Human decidual natural killer cells express the receptor for and respond to the cytokine interleukin 15

Trafficking of peripheral blood CD56(bright) cells to the decidualizing uterus--new tricks for old dogmas?

CD56(bright) lymphocytes become abundant in the human uterus during every menstrual cycle, following the surge in pituitary-derived luteinizing hormone (LH), which initiates final oocyte maturation. While the uterus is host to some CD56(bright) cells prior to ovulation, the rapid increase is thought to be due to proliferation of the resident population, accompanied by recruitment of CD56(bright) lymphocytes from the circulation. The rapid increase in CD56(bright) cells is concurrent with the onset of decidualization, the transformation of uterine stromal cells into secretory decidual cells. Uterine CD56(bright) cells proliferate and differentiate to become the predominant lymphocytes of the post-ovulatory uterus. These distinct, tissue-specific natural killer (NK) cells either die prior to menses or increase in number during early pregnancy, and then decline toward the end of the first trimester. Since lymphocytes home to tissues from the circulation, we investigated mechanisms of NK cell traffic over the course of natural menstrual cycles by measuring functional interactions between CD56+ cells from blood and endothelial cells using the Stamper-Woodruff assay of lymphocyte adhesion to frozen tissue sections. While a baseline level of adhesion was maintained throughout the cycle, elevated l-selectin-dependent adhesion of peripheral blood CD56(bright) cells occurred during a peri-ovulatory window. However, there were no significant menstrual cycle-induced changes in the transcription of l-selectin, alpha 4 integrin or LFA-1, or in expression of these proteins by NK cells, suggesting that the enhanced adhesion was due to post-translational modifications of these molecules. Quantitative RT-PCR failed to amplify the message for LH receptor or the alpha or beta forms of progesterone or estrogen receptors from blood NK cell subsets. Thus, we conclude that the actions of LH, E(2,) and P(4) on NK cells that promote interactions with endothelium and potential uterine homing are indirectly mediated through the responsiveness of other cell types.

Cytokines, chemokines and growth factors in endometrium related to implantation

The complexity of the events of embryo implantation and placentation is exemplified by the number and range of cytokines with demonstrated roles in these processes. Disturbance of the normal expression or action of these cytokines results in complete or partial failure of implantation and abnormal placental formation in mice or humans. Of known importance are members of the gp130 family such as interleukin-11 (IL-11) and leukaemia inhibitory factor (LIF), the transforming growth factor beta (TGFbeta) superfamily including the activins, the colony-stimulating factors (CSF), the IL-1 system and IL-15 system. New data are also emerging for roles for a number of chemokines (chemoattractive cytokines) both in recruiting specific cohorts of leukocytes to implantation sites and in trophoblast differentiation and trafficking. This review focuses on those cytokines and chemokines whose expression pattern in the human endometrium is consistent with a potential role in implantation and placentation and for which some relevant actions are known. It examines what is known of their regulation and action along with alterations in clinically relevant situations.

Menstrual cycle hormones induce changes in functional interactions between lymphocytes and decidual vascular endothelial cells

During the secretory phase of the menstrual cycle, a natural killer (NK) cell subset expressing cluster of differentiation (CD)56bright appears in the decidualizing uterus and remains until onset of menses. If pregnancy occurs, decidual NK cells increase to become the predominant uterine lymphocytes of early pregnancy. To elucidate mechanisms of CD56bright cell recruitment to the uterus, an in vitro adhesion assay was used to assess the effect of the menstrual cycle, as well as cycle-associated hormones on adhesive properties of human lymphocytes. Adhesion of human peripheral blood lymphocytes to pregnant mouse lymph nodes and Peyer's Patches tissue sections was constant throughout the cycle. When uterine tissue was used as the substrate, adhesive CD56+ cells were found only in decidua basalis. Adhesion increased at the LH surge. Adhesion was mediated through both L-selectin and alpha4-integrin-dependent mechanisms. Furthermore, we observed increased adhesive function in CD56+ cells from male donors which had been cultured with estradiol or LH compared with cell aliquots cultured without additives. Lymphocytes adherent to mouse uterine tissue were predominantly CD56bright, suggesting that peripheral NK cells may be actively recruited to the uterus in an important, brief endocrine-regulated fashion at the time of ovulation to establish the decidual NK population of early pregnancy.

Immunological Similarities between Implantation and Pre-eclampsia

PROBLEM

Cytokines are involved in implantation success and failure. We envisage that they could be similarly involved in pre-eclampsia (PE).

MATERIALS AND METHODS

First, we review the primipaternity and primiparity concepts and then why natural killer (NK) cells are involved in implantation. We stress that the common event in all PE is vascular remodelling.

RESULTS AND CONCLUSION

We conclude that PE could involve cytokine and/or NK dysfunctions, and propose a working hypothesis.

The immune environment in human endometrium during the window of implantation

PROBLEM

Changes in the immune environment in the endometrium are believed to be important for successful implantation and maintenance of pregnancy. We have previously investigated global gene profiling in human endometrium during the window of implantation by oligonucleotide microarray technology, and analysis of these data underscore the regulation of a group of immune-related genes. The present study was therefore conducted to examine the pattern of expression and regulation of these genes including decay accelerating factor (DAF), indoleamine 2,3 dioxygenase (IDO), interleukin-15 (IL-15), IL-15 receptor alpha subunit (IL-15Ralpha), interferon regulatory factor-1 (IRF-1), lymphotactin (Lpn), natural killer-associated transcript 2 (NKAT2) and NKG5 in secretory and proliferative human endometrium.

METHOD OF STUDY

Endometrial biopsies were obtained from normally cycling women in the late proliferative and mid-secretory phase of the menstrual cycle. Semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and Northern blot analysis were used to determine the expression and regulation of these genes in secretory and proliferative human endometrium. Cellular localization of NKG5, Lpn and IDO by in situ hybridization in secretory-phase endometrium was also examined.

RESULTS

Semi-quantitative RT-PCR and Northern blot results demonstrate that there is a coordinated upregulation of this group of genes during the window of implantation.

CONCLUSIONS

We demonstrate the upregulation of immune-related genes IL-15Ralpha, Lpn and NKG5 in secretory versus proliferative human endometrium. We also demonstrate a similar upregulation in secretory endometrium of other immune-related genes, viz, DAF, IDO, IL-15, IRF-1 and NKAT2. The functions of these genes include stimulation of proliferation of uterine natural killer (uNK) cells, inhibition of cytolytic activity of uNK cells, inhibition of cell growth of T cells and other pathogens and inhibition of the classical complement pathway. Upregulation of these immune-related genes in the window of implantation suggests their role during the process of implantation and in immune tolerance of the implanting conceptus.

The presence of functional mannose receptor on macrophages at the maternal-fetal interface

BACKGROUND

The mannose receptor (MR) is involved in the initiation of the immune response and regulation of homeostasis during inflammation and tissue remodeling.

METHODS

Distribution, endocytosis and possible natural ligand tumor associated glycoprotein-72 (TAG-72) for the MR have been examined by immunohistology, immunocytochemistry and flow cytometry at the maternal-fetal interface, characterized by extensive tissue remodeling.

RESULTS

Contrary to disseminated distribution of the MR positive (MR+) cells in term placenta, the MR+ cells of early pregnancy decidua intimately surrounded glands and followed tissue distribution of CD14 positive cells. The mannose receptor was present on freshly isolated first trimester decidual mononuclear cells and distributed mostly on macrophages (77.08 +/- 10.55%, mean +/- SD). The expression of the MR on CD14 positive cells decreased following 18 h culture (P < 0.01) and was accompanied by the reduction of fluorescein isothiocyanate (FITC)-dextran uptake. PAM-1 anti-MR antibody, mannan and TAG-72 reduced FITC-dextran uptake by decidual macrophages.

CONCLUSIONS

These data indicate that the MR+ macrophages, surrounding early decidual glands, are able to internalize ligands for carbohydrate recognition domain of the receptor, including decidual secretory phase mucin TAG-72.

Natural killer cells in pregnancy and recurrent pregnancy loss: endocrine and immunologic perspectives

The endocrine system and the immune system interact closely during implantation and maintenance of pregnancy. One of the most striking examples of this communication is at the level of the decidua (endometrium of pregnancy). Here, under the influence of sex steroids, there is a dramatic increase of a unique population of lymphocytes, the uterine natural killer (uNK) cells, in early pregnancy. These cells derive predominantly from a subset of peripheral blood NK cells, which under hormonal influence gets recruited to the uterus. In mice, uNK cells play an important role in the development of placental vasculature. The role of these cells in human pregnancy is still not definitively established; however, they are believed to promote placental and trophoblast growth and provide immunomodulation at the maternal-fetal interface. In contrast to their presumptive role in the maintenance of a healthy pregnancy, uNK cells and peripheral NK cells are dysregulated in unexplained recurrent pregnancy loss. Herein, we review NK cell populations, their changes in number and function in altered endocrine environments during the menstrual cycle and pregnancy, the current data on their potential role in unexplained recurrent pregnancy loss, and mechanisms for potential therapies targeted to NK cell function for this enigmatic disorder.

Ultrastructural Study of Uterine Natural Killer Cells Found in Pregnant, Interleukin-2 Receptor .BETA.-chain Overexpressed Transgenic Mice

We previously reported that all fetuses died or were resorbed on day 12 of pregnancy (Day 1= the day of plug) in interleukin-2 (IL-2) receptor beta-chain overexpressed transgenic (Tg2Rbeta) mice. In this study, to clarify the role of uterine natural killer (uNK) cells in pregnancy, the ultrastructure of Tg2Rbeta mouse uNK cells was analyzed using a transmission electron microscope. uNK cells and their granules on day 10 of pregnancy were larger in Tg2Rbeta mice than control mice, indicating that differentiation of uNK cells in Tg2Rbeta mice progressed rapidly. Additionally, the granules of uNK cells in Tg2Rbeta mice on day 10 of pregnancy had an irregular morphology. The multivesicular regions were present in the cap structure of these granules, suggesting that the uNK cells of the Tg2Rbeta mice had cytotoxic activity.

Functional involvement of P-selectin and MAdCAM-1 in the recruitment of ?4?7-integrin-expressing monocyte-like cells to the pregnant mouse uterus

Leukocyte recruitment to the pregnant mouse uterus has been suggested to be associated with highly regulated expression of distinct patterns of vascular adhesion receptors. One of the most striking observations is the combined expression of mucosal addressin cell adhesion molecule-1 (MAdCAM-1) and P-selectin by maternal vessels of the vascular zone during the critical period of initial placenta development. The predominant cell population within these vessels is of the monocyte/macrophage lineage and expresses the mucosal integrin alpha4beta7, which represents the ligand for MAdCAM-1; neutrophils and lymphocytes are rare. To directly assess the importance of identified adhesion receptors, we undertook long-term in vivo inhibition studies using monoclonal antibodies to inhibit the contribution of MAdCAM-1 in leukocyte trafficking to the decidua or to deplete alpha4beta7(+) leukocytes. In addition, implantation sites of mouse strains genetically deficient in specific adhesion receptors were investigated. Our results underline the importance of predicted adhesion pathways in the recruitment of monocyte-like cells, especially those expressing alpha4beta7. Interestingly, maternal/fetal units with inhibited recruitment of alpha4beta7(+) leukocytes or the absence of these cells are characterized by reduced size and frequency of uterine NK cells.

Unique phenotype of human uterine NK cells and their regulation by endogenous TGF-β

Natural killer (NK) cells are a major population of lymphocytes in the human endometrium (EM), and NK cells can be a significant source of cytokines that alter local immune responses. The aim of this study was to determine the expression of NK cell receptors in situ and to test whether uterine NK (uNK) cells produce cytokines and how this activity may be regulated by transforming growth factor-beta (TGF-beta). We observed that human uNK cells were CD56+, CD3-, CD57-, CD9+, CD94+, killer inhibitory receptor+, and CD16+/- in situ by confocal microscopy. We examined cytokine production by uNK cells and uNK cell clones derived from human EM. Stimulation of uNK cells with interleukin (IL)-12 and IL-15, both of which are expressed in the human EM, induced interferon-gamma (IFN-gamma) and IL-10 production. IFN-gamma production by uNK cell clones was completely inhibited by TGF-beta1 in a dose-dependent manner with an inhibitory concentration 50% value of 20 pg/ml. IL-10 secretion by uNK cell clones was also inhibited by TGF-beta1 at similar concentrations. Furthermore, blocking endogenous TGF-beta in fresh human endometrial cell cultures increased the production of IFN-gamma by uNK cells. These data indicate that uNK cells have a unique phenotype that is distinct from blood NK cells. Further, data demonstrate that uNK cells can produce immunoregulatory cytokines and that inhibition of uNK cells by locally produced TGF-beta1 is a likely mechanism to regulate NK cell function in the human EM.

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.

Osteopontin is up-regulated in human decidual stromal cells

OBJECTIVE

To analyze expression and regulation of osteopontin in human stromal endometrial and decidual cells.

DESIGN

Study by immunohistochemistry, RNase protection assay, and in vitro study.

SETTING

Academic research unit.

PATIENT(S)

Twenty-five fertile women.

INTERVENTION(S)

Expression of osteopontin mRNA and protein was analyzed by RNase protection assay (RPA) and immunohistochemistry in secretory endometrium and decidua. Regulation of osteopontin expression in endometrial epithelial cell and stromal cells was analyzed by incubation with 17beta-estrogen, progesterone, IL-1beta, IL-6, and LIF and by incubation with cell culture supernatants of decidual natural killer cells. Furthermore, osteopontin expression was studied in stromal cells, decidualized in vitro.

MAIN OUTCOME MEASURE(S)

mRNA and protein expression and regulation of endometrial stromal osteopontin.

RESULT(S)

Osteopontin mRNA and protein are expressed at increasing concentrations in human secretory endometrium and in decidua. High concentrations in total decidua were due to high osteopontin concentrations in decidualized stromal cells. Osteopontin mRNA and protein expression was not regulated by incubation of endometrial epithelial and stromal cells with steroids, cytokines, and natural killer cell supernatant for 6 and 24 hours. In contrast, decidualization of stromal cells for 7, 14, and 21 days resulted in significant up-regulation of osteopontin mRNA and protein.

CONCLUSION(S)

Osteopontin is expressed at high concentrations in secretory endometrium in epithelial cells and in decidua in stromal cells. Decidual stromal expression of osteopontin is up-regulated by decidualization.

Expression of macrophage inflammatory protein-3β in human endometrium throughout the menstrual cycle

OBJECTIVE

To determine the expression of macrophage inhibitory protein-3beta (MIP-3beta), a potential chemoattractant for endometrial natural killer (NK) cells, in the human endometrium.

DESIGN

An experimental study.

SETTING

University department of obstetrics and gynecology.

PATIENT(S)

Thirty-seven fertile women with regular menstrual cycles and nonpathological endometrium, undergoing hysterectomy.

INTERVENTION(S)

Endometrium was obtained from operative samples.

MAIN OUTCOME MEASURE(S)

Paraffin-embedded endometrium was immunostained to determine the localization of MIP-3beta. The number of NK cells was counted in 10 nonoverlapping stromal areas. The MIP-3beta concentration in the homogenized endometrium was determined by ELISA.

RESULT(S)

Immunoreactivity for MIP-3beta was observed in the surface epithelia, glandular epithelia, and stroma with some menstrual cycle-dependent fluctuation. The MIP-3beta concentration was significantly higher in the late secretory phase than in the other phases. It showed a trend toward correlation with the number of endometrial NK cells.

CONCLUSION(S)

MIP-3beta was expressed in the human endometrium, but our results could not strongly support the hypothesis that MIP-3beta is a potential chemoattractant for endometrial NK cells.

Differential expression of KIR/NKAT2 and CD94 molecules on decidual and peripheral blood CD56bright and CD56dim natural killer cell subsets

OBJECTIVE

To investigate killer inhibitory receptor (KIR) expression by natural killer (NK) cells in early pregnancy.

DESIGN

Case-control study of immunologic markers.

SETTING

University hospital.

PATIENT(S)

Thirty pregnant women and 22 nonpregnant women.

INTERVENTION(S)

Peripheral venous blood sampling and decidual tissue collection after elective abortion.

MAIN OUTCOME MEASURE(S)

Flow cytometry was used to assess expression of KIR by NK cells in the cell samples.

RESULT(S)

In contrast to CD56(bright) peripheral blood NK cells, CD56(dim) cells express killer cell Ig-like receptor KIR/NKAT2. However, KIR/NKAT2 and lectin-like CD94 are present on both subsets of decidual NK cells. We found no differences between peripheral blood NK cell subsets from pregnant and nonpregnant women.

CONCLUSION(S)

Our findings demonstrate that NK cell subsets, distributed in accordance with CD56 molecule density on cell surface, express killer inhibitory receptors CD94 and KIR/NKAT2 in a different way. Our data support the view that CD56(bright)KIR/NKAT2+CD94+ decidual NK cells are specialized NK cells that have an important role to play in early pregnancy.

Interleukin-1 inhibits interleukin-15 production by progesterone during in vitro decidualization in human

Interleukin (IL)-15 is a novel cytokine that plays important roles in uterine natural killer cell function and one of the candidate genes that is upregulated during the window of implantation for human endometrium. IL-15 expression and production by human endometrial stromal cells (ESCs) is elevated during in vitro decidualization by progesterone (P). In the present study, we evaluated the effects of IL-1beta, a proinflammatory cytokine, on IL-15 production in ESCs. By enzyme-linked immunosorbent assay (ELISA), IL-1beta had no effect on IL-15 production from ESCs in short-term culture (for 24 h), whereas IL-1beta stimulated production of IL-8. However, using ELISA and Northern blot analyses we found that IL-1beta significantly inhibited P-induced IL-15 production and mRNA expression in long-term culture (for 12 days) of ESCs in vitro (P<0.01). This inhibition was not due to IL-1beta-mediated cytotoxicity, as ESCs cultured in the presence of IL-1beta showed no evidence of significant change in their viability. These results suggest that ovarian steroid hormones and IL-1beta regulate IL-15 mRNA expression and protein production in long-term culture, and that IL-1beta plays a role as a negative regulator of IL-15 production during decidualization in human endometrium.

Human uterine leukocytes and pregnancy

In human pregnancy, the embryo implants into the specialized mucosal wall of the uterus (decidua) and the placenta starts to form. Cells from the placenta (trophoblasts) invade into the uterine mucosa in order to open up maternal uterine arteries to ensure an adequate supply of blood to the developing fetus. The trophoblasts have a unique immunological phenotype compared to most cells especially with regard to their expression of major histocompatibility complex (MHC) antigens. On the other side of the interaction, the uterine mucosa (endometrium) differentiates in preparation for implantation. One of the changes that takes place is the appearance in the endometrium of a large number of maternal leukocytes in the final part of the menstrual cycle. If pregnancy ensues, these leukocytes continue to increase in number and are found in close contact with trophoblasts. The composition of this population of maternal immune cells is unusual compared to that seen at other mucosal sites. A lot of research has focused on whether maternal T-cell responses are suppressed or modified during pregnancy. Research has also concentrated on the specialized uterine natural killer (NK) cells, which are found in the decidua in large numbers during early pregnancy. These uterine NK cells have been shown to express receptors for trophoblast MHC antigens, but their role in pregnancy is still mysterious. The purpose of this review is to give an overview of what is known about the immunology at the implantation site and also to provide an update of some of the most recent findings in this field.

Interferon-tau stimulates secretion of macrophage migration inhibitory factor from bovine endometrial epithelial cells

During early pregnancy in ruminants, the embryo not only prevents prostaglandin F2alpha release, but it also modifies protein synthesis in the endometrium. This is accomplished by the secretion of interferon-tau (IFN-tau) from the embryo. The objective of this study was to identify and characterize specific proteins secreted from endometrial epithelial cells in response to IFN-tau that could be important for endometrial function and/or embryo development. The epithelial cells were prepared and cultured to confluence and then incubated with or without 100 ng/ml IFN-tau. At the end of the incubation, the proteins in the medium were analyzed by two-dimensional PAGE. The result showed that two major protein spots were induced by IFN-tau. One has a molecular mass of approximately 12 kDa and an isoelectric point (pI) of 6.7; the other has a molecular mass of 76 kDa and pI of 4.8. Protein sequence analysis showed that the 12-kDa protein contained a partial amino acid sequence that corresponded to macrophage migration inhibitory factor (MIF). To determine whether MIF is expressed in endometrial cells, isolated stromal or epithelial cells were incubated with or without 100 ng/ml IFN-tau for 0, 3, 6, 12, 24, and 48 h. After incubation, the MIF protein in cells was examined by Western blotting analysis, and the steady-state mRNA for MIF was examined by Northern analysis. Results showed that MIF protein and mRNA were present in the epithelial cells but not the stromal cells. The presence of MIF in the luminal epithelium of endometrial tissue was confirmed by immunohistochemistry. However, there was no effect of IFN-tau on MIF expression in the epithelial cells. The concentration of MIF in the medium was quantified by Western blotting analysis to determine if IFN-tau altered MIF protein secretion from the epithelial cells. The results showed that IFN-tau significantly stimulated the secretion of MIF protein from the cells. These data show that MIF is expressed in the epithelial, but not the stromal, cells of the endometrium and that MIF secretion from the epithelial cells is stimulated by IFN-tau. It is therefore likely that MIF plays a role in early embryo development, and further characterization of MIF expression and its regulation in the endometrium will add significantly to our understanding of early embryo-uterine interactions.

Dendritic cells in the human decidua

Dendritic cells (DCs) in the pregnant human uterine mucosa have been poorly characterized, although they are likely to regulate immune responses to both placental trophoblast cells and uterine infections. In this study an HLA-DR+, CD11c+ lin- (CD3-, CD19-, CD56-, CD14-) population has been identified by three-color flow cytometry. The cell isolates were prepared either by collagenase digestion or mechanically from first-trimester decidual tissue. The decidual DCs comprised approximately 1.7% of CD45+ cells in the isolates and had the phenotype of immature myeloid DCs. No CD1a+ Langerhans cells or CD123+ plasmacytoid DCs were detected. The decidual DCs were DC-SIGN-, DEC-205+, CD40+. Two subsets could be distinguished on the basis of relative expression of HLA-DR, which also differed in expression of DC-activation markers. The DCs were identified in situ by immunohistology by DEC-205 staining. Cells with dendritic processes were found scattered through both the decidua basalis (in which trophoblast cells are infiltrating) and the decidua parietalis. They were also visible in endothelial-lined spaces. This is the first study to identify and describe the phenotype and distribution of human decidual DCs.

Assessment of requirements for IL-15 and IFN regulatory factors in uterine NK cell differentiation and function during pregnancy

In mouse and human, precursors of NK cell lineage home to decidualizing uteri. To assess the requirement for IL-15, an essential cytokine for NK differentiation in lymphoid tissue, on uterine NK (uNK) cell differentiation, implantation sites from IL-15(-/-) mice were analyzed histologically. IL-15(-/-) implantation sites had no uNK cells, no spiral-artery modification, and lacked the decidual integrity found in normal mice. IL-15(-/-) recipients of C57BL/6 marrow displayed similar pathology. However, implantation sites from recombination-activating gene-2(-/-)gamma(c)(-/-) (alymphoid) recipients of IL-15(-/-) marrow showed normal uNK cells, modified spiral arteries, and well-developed decidua basalis. Deletion of the IFN-regulatory factor (IRF)-1, but not IRF-2 (factors important in peripheral NK cell differentiation) limited but did not prevent uNK cell development. In situ hybridization localized IRF-1 largely to placental trophoblast cells. IRF-1(-/-) marrow transplanted into recombination-activating gene-2(-/-)gamma(c)(-/-) displayed competence for full uNK cell differentiation. IL-15 mRNA expression at implantation sites of IRF-1(-/-) and C57BL/6 was similar, suggesting that, unlike in bone marrow and spleen, IRF-1 does not regulate IL-15 in the pregnant uterus. Terminal differentiation of uNK cells was not promoted in pregnant IRF-1(-/-) mice by 5-day infusion of murine rIL-15, suggesting that IRF-1 deficiency rather than IL-15 deficiency limits uNK cell differentiation in these mice. Further, IRF-1 regulates placental growth, birth weight, and postnatal growth of offspring. These studies indicate that uNK cell development and maturation share some aspects with NK cell development in other tissues, but also display distinctive tissue-specific regulation.

CXCL12 expression by invasive trophoblasts induces the specific migration of CD16- human natural killer cells

In the maternal decidua, natural killer (NK) cells, characterized by lack of CD16, are found in direct contact with the fetal extravillous trophoblasts (EVTs). It is yet unknown which factors contribute to the specific homing of this unique NK subset to the decidua. In this study we analyze the chemokine receptor repertoire on various NK populations derived from the peripheral blood and decidua. We show that CXCR4 and CXCR3 receptors are preferentially expressed on CD16- NK subsets derived either from the peripheral blood or the decidua and that these receptors are involved in migration of all NK subsets to their ligands. We further demonstrate in vivo that invading EVTs that eventually perform endovascular invasion express CXCL12, the ligand for CXCR4, but not ligands for CXCR3. Indeed, specific accumulation of the CD16- NK cells at the expense of CD16+ cells was observed only when in vitro migration was performed with ligands for CXCR4. Finally, incubation of the peripheral blood CD16- NK cells with cytokines present in the decidua, especially interleukin 15 (IL-15), resulted in the expression of chemokine receptor repertoire similar to that observed on decidual NK cells, suggesting an additional important regulatory effect of local decidual cytokines.

Regulation of innate and adaptive immunity by the female sex hormones oestradiol and progesterone

Women mount more vigorous antibody- and cell-mediated immune responses following either infection or vaccination than men. The incidence of most autoimmune diseases is also higher in women than in men; however, during pregnancy many autoimmune diseases go into remission, only to flare again in the early post-partum period. Successful pregnancy requires that the female immune system tolerate the presence of a semi-allogeneic graft for 9 months. Oral contraceptive use can increase susceptibility to certain genital tract infections and sexually transmitted diseases in women. Moreover, treatment of mice and rats with female sex hormones is required to establish animal models of genital tract Chlamydia, Neisseria and Mycoplasma infection. This review describes what is currently known about the effects of the female sex hormones oestradiol and progesterone on innate and adaptive immune responses in order to provide a framework for understanding these sex differences. Data from both human and animal studies will be reviewed.

The uterine NK cell population requires IL-15 but these cells are not required for pregnancy nor the resolution of a Listeria monocytogenes infection

During pregnancy in mice, uterine natural killer (uNK) cells abundantly accumulate on the mesometrial side of the placenta. In this study, we show that the presence of both mature and immature uNK cells requires IL-15. Bone marrow transplantation of NK cell-negative mice due to null mutations in the recombination-activating gene (Rag) 2/common cytokine receptor gamma-chain (Rag2(-/-)gamma(c)(-/-)) genes indicated that uNK cells originate from the bone marrow and require IL-15 to develop. NK cells are thought to be central players in the immune response to intracellular pathogens such as Listeria monocytogenes, a bacterium that also has a predilection for replication in the placenta. However, IL-15(-/-), NK cell-deficient mice were relatively protected from this infection compared with wild-type mice, and during pregnancy the absence of NK cells did not compromise the immune response at this site. The loss of uNK cells results in decidual abnormalities, including thickening of the arterial walls with luminal narrowing and a hypocellular decidua basalis. These defects were rescued by bone marrow transplantation of the Rag2(-/-)gamma(c)(-/-) mice that restored the uNK cell population. The decidual abnormalities in the IL-15(-/-) mice however did not result in infertility as gestation times and litter sizes were comparable to those of wild-type mice. Fetal weights were mildly compromised, consistent with the arterial pathologies. These results show that uNK cells are not required for successful pregnancy and that NK cells are not essential for an adequate immune response to L. monocytogenes in either pregnant or nonpregnant mice.

Cytokine microenvironments in human first trimester decidua are dependent on trophoblast cells

OBJECTIVE

To compare cytokine expression profiles of decidua basalis (containing trophoblast cells) and decidua parietalis (without trophoblast cells) for determination of microenvironments in human first trimester decidua.

DESIGN

Retrospective study.

SETTING

School of Medicine, RWTH University of Aachen, Aachen Germany, and Bourgognekliniek Maastricht, Maastricht, The Netherlands.

PATIENT(S)

Forty-six women who had undergone elective first-trimester termination of viable pregnancy at 5 to 12 weeks.

MAIN OUTCOME MEASURE(S)

Quantitative cytokine protein analysis in decidual tissues by enzyme-linked immunosorbent assay, qualitative cytokine messenger (m)RNA analysis in isolated decidual cell samples, and comparative mRNA and protein analysis in tissues of decidua basalis compared with decidua parietalis.

RESULT(S)

Interleukin-2, interferon-gamma (Th-1), interleukin-4 (Th-2), and interleukin-1beta proteins are expressed in the human first-trimester decidua. Interleukin-2, interferon-gamma, and interleukin-4 mRNA mainly derive from the decidual tissue leukocytes. Interleukin-1beta mRNA is expressed by all decidual cell types. Interferon-gamma mRNA and protein is detected predominantly in the decidua basalis, which contains trophoblast cells.

CONCLUSION(S)

Microenvironments are established topographically by different expression of cytokines in decidua basalis and decidua parietalis. These locally specific patterns are indicative of fetomaternal cross-talk. Higher interferon-gamma concentrations in decidua basalis may influence leukocyte differentiation (e.g., macrophage activation) and trophoblast invasion (e.g., by induction of expression of major histocompatibility complex).

Expression of macrophage inflammatory protein-1beta in human endometrium: its role in endometrial recruitment of natural killer cells

Human endometrium is infiltrated by natural killer (NK) cells throughout the menstrual cycle. The number of endometrial NK cells is low in the proliferative phase, but acutely increases after ovulation, and reaches a peak in the late secretory phase, suggesting that endometrium recruits these leukocytes selectively from circulating peripheral blood. We investigated the expression of macrophage inflammatory protein (MIP)-1beta, a potential chemoattractant for NK cells, in the endometrium. RT-PCR and ELISA revealed that MIP-1beta is expressed in the endometrium throughout the menstrual cycle at both the message and protein levels. MIP-1beta expression is stronger in the secretory phase endometrium than in the proliferative phase endometrium. Immunohistochemistry revealed that MIP-1beta is localized in the surface epithelial cells, glandular epithelial cells, and perivascular stromal cells throughout the menstrual cycle. Stromal cells in a wider perivascular area became immunoreactive in the secretory phase. There was a strong correlation between the endometrial MIP-1beta concentration and the number of endometrial NK cells. Progesterone significantly induced MIP-1beta secretion from cultured endometrial stromal cells, whereas 17beta-estradiol had a weak effect. These results suggest that endometrial MIP-1beta may be involved in the recruitment of NK cells from circulating peripheral blood.

Effect of female sex steroids on human endometrial CD16neg CD56bright natural killer cells

OBJECTIVE

To clarify whether female sex steroids directly affect the bioactivity of the human endometrial CD16neg CD56bright natural killer (NK) cells.

DESIGN

In vitro study.

SETTING

University obstetrics and gynecology department.

PATIENT(S)

Thirteen women with histologically normal endometrium who were undergoing hysterectomy and seven women during the first trimester of pregnancy who were undergoing selective termination.

INTERVENTION(S)

Endometrium or decidua was obtained.

MAIN OUTCOME MEASURE(S)

The effects of 17beta-estradiol or progesterone (10(-6), 10(-7), and 10(-8) M) on the proliferation, cytolytic activity, and cytokine secretion of the isolated endometrial CD16neg CD56bright NK cells were examined using a 3H-thymidine incorporation assay, 51Cr-releasing assay, and enzyme-linked immunosorbent assay, respectively.

RESULT(S)

Neither 17beta-estradiol nor progesterone had significant effects on the proliferation, cytolytic activity, and cytokine secretion of endometrial CD16neg CD56bright NK cells.

CONCLUSION(S)

Female sex steroids do not directly affect the bioactivity of the human endometrial CD16neg CD56bright NK cells.

Differential expression of interleukins (IL)-13 and IL-15 in ectopic and eutopic endometrium of women with endometriosis and normal fertile women

PROBLEM

Interleukins (IL) 13 and 15 are key regulators of inflammatory and immune responses, processes that are central to endometriosis and associated abnormalities. The present study examined (1) whether ectopic endometrial tissue expresses IL-13 and IL-15 (2) if their expression differs compared with matched eutopic endometrium and control endometrium from normal fertile women, and (3) if peritoneal fluids (PF) content of these cytokines reflects the disease compared with PF from women with peritoneal adhesions unrelated to endometriosis and those without pelvic pathology.

METHODS

The expression of IL-13 and IL-15 mRNA and protein was determined using quantitative RT-PCR, ELISA and immunohistochemistry.

RESULTS

Ectopic endometrium expresses IL-13 and IL-15 mRNA and protein with elevated levels compared with eutopic and control endometrium, irrespective of the phases of the menstrual cycle, with predominance in IL-13 expression. Endometrial epithelial cells were found to be the primary site of IL-13 and IL-15 expression. The PF content of IL-13 and IL-15 show a trend toward higher concentrations in women with adhesion and endometriosis, respectively, compared with fertile control without pelvic pathology.

CONCLUSION

Interleukins 13 and 15 are expressed in ectopic endometrium and present in PF of women with endometriosis and their elevated expression in ectopic endometrium suggests that these cytokines play a key role in local inflammatory/immune responses that are critical in endometriosis-associated abnormalities.

IL-1beta and IFN-gamma induce the expression of diverse chemokines and IL-15 in human and rat pancreatic islet cells, and in islets from pre-diabetic NOD mice

AIMS/HYPOTHESIS

Cytokines and chemokines are important mediators of immune responses due to their ability to recruit and activate leukocytes. Using microarray analysis we observed that rat beta cells exposed to IL-1beta and IFN-gamma have increased mRNA levels of chemokines and IL-15. The aim of this study was to characterize the expression of IP-10, MIP-3alpha, fractalkine and IL-15 in rat beta cells, human pancreatic islets, and in islets isolated from NOD mice, both during the pre-diabetic period and following islet transplantation.

METHODS

FACS-purified rat beta cells and human islets were cultured with IL-1beta, IFN-gamma and/or TNF-alpha. Islets were isolated from NOD or BALB/c mice at different ages. For syngeneic islet transplantation, 2- or 3-week-old NOD islets were grafted under the kidney capsule of spontaneously diabetic NOD recipients. Chemokine and IL-15 mRNA expression and protein release were evaluated, respectively, by RT-PCR and ELISA.

RESULTS

Human islets and rat beta cells express IP-10, MIP-3alpha, fractalkine and IL-15 mRNAs upon exposure to cytokines. The expression of IL-15, IP-10 and fractalkine is regulated by IFN-gamma, while the expression of MIP-3alpha is IL-1beta-dependent. Moreover, cytokines induced IL-15, IP-10, Mig, I-TAC and MIP-3alpha protein accumulation in culture medium from human islets. In vivo, there was an age-related increase in IL-15, IP-10 and MIP-3alpha expression in islets isolated from NOD mice. Following syngeneic islet transplantation, increased expression of IL-1beta, IFN-gamma, fractalkine, IP-10, MCP-1 and MIP-3alpha mRNAs were observed in the grafts.

CONCLUSION/INTERPRETATION

Cytokine-exposed islets or beta cells express chemokines and IL-15. This could contribute to the recruitment and activation of mononuclear cells and development of insulitis in early Type 1 diabetes and during graft destruction.

Inflammatory mediators and endometrial function--focus on the perivascular cell

Human endometrium has a unique vascular architecture that allows menstruation, the shedding of a well-vascularised tissue layer, with limited bleeding. Blood loss is controlled at least in part by constriction of the perivascular cells, myofibroblasts that surround the spiral arterioles and have contractile activity. These perivascular cells, which are coupled to endothelial cells by processes, are responsive to changes in progesterone levels and express chemokines, cytokines and prostaglandins (PG) crucial to the control of leukocyte entry into endometrium. In this location the chemokine interleukin-8 (IL-8) and prostaglandin E (PGE) will have synergistic effects on leukocyte entry. CD40 is also expressed on the perivascular cells. Activation of CD40 by CD40 ligand is known to increase COX-2 and IL-8 expression in endometrial fibroblasts. The likely source of CD40 ligand in the uterus is platelets. Thus ingress of platelets will up-regulate NFkappaB by activating CD40 and increase agents such as PGE which will stimulate further the ingress of platelets. There is thus the possibility of a spiralling inflammatory response. This response however, is normally modulated by progesterone raising the threshold of the NFkappaB pathway and in the presence of high progesterone levels activation of CD40 will be ineffective. When progesterone falls at the end of the ovarian cycle and the restrictions on activation are lost, the perivascular cells will respond, initiating leukocyte entry, vasoconstriction-vasodilatation cycles with associated hypoxia and consequent sloughing off of the endometrium. The perivascular cell in endometrium is pivotal in both menstruation and early pregnancy and we need to understand this cell better to devise more effective medical treatment for menstrual dysfunction.

Leukocyte networks and human endometrial remodelling

Remodelling of the human endometrium occurs during the normal menstrual cycle. This process involves the disintegration of the superficial or functionalis layer of the endometrium following the fall in progesterone resulting from the demise of the corpus luteum and the reconstruction of a new layer without scarring. The degradative properties of matrix metalloproteinases (MMP) and their presence in the endometrium during remodelling events suggests that they are effector molecules in this process. The features of menstruation parallel those of an inflammatory response and the abundance of leukocytes in the endometrium prior to the onset of menstruation indicates a role for these cells in the remodelling process. This review examines the relationship between leukocytes and the local production and activation of MMP within the endometrium.

Progesterone induced blocking factor (PIBF) mediates progesterone induced suppression of decidual lymphocyte cytotoxicity

PROBLEM

Progesterone induced blocking factor (PIBF) is a mediator of progesterone that blocks peripheral blood lytic natural killer (NK) activity. Progesterone or PIBF stimulated decidual macrophages block up-regulation of perforin expression in decidual lymphocytes (DL). Therefore, we investigated whether progesterone regulates cytotoxicity of DL. METHOD OD STUDY: Decidual mononuclear cells were cultured with progesterone. PIBF, progesterone and anti-PIBF antibody or in the medium only. Cytolytic activity of non-adherent DL was measured by PKH-26 (red) 2 hr cytolytic assay and flow cytometry. Perforin positive DL were detected by immunofluorescency and PIBF-positive cells by immunohistology.

RESULTS

Progesterone and PIBF, in a dose-dependent manner decreased cytotoxicity of DL against K-562 targets, and perforin egzocytosys was blocked. Anti-PIBF antibodies reversed the progesterone mediated reduction in cytolytic activity of DL. PIBF positive cells were found in first trimester pregnancy decidua.

CONCLUSION

The results indicate possible role for PIBF, as a mediator of progesterone in regulation of DL cytolytic activity at the maternal-foetal (M-F) interface.

Decidual natural killer cells: key regulators of placental development (a review)

Establishment of pregnancy initiates a dynamic and predictable series of changes in the uterus. In rodents, the trophectoderm of the blastocyst develops through the stage of an ectoplacental cone to become the placenta. The inner cell mass becomes the fetus and its associated extra-embryonic ectoderm and mesoderm. Maternal changes support development of the conceptus. These begin in the uterine stroma, which undergoes a process known as decidualization, and progress to include dilation and elongation of the uteroplacental arteries and activation and proliferation of specialized large granulated lymphocytes in the decidua basalis. This review focuses on these pregnancy-associated lymphocytes, known as uterine Natural Killer (uNK) cells and on their interactions with the other tissues that form the mesometrial aspect of the mouse maternal-fetal interface. Analogous lymphocytes are present in the decidualized human uterus. Understanding of uNK cell biology has advanced significantly through histological studies of implantation sites in immune deficient mice. Here, we summarize the key studies in lymphocyte-, cytokine- and cytokine receptor-deficient mice and in four enhanced models of gestation in these mice that incorporate transplantation or therapy with biologically active molecules.

Differential expression of interleukins (IL) IL-13 and IL-15 throughout the menstrual cycle in endometrium of normal fertile women and women with recurrent spontaneous abortion

Interleukins (IL)-13 and IL-15 are novel cytokines and key regulators of immune/inflammatory related responses that are critical in the outcome of various normal biological and associated abnormalities of the endometrium. The present study determined the temporal and spatial expression of IL-13 and IL-15 mRNA and protein in endometrium of normal fertile women throughout the menstrual cycle, and examined whether profiles of their expression differ from endometrium of women with unexplained recurrent spontaneous abortion (RSA). Using quantitative RT-PCR, ELISA and immunohistochemistry we found that IL-13 and IL-15 mRNA and protein are expressed in control endometrium throughout the menstrual cycle and in RSA (cycle days 21-23) with peak expression detected immediately after and prior to onset of menses, and two distinct periods corresponding to late proliferative and the early-mid secretory phases, respectively. The ratio of IL-13:IL-15 expression revealed a predominance in IL-13 expression during late proliferative/early secretory phase and IL-15 during the mid secretory phase. Compared to control endometrium, endometrium of women with RSA expresses elevated levels of IL-13 and IL-15, with IL-13:IL-15 ratio favoring IL-13. The immunoreactive IL-13 and IL-15 were localized primarily in endometrial luminal epithelial cells with an increased intensity in glandular epithelial and stromal cells in RSA. In conclusion, the results indicate that endometrium of normal fertile women expresses IL-13 and IL-15, with a distinct profile during the menstrual cycle and elevated expression in women with RSA. Although the biological significance of IL-13 and IL-15 in human endometrium and their elevated expression in RSA await investigation, these cytokines with distinct biological functions may regulate endometrial inflammatory/immune responses, tissue repair and receptivity for embryo implantation.

Conceptus influences the distribution of uterine leukocytes during early porcine pregnancy

Pregnancy in humans and rodents is associated with dramatic changes in leukocyte populations within the uterus. In these species, recruitment of leukocytes, mostly natural killer (NK) lymphocytes, accompanies decidualization of endometrial stroma even in the absence of pregnancy. In the pig, a nondecidualizing species, the predominant lymphocytes in the pregnant uterus are T and/or NK cells, but their distribution relative to embryonic attachment sites has not been reported. The objective of this study was to compare the abundance of leukocytes in porcine endometrium in contact with trophoblast with that between attachment sites during the early postattachment period. Uteri were recovered on Days 15-17 (n = 4), 18 and 19 (n = 4), 21 and 22 (n = 5), and 25-27 (n = 2) of gestation and from cycling pigs during the luteal phase (Day 15; n = 3). Leukocytes were identified in uterus obtained at versus between attachment sites using an antibody reactive with all leukocytes (CD44). In all pregnant animals, leukocytes were diffusely scattered throughout the endometrial stroma but were rare or absent in the luminal epithelium. Leukocyte density was approximately 3-fold greater in endometrium in contact with conceptuses than in endometrium between attachment sites throughout the early postattachment period. Leukocyte density during the luteal phase was similar to that between attachment sites, suggesting that leukocyte recruitment was a localized response to the embryo. The ability of an individual porcine conceptus to recruit maternal leukocytes to the adjacent stroma may be a vital step in early placental development and embryo survival.

Cytokines of the placenta and extra-placental membranes: biosynthesis, secretion and roles in establishment of pregnancy in women

Virtually all known cytokines have been demonstrated to be expressed in the placenta and associated fetal and maternal membranes during normal gestation. In addition to playing their traditional roles as modulators of immunological function, cytokines derived from the placenta and extraplacental membranes, together with other locally-derived growth factors, appear to be implicated in various aspects of implantation and placental development. Imbalances in the intrauterine cytokine milieu around the time of implantation and invasion may play a causative role in disorders associated with early pregnancy failure, and are also associated with the abnormal trophoblast development seen in gestational trophoblastic disease. Cytokines thus appear to be an important component of a paracrine/autocrine communication network operating within the feto-maternal interface to ensure the successful establishment of pregnancy.

Interleukin 2 receptor gamma chain (gamma(c)) knockout mice show less regularity in estrous cycle but achieve normal pregnancy without fetal compromise

PROBLEM

Implication of cytokines in pregnancy suggested but remains to be established. We studied the effect of cytokines on reproductive functions such as ovulation and pregnancy, with mutant mice lacking interleukin 2 receptor gamma (IL-2Rgamma), the so-called common gamma chain (gamma(c)), which is shared among receptors for multiple cytokines such as IL-2, IL-4, IL-7, IL-9 and IL-15.

METHOD OF STUDY

Regularities of estrous cycles were observed by vaginal smear. Ovaries stimulated with postmenopausal serum gonadotropin (PMSG) were examined for the ovarian capacities. The uteri at 13 days of gestation were used for histological analysis of the maternal-fetal interface.

RESULTS

The estrous cycles in gamma(c) knockout (gamma(c) KO) mice were irregular compared with wild-type mice, although, the mutants could become pregnant. No uterine natural killer (uNK) cell was found in the uterus at 13 days of pregnancy, and poor decidual formation and thickness of blood vessel walls were observed. Apparent differences were not seen in the numbers and weight of the fetuses between wild type and mutant animals, and fetuses were not compromised throughout pregnancy.

CONCLUSIONS

The gamma(c) KO mice showed irregular estrous cycle but they could carry out normal pregnancy despite lacking uNK and cytokines actions of IL-2, 4, 7, 9 and 15.

The biology of natural killer cells in cancer, infection, and pregnancy

OBJECTIVE

NK cells are important cells of the immune system. They are ultimately derived from pluripotent hematopoietic stem cells. NK cell cytotoxicity and other functions are tightly regulated by numerous activating and inhibitory receptors including newly discovered receptors that selectively recognize major histocompatibility complex class I alleles. Based on their defining function of spontaneous cytotoxicity without prior immunization, NK cells have been thought to play a critical role in immune surveillance and cancer therapy. However, new insights into NK cell biology have suggested major roles for NK cells in infection control and uterine function. The purpose of this review is to provide an update on NK cell function, ontogeny, and biology in order to better understand the role of NK cells in health and disease.

DATA SOURCES

In the Medline database, the major subject heading "Natural Killer Cells" was introduced in 1983, identifying 16,848 citations as of December 31, 2000. Since 1986, there have been approximately 1000 citations per year under this subject heading. In this database, 68% of manuscripts are limited to human NK cells; 40% of citations cross with the major sub-heading of cytotoxicity, 40% with cytokines, 36% with neoplasm, 5% with antibody-dependent cellular cytotoxicity, 2.8% with pregnancy, and 1.3% with infection. Of references from the year 2000-2001, 46 were selected to combine with contributions from earlier literature.

CONCLUSIONS

NK cells should no longer be thought of as direct cytotoxic killers alone as they clearly serve a critical role in cytokine production which may be important to control cancer, infection, and fetal implantation. Understanding mechanisms of NK cell functions may lead to novel therapeutic strategies for the treatment of human disease.

Macrophage migration inhibitory factor in the human endometrium: expression and localization during the menstrual cycle and early pregnancy

Macrophage migration inhibitory factor (MIF) was discovered as an activated T-lymphocyte-derived protein that inhibits the random migration of macrophages in vitro. Subsequently, knowledge of the physiological actions of MIF was extended to include its role as a proinflammatory cytokine that affects several functions of macrophages and lymphocytes. Previous reports have suggested an involvement of MIF in reproduction. However, no data are currently available on the presence of this cytokine in the human endometrium. In this study, the expression and tissue localization of MIF was evaluated in specimens of cycling endometrium, first trimester placenta bed biopsy, and isolated endometrial glands by Western blot analysis, immunohistochemistry, ELISA, and reverse transcription-polymerase chain reaction. The results demonstrated that MIF is expressed in human endometrium across the menstrual cycle and in early pregnancy. Immunohistochemical localization identified the protein in glandular epithelium, in stromal and predecidualized stromal cells of cycling endometrium, as well as in the decidua of first-trimester placenta. The proinflammatory features and specific actions of MIF on lymphoid cells suggest its potential involvement in several aspects of endometrial physiology.

Angiogenic growth factor messenger ribonucleic acids in uterine natural killer cells

Angiogenesis is essential for endometrial growth and repair, and disruption of this process may lead to common disorders of women, including menorrhagia and endometriosis. In pregnancy, failure of the endometrial spiral arterioles to undergo remodeling leads to preeclampsia. Here we report that in addition to vascular endothelial growth factor A (VEGF-A), human endometrium expresses messenger ribonucleic acids (mRNAs) encoding VEGF-C, placenta growth factor (PlGF), the angiopoietins, angiopoietin 1 (Ang1) and Ang2, and the receptors VEGFR-3 (Flt-4), Tie 1, and Tie 2. Levels of VEGF-C, PlGF, and Tie 2 changed during the menstrual cycle. Intense hybridization for VEGF-C and PlGF mRNAs was found in uterine nature killer cells in secretory phase endometrium and for Ang2 mRNA in the same cells in the late secretory phase. Interleukin-2 (IL-2) and IL-15 up-regulated VEGF-C, but not PlGF or Ang2, mRNA levels in isolated NK cells. Conditioned medium from decidual NK cells did not induce human umbilical vein endothelial cell apoptosis. These results indicate that human endometrium expresses a wide range of angiogenic growth factors and that uterine nature killer cells may play an important role in the abnormal endometrial angiogenesis that underlies a range of disorders affecting women.

Expression of Fas/Fas ligand by decidual leukocytes in hydatidiform mole

Complete hydatidiform moles are entirely paternally derived and, therefore, represent a complete intrauterine allograft that might be expected to provoke an altered maternal immune response compared with that of normal pregnancy. Uterine decidua contains a large leukocyte population, of which 10%-20% are T lymphocytes. Fas ligand (FasL) expression by placental trophoblast may induce apoptosis of Fas+ lymphocytes, thereby facilitating immune tolerance and survival of the molar trophoblast. Our previous studies have shown an increase in activated CD4+ decidual T cells in molar pregnancy compared with normal pregnancy. This study was designed to characterize and quantitate Fas/FasL expression by decidual leukocytes in complete and partial hydatidiform mole compared with that in normal early pregnancy using single and double immunohistochemical labeling (i.e., avidin-biotin-peroxidase and avidin-biotin-alkaline phosphatase). A significant increase was found in Fas and FasL expression by decidual CD4+ T cells in complete (Fas+, P = 0.0106; FasL+, P = 0.0081) and partial (Fas+, P = 0.0131; FasL+, P = 0.0051) hydatidiform moles, as was a significant decrease in Fas expression by decidual CD8+ T cells in complete (P = 0.0137) and partial (P = 0.0202) hydatidiform mole compared with normal early pregnancy. The implications of altered Fas/FasL status of decidual T-cell subsets in hydatidiform mole are also discussed.

Progesterone enhances interleukin-15 production in human endometrial stromal cells in vitro

Interleukin-15 (IL-15) is a novel cytokine that stimulates lymphocyte proliferation and migration via a trimeric receptor sharing the ss and gamma signal-transducing chains with the IL-2 receptor. It is suggested that IL-15 is involved in regulating the proliferation and differentiation of uterine natural killer cells. In the human endometrium, we have recently reported that IL-15 messenger ribonucleic acid (mRNA) levels significantly increased during the secretory phase compared with those during the proliferative phase. In this study we investigated whether the female sex steroids progesterone (P) and estradiol (E(2)) regulate IL-15 messenger RNA (mRNA) and the secretion in human endometrial stromal cells (ESC) in vitro. Northern blot analyses revealed a significant increase in IL-15 mRNA levels in ESC treated with P alone or E(2) plus P compared with vehicle. Furthermore, P is a potent inducer of IL-15 mRNA expression in ESC in a dose-dependent manner. On the other hand, E(2) alone did not increase IL-15 mRNA expression. By enzyme-linked immunosorbent assay, IL-15 protein secretion was stimulated by P and further enhanced by combined treatment with E(2) and P, whereas E(2) alone was ineffective. It is suggested that IL-15 is deeply involved in the hormonal control of the human endometrium by P and E(2).