Human uterine lymphocytes

During the luteal phase and the early months of pregnancy, there is a dense mucosal infiltration of CD56+ natural killer (NK) cells. These uterine NK cells have a phenotype (CD56bright, CD16-, mCD3-) which distinguishes them from peripheral blood NK cells (CD56dim, CD16bright, mCD3-). The uterine NK cells are in close association with extravillous trophoblast (EVT) cells which infiltrate into the decidua and maternal spiral arteries. This subpopulation of trophoblast expresses two human leukocyte antigen (HLA) class I molecules, HLA-G and HLA-C. Circulating NK cells express receptors for HLA class I molecules. We have recently found evidence that similar receptors are present on decidual NK cells belonging to both the Killer Inhibitory Receptor (KIR) and CD94 families. The repertoire of NK receptors expressed varies between different women. The findings indicate that decidual NK cells do have receptors for trophoblast HLA class I molecules. Experiments are underway to determine the effects of this interaction on NK cell function.     

Uterine NK Cells and Trophoblast HLA Class I Molecules

PROBLEM: To investigate the proposal that NK cells in decidua may control trophoblast migration during implantation of the human placenta. METHOD: Use Mab specific for HLA-G and for HLA-C in association with flow cytometry and immunoprecipitation to determine the expression of these HLA molecules by trophoblast. Expression of Killer inhibitory/activatory receptors (KIR/KAR) and the CD94 receptor by decidual NK cells was also studied. RESULTS: Extravillous trophoblast expressed HLA-G and HLA-C in both β₂m-associated form and as free heavy chains. KIR and KAR are expressed by decidual NK cells. The repertoire of receptors varied between different women and also between blood and decidual NK cells from the same women. The expression of CD94 was also different between blood and decidual NK cells. CONCLUSION: The recognition of HLA-G/HLA-C by KIR/KAR and CD94 could provide a mechansm by which decidual NK cells control trophoblast migration.     

Leukocyte activation in the decidua of chromosomally normal and abnormal fetuses from women with recurrent abortion

As part of our continuing programme to investigate immunological causes of unexplained recurrent pregnancy losses, we studied subpopulations of white blood cells and their activation status in decidua of women with a history of recurrent spontaneous abortion (RSA). We differentiated specifically between normal karyotyped male fetuses and abnormal karyotyped fetuses with trisomy 16 because trisomy 16 is not compatible with life and is thus a non-controversial cause of spontaneous miscarriage. Leukocytes were counted in paraffin-embedded decidua after immunohistological staining for CD45 (LCA), CD3, CD56, CD68, CD69 and CD25. Numbers of activated versus non-activated T lymphocytes, NK cells and macrophages were compared in decidua from women with: (i) unexplained RSA who had a normal male karyotype (n = 17) miscarriage; (ii) unexplained RSA who had a trisomy 16 (n = 21) miscarriage; and (iii) normal gestationally age-matched first trimester pregnancies following elective termination procedures (n = 20). Significantly more activated leukocytes were detected in the decidua of women with unexplained RSA who had a normal male karyotype compared to the other groups (P < 0.0001). In addition, numbers of cells comprising the major leukocyte subpopulation, CD56+ NK cells, appeared reduced in the decidua of women with unexplained RSA compared to decidua from women having elective terminations. Increased numbers of activated leukocytes in the decidua of women with a history of unexplained recurrent pregnancy loss who had a normal karyotyped pregnancy provide evidence that cellular immunity may be involved in unexplained recurrent pregnancy loss.     

HLA-E is expressed on trophoblast and interacts with CD94/NKG2 receptors on decidual NK cells

Non-classical MHC class I molecule HLA-E is the ligand for CD94/NKG2 NK cell receptors. Surface expression of HLA-E requires binding of specific HLA class I leader sequences. The uterine mucosa in early pregnancy (decidua) is infiltrated by large numbers of NK cells, which are closely associated with placental trophoblast cells. In this study we demonstrate that trophoblast cells express HLA-E on their cell surface in addition to the previously reported expression of HLA-G and HLA-C. Furthermore, we show that the vast majority of decidual NK cells bind to HLA-E tetrameric complexes and this binding is inhibited by mAb to CD94. Thus, recognition of fetal HLA-E by decidual NK cells may play a key role in regulation of placentation. The functional consequences of decidual NK cell interaction were investigated in cytotoxicity assays using polyclonal decidual NK cells. The overall effect of CD94/NKG2 interaction with HLA-E is inhibition of cytotoxicity by decidual NK cells. However, since decidual NK cells are unable to kill trophoblast even in the presence of mAb to MHC class I molecules and NK cell receptors, HLA-E interaction with CD94/NKG2 receptors may regulate other functions besides cytolysis during implantation.     

Immunopathology of the implantation site utilizing monoclonal antibodies to natural killer cells in women with recurrent pregnancy losses

PROBLEM: Placental lesions of 71 women with documented recurrent spontaneous abortions of unknown etiology were evaluated using immunohistochemical staining. METHOD OF STUDY: Placental tissue blocks (less than 12 weeks gestation) from prior pregnancy losses were obtained, recut, and analyzed utilizing monoclonal antibody to identify the trophoblast (cytokeratin 8/18) and natural killer (NK) cells (CD57) at the implantation site. The following features were evaluated: trophoblast invasion pattern; syncytium formation; vasculitis and thromboembolism of decidual vessels; decidual inflammation; decidual necrosis; fibrin deposition at the decidual necrosis site; mononuclear-cell infiltration in villi and intervillous space; perivillous fibrin deposition; trophoblast morphology; and quantitation of CD57+ NK cells within the decidual tissue near the implantation site. Controls consisted of 20 healthy women with no history of recurrent pregnancy losses, who had their pregnancies electively terminated. RESULTS: Of the women studied, 29.6% demonstrated elevated CD57+ NK cells at the implantation site (P = 0.030), 54.1% had inadequate cytotrophoblast invasion depth (P = 0.000), 44.1% demonstrated inadequate syncytium formation (P = 0.004), and 33.9% presented thromboembolism in decidual vessels (P = 0.025). CONCLUSION: Some women with recurrent spontaneous abortions demonstrate abnormal placental lesions at the implantation site. Immunopathologic evaluation of the placental implantation site that terminated in a spontaneous abortion may reveal the immunopathogenesis of previous pregnancy losses.     

Decidual natural killer cells in recurrent spontaneous abortion with normal chromosomal content.

PROBLEM: The maternal local immune responses in unexplained recurrent spontaneous abortion (RSA) are not yet well known. Maternal peripheral and decidual natural killer (NK) cells were evaluated in RSA with normal chromosomal content. METHOD OF STUDY: Maternal peripheral blood, villous trophoblast, and decidua were taken from 15 normal pregnancies and 9 RSA patients with normal chromosomes. The NK cells in decidual lymphocytes were evaluated by flow cytometry using monoclonal antibodies for CD56, CD16, and CD3. RESULTS: The percentages of CD56+ CD16- CD3- cells in decidual lymphocytes in RSA were lower than in normal pregnancies (P < 0.002). The CD56+CD16+/CD56+CD16- cells ratio in RSA was higher than in normal pregnancies (P < 0.02). CONCLUSION: The lower percentages of CD56+CD16-CD3- cells in RSA cases may show an inappropriate accumulation of NK cells in the decidua, and this finding may be a factor involved in RSA.     

Investigation of the effects of heparin and low molecular weight heparin on E-cadherin and laminin expression in rat pregnancy by immunohistochemistry

BACKGROUND: Heparin and low molecular weight heparin (LMWH) are used widely to improve the pregnancy outcome in women with thrombophilia, miscarriage, recurrent miscarriage and fetal death. This study was designed to investigate the effects of heparin and LMWHs, enoxaparin and tinzaparin, on E-cadherin and laminin expression in placental and decidual tissues in rat pregnancy. METHODS: Wistar albino female rats (n = 48) were randomly assigned to four study groups (normal saline, heparin, enoxaparin and tinzaparin) in the preconceptional period. Tissue sections of placenta and decidua were immunohistochemically examined for the expression of E-cadherin and laminin. RESULTS: E-cadherin placental staining score of heparin group was significantly lower and E-cadherin decidual staining score of heparin and enoxaparin groups were significantly lower than control group. There were no significant differences in placental and decidual laminin staining scores among the study groups. CONCLUSIONS: Heparin and enoxaparin can reduce E-cadherin expression but not laminin expression in rat pregnancy. They might modulate trophoblast invasion. We suggest that this is the possible underlying mechanism involving in improvement of trophoblast invasion by the use of heparin and LMWH in patients with the history of miscarriage.     

Activation status of T and NK cells in the endometrium throughout menstrual cycle and normal and abnormal early pregnancy

Endometrial lymphocytes were studied at all stages throughout the menstrual cycle and early pregnancy by flow cytometry to examine different lymphocyte subpopulations and the expression of the T- and NK-cell activation markers. After pregnancy, CD8⁺CD3⁺ lymphocytes were decreased in the decidua. In both endometrium and decidua, more T cells expressed CD69, CD71, HLA-DR, and CD38 antigens than in peripheral blood. After pregnancy, CD71⁺CD3⁺ lymphocytes were further increased. CD25⁺CD3⁺ lymphocytes decreased significantly in the endometrium and decidua of ectopic pregnancies, but not in the decidua of normal pregnancies. These findings indicate that T cells are regionally activated in the first trimester, and it may be the result of the stimulation by fetal antigens. NK cells were the most abundant cell type in the decidua, which expressed the phenotype CD16⁻ CD56⁺, and CD57⁻CD56⁺. The proportion of activated decidual NK cells was increased in anembryonic pregnancies more than in normal pregnancies, although the total NK subpopulation was similar in both groups. This might result in increased NK cytotoxicity in anembryonic pregnancies. In conclusion, T cells are activated, but NK cytotoxicity is decreased in the decidua of early normal pregnancies. This might be important in the control of trophoblast growth and placental development.     

Decidual Natural Killer Cytotoxicity Decreased in Normal Pregnancy but Not in Anembryonic Pregnancy and Recurrent Spontaneous Abortion

PROBLEM : The natural killer (NK) cell activity is depressed in the decidua of early normal pregnancy. Recently Morii et al. (Am J Reprod Immunol 1993;29:1–4) found that all early intradecidual CD3⁺ T cells expressed either T cell receptor (TCR) α/β or γ/δ but that the expression of the CD3⁺/TCR complex was down-regulated. METHOD : To test whether these changes in decidual cellular immunity are different among normal pregnancy, anembryonic pregnancy and recurrent spontaneous abortion, we examined the immune cell subpopulations in the decidua from these three types of pregnancy using flow cytometry and an NK cytotoxicity assay. RESULTS : Intradecidual CD3⁺ T cells expressed either TCR α/β or γ/δ, and the level of expression of the CD3/TCR complex was down-regulated in normal pregnancy, anembryonic pregnancy, and recurrent spontaneous abortion. Although the relative proportion of decidual NK cells was increased to approximately the same extent in all three types of pregnancy, decidual NK activity was higher in anembryonic pregnancies and in recurrent spontaneous abortions than it was in normal pregnancies. CONCLUSION : Decidual NK cell responses are different in anembryonic pregnancies and in recurrent spontaneous abortions than in normal pregnancies. Whether this difference is pathogenic or is the response to a dead embryo remains to be elucidated.     

Aberrant positioning of trophoblast and lymphocytes in the feto-maternal interface with pre-eclampsia

Pregnancy represents the growth of an allograft where fetal trophoblast cells evade immune rejection and invade maternal tissue. There should be a balance between fetal trophoblast and maternal immune-responsive cells and alterations in the proportion of these cells may relate to pregnancy disorders. To test this, the decidual tissue of placental bed biopsies was examined and trophoblast cells and lymphocytes were quantified morphometrically; spiral arteries were classified as unchanged, transformed or affected by acute atherosis. Normal pregnancy (n=19) was characterized by the transformation of about one half of all spiral arteries within the placental bed. We found that 40% of all lymphocytes were CD56+ uterine NK cells and 60%, CD3+ T-lymphocytes; about 30% of these were CD8+ T cells. Intrauterine growth retardation in the context of preeclampsia (n=15) was accompanied by reduced trophoblast numbers within smaller and more tortuous arteries and an increase in the proportion of CD56+ uterine NK cells and CD8+ T lymphocytes in the decidua (70% of all CD3+ cells). In the case of pre-eclampsia without fetal growth retardation (n=14) no increase in CD56+ uterine NK cells was seen, while CD8+ T lymphocytes were significantly increased compared with the normal level (50% of all CD3+ cells). Fetal growth retardation is associated with poor transformation of spiral arteries and characterized by an increase of uterine NK cells. Symptoms of pre-eclampsia are independently associated with an increase in the cytotoxic T subset of decidual lymphocytes. Pre-eclampsia and related fetal growth retardation are seemingly caused by an enhancement of the maternal cytotoxic defence against the fetal allograft.     

Role of decidual natural killer (NK) cells in patients with missed abortion: differences between cases with normal and abnormal chromosome.

In order to study the mechanism of abortion, the proportions of NK cells in the peripheral blood and decidual lymphocytes were evaluated in both chromosomally normal and abnormal missed abortions. In normal pregnancy, CD56+16-3- NK cells are a major element of decidual lymphocytes. The percentages of CD56+16-3-NK cells of peripheral lymphocytes in normal pregnancies were not statistically significantly different from those of chromosomally normal and abnormal abortions. In the decidua, the percentages of CD56+16-3- NK cells of decidual lymphocytes showed no statistically significant differences between normal pregnancies and chromosomally abnormal abortions. However, the percentages of CD56+16-3-NK cells of chromosomally normal abortions were lower than those of chromosomally abnormal (P = 0.0025). Moreover, the percentages of CD56+16- NK cells in abortions with normal chromosomes were lower than those in normal pregnancies or abortions with abnormal chromosomes (P = 0.0037, P = 0.0025). However, when the proportion of CD56+ NK cells expressing CD16 was evaluated, there were no statistically significant differences in the percentages of CD56+16+ NK cells in normal pregnancies and missed abortions with normal chromosomes and abnormal chromosomes. We conclude that the expression of decidual CD56+16-3- NK cells in missed abortions with normal chromosomes is different from abortions with abnormal chromosomes and that this phenomenon may depend on an abnormal immune response of the maternal side.     

No evidence for apoptosis of decidual leucocytes in normal and molar pregnancy: implications for immune privilege

Complete hydatidiform moles are totally paternally derived and represent complete allografts that might be expected to provoke maternal immune rejection. Our previous and other studies have shown expression of Fas by increased numbers of activated decidual CD4(+) T cells in both complete and partial molar pregnancy as well as increased FasL(+) expression by molar trophoblasts compared with trophoblasts in normal pregnancies. As the Fas/FasL system represents a major apoptotic pathway that can play a role in immune privilege, the aim of this study was to investigate whether apoptosis of decidual immune cells, particularly T cells, could be responsible for maternal immune tolerance in molar pregnancy. Using terminal deoxynucleotidyl transferase (TdT)-mediated nick end-labelling (TUNEL), a significant increase in TUNEL(+) cells was demonstrated in decidua associated with partial (P = 0.0052) and complete (P = 0.0096) hydatidiform mole compared with normal early pregnancy. Co-labelling immunoperoxidase studies showed that the TUNEL(+) cells in both normal and molar pregnancies were not activated CD45RO(+) immune cells, CD3(+) T cells, CD56(+) uterine natural killer (NK) cells or CD14(+) CD68(+) macrophages. Double immunohistochemical labelling with antiactive caspase-3 and leucocyte markers confirmed the lack of leucocyte apoptosis. Double immunostaining with anticytokeratin to detect trophoblast and M30 CytoDeath, which detects a neoepitope of cytokeratin 18 revealed after caspase-mediated cleavage, revealed apoptotic extravillous trophoblast cells within decidual tissue. We conclude that there is no evidence that apoptosis of decidual leucocytes plays a role in maintaining maternal tolerance in either normal or molar pregnancy.     

Simple enumerations of peripheral blood natural killer (CD56+ NK) cells, B cells and T cells have no predictive value in IVF treatment outcome

BACKGROUND: To evaluate the association between the absolute counts of the peripheral natural killer (NK) cells (including total CD56(+) NK cells, CD56(dim) NK cells and CD56(bright) NK cells), B cells and T cells on the implantation rate and miscarriage rate after IVF treatment. METHODS: This was a prospective observation study. A total of 138 patients who underwent IVF treatment from December 2002 to July 2003 were recruited to the study. Blood samples were obtained on the day of vaginal oocyte retrieval prior to the procedure. The absolute counts of lymphocytes, NK cells, B cells and T cells were identified by flow cytometry. These absolute counts and their relationships to IVF treatment outcome and miscarriage rate were analysed. RESULTS: There were no significant differences with regard the mean values of absolute lymphocyte count, T cell count, B cell count and NK cell count (including total CD56(+) NK, CD56(dim) NK and CD56(bright) NK cells) between the pregnant and non-pregnant groups and also between the ongoing pregnancy and miscarriage groups. The cause of infertility, duration of infertility, basal FSH levels, number of previous failed IVF treatments, number of previous miscarriages and stimulation characteristics were not significantly different between the pregnant and non-pregnant groups. Previous studies have suggested that women with a history of recurrent miscarriage and those with infertility accompanied by recurrent failed IVF treatments are associated with a peripheral blood NK cell percentage >12%, therefore further analysis of peripheral CD56(+) NK cell levels <12% (group A) and >12% (group B) was performed. There was no significant difference in implantation rate (group A: 17.0%; group B: 23.2%), pregnancy rate (group A: 36.6%; group B: 47.7%) or miscarriage rate (group A: 23.3%; group B: 28.6%). CONCLUSION: There were no significant differences between simple enumerations of peripheral blood NK cells (including total CD56(+) NK, CD56(dim) NK and CD56(bright) NK cells), B cells and T cells with IVF treatment outcome and pregnancy outcome. Women who had a peripheral NK cell level >12% did not have higher number of previous pregnancy losses. Importantly their pregnancy rate was not reduced and their miscarriages were not increased compared to women who had a peripheral NK cells level <12%.     

Interaction of Decidual CD56+ NK with Trophoblast Cells during Normal Pregnancy and Recurrent Spontaneous Abortion at Early Term of Gestation

The immunological paradox of pregnancy, when maternal immune system recognizes but does not reject the semiallogenic foetus, is not yet fully understood. The aim of this work was to detail the mechanisms of the interaction of decidual CD56+ NK, infiltrating the maternal part of placenta, and trophoblast cells of foetal origin. Samples of the endometrial tissue from 13 healthy non‐pregnant women, 37 placentas, obtained after medical abortion of viable pregnancy at 7–10 weeks of gestation, and 26 samples of placentas from first‐trimester recurrent spontaneous abortion (RSA) were used as the material for investigation. Phenotype of NK was assessed by flow cytometry. The influence of trophoblast cells upon IFNγ and GrB mRNAs expression by dNK was investigated by RT‐PCR. The influence of dNK upon trophoblast cells migration and invasion was studied using collagen and Matrigel systems. In RSA group comparing to the normal pregnancy, the decrease of dNK with inhibitory receptors (NKG2A) and elevation of activated dNK were seen. In normal pregnancy, but not in RSA, trophoblast cells increased the expression of IFNγ and GrB mRNAs by CD56+ dNK. Both in normal and RSA pregnancy, dNK inhibited the migration and invasion of trophoblast cells. Initially, low invasive and migration capacities of trophoblast cells were seen during RSA. Thus, unbalanced activation of dNK can lead to the impairment of dNK and trophoblast cells interaction during RSA.     

Immunoregulatory properties of decidua macrophages

It has been suggested that decidual NK cells play a regulatory role in pregnancy with their heterocladic (activating/inhibitory) receptor repertoire to control trophoblast infiltration. Most of the NK receptors (NKRs) have as ligands HLA molecules (HLA-C,-G,-E), which are expressed on invading trophoblast and they may interact with their NKR counterparts and provide self-signals to evade trophoblastic damage.
When we studied the NKR repertoire in couples with unexplained recurrent spontaneous abortions by genotyping partners for NKRs (KIR and CD94/NKG receptors, known to have as ligands HLA molecules present on trophoblast), we found that aborting women usually have a limited inhibitory KIR (inhKIR) repertoire.
Our hypothesis that a limited inhKIR repertoire predisposes to miscarriage, because it is ineffective to abort activating signals and protect trophoblast, is supported by studies in selected couples, known to posses HLA-Cw antigens interacting with inhKIRs and by studies on the placental material of spontaneously lost or electively terminated pregnancies. Most of the aborters did not have inhKIRs specific for the HLA-C antigens possibly expressed on trophoblast and this seems to be confirmed when KIRs and HLA-Cs are genotyped using DNA extracted from decidual and trophoblastic cells, respectively.
Increasing knowledge about KIR haplotypes is expected to be helpful in the study of the suggestedinhKIR – HLA-C allorecognition system in pregnancy.     

The expression of killer cell inhibitory receptors on natural killer cells and activation status of CD4+ and CD8+ T cells in the decidua of normal and abnormal early pregnancies.

The establishment of the human placenta in early pregnancy is characterized by the presence of large numbers of natural killer cells within the maternal decidua. These NK cells have an unusual phenotype, CD3- CD16- CD56(bright), distinguishing them from peripheral blood NK cells. They may control trophoblast migration and placentation. Using a panel of monoclonal antibodies to several members of the KIR family and flow cytometry, we found that KIRs are expressed on decidual NK cells. There is variation in both the percentage of cells expressing a particular receptor and the density of receptor expression between decidual NK cells from different individuals. In anembryonic pregnancy, the proportions of decidual NK cells with a particular KIRs (GL183 and EB6) decreased significantly when compared with normal pregnancy (p = 0.01 and 0.01, respectively), raising the possibility that these NK receptors may be involved in recognition of the allogeneic fetus by the mother at the implantation site. In the decidua, more CD4+ and CD8+ T cells expressed CD69 and HLA-DR than in blood, indicating that T cells are regionally activated during early pregnancy. When compared with normal pregnancy, decidual HLA-DR+CD4+CD3+, CD69+CD8+CD3+ and HLA-DR+CD8+CD3+ T lymphocytes are significantly increased in anembryonic pregnancy. The over-activation of decidual T cells during anembryonic pregnancy may thus contribute to the increased NK cytotoxicity activity.     

Leukocyte populations, hormone receptors and apoptosis in eutopic and ectopic first trimester human pregnancies

The implantation of trophoblast cells at extrauterine sites still results in decidualization. The objective of the present study was to compare decidualization at eutopic and ectopic implantation sites. Tissues from women undergoing elective termination of uterine pregnancy and from women with ectopic pregnancy were used to detect the presence of cells important for the maintenance of pregnancy, such as BCL-2+, CD56+, CD3+, CD8+ and CD68+ cells, and the presence of oestrogen (ER) and progesterone receptors (PR) by immunohistochemistry. In-situ detection of fragmented DNA was performed to identify apoptotic cells. The percentage of CD3+ cells among all immunocompetent cells in the tubal epithelium was 46.6% (39.9% of CD3+ were also CD8+); the other 53.4% were CD68+ cells. CD56+ cells were undetectable in ectopic decidua at the feto-maternal interface in ectopic tissue. In uterine decidua, we found 29.9% CD3+ cells (2.2% of CD3+ were CD8+), 51.6% CD56+ cells and 18.5% CD68+ cells. The ratio of BCL2+ to CD3+ cells in ectopic pregnancy was 0.41. In uterine pregnancy, the ratio of BCL-2 to CD3 was 0.44 and 0.39 for CD56. Tissues from both ectopic and uterine pregnancies were positive for PR. Fewer apoptotic cell bodies were present in ectopic pregnancy. The use of tissue obtained from ectopic pregnancy may become an excellent model to identify the mechanism of trophoblast invasion in eutopic pregnancies.     

Expression of Kisspeptin and its receptor GPR54 in the first trimester trophoblast of women with recurrent pregnancy loss

Citation Park D‐W, Lee S‐K, Hong SR, Han A‐R, Kwak‐Kim J, Yang KM. Expression of kisspeptin and its receptor GPR54 in the first trimester trophoblast of women with recurrent pregnancy loss (RPL). Am J Reprod Immunol 2012; 67: 132–139 Problem Kisspeptin and its receptor GPR54 play a major role in trophoblast invasion. The expression of kisspeptin and GPR54 in trophoblast and decidua and their relationship with decidual and peripheral blood natural killer (NK) cells are investigated in women with RPL. Method of study Trophoblast and decidual tissues were collected from 38 RPL women who miscarried a genetically normal fetus and 14 women who had elective abortion. Kisspeptin, GPR54, and decidual NK cells were investigated with immunohistochemistry, and peripheral blood NK cells were analyzed by flow cytometry. Results Kisspeptin expression in syncytiotrophoblast was significantly decreased in RPL women with normal (<15%) peripheral blood NK cells (npNK) (P = 0.021) and high (≥15%) peripheral blood NK cells (hpNK) (P = 0.024) as compared to controls. Kisspeptin expression in cytotrophoblast was significantly decreased hpNK group (P = 0.009) as compared to controls. GPR54 expressions were not different among study groups and controls. The number of CD56⁺ decidual NK cells are significantly higher in hpNK group as compared to npNK group (P = 0.041) and showed a correlation with kisspeptin expression in syncytiotrophoblasts (r = 0.738, P < 0.001). Conclusion Decreased kisspeptin expression in trophoblasts is associated with RPL and kisspeptin may engage the regulation of decidual NK cell infiltration.     

Tubal versus uterine placentation: similar HLA-G expressing extravillous cytotrophoblast invasion but different maternal leukocyte recruitment

The nonclassical HLA-G class I gene is expressed by extravillous cytotrophoblast that invades decidua in uterine pregnancy, suggesting that it may contribute to the immunological mechanisms that protect the fetus against maternal alloimmune response and/or pathogen infections. We first addressed the question of whether HLA-G expression was dependent on maternal tissue environment by comparing uterine and ectopic tubal pregnancies. Using HLA-G-specific mAb on placental cryosections, we found by immunohistochemistry that all subtypes of extravillous cytotrophoblast similarly expressed HLA-G in pregnant tubes, demonstrating that its expression was independent of the site of implantation. We next compared by immunohistochemistry the phenotype of maternal leukocytes recruited in both pregnant tissues. In contrast to decidua, pregnant tubes were characterized firstly, by the lack of natural killer (NK) cells and of cells expressing CD94 receptor specific for HLA-E, secondly, by a prominent increase of CD8+ T cells, dendritic cells, and macrophages, the latter co-expressing the LIR1/ILT2 killer immunoglobulin-like receptor (KIR), and finally, by the presence of cells expressing LIR2/ILT4 KIR or BY55 NK receptors, known to bind to HLA-G. Such cell types may favor a unique innate defense in pregnant tubes. These observations also suggest that trophoblast HLA-G expression does not influence the recruitment of particular maternal leukocytes in pregnant tissues.     

Störungen des intrauterinen Immunsystems bei Frauen mit wiederholten Aborten

In contrast to fertile women with successful pregnancies, women with a history of recurrent spontaneous abortion show a variety of alterations in their cellular and humoral immune system, which are primarily detectable in the uterine compartment, but only in part in the peripheral circulation. Some of these phenomena are presumably causally related to the adverse outcome of pregnancy, whereas others may be due to changes in the endocrine and paracrine regulation of the fetoplacental unit occurring during the course of miscarriage. During the luteal phase of the cycle with conception, at the period of implantation, women with recurrent spontaneous abortion exhibit distinct differences in the population of endometrial lymphocytes, an increased number and activity of CD16 + CD56 + natural killer (NK) cells and a shift in cytokine production by T helper (Th) cells towards the inflammatory Th 1-type (IL-2, IL-12, interferon-γ) when compared with fertile women. In the peripheral circulation, there are an exaggerated number and activity of NK cells and an increased Th 1-response by T effector cells. Organ-specific, nonorgan-specific and procoagulatory antibodies are indicative of a general activation of the humoral immune system. At the time of another miscarriage, the depth of myometrial invasion of the invading trophoblast is usually shallow. The concentration of NK cells at the site of implantation is increased, and the production of antiinflammatory and protective Th 2 cytokines (LIF, IL-4, IL-10) by decidual T lymphocytes is decreased. These mechanisms are at least in part amenable to immunization with allogenic lymphocytes, immunoglobulins and medical interventions (aspirin, heparin, prednisone).