Number Of uNK Cells Research Articles

Prednisolone Trial: Study protocol for a randomised controlled trial of prednisolone for women with idiopathic recurrent miscarriage and raised levels of uterine natural killer (uNK) cells in the endometrium

BackgroundIdiopathic recurrent miscarriage is defined as 3 consecutive pregnancy losses with no contributing features found on investigations. At present there are no treatments of proven efficacy for idiopathic recurrent miscarriage. Uterine natural killer (uNK) cells, the most predominant leucocyte in the endometrium are adjacent to foetal trophoblast cells and thought to be involved in implantation. The exact mechanisms of how uNK cells affect implantation are not clear but are probably through the regulation of angiogenesis. Multiple studies have shown an association between high density of uterine natural killer cells and recurrent miscarriage. We have shown that prednisolone reduces the number of uNK cells in the endometrium. The question remains as to whether reducing the number of uNK cells improves pregnancy outcome.MethodsWe propose a randomised, double-blind, placebo controlled trial of prednisolone with a pilot phase to assess feasibility of recruitment, integrity of trial procedures, and to generate data to base future power calculations. The primary aim is to investigate whether prednisolone therapy during the first trimester of pregnancy is able to improve live birth rates in patients with idiopathic recurrent miscarriage and raised uNK cells in the endometrium. Secondary outcomes include conception rate, karyotype of miscarriage, miscarriages (first and second trimester), stillbirths, pregnancy complications, gestational age at delivery, congenital abnormality and side effects of steroids. The trial has 2 stages: i) screening of non-pregnant women and ii) randomisation of the pregnant cohort. All patients who fit the inclusion criteria (<40 years old, ≥3 consecutive miscarriages with no cause found and no contraindications to prednisolone therapy) will be asked to consent to an endometrial biopsy in the mid-luteal phase to assess their levels of uNK cells. Women with high levels of uNK cells (≥5%), will be randomised to either prednisolone or placebo when a pregnancy is confirmed. Follow-up includes 2 weekly ultrasound scans in the first trimester, an anomaly scan at 20 weeks gestation, growth scans at 28 and 34 weeks gestation and a postnatal follow-up at 6 weeks.Trial RegistrationCurrent Controlled Trials ISRCTN28090716

DC within the pregnant mouse uterus influence growth and functional properties of uterine NK cells

The vascular addressins mucosal addressin cell adhesion molecule-1, P-selectin and ICAM-1 permit alpha(4)beta(7)-integrin-expressing DC, especially those of the myeloid lineage (CD11c(+)CD11b(+) DC), to access the pregnant mouse uterus. Injection of blocking monoclonal antibodies against mucosal addressin cell adhesion molecule-1 in P-selectin(-/-) mice or experimental approaches with beta7-integrin(-/-) or ICAM-1(-/-) mice revealed that limited access or absence of CD11c(+)CD11b(+) DC at the maternal/fetal interface negatively affects the frequency, size and functional properties of uterine NK (uNK) cells. Adoptive transfer of DC obtained from WT mice into beta7-integrin(-/-) mice abrogates these effects and emphasizes the importance of DC in uNK cell differentiation. Interestingly, those implantation sites lacking CD11c(+)CD11b(+) DC are characterized by decreased IL-15 and IL-12 mRNA and/or protein levels. Chronic administration of IL-15 in these mice gives rise to uNK cell numbers and size comparable to those of WT mice, whereas additional injection of IL-12 positively affects the IFN-gamma expression of uNK cells. Real-time RT-PCR and protein arrays performed with isolated uterine DC underline the role of DC as a source of IL-15 and IL-12 in the pregnant mouse uterus.

Implication of Interferon Stimulated Gene 15 (ISG15) in the Recruitment of Uterine Natural Killer Cells into the Murine Implantation Site.

Interferon stimulated gene 15 (ISG15) encodes a ubiquitin-like protein that has being implicated in a number of physiological events including innate immune response, interferon signaling and cancer. ISG15 also is induced by pregnancy in the endometrium of rodents, primates and ruminants. Previous reports from our laboratory indicate that expression of ISG15 in the uterus is functionally required for maintenance of pregnancy in mice. Isg15 null females (Isg15-/-) exhibit embryo mortality ranging from 30-70% by 12.5 days post coitum (dpc), in contrast to 4% embryo mortality observed in wild type control females (Isg15+/+). As a consequence, Isg15+/+ mice have larger litters (7.94 ± 0.32 pups/ litter) when compared to Isg15-/- mice (4.2 ± 0.24). Additionally, Isg15-/- females carrying heterozygous embryos showed similar embryonic mortality rates when compared to Isg15-/- females carrying Isg15-/- embryos. This finding suggests that maternal Isg15 genotype contributes to embryonic death. Uterine natural killer cells (uNK) are the most prevalent maternal uterine immune cell and they are found in large number at the feto-maternal interface in mice. They interact closely with the invading placental trophoblast cells, which are responsible for remodeling of spiral arteries. This process is essential to ensure a normal blood supply to the fetus and placenta throughout pregnancy. Uteirne NK cells also produce cytokines (interferon gamma and interleukins 18 and 27), and proliferate within the myometrium at each implantation site forming the mesometrial lymphoid aggregate of pregnancy (MLAp). Uterine NK cells have been linked with failure of pregnancy: studies in mice lacking uNK cells and components of IFN-gamma pathway indicate that uNK cell-derived IFN-gamma is essential for spiral artery remodeling. Because Isg15 is a component of the IFN pathway, we hypothesized that uNK population may be altered in Isg15-/-. To address this question we designed a set of experiments to compare the number and distribution of uNK cells at implantation sites between Isg15+/+ and Isg15-/- mice. Implantation sites of 7.5 dpc and 12.5 dpc (n=5 each genotype and day) were fixed in 4% parformaldehyde and embedded in paraffin. Five μm sections were cut from paraffin-embedded tissues and uNK cells were identified using Dolichos biflorus agglutinin (DBA) lectin histochemistry. The number of uNK was assessed through a computer-assisted image analysis (Image Pro Plus for Windows, Ver 4.0, Media Cybernetics, Silver Spring, MD) at 200 X. A minimum of 3 non-adjacent mid-sagittal sections 40 μm apart were analyzed per implantation site. There was a very conspicuous difference in the density and distribution of uNK cells between Isg15+/+ and Isg15-/- mice. On 7.5 dpc, Isg15-/- mice showed reduced (P<0.001) uNK cell numbers and substantially reduced migration into the mesometrial pole of the decidua when compared to Isg15+/+ mice. By 12.5 dpc, there was a dramatic difference in the distribution of uNK cells in histological sections of Isg15-/- mice when compared with Isg15+/+. In Isg15-/- uNK cells were more concentrated in the decidua basalis in addition to an apparent impaired development of the metrial zone. The present study suggests that ISG15 may play a role in the recruitment of uNK cells in the uterus during early gestation. We suspect that faulty uNK migration and distribution contributes to embryonic mortality observed in ISG15-/- mice. (poster)

Proliferation of uterine natural killer cells is induced by human chorionic gonadotropin and mediated via the mannose receptor.

The endometrial lining of the human uterus contains a population of phenotypically distinct (CD56(bright), CD16(dim)), tissue-specific, natural killer [uterine natural killer (uNK)] cells that play a key role in the establishment of a successful pregnancy. An increase in the number of endometrial uNK cells occurs when the conceptus implants, and there is a further increase during the early stages of placentation. Here, we describe studies that have identified human chorionic gonadotrophin (hCG), a glycoprotein synthesized by the preimplantation conceptus, as a novel regulator of uNK cell proliferation. The impact of hCG on uNK cells was mediated via the mannose receptor (CD206) rather than by the classical hCG/LH receptor that was not expressed. The mannose receptor and hCG were colocalized on the surface of uNK cells, and proliferation did not occur if cells were incubated with deglycosylated hCG or intact hCG in the presence of excess d-Mannose. These novel observations provide new insight into the endocrine-immune dialogue that exists between the conceptus and immune cells within the receptive endometrium, and have implications for the role of uNK cell-trophoblast interactions and pregnancy outcome.

Evidence for participation of uterine natural killer cells in the mechanisms responsible for spontaneous preterm labor and delivery

The purpose of this study was to determine in a mouse model whether uterine natural killer (uNK) cell cytotoxic activation induces infection/inflammation-associated preterm labor and delivery. Wild type or interleukin (IL)-10(-/-) mice were injected intraperitoneally with lipopolysaccharide on gestational day 14. Mice were either killed for collection of uteroplacental tissue, spleen, and serum or allowed to deliver. Uteroplacental tissue was used for histology and characterization of uNK cells. Low-dose lipopolysaccharide treatment triggered preterm labor and delivery in IL-10(-/-), but not wild type mice, in a manner independent of progesterone levels. Preterm labor and delivery in IL-10(-/-) mice was associated with an increased number and placental infiltration of cytotoxic uNK cells and placental cell death. Depletion of NK cells or tumor necrosis factor (TNF)-alpha neutralization in these mice restored term delivery. Furthermore, TNF-alpha neutralization prevented uNK cell infiltration and placental cell apoptosis. The uNK cell-TNF-alpha-IL-10 axis plays an important role in the genesis of infection/inflammation-induced preterm labor/delivery.

O.344 Reconstructive strategies in case of orbital tumors

There is conflicting evidence on the role of autoimmune disorders in reproductive failure, including recurrent miscarriage (RM) and recurrent implantation failure (RIF), after in vitro fertilisation (IVF). Several commonly studied autoimmune markers in women with reproductive failure include antiphospholipid antibodies (APAs), thyroid peroxidase antibodies (TPA) and uterine natural killer (uNK) cells. However, there have not been any studies that have examined the correlation of these markers in women with reproductive failure. To determine if women who tested positive for autoantibodies (APA and thyroid peroxidase antibodies) have significantly higher uNK cell numbers than women who tested negative for these antibodies, the percentage of stromal cells that stained positive for CD56 was identified by immunocytochemistry in endometrial biopsies from 42 women with unexplained RM (29 women tested negative for autoantibodies and 13 women tested positive for autoantibodies) and 40 women with unexplained RIF (30 women tested negative for autoantibodies and 10 women tested positive for autoantibodies). Biopsies were obtained on days LH + 7 to LH + 9. There was no significant difference in uNK cell numbers between women with unexplained RM who tested negative and those who tested positive for autoantibodies. Similarly, there was no significant difference in uNK cell numbers between women with unexplained RIF who tested negative and those who tested positive for autoantibodies. In women with reproductive failure the presence of autoantibodies does not appear to affect the numbers of uNK cells in the endometrium around the time of implantation.

Role of uterine natural killer cells in angiogenesis of human decidua of the first-trimester pregnancy

Decidualization is accompanied by extensive angiogenesis, which is an essential step in the maturation of new blood vessels in mammalian pregnancy. The purpose of this study was to determine a distribution of uNK cells (CD56(+) uNK or CD56(bright) cells) in human decidua of the first-trimester pregnancy, and investigate whether uNK cells in human decidua could express vascular endothelial growth factor (VEGF-A) and/or angiopoietin2 (Ang2). Our immunohistochemical staining results demonstrated that a great amount of uNK (CD56(+)) cells scattered throughout the decidual stroma and near endometrial gland and spiral vessels in human decidua. The protein expression of VEGF-A and Ang2 was detected in decidual stroma cells, capillary endothelial cells and glandular cells in tissue specimens. There was a positive correlation between microvessel density (MVD) and the number of the CD56-positive uNK cells in decidual stroma, and also between the number of the CD56-positive uNK cells and VEGF-A protein expression in the tissue. In addition, we found that uNK cells in human decidua could express VEGF-A mRNA, but not Ang2 mRNA, in isolated uNK cells in human decidua of the first-trimester gestation by combination of LCM and Nested-PCR. Our study indicated that uNK cells, through expressing VEGF-A, may play an important role in the angiogenic response at the time of human decidualization and early placenta development.

Pericellular-acting proteases in human first trimester decidua

Proteolysis is essential for decidual development during embryonic implantation, but little is known regarding the expression and functions of membrane-type matrix metalloproteinases (MT-MMPs) and urokinase-type plasminogen activator (uPA) and its receptor uPAR in decidua. Therefore, their protein and mRNA levels were analysed in three first trimester decidual tissues, decidual secretory endometrium (DSE), decidua parietalis (DP) and basalis (DB). Decidua was obtained during first trimester pregnancy termination. uPA, uPAR, and MT1/2/3/5-MMP expression were studied by RT-PCR and immunohistochemistry, and CD56-positive uNK cells and CD68-positive macrophages were quantified in serial sections. The mRNAs and antigens of all proteases and uPAR were detectable in the decidual tissues and extravillous trophoblasts (EVT). mRNA levels of all proteases and uPAR, except MT5-MMP, were elevated in both DB and DP compared to DSE, being significant for MT1-MMP and uPAR in DP. MT2- and MT3-MMP mRNAs in DB were 24- and 10-fold higher than in DSE, and 19- and 7-fold increased compared to DP. At the protein level uPA and uPAR were particularly elevated in DB, while pro-angiogenic MT1- and MT3-MMPs were elevated in both DB and DP compared to DSE. MT2-MMP was prominently present in all conditions. The number of uNK cells was increased in DB and DP versus DSE, while a comparable increase in macrophages did not reach statistical significance. These data are consistent with a differential regulation of pericellular proteases in decidua by pregnancy-induced hormones, immune cells and EVT.

Uterine NK cells in murine pregnancy

Murine uterine natural killer (uNK) cells are transient, short-lived, terminally differentiated lymphocytes found in decidualized endometrium. Cells expressing natural killer cell surface markers are present in uteri of infant mice. Terminal uNK cell differentiation coincides with mesometrial decidual development subsequent to blastocyst implantation and begins about gestation day 5. uNK cells proliferate rapidly and, within 3 days, senescent uNK cells appear in normal implantation sites. Mid-gestation, senescent cells become dominant and uNK cell numbers decline until term when remaining cells are shed with the placenta. Transplantable uNK cell progenitors occur outside the uterus, suggesting that blood cell homing augments any in-utero progenitors. Early in healthy pregnancies, uNK cells produce cytokines and angiogenic molecules. Their lytic capacity in normal gestation and in pregnancy failure is incompletely defined. A significant shift recently occurred in thinking about major uNK cell functions. Activated uNK cells are now considered critical for appropriate endometrial angiogenesis in early implantation site development and in non-gestational endometrium. Because analogous cells appear in the endometria of women during each menstrual cycle and become abundant in early pregnancy, studies involving experimental pregnancy termination in genetically manipulated mice continue to have great importance for understanding regulation at the human maternal–fetal interface.

Vascular Addressins in the Uterus and Pancreas of Type 1 Diabetic Mice in Early Pregnancy

Distinctive patterns of vascular cell adhesion molecule expression in early mouse decidua establish niches that recruit different subtypes of immune cells. In normal gestation day (gd)8 decidua, vascular cell adhesion molecule (VCAM)-1 and mucosal addressin cell adhesion molecule (MAdCAM)-1 occur in different regions enriched by uterine Natural Killer (uNK) cells and monocytes, respectively. UNK cells prepare endometrial spiral arteries for pregnancy-induced structural modifications, a process deficient in decidua of type 1 diabetic mice and women. In non-obese diabetic (NOD) mice, onset of insulitis coincides with islet expression of VCAM-1, MAdCAM-1 and peripheral lymph node addressin (PNAd), a molecule implicated in extravasation of human uNK precursor cells. We used immunohistochemistry to address the combined effects of diabetes and pregnancy on gd6 and 8 pancreatic and decidual expression of VCAM-1, MAdCAM-1 and PNAd and assessed the effect of diabetes on early uNK cell numbers. Normoglycemic (n) and diabetic (d) NOD and C57Bl/6 (B6) mice were studied. Pregnancy increased addressin expression in the pancreata of all mice with n- and d-NOD pancreata having stronger endothelial expression of VCAM-1, MAdCAM-1 and PNAd than B6. VCAM-1 expression was localized to uterine endothelium, including that of spiral arteries and was lower in d- than in n-NOD or B6 mice. MAdCAM-1 was localized to uterine endothelium and was lower in n- and d-NOD than in B6. PNAd expression was only observed in uterine epithelium and was stronger in d- than in n-NOD or B6. In all groups, only VCAM-1 had stronger expression in decidua than in pancreas. A mild elevation in uNK cells was present in n-and d-NOD mice at gd6 but not at gd8 when a higher proliferation index was found compared with B6. Thus, in type 1 diabetic gestations in mice, signals for the recruitment of circulating cells are reduced in uterus and elevated in pancreas.

Aberrant endometrial features of pregnancy in diabetic NOD mice.

Pregnant diabetic women are at a 4-12 times higher risk for preeclampsia, an urgent acute-onset complication of mid- to late gestation, than normal pregnant women. Hallmarks of preeclampsia are hypertension, proteinuria, and incomplete modification of endometrial spiral arteries. Transient proangiogenic lymphocytes called uterine natural killer (uNK) cells are implicated in human and rodent spiral artery modification. We studied mid- to late gestations in spontaneously type 1 diabetic NOD mice to investigate whether diabetes alters uNK cell homing and/or function. Normoglycemic, pre-diabetic, and diabetic NOD mice and controls were mated. Lymphocytes and endometrial endothelium and decidua were studied histologically and in functional assays. Conception accelerated progression to overt diabetes in NOD females who had limited spiral artery development, heavier placentas, and lighter fetuses displaying numerous birth defects compared with controls. UNK cell numbers were reduced in the decidua basalis of diabetic females, whereas interferon-gamma production was elevated. In diabetic NOD mice, decidual expression of the mucosal vascular addressin cell adhesion molecule (MAdCAM)-1 was aberrant in position, whereas vascular cell adhesion molecule (VCAM)-1 expression was reduced. Assays of lymphocyte adhesion to tissue sections under shear forces indicated that diabetes compromises the potential homing functions of both endometrial endothelium and peripheral NK cells. In diabetes, gestational endometrium has immune and vascular defects that likely contribute to murine fetal loss and birth defects. Analogous problems and preeclampsia in diabetic women may involve similar mechanisms.

Prognostic value of the measurement of uterine natural killer cells in the endometrium of women with recurrent miscarriage

Studies in mice suggest that CD56 + uterine natural killer (uNK) cells play an important role in implantation. Studies in humans have described an increase in the number of uNK cells in the non-pregnant mid-secretory endometrium of women with unexplained recurrent miscarriage (RM). However, the predictive value of uNK cell number in the maintenance of pregnancy is controversial. A blind retrospective study was undertaken. The percentage of stromal cells positive for CD56 was identified by immunocytochemistry in endometrial biopsies from 10 normal control women and 87 women with unexplained RM, of whom 51 became pregnant following biopsy. Biopsies were obtained on days LH + 7 to LH + 9. As in previous studies, the number of uNK cells in the 87 women with RM (mean 11.2% range 1.1-41.4%) was significantly higher (P = 0.013) than in the control women (mean 6.2% range 2.2-13.9%). No significance difference in uNK numbers was observed between 19 women who miscarried (mean 9.6% range 1.7-25.0%) and 32 women who had a live birth (mean 13.3% range 1.1-41.4%) in a subsequent pregnancy. In this study numbers of uNK cells in the peri-implantation endometrium of women with unexplained recurrent miscarriage did not predict subsequent pregnancy outcome.

Genetic Deletion of Placenta Growth Factor in Mice Alters Uterine NK Cells

Placenta growth factor (PlGF; formerly PGF), a vascular endothelial growth factor gene family member, is expressed in human implantation sites by maternal uterine NK (uNK) and fetal trophoblast cells. Lower than normal concentrations of blood and urinary PlGF have been associated with impending onset of pre-eclampsia, a hypertensive disease of late human gestation characterized by limited intravascular trophoblast invasion. In pregnant rodents, delivery of the PlGF antagonist sFlt-1 or S-endoglin induces pre-eclampsia-like lesions. Mice genetically deleted in PlGF reproduce, but neither their implantation sites nor their uNK cell development are described. We combined real-time PCR of endometrium from nonpregnant and gestation day (gd)6-18 C57BL6/J (B6) mice with immunohistology to analyze PlGF expression in normal mouse pregnancy. To estimate the significance of uNK cell-derived PlGF, PlGF message was quantified in mesometrial decidua from pregnant alymphoid Rag2 null/common gamma chain null mice and in laser capture-microdissected B6 uNK cells. Histopathologic consequences from PlGF deletion were also characterized in the implantation sites from PlGF null mice. In B6, decidual PlGF expression rose between gd8-16. uNK cells were among several types of cells transcribing PlGF in decidualized endometrium. Immature uNK cells, defined by their low numbers of cytoplasmic granules, were the uNK cells displaying the greatest number of transcripts. PlGF deletion promoted the early differentiation high numbers of binucleate uNK cells (gd8) but had no other significant, morphometrically detectable impact on implantation sites. Thus, in mice, PlGF plays an important role in successful uNK cell proliferation and/or differentiation.

Toll-like receptor 3 agonist enhances IFN-γ and TNF-α production by murine uterine NK cells

To understand the response of murine uterine natural killer (uNK) cells to Toll-like receptor (TLR) 3 agonist at the early gestation stage, CBA × DBA/2 mice were intraperitoneally (i.p.) injected with polyinosinic–polycytidylic acid (poly I:C), the specific TLR3 agonist, at a dose of 10 μg/g BW or PBS at gestation day (gd) 6.5. The CD69 expression of uNK (DX5 +CD3 −) cells was highly up-regulated and reached 92.3 ± 0.9%, the percentage of intracellular TNF-α + or IFN-γ + uNK (DX5 +CD3 −) cells in the implantation sites of CBA × DBA/2 matings was also significantly increased 24 h after poly I:C injection. Surprisingly, poly I:C treatment significantly decreased the total number of uNK cells (either DX5 +CD3 − or DBA +) at fetal–maternal surface, but had no influence on local NKT cells, T cells and DCs. This investigation will help to explain the central role for hyperactivated uNK cells in the progress of mice pregnancy.

Effect of the Conceptus on Uterine Natural Killer Cell Numbers and Function in the Mouse Uterus During Decidualization1

Uterine natural killer (uNK) cells are the most abundant lymphocytes in the uterus during early pregnancy and play a role in spiral arteriole modifications. In the present study, we investigated whether uNK cell populations differed between mouse decidua and deciduoma. Histochemical staining using the Dolichos biflorus agglutinin (DBA) lectin was used to identify uNK cells and classify their stages of maturation. We found differences in the pattern of localization and density of uNK cells between the decidua and deciduoma at Days 2-4 after the onset of decidualization. The cells were more distributed and the densities were significantly greater in the mesometrial region of the decidua than in the deciduoma. Using double-labeling for DBA lectin binding and bromodeoxyuridine incorporation, we found that the higher number of uNK cells in the decidua was not due to an increase in uNK cell proliferation. Western blot analyses revealed that the increase in uNK cell number was accompanied by significant increases in the levels of interferon gamma (IFNG) and prointerleukin 18 when a conceptus was present. Vascular morphometry revealed that modifications of the spiral arterioles occurred in the mesometrial decidua but not in the deciduoma, which could be attributed to the differences observed in uNK cell number and IFNG production. The present study demonstrates that differences exist in uNK cell populations between the decidua and deciduoma, providing evidence that the conceptus generates signals that regulate uNK cell number and function in the uterus during implantation.

Uterine natural killer cells, implantation failure and recurrent miscarriage

Uterine natural killer (uNK) cells are the most abundant leukocytes in preimplantation endometrium and early pregnancy decidua. Maternal uNK cells are adjacent to, and have the ability to interact directly with, fetal trophoblasts. uNK cells can secrete an array of cytokines that are important in angiogenesis and thus placental development and the establishment of pregnancy. Increased numbers of uNK cells have been associated with reproductive failure. The number of preimplantation uNK cells has been reduced with prednisolone. However, despite these exciting advances in understanding of the uNK cells, considerably more work needs to be done to establish a specific role for uNK cells and to use uNK cells as a test of malfunctioning endometrium and the basis for future treatment for reproductive failure.

Distribution patterns of immunocompetent cells in the pregnant mouse uteri carrying allogeneic mouse and xenogeneic vole embryos.

Mouse and vole embryos were allogeneically and xenogeneically transferred into pseudopregnant CD-1 and immunodeficient (scid) female mice, and we investigated the distribution of immunocompetent cells, uterine natural killer (uNK) cells, mast cells and macrophages, in the implantation sites on days 6, 7 and 8 of gestation. The survival rate of the vole embryos decreased gradually with increased gestation, but the rate was higher in the scid uteri than in the CD-1 mice. The number of uNK cells increased markedly at the mesometrial triangle and the outer decidual area in the CD-1 uteri containing vole embryos; by contrast, scid uteri having vole embryos showed almost the same number as those having mouse embryos. Mast cells were present in large numbers at the myometrium, but rarely in the decidua in all types of pregnant uteri. Cells at the myometrium were more numerous in xenogeneic than in allogeneic transfer. Many mast cells appeared in the inner decidua where xenogeneically transferred vole embryos were dead and aborted. Macrophages were present in the outer decidua and myometria in all types of pregnant uteri, and their distribution pattern did not change even in aborted uterine sites. These results suggest: (1) the response of macrophages to dead embryos is completely inhibited, (2) uNK cells and mast cells increase near dead and aborted embryos, and (3) the increment in uNK cells responding to xenogeneic embryos is suppressed in scid mice, and the suppression may contribute partly to survival of the embryos.

Uterine natural killer cells: insights into their cellular and molecular biology from mouse modelling.

In primates, including women, and in rodents, natural killer lymphocytes (NK cells) have a unique relationship with the decidualizing uterus. Implantation sites from genetically modified and transplanted mice have proven useful models for understanding potential mechanisms involved in the recruitment, activation and functions of human CD56(bright) uterine (u)NK cells. Key findings are reviewed in this article. In mice, uNK precursor cells are recruited from secondary lymphoid tissues and are activated coincident with their uterine arrival. uNK cells proliferate, produce cytokines (interferon gamma (IFN-gamma) and interleukin 18 (IL-18) and IL-27), and terminally differentiate into granulated lymphocytes. Many uNK cells proliferate within the myometrium at each implantation site forming a structure, the mesometrial lymphoid aggregate of pregnancy (MLAp) that surrounds blood vessels servicing each placenta. Post-mitotic uNK cells are abundant within decidua basalis; frequently (<25%) associating with spiral arteries, intramurally and intraluminally. From mid-gestation, numbers of uNK cells decline. Studies of implantation sites in mice lacking uNK cells, IFN-gamma, components of IFN-gamma-induction and -signalling pathways or IFN-gamma-regulated genes indicate that uNK cell-derived IFN-gamma is essential in triggering pregnancy-induced spiral artery modification. Decidual maintenance and uNK cell death are additional effects of uNK cell-derived IFN-gamma. Thus, during the first half of gestation, uNK cells contribute to and sustain important changes in the maternal placental bed.

Uterine natural killer cells: insights into their cellular and molecular biology from mouse modelling

In primates, including women, and in rodents, natural killer lymphocytes (NK cells) have a unique relationship with the decidualizing uterus. Implantation sites from genetically modified and transplanted mice have proven useful models for understanding potential mechanisms involved in the recruitment, activation and functions of human CD56(bright) uterine (u)NK cells. Key findings are reviewed in this article. In mice, uNK precursor cells are recruited from secondary lymphoid tissues and are activated coincident with their uterine arrival. uNK cells proliferate, produce cytokines (interferon gamma (IFN-gamma) and interleukin 18 (IL-18) and IL-27), and terminally differentiate into granulated lymphocytes. Many uNK cells proliferate within the myometrium at each implantation site forming a structure, the mesometrial lymphoid aggregate of pregnancy (MLAp) that surrounds blood vessels servicing each placenta. Post-mitotic uNK cells are abundant within decidua basalis; frequently (<25%) associating with spiral arteries, intramurally and intraluminally. From mid-gestation, numbers of uNK cells decline. Studies of implantation sites in mice lacking uNK cells, IFN-gamma, components of IFN-gamma-induction and -signalling pathways or IFN-gamma-regulated genes indicate that uNK cell-derived IFN-gamma is essential in triggering pregnancy-induced spiral artery modification. Decidual maintenance and uNK cell death are additional effects of uNK cell-derived IFN-gamma. Thus, during the first half of gestation, uNK cells contribute to and sustain important changes in the maternal placental bed.

Functional Analysis of Murine Uterine Natural Killer Cells Genetically Devoid of Oestrogen Receptors

Uterine Natural Killer (uNK) cell differentiation in vivo requires oestrogen (E) priming prior to progesterone (P). Hybridomas between uNK precursor and SP2/0 cells express message for E receptor (ER)α but nor PR. However, mature, rodent and human uNK cells lack these receptors. To functionally assess requirements for uNK cell expression of ERα or ERβ during precursor differentiation, marrow was transplanted from either ERαo/o (αERKO) or ERβo/o (βERKO) mice into alymphoid RAG-2o/o/γco/o females. Recipients were mated and their implantation sites were examined by light microscopy, morphometry and ultrastructure. High numbers of uNK cells were established from each donor strain. Graft-derived uNK cells were similar in number and morphology to uNK cells of normal mice, suggesting that neither α- nor β-ER is required for uNK precursor cell differentiation. Induction of spiral artery modification in the transplant recipients indicated that graft-derived uNK cells had functional properties. A novel technique for rapid isolation of highly purified uNK cells from normal mice using Dolichos biflorus agglutinin (DBA) lectin-conjugated magnetic beads was employed to obtain RNA. Expression of α- and β-ER was absent by RT–PCR from NK cells isolated from the uterus, supporting the conclusions from the in vivo study.