed at a dose of 15 micrograms/ml in drinking water after implantation had a slight augmenting effect when the endogenous resorption rate was < 30%, but had no effect when the endogenous rate was higher or when bacterial lipopolysaccharide (LPS) was given. ASA fed at 50 micrograms/ml had no augmenting effect and did not increase sensitivity to the abortogen LPS in either CBA/J (LPS sensitive) or C3H/HeJ (LPS resistant) mice. Both INDO and ASA fed to CBA/J mice significantly reduced endogenous PGE2 extractable from the uteri of hormonally pseudopregnant mice after deciduoma induction. Feeding INDO at doses up to 30 micrograms/ml from day 2.5 of pregnancy impaired but failed to completely block implantation in CBA/J mice, and with daily administration, some of the mice became sick: all of the implants in sick mice resorbed. INDO at doses of 150-200 micrograms per day known to inhibit implantation in vivo by sufficiently blocking PGE2 synthesis, was injected on one or more days beginning after the time of implantation. This failed to cause abortion in CBA/J mice and although some mice became ill, provided this happened after day 8.5 of pregnancy when sensitivity to the abortogenic effects of injected LPS decreased substantially in these mice, all implants in the sick mice were 'healthy' (i.e. non-resorbing). We were unable to increase the rate of resorption in syngeneically pregnant CD1 mice above 13% with 15 ml INDO in drinking water. Our data do not support the view that PGE2 represents an important intrauterine suppressor molecular blocking the processes mediating embryo death at the time of abortion. Spontaneous abortion in DBA/2-mated CBA/J mice appears to be determined by the level of bacterial LPS (endotoxin) and treatment with antibiotics or intralipid (which enhances endotoxin clearance), reduces the abortion rate. A sufficient dose of INDO may cause abortion, but the data taken together suggest this may be due to effects on the gut whereby permeability to bacterial LPS is increased.

Adaptive immune responses during murine pregnancy: pregnancy-induced regulation of lymphokine production by activated T lymphocytes

OBJECTIVE

We hypothesized that the lymphokine production by splenocytes and decidual lymphocytes would be altered because of changes in immunoregulation during pregnancy.

STUDY DESIGN

Splenocytes and decidual lymphocytes were isolated from syngeneic and allogeneic pregnant mice at different times of gestation. The lymphocytes (10(7) cells/ml) were stimulated with anti-CD3 antibody, and culture supernatants were assayed for several lymphokines, including interleukin-2, interferon-gamma, interleukin-4, interleukin-6, granulocyte-macrophage colony-stimulating factor, and interleukin-3. Statistical analysis was by analysis of variance or paired t test.

RESULTS

Activated splenocytes produced significantly less interleukin-2 and more interleukin-4, interleukin-6, and interleukin-3 as murine pregnancy advanced. Production of interferon-gamma and granulocyte macrophage colony-stimulating factor by activated splenocytes peaked in the first 8 to 14 days of pregnancy. Stimulated decidual lymphocytes produced modest amounts of interleukin-6, granulocyte-macrophage colony-stimulating factor, and interleukin-3 during pregnancy but no interleukin-2, interferon-gamma, or interleukin-4. Similar results were found for both syngeneic and allogeneic matings.

CONCLUSIONS

Our findings indicate that splenocyte lymphokine production favors interleukin-4 production over interleukin-2 production. This finding suggests that antibody production would be enhanced and cytotoxic cellular immune responses inhibited during pregnancy. These changes occurred regardless of mating partner, suggesting that the specific antigenic stimulus during normal pregnancy does not regulate lymphokine production. Activated splenocytes and decidual lymphocytes were found to differ in their capacity to produce lymphokines, indicating that the decidua constitutes a distinct and unique immunologic microenvironment.

Pregnancy-associated suppressor cells in mice: functional characteristics of CD3+4-8-45R+ T cells with natural suppressor activity

Natural suppressor (NS) cells are MHC-unrestricted regulatory cells with non-specific inhibitory activity for immune responses. In adult mice, NS cells are characteristically found in bone marrow and in splenic tissue following total lymphoid irradiation and cyclophosphamide treatments. Recently, we have shown that the spleens of pregnant mice harbour a population of lymphocytes which resemble NS cells in terms of phenotype and inhibitory activity. In this study, we use positive and negative selection techniques to further characterize splenic pregnancy-associated NS (SPANS) cells as predominantly 'double negative' T cells (CD3+4-8-) bearing receptors for the lectins wheat germ agglutinin and soybean agglutinin, as well as expressing CD45R and the heat-stable J11d.2 antigen. Taken together, these findings lead us to conclude that SPANS cells belong to an immature T cell lineage. In keeping with their T cell phenotype, SPANS cells do not express the natural killer (NK) cell-specific markers NK2.1 and asialoGM1 and do not mediate lytic activity against NK-sensitive YAC-1 cells, although natural cytotoxic activity against WEHI-164 cells was found to co-purify with SPANS cells. Suppressive activity of SPANS cells in mixed lymphocyte reactions (MLR) is abolished by treatment with mitomycin C, suggesting that natural suppression in this system is a proliferation-dependent phenomenon. Preincubation of SPANS cells with conditioned medium from Con A-stimulated T cell cultures results in augmented NS activity, indicating that SPANS cells respond to T cell signals. Our data suggest that SPANS cells mediate suppression via the elaboration of a soluble suppressor factor since SPANS cells do not require cell-cell contact to mediate suppression and supernatants from short-term cultures of SPANS cell-enriched SBA+ pregnancy spleen cells inhibit MLR. We believe that SPANS cell may be important in regulating hematopoiesis and maternal anti-fetal immunity during murine pregnancy.

PGE2-independent immunosuppressive activity of horse trophoblast tissue

It has been proposed that PGE2 is an important immunosuppressant acting at the fetal-maternal interface during pregnancy. We have previously shown that horse conceptus-conditioned medium suppresses lymphocyte proliferation. This experiment was designed to determine if horse conceptus-derived immunosuppressive activity could be attributed to PGE2 production by the trophoblast tissue. Trophoblast tissue from 21-day-old conceptuses was cut into equal sections and cultured in the presence or absence of the prostaglandin inhibitor, indomethacin. Following culture, immunosuppressive activity and the concentration of PGE2 were determined for each sample of both horse-trophoblast conditioned medium (HTCM) and indomethacin-treated HTCM (I-HTCM). Suppressive activity was identified in lymphocyte proliferation assays via reduced [3H]thymidine uptake by pokeweed mitogen stimulated horse lymphocytes. A radioimmunoassay was used to quantify PGE2. While PGE2 production was greatly reduced in cultures containing indomethacin, trophoblast-derived immunosuppressive activity was not affected. These data indicate that PGE2 is not the primary immunosuppressant produced by horse trophoblast tissue.

Pregnancy is associated with a reduction in the pattern of the cytotoxic activity displayed by lymphokine-activated killer cells

Several modifications in the homeostasis of the maternal immune system have been implicated in the survival of the fetoplacental graft. We have investigated the adaptive response of the cytotoxic nonmajor histocompatibility complex (MHC)-restricted effector lymphocytes in pregnancy, and have found that the spontaneous lytic activity against both natural killer (NK)-sensitive and NK-resistant target cells is either decreased or lacking in peripheral blood mononuclear cells (PBMNC) from pregnant women. Recombinant interleukin-2 (rIL-2) normalizes the cytotoxic activity of PBMNC from pregnant women against NK-sensitive target cells in a dose- and time-dependent manner, without modification in the normal amounts of HNK-1+, CD16+ (Leu 11, or CD11b+ (OKM-1) present in these effector populations. However, the pattern of lytic activity against NK-resistant target cells found in PBMNC from pregnant women after short- and long-term incubation with rIL-2 was reduced in comparison with that observed in PBMNC from nongravid women in similar conditions. Moreover, rIL-2 incubation of PBMNC from pregnant subjects was not associated with an enhancement of the lytic binding against NK-resistant target cells. These findings demonstrate that pregnancy is not only associated with a reduction in the NK lytic activity of PBMNC, but also with a reduction in the generation of lymphokine-activated killer activity, in terms of the pattern of lytic activity developed.

Suppression by human placental protein 14 of natural killer cell activity

Human decidua of early pregnancy contains considerable numbers of CD3-CD56+ natural killer (NK) cells. In this study, two major protein products of the decidua, placental protein 14 (PP14) and placental protein 12 (PP12), were tested for the ability to regulate human NK cell activity. In vitro overnight exposure to PP14 of blood lymphocytes or purified large granular lymphocytes (LGL) resulted in suppression of cytotoxicity against K562 target cells in a 4-h 51Cr release assay. The NK inhibition was dependent on concentrations of PP14, being detectable at 5 micrograms/ml and reaching maximum at 50 micrograms/ml. Manifestation of PP14-induced NK suppression required 18-h contact with NK cells. The suppression of NK activity by PP14 was not abolished by indomethacin. In a target binding assay the number of PP14-treated LGL binding to K562 was comparable to that of untreated ones. By contrast with PP14, PP12 produced no effects on NK cells. These results indicate that PP14 suppresses the function of NK cells, which might be involved in prevention of maternal immune rejection of fetus at the fetomaternal interface.

Macrophages and migratory cells in endometrium relevant to implantation

The implantation of an appropriately developed embryo into a suitably conditioned uterine lining depends on the synchronous maturation of the preimplantation embryo and uterine lining. The pre- and postimplantation embryo also requires protection from immunocompetent maternal immune effectors. Preimplantation embryo development is affected by genotype, intercellular communication and autocrine growth factors (polyamines, TGF-alpha, TGF-beta 1, PAF). Factors of maternal origin may also enhance embryo development (EGF, TGF-alpha, TGF-beta 1, IGF, polyamines). The preimplantation embryo signals its presence to the mother by release of factor(s) such as IFN-alpha-II and a PAF-like factor. PAF may induce EPF in the mother and enhances vascular permeability at the implantation site. Uterine or peritoneal leukocytosis may inhibit development via toxic effects of lymphokines/monokines (IL-2, IL-1?, IFN-gamma, TNF-alpha). Immunoprotection of the preimplantation embryo is conferred by embryo derived maternal factors (EPF, T-cell suppressor factors). The uterus is receptive during a limited period of time (implantation window) and the substrate adhesion molecules produced by uterine and embryonic trophectoderm cells are crucial for the initial stages of implantation. At implantation, trophoblast expression of MHC and non-MHC antigens is shut off and both immunocompetent maternal cells (macrophages, dendritic cells, granulocytes, IELs, immunocytes) and lymphatics become sparse at implantation sites. Peri-implantation cytokines of maternal origin, such as CSF-1, GM-CSF and IGF-1 binding protein, are probably important for trophoblast growth and development. Immuno-protection of the embryo at this stage may be mediated by embryo derived factors that inactivate macrophages and by a population of large, hormone dependent Lyt 2+ (CD8+) suppressor cells. It is possible that these CD8+ cells respond to progesterone and secrete molecules that inactivate natural effector (NK-type) cells against trophoblast. Prostaglandins (PGE2) may play a brief role in immunosuppression at the time of implantation but its role is probably more important with respect to the decidual response. Defects in the pre- and peri-implantation stages of pregnancy may lead to delayed failure in the form of clinical miscarriage.

Prostaglandin-mediated inactivation of natural killer cells in the murine decidua

Previous studies from this laboratory have demonstrated a large influx of null lymphocytes into the murine decidua during pregnancy. We had also shown that trophoblast cells of the murine placenta bear target structures recognized by NK cells. Since NK lineage cells belong to the null category of lymphocytes, we examined whether cells of this lineage appear in the murine decidua, and if so, whether their activity is locally regulated by NK suppressor cells. We further investigated the identity of the suppressor cells as well as their suppressor products. NK lineage cells, irrespective of their activation status, were identified morphologically in radioautographic preparations as the non-T, non-B (null) lymphocytes capable of binding YAC-1 lymphoma targets. NK activity of nucleated cells was measured with a 4-hr 51Cr-release assay against labeled YAC-1 targets. Studies with outbred CD1 mice, and to a smaller extent, inbred CBA mice revealed that the incidence of NK lineage cells remained fairly constant within the decidua throughout pregnancy, but their activity decreased steadily to negligible levels by Day 12-14 of gestation. This was found to result from an inactivation caused by NK-suppressor cells in the decidua. A mixing of Ficoll-Paque-separated nucleated cells of the decidua with normal splenic effector cells (at 1:1 ratio) led to a suppression of their NK activity tested immediately or after a 20-hr coculture. This suppression was MHC unrestricted. Suppressor cells were identified both in plastic nonadherent fraction highly enriched for typical decidual cells as well as in the plastic adherent fraction containing decidual cells and macrophages. Addition of indomethacin (10(-5) M), an inhibitor of prostaglandin synthesis, or anti PGE2 antibody, revived the NK activity in the mixed population, as well as in the decidua, suggesting a PGE2-mediated suppression. High levels of PGE2 were detectable in decidual cell supernatants with a sensitive radioimmunoassay. Addition of pure PGE2 (10(-7)-10(-6) M) but not PGF2 alpha (10(-6) M) during the NK assay or to the effector cells for a 20-hr period prior to the assay led to an inhibition of NK activity. These results reveal that NK cells appearing in the murine decidua are progressively inactivated by PGE2 produced by decidual cells and decidual macrophages.