Maternal cells in chorionic villi from placentae of normal and abnormal human pregnancies

Discordant Eosinophilic/T-Cell Chorionic Vasculitis in a Dichorionic Diamniotic Placenta

Eosinophilic/T-cell chorionic vasculitis (ETCV) is an idiopathic lesion composed of eosinophils, CD3+ T lymphocytes, and histiocytes. In twins, ETCV may affect only one chorionic plate, a feature defined as "discordant". We present a case of ETCV discordance in a diamniotic dichorionic placenta at 38 weeks of gestation, in which the female twin was small for gestational age, weighing 2670 g (25th percentile). The corresponding placental territory presented ETCV in two close chorionic vessels with concordance of the fetal inflammatory response. Immunohistochemistry showed an abundance of CD3+/CD4+/CD25+T lymphocytes, CD68 PG M1+ macrophages, and scattered CD8+ T cells with focal TIA-1 positivity. Granzyme B, CD20 B lymphocytes, and CD56 natural killer cells were negative. High-grade villitis of unknown etiology (VUE) was additionally found and displayed comparable ETCV findings, except for an equivalent ratio of CD4+/CD8+ T cells, but TIA-1 was focally expressed. VUE was associated with chronic histiocytic intervillositis (CHI). The combination of ETCV, VUE, and CHI may have been responsible for reduced fetal growth. Concordance was observed in the ETCV and TIA-1 expression, both in ETCV and in VUE, which is a maternal response. These findings may suggest a common antigen or chemokine pathway to which both mother and fetus accordingly responded.

Maternal-Fetal Inflammation in the Placenta and the Developmental Origins of Health and Disease

Events in fetal life impact long-term health outcomes. The placenta is the first organ to form and is the site of juxtaposition between the maternal and fetal circulations. Most diseases of pregnancy are caused by, impact, or are reflected in the placenta. The purpose of this review is to describe the main inflammatory processes in the placenta, discuss their immunology, and relate their short- and long-term disease associations. Acute placental inflammation (API), including maternal and fetal inflammatory responses corresponds to the clinical diagnosis of chorioamnionitis and is associated with respiratory and neurodevelopmental diseases. The chronic placental inflammatory pathologies (CPI), include chronic villitis of unknown etiology, chronic deciduitis, chronic chorionitis, eosinophilic T-cell vasculitis, and chronic histiocytic intervillositis. These diseases are less-well studied, but have complex immunology and show mechanistic impacts on the fetal immune system. Overall, much work remains to be done in describing the long-term impacts of placental inflammation on offspring health.

Eosinophilic/T-cell Chorionic Vasculitis: Histological and Clinical Correlations

Eosinophilic T-cell chorionic vasculitis (E/TCV) is composed of eosinophils and T-lymphocytes originating within chorionic vessels, radiating toward the intervillous space and away from the amnion in a fashion different from the fetal vascular response seen in amnionitis. Clinical significance and risk factors are not well established. We report four pregnancies (five infants, one triplet was spared) with E/TCV, gestational ranging from 23 weeks to term. All had concurrent acute chorioamnionitis, three had the typical acute fetal inflammatory response. One had placental fetal obstructive vasculopathy and an upper extremity reduction defect (radio-ulnar synostosis), the mother had pre-eclampsia. A second case involved 2 of 3 23 week previable triplets. Our third case had a metatarsus varus resistant to casting, the mother had gestational diabetes. The last case was a normal infant. We review the literature, discuss the clinical findings and present the histologic characteristics of this infrequently recognized lesion.

Chronic villitis of unknown etiology and massive chronic intervillositis have similar immune cell composition

INTRODUCTION

Chronic villitis of unknown etiology (CVUE) and massive chronic intervillositis (MCI) are placental lesions associated with infiltration of mononuclear cells in the chorionic villi and the intervillous spaces, respectively. It is not well known whether immune cells in CVUE and MCI have similar phenotypic characteristics.

METHODS

A cross-sectional study of third trimester placentas was conducted to identify immune cell subpopulations in CVUE and MCI (n = 17/group). CVUE was diagnosed with H&E staining and antibody to CD3 in serial sections; and MCI, by the presence of massive infiltration of mononuclear cells in the intervillous spaces. Immune cells, ICAM-1 expression and nuclear factor κB (NF-κB) activation were determined immunohistochemically.

RESULTS

CVUE and MCI showed similar infiltrates, mainly CD68+ and CD3+ cells. Most cells (>80%) were CD45RB+, and one third were CD45RO+ in both lesions. There were slightly more CD8+ than CD4+ cells in both CVUE and MCI. More than 90% of cells in CVUE and MCI were ICAM-1+ with NFκB nuclear localization. Syncytiotrophoblast ICAM-1 expression was significantly (p < 0.001) higher in MCI (mean of 81.0; range of 71.6-86.0) than in CVUE (52.4; 36.4-59.4) or normal placentas (0.2; 0.0-0.6). Both, failure of physiologic transformation of spiral arteries and placental atherosclerosis-like lesions of atherosis were significantly more frequent in MCI than in CVUE or normal placentas (p = 0.044 and p = 0.007, respectively).

DISCUSSION

These finding suggest that MCI and CVUE have very similar infiltration of immune cells although MCI has more severe placental lesions.

Metalloprotease dependent release of placenta derived fractalkine

The chemokine fractalkine is considered as unique since it exists both as membrane-bound adhesion molecule and as shed soluble chemoattractant. Here the hypothesis was tested whether placental fractalkine can be shed and released into the maternal circulation. Immunohistochemical staining of human first trimester and term placenta sections localized fractalkine at the apical microvillous plasma membrane of the syncytiotrophoblast. Gene expression analysis revealed abundant upregulation in placental fractalkine at term, compared to first trimester. Fractalkine expression and release were detected in the trophoblast cell line BeWo, in primary term trophoblasts and placental explants. Incubation of BeWo cells and placental explants with metalloprotease inhibitor Batimastat inhibited the release of soluble fractalkine and at the same time increased the membrane-bound form. These results demonstrate that human placenta is a source for fractalkine, which is expressed in the syncytiotrophoblast and can be released into the maternal circulation by constitutive metalloprotease dependent shedding. Increased expression and release of placental fractalkine may contribute to low grade systemic inflammatory responses in third trimester of normal pregnancy. Aberrant placental metalloprotease activity may not only affect the release of placenta derived fractalkine but may at the same time affect the abundance of the membrane-bound form of the chemokine.

Chronic chorioamnionitis is the most common placental lesion in late preterm birth

OBJECTIVES

The pathogenesis of late preterm birth remains elusive for the mechanisms of disease responsible. Placental examination can often provide important clues for the pathogenesis of pregnancy complications. This study was conducted to determine placental pathologic findings according to the gestational age and the clinical circumstances of preterm birth.

STUDY DESIGN

Placental pathologic findings and obstetrical and neonatal outcomes were reviewed in a consecutive preterm birth cohort from a single tertiary center (N = 1206). Placentas of term births (N = 300) were used as normal controls.

RESULTS

Acute chorioamnionitis (22.7% vs. 16.7%), maternal vascular underperfusion (6.4% vs. 0.5%), and chronic chorioamnionitis (20.8% vs. 10.5%) were significantly more frequent in preterm births than in term births (P < 0.05, for each). Among preterm births, chronic chorioamnionitis was the most common pathology of late preterm birth (gestational age <37 and ≥34 weeks), while acute chorioamnionitis was the most common lesion of extremely preterm birth (gestational age <28 weeks). While the frequency of acute chorioamnionitis decreased with advancing gestation, that of chronic chorioamnionitis increased (P < 0.001, for each). The upward trend of the frequency of chronic chorioamnionitis was related to advancing gestation in both spontaneous and indicated preterm births (P < 0.001, for each).

CONCLUSIONS

Chronic chorioamnionitis is a common pathology of late preterm birth. It is suggested that chronic chorioamnionitis, a feature of maternal anti-fetal rejection, is an important etiology of preterm birth, especially of late preterm birth.

Villitis of Unknown Etiology and Massive Chronic Intervillositis

Villitis of unknown etiology (VUE) is a common lesion affecting from 6.6% to 33.8% of third-trimester placentas. VUE needs to be distinguished from villitis of infectious etiology, most commonly cytomegalovirus and syphilis. Clinically, this lesion is associated with intrauterine growth retardation, intrauterine fetal demise, fetal neural impairment, maternal alloimmune and autoimmune disease, and maternal hypertension. It has a tendency to recur in subsequent pregnancies. Massive chronic intervillositis (MCI), also known as chronic histiocytic intervillositis, is a rare lesion that has an unclear relationship with VUE. MCI is associated with recurrent abortions.

Positive C4d immunostaining of placental villous syncytiotrophoblasts supports host-versus-graft rejection in villitis of unknown etiology

ABSTRACT Chronic villitis of unknown etiology (VUE) occurs in 5% of placentas submitted to pathology and is characterized by lymphohistiocytic infiltration of chorionic villi. VUE is associated with fetal growth restriction, preterm birth, and recurrent pregnancy loss. Accumulating evidence indicates that VUE may represent a host-versus-graft reaction analogous to transplant rejection. Pathologists routinely screen for antibody-mediated rejection in transplant biopsies by immunostaining for C4d, which highlights the recognition of donor cells by the host immune system. Since the hemochorial placenta is bathed in maternal blood, we hypothesized that cases of VUE may show C4d deposition onto villous syncytiotrophoblasts (STB). Chronic villitis was diagnosed in 82 of 1986 (4%) singleton placentas submitted to our department from 2007 through 2011. Forty randomly selected cases were gestational age-matched with 40 negative controls. Patient charts were reviewed and representative placental sections were immunostained for C4d. A positive C4d result was defined as circumferential immunostaining of the STB around at least one villous, or strong staining of fetal endothelial cells in the chorionic plate or stem villi. Our data indicate that VUE usually occurs in the 3rd trimester (37 ± 0.5 weeks) and is associated with significantly reduced placental weight (P  =  0.006). Positive C4d staining of STB was more common in VUE (35/40, 88%) compared with negative controls (2/40, 5%) (P < 0.0001). It was also more common in multiparous (35/66, 53%) than primiparous (2/14, 14%) women (P < 0.01). Although the precise mechanism remains to be determined, our data support the hypothesis that VUE may represent host-versus-graft rejection by the mother.

Maternal HLA panel-reactive antibodies in early gestation positively correlate with chronic chorioamnionitis: evidence in support of the chronic nature of maternal anti-fetal rejection

PROBLEM

Maternal tolerance of the fetus is essential for viviparity, yet anti-fetal rejection occurs in several pregnancy complications. Chronic chorioamnionitis is a feature of anti-fetal cellular rejection. There is a robust association between chronic chorioamnionitis and maternal seropositivity for anti-human leukocyte antigen (HLA) panel-reactive antibodies (PRA) at the time of delivery. This longitudinal study was performed to assess maternal HLA PRA status in early gestation and the temporal evolution of maternal HLA PRA in the context of chronic chorioamnionitis and, thereby, to determine whether HLA PRA during the course of pregnancy is useful for the detection of anti-fetal rejection.

METHOD OF STUDY

Maternal sera obtained before 16 weeks of gestation and at delivery were analyzed for HLA PRA in cases with (N = 100) and without (N = 150) chronic chorioamnionitis.

RESULTS

IgG (but not IgM) HLA class I and II PRA positivity at delivery was higher in cases with chronic chorioamnionitis than in those without chronic chorioamnionitis. IgG HLA class I PRA positivity before 16 weeks of gestation was higher in cases with chronic chorioamnionitis than in those without (30.3 versus 13.3%; P = 0.001). Positive conversion (negative HLA PRA before 16 weeks of gestation but positive at delivery) of IgG HLA class I and II PRA was significantly associated with chronic chorioamnionitis. Fetal HLA class I antigen-specific antibodies were confirmed in 12 of 16 mothers tested who were sensitized to HLA class I antigens before 16 weeks of gestation.

CONCLUSION

Positive maternal HLA PRA before 16 weeks of gestation and the temporal evolution of maternal HLA PRA are associated with the presence of chronic chorioamnionitis at the time of delivery. Maternal IgG HLA PRA has the potential to be a monitoring tool of anti-fetal rejection. Furthermore, the findings herein indicate that subsets of fetuses are exposed to alloimmune HLA antibodies for months, especially in cases with chronic chorioamnionitis.

Chronic intervillositis of the placenta: a systematic review

OBJECTIVE

Chronic intervillositis of the placenta is known to be associated with poor reproductive outcome and a high risk of recurrence. The aims of the present study were to quantify the risk of recurrence of chronic intervillositis in subsequent pregnancies, to explore if there are possible interventions and to assess the success of interventions.

METHODS

Systematic review of published literature using published guidelines.

RESULTS

No randomised controlled trials were identified. Sixty-one papers, published between 1977 and 2009 were identified after abstract screening but only 6 studies could be included in the systematic review. From the 6 selected studies, 69 pregnancies at gestational age of 14 weeks or over, with a histopathologic diagnosis of chronic intervillositis were available for analysis. The rate of intrauterine growth restriction in the study population was 66.7%, the overall rate of livebirth was 53.6%. In 16/20 (80.0%) cases recurrence of CI was confirmed at histopathology. The livebirth rate reported with treatment was 30.8% against 58.9% without treatment (RR=0.47, 95% CI=0.2-1.1). This difference was not statistically significant.

CONCLUSIONS

Chronic intervillositis has a high (80.0%) recurrence risk. In pregnancies reaching 14 weeks, the chance of a livebirth is 53.6%. The livebirth rate reported with treatment was 30.8% against 58.9% without treatment (RR=0.47, 95% CI=0.2-1.1). This difference was not statistically significant. Intervention with drug therapy is of no demonstrable benefit, and may even be harmful.

B7 family molecules as regulators of the maternal immune system in pregnancy

Placental and fetal growth and development are associated with chronic exposure of the maternal immune system to fetally derived, paternally inherited antigens. Because maternal lymphocytes are aware of fetal antigens, active tolerance mechanisms are required to ensure unperturbed progression of pregnancy and delivery of a healthy newborn. These mechanisms of tolerance may include deletion, receptor downregulation, and anergy of fetal antigen-specific cells in lymphoid tissues, as well as regulation at the maternal-fetal interface by a variety of locally expressed immunoregulatory molecules. The B7 family of costimulatory molecules comprises one group of immunoregulatory molecules present in the decidua and placenta. B7 family members mediate both inhibitory and stimulatory effects on T-cell activation and effector functions and may play a critical role in maintaining tolerance to the fetus. Here, we review the known functions of the B7 family proteins in pregnancy.

Villitis of unknown etiology is associated with a distinct pattern of chemokine up-regulation in the feto-maternal and placental compartments: implications for conjoint maternal allograft rejection and maternal anti-fetal graft-versus-host disease

The co-presence of histoincompatible fetal and maternal cells is a characteristic of human placental inflammation. Villitis of unknown etiology (VUE), a destructive inflammatory lesion of villous placenta, is characterized by participation of Hofbauer cells (placental macrophages) and maternal T cells. In contrast to acute chorioamnionitis of infection-related origin, the fundamental immunopathology of VUE is unknown. This study was performed to investigate the placental transcriptome of VUE and to determine whether VUE is associated with systemic maternal and/or fetal inflammatory response(s). Comparison of the transcriptome between term placentas without and with VUE revealed differential expression of 206 genes associated with pathways related to immune response. The mRNA expression of a subset of chemokines and their receptors (CXCL9, CXCL10, CXCL11, CXCL13, CCL4, CCL5, CXCR3, CCR5) was higher in VUE placentas than in normal placentas (p < 0.05). Analysis of blood cell mRNA showed a higher expression of CXCL9 and CXCL13 in the mother, and CXCL11 and CXCL13 in the fetus of VUE cases (p < 0.05). The median concentrations of CXCL9, CXCL10, and CXCL11 in maternal and fetal plasma were higher in VUE (p < 0.05). Comparison of preterm cases without and with acute chorioamnionitis revealed elevated CXCL9, CXCL10, CXCL11, and CXCL13 concentrations in fetal plasma (p < 0.05), but not in maternal plasma with chorioamnionitis. We report for the first time the placental transcriptome of VUE. A systemic derangement of CXC chemokines in maternal and fetal circulation distinguishes VUE from acute chorioamnionitis. We propose that VUE be a unique state combining maternal allograft rejection and maternal antifetal graft-vs-host disease mechanisms.

The fetus, not the mother, elicits maternal immunologic rejection: lessons from discordant dizygotic twin placentas

AIMS

Our objective was to elucidate the pathogenesis of twin discordance in four dizygotic pregnancies where only one of the twins had IUGR due to chronic villitis.

METHODS

We identified four cases of dizygotic twin placentas over a period of four years with evidence of chronic villitis. There was no clinical or pathologic evidence of TORCH, bacterial infection, preeclampsia or autoimmune disorders. Placentas were weighed, processed for histologic examination and stained with CD45RO (clone UCHL1) mouse monoclonal antibody, which identifies T-cells.

RESULTS

All placentas were dichorionic, with two being fused. Birth weight differences were 29%, 41%, 17% and 10%. Villitis was more marked in the placenta of the twin that weighed less and correlated with the degree of weight discordance. On examining the junction between the fused dichorionic placentas, the chorionic villi from the smaller twin contained numerous T-cells, whereas the villi associated with the less affected twin, showed little to no T-cells.

CONCLUSION

We describe a series of dizygotic twin placentas where the more severe the chronic villitis, the more affected the placenta and fetus. Since the maternal environment was constant for each of these twins, differences in villitis severity appears to be attributable to differences in the ability of each placenta to induce a maternal immune response.

Histopathological examination of the placenta: key issues for pathologists and obstetricians

The placenta is often not submitted for histopathological examination and obstetricians may be sceptical of the value of the examination. This article looks at the reasons for histopathological assessment of the placenta, examines what clinical information should be provided to pathologists and reviews what information can be gained from this 'diary of the pregnancy', especially for explaining adverse outcomes and potentially guiding the management of future pregnancies.

Involvement of Hofbauer cells and maternal T cells in villitis of unknown aetiology

AIMS

The nature of villitis of unknown aetiology (VUE) is intriguing in terms of its aetiology, origin of inflammatory cells and immunophenotype of T cells involved. The aim was to determine the origin of macrophages and the immunophenotype of T lymphocytes in VUE associated with various complications of pregnancy.

METHODS AND RESULTS

Placentas with VUE (n = 45) were studied by chromogenic in-situ hybridization (CISH) for Y chromosome (DYZ1) and immunohistochemistry for CD14, CD68, Ki67 (n = 10; all from male neonates) and a panel of T-cell antigens (CD3, CD4 and CD8) (n = 35). All of the placentas from male neonates showed CISH+ signals from Y chromosomes in the majority of macrophages, but not in lymphocytes, indicating that the macrophages were of fetal origin. Many macrophages of the affected chorionic villi were Ki67+, suggesting that they are hyperplastic Hofbauer cells. Among the lymphocytes, CD8+ T cells outnumbered CD4+ T cells in all placentas with different obstetrical conditions.

CONCLUSIONS

We define primary components of VUE as maternal CD8+ T cells and hyperplastic Hofbauer cells. We propose that VUE is a unique inflammatory reaction where the leucocytes from two hosts are key partners, analogous to either allograft rejection or graft-versus-host disease.

Maternal microchimerism in human fetal tissues

OBJECTIVE

The aim of the present study was to analyze the presence of maternal cells in human fetal tissues in the second trimester.

STUDY DESIGN

Tissues from 11 second-trimester fetuses terminated because of social reasons or because of malformations and/or trisomy were investigated. By cell sorting and polymerase chain reaction amplification, we studied the presence of maternal CD3+, CD19+, CD34+, and CD45+ in different fetal tissues and in placenta.

RESULTS

In the group of fetuses with normal karyotype and normal autopsy findings, 4 of 5 fetuses were positive for maternal microchimerism. In the group in which the fetuses were diagnosed with trisomy 21 and/or malformations, we found cells of maternal origin in 3 of 6 fetuses.

CONCLUSION

The results from this study indicate that maternal microchimerism is a common phenomenon in the second-trimester fetuses. Maternal cells of lymphoid and myeloid lineages and hematopoietic progenitors are widely distributed in the second-trimester fetuses.

Chronic villitis of unknown etiology

The diagnosis of chronic villitis of unknown etiology (CVUE), characterized by focal areas of inflammation with mononuclear cells and areas of fibrinoid necrosis in chorionic villi, can only be set-up after exclusion of a latent maternal-fetal transmission of infectious agents by sophisticated techniques such as polymerase chain reaction. Significant associations of CVUE with maternal body mass index, multigravidity and ethnicity were reported. While a fetal origin of the inflammatory cells has been evoked, there are many more arguments drawn from histopathology and immunohistology for a maternal immune response against the foreign fetal allograft. CVUE is detected in 7-33% of placentas, mainly after idiopathic intrauterine growth retardation, unexplained prematurity, preeclampsia, perinatal asphyxia and intrauterine fetal death. CVUE is also more frequent in pregnancies affected by autoimmune or alloimmune diseases. Considering the high rate of recurrences after an index case of CVUE, we would suggest to associate aspirine and corticosteroids in further pregnancies, a regimen that was successful in our experience but must be confirmed by other studies. The same is true for the alleviated inflammatory immunologic response recently obtained by a weekly use of maternal intravenous immunoglobulins.

Villitis of unknown etiology: noninfectious chronic villitis in the placenta

Villitis of unknown etiology (VUE) is an important pattern of placental injury occurring predominantly in term placentas. Although overlapping with infectious villitis, its clinical and histologic characteristics are distinct. It is a common lesion, affecting 5% to 15% of all placentas. When low-grade lesions affecting less than 10 villi per focus are excluded, VUE is an important cause of intrauterine growth restriction and recurrent reproductive loss. Involvement of large fetal vessels in the placenta (obliterative fetal vasculopathy) in cases of VUE is a strong risk factor for neonatal encephalopathy and cerebral palsy. Although the etiology of the eliciting antigen is unknown, many other characteristics of the immune response have been clarified. VUE is caused by maternal T lymphocytes, predominantly CD8-positive, that inappropriately gain access to the villous stroma. Fetal antigen-presenting cells (Hofbauer cells) expand and are induced to express class II major histocompatibility complex molecules. Maternal monocyte-macrophages in the perivillous space likely amplify the immune response. Although much speculation exists that VUE represents a host-versus-graft reaction analogous to transplant rejection, other eliciting antigens have not been excluded. Irrespective of target antigen or antigens, the pathophysiologic implications of having activated maternal lymphocytes within vascularized fetal tissues are not trivial.

Pronostic périnatal des grossesses compliquées d’intervillites chroniques placentaires

SUBJECT. Massive Chronic Intervillositis is an infrequent inflammation lesion of the placenta, characterized by lymphohistiocytic intervillous infiltration, associated with fibrinoid deposition. The purpose of this study was to evaluate the perinatal outcome of pregnancies complicated by such lesions.

MATERIAL AND METHODS

We conducted a descriptive retrospective multicentric analysis of a series of pregnancies for which placenta or products of abortion were analyzed between January 1995 and September 2005, at the University Hospital of Bordeaux. After re-examining the histology slides, we performed a semi-quantitative graduation of the cell infiltration and fibrinoid deposition.

RESULTS

Twenty-five women were included (one twin-pregnancy and two histologic recurrences). We found three spontaneous abortions before 22 weeks, four intrauterine fetal deaths and three neonatals deaths. Seven of eight elective inductions pregnancies, were performed for intrauterine growth restriction less than 2.5 percentile. The rate of pregnancy loss was 55% and the perinatal mortality was 29%. 77% of fetuses are small for gestational age. Three mothers were pre-eclamptic. 21% of the fetuses had a congenital malformation. Only 32% of the fetuses were alive one week after birth. Histologically, 25% were associated with lesions of Villitis of Unknown Etiology. 77% of the cell infiltration was grade 3 and seemed to be correlated with severe growth restriction. We describe 3 cases of antenatal diagnosis of Chronic Intervillositis, realised after immunofixation on chorionic villous sampling.

CONCLUSION

Massive Chronic Intervillositis is a recurrent lesion with a poor prognosis complicated by spontaneous abortion, intrauterine growth restriction and perinatal fetal death. Currently, there is no treatment. Chorionic villous sampling in severe growth restriction might be useful in order to obtain at the same time the fetal karyotype and an histological probe of the placenta.

Inflammatory responses in the placenta and umbilical cord

Histopathological examination of the placenta is the gold standard for evaluating antenatal inflammatory processes that might influence fetal development. Histological chorioamnionitis develops through a well-characterised stereotyped progression of maternal and fetal cellular stages that vary from patient to patient and are amenable to quantification. Increases in the intensity of these responses and their gradual transformation into a chronic phase are important variables that can adversely affect fetal physiology. Under recognised placental inflammatory lesions affecting the decidua, placental villi and fetal vessels are also potentially informative factors that should be taken into account in the studies of adverse pregnancy outcomes. This review summarises the relationships between aetiology, intensity, duration, characteristics and site of histological placental inflammation and suggests how these data may help to better understand the antenatal environment.

LPS induces secretion of chemokines by human syncytiotrophoblast cells in a MAPK-dependent manner

The maintenance of pregnancy depends on the nature and magnitude of the immune responses induced within the placenta. An elevated proinflammatory response in the intervillous space (IVS) is associated with adverse pregnancy outcomes. It is becoming more apparent that the syncytiotrophoblast (ST) cells, which are in direct contact with maternal blood, are capable of contributing to the local immune environment in response to maternal hematogenous infections or exposure to proinflammatory stimuli. In this study, we investigated mechanisms by which ST might recruit maternal immune effectors to the IVS in response to bacterial infections. To assess this, primary trophoblasts were isolated from fresh term placentas and stimulated with lipopolysaccharide (LPS). LPS induced time-dependent expression and secretion of IL-8, macrophage inflammatory protein (MIP)-1alpha and MIP-1beta from ST cells and an upregulation of ICAM-1. The stimulation also resulted in the activation of ERK1/2 mitogen-activated protein kinase (MAPK) but not p38 or JNK1/2. Inhibition of ERK1/2 lead to a reduction in the secretion of MIP-1beta and IL-8 suggesting that their production is at least partly dependent on ERK1/2 activation. Results from this study reveal a potential mechanism by which differentiated ST cells modulate the local maternal immune responses during an intrauterine bacterial infection. Such responses could contribute to the clearance of the infection but also pathological features observed in intrauterine infections of the placenta.

The pathogenesis of villitis of unknown etiology: analysis with a new conjoint immunohistochemistry-in situ hybridization procedure to identify specific maternal and fetal cells

The conjoint immunohistochemistry-in situ hybridization (IHC-ISH) procedure permits, under routine light microscopic conditions, simultaneous documentation of either a male or female karyotype plus the immunological phenotype of individual cells within paraffin-embedded tissues. We have used this technique to characterize the inflammatory response in placental villitis of unknown etiology (VUE). A male placenta with severe VUE and appropriate control placentas were analyzed. In situ hybridization probes concurrently label both the X and Y chromosomes. On the same tissue section, individual cells were characterized with antibodies to CD3, CD68, or CD20. The amnion and syncytiotrophoblast were delineated by cytokeratin antibody (AE1/AE3). A complete karyotyping was performed on amnion cells to validate the procedure. Amnion cell karyotyping confirmed the accuracy of the procedure. The VUE case revealed that 88.8% of intravillous CD3+ lymphocytes were female (maternal), while 11.2% were male (fetal). Intervillous CD3+ lymphocytes and CD68+ macrophages were universally female. Intravillous CD68+ cells were only 10.5% female. Perivillous CD68+ cells were 94.6% female. Remarkably, multinucleated giant cells were exclusively maternal. This study confirms that lymphocytes in VUE are predominately but not exclusively maternal T cells. Our findings indicate that invasion of fetal villi by maternal T cells is associated with focal destruction of the syncytiotrophoblast, clarifying how placental immuno-defensive mechanisms may be contravened.

ICAM-1 is Overexpressed by Villous Trophoblasts in Placentitis

Although an in vitro study has hypothesized that expression of ICAM-1 by villous trophoblasts could be important for the influx of maternal immune cells in villitis, it remains to be shown whether the same phenomenon occurs in human villitis. To investigate the expression of ICAM-1 by villous trophoblasts, its relationship with rupture of the trophoblastic barrier and influx of immune cells into the villi, we analysed 18 paraffin-embedded placentas with placentitis (5 by Toxoplasma gondii, 3 by Trypanosoma cruzi, 2 by Paracoccidioides brasiliensis and 8 of unknown aetiology - VUE) and 8 control placentas for detection of ICAM-1 by immunohistochemistry. All cases but one of placentitis showed trophoblast overexpression of ICAM-1 in the inflamed villi, located almost exclusively next to the areas of trophoblastic rupture. The villitis cases (caused by T. cruzi, T. gondii and VUE) presented leukocyte adherence in the areas of trophoblastic rupture. When the inflammatory reaction was situated in the intervillous space (placentitis by P. brasiliensis), in spite of the trophoblastic rupture and ICAM-1 overexpression there was no leukocyte influx into villi. None of the control placentas showed ICAM-1 expression by the trophoblast. We concluded that overexpression of ICAM-1 by villous trophoblasts occurs during placentitis characterized by accumulation of leukocytes in the villous or intervillous space and probably plays an important role in the rupture of the trophoblastic barrier. The influx of immune cells into the villi appears to be mediated by ICAM-1 but the location of the antigen within villous stroma is certainly a crucial factor for its occurrence.

Syncytiotrophoblast intercellular adhesion molecule-1 expression in placental villitis of unknown cause

OBJECTIVE

The purpose of this study was to determine syncytiotrophoblast intercellular adhesion molecule-1 expression in villitis and in normal chorionic villi from term (37-42 weeks of gestation) placentas with or without villitis.

STUDY DESIGN

A cross-sectional study was conducted to determine syncytiotrophoblast intercellular adhesion molecule-1 expression in villitis (n = 16) and in normal villi from placentas with or without villitis (n = 16). Villitis was diagnosed with antibodies to human leukocyte antigen-DR and CD3 and hematoxylin and eosin staining of serial sections; intercellular adhesion molecule-1 reactivity in syncytiotrophoblast was confirmed with antibodies to intercellular adhesion molecule-1 and cytokeratin.

RESULTS

Villitis lesions had higher syncytiotrophoblast intercellular adhesion molecule-1 expression than normal chorionic villi from placentas with (19.9% vs 3.5% villi; P < .001) or without (19.9% vs 0.31% villi; P < .001) villitis. Normal villi from placentas with villitis had higher syncytiotrophoblast intercellular adhesion molecule-1 than villi from placentas without villitis (3.5% vs 0.31% villi; P < .001).

CONCLUSION

Placentas with villitis have significantly more syncytiotrophoblast intercellular adhesion molecule-1 expression than placentas without villitis. The finding that normal villi from placentas with villitis have more syncytiotrophoblast intercellular adhesion molecule-1 than normal villi from placentas without villitis suggests that syncytiotrophoblast intercellular adhesion molecule-1 could be the first step in villitis development.

Maternal origin of inflammatory leukocytes in preterm fetal membranes, shown by fluorescence in situ hybridisation

The aim of this study was to determine the maternal or fetal origin of inflammatory leukocytes in fetal membranes from cases of chorioamnionitis. Fetal membranes were collected from male preterm infants and chorioamnionitis was diagnosed histologically. Fluorescence in situ hybridisation for X and Y chromosomes was used to determine the gender of infiltrating leukocytes in the chorion and amnion. Leukocytes, trophoblast and mesenchymal cells were identified using immunohistochemistry for CD45, cytokeratin-7 and vimentin, respectively. Leukocytes present in the chorion and amnion were labelled XX, indicating maternal origin, and these cells were immunoreactive for the leukocyte marker CD45 but not for vimentin or cytokeratin-7. All other cells in the chorion and amnion were labelled XY and of fetal origin. The results indicated that maternal leukocytes invade the amnion and chorion in chorioamnionitis and we suggest that this is part of the maternal inflammatory response to intrauterine infection.

Characterization of inflammation in syphilitic villitis and in villitis of unknown etiology

Chronic villitis is a histologic diagnosis that may be either associated with infection, or termed villitis of undetermined etiology (VUE). The lymphocytic infiltrate in VUE has been reported to consist of maternal lymphocytes, but the origin of the lymphocytic infiltrate in infectious villitis has not been identified. The purpose of our study was to compare the maternal vs. fetal origin of the infiltrating lymphocytes in VUE and syphilitic villitis, and to expand the immunophenotypic data provided by previous studies. Paraffin-embedded placentas from four males with VUE and two males with syphilitic villitis were subjected to fluorescence in situ hybridization (FISH) for the X and Y chromosomes. Serial sections were stained with antibodies to CD3, CD4, CD8, CD68, HLA-DR, and CD20. Quantitation of the relative number of cells marking with each antibody was done for four villi in each slide. CD3 lymphocytes predominated in both VUE and syphilitic villitis, with slightly more CD8 cells compared to CD4 cells. CD68 and HLA-DR positive cells were as frequent as CD3 cells, and B-lymphocytes were rare. Maternal cells were the predominant intravillous population in both VUE and syphilitic villitis, and neutrophils in syphilitic villitis were also maternal. These data indicate that the immune response in both syphilitic villitis and VUE is similar, raising the possibility of a similar immunopathogenetic pathway.

Fetal vascular obstructive lesions: nosology and reproducibility of placental reaction patterns

The purpose of this study was to assemble and test the reliability of a complete set of the placental reaction patterns seen with chronic fetal vascular obstruction in the hope that this might provide a standardized diagnostic framework useful for practicing pathologists. Study cases (14 with fetal vascular obstructive lesions, 6 controls) were reviewed blindly by seven pathologists after agreement on a standard set of diagnostic criteria. Majority vote served as the gold standard and 80% of the 180 diagnoses rendered (9 diagnoses each for 20 cases) were agreed upon by at least six of the seven scores. The sensitivity of individual diagnosis relative to the group consensus averaged 83% (range, 69-100%) and specificity averaged 91% (range, 86-100%). Reproducibility was measured by unweighted kappa-values and interpreted as follows: < 0.2, poor; 0.2-0.6, fair/moderate; > 0.6, substantial. Kappa values for lesions of distal villi were generally superior to those for lesions involving large fetal vessels: avascular villi (0.49), villous stromal-vascular karyorrhexis (0.58), and villitis of unknown etiology (VUE) with stem villitis and avascular villi (0.65) versus large vessel thrombi (any vessel, 0.34; chorionic plate vessel, 0.40) and intimal fibrin cushions (recent, 0.47; remote, 0.78). Reproducibility for a global impression of any villous change consistent with chronic fetal vascular obstruction was substantial (0.63), while that for a more severe subgroup was moderate (0.44). Three points are worthy of emphasis. Our system separately recognizes, but later combines, uniformly avascular villi and villous stromal-vascular karyorrhexis as manifestations of the same underlying process. We propose that this combined group of villous lesions be dichotomized with the terms fetal thrombotic vasculopathy or extensive avascular villi (and/or villous stromal-vascular karyorrhexis) being reserved for the group with 15 or more affected terminal villi per section. Scattered foci of avascular villi (and/or villous stromal-vascular karyorrhexis) could be used to describe less severe cases. Finally, we distinguish VUE with stem villitis and avascular villi (obliterative fetal vasculopathy) as a distinct process with substantial perinatal morbidity.

Placental Trophoblast from Successful Human Pregnancies Expresses the Tolerance Signaling Molecule, CD200 (OX-2)*

PROBLEM

Th1 cytokine-dependent abortions in the CBA x DBA/2 mouse model have been linked to down-regulation of expression of the CD200 (OX-2) 'tolerance' signal on trophoblast and in decidua prior to onset of the abortion process. Abortions could be prevented by administration of a soluble CD200. Is CD200 expressed on trophoblast in successful human pregnancy?

METHOD OF STUDY

As one cannot easily obtain trophoblasts in large quantities from successful human pregnancies in the first trimester prior to the onset of the abortion process at 6 weeks gestation, we examined as a first step, trophoblast isolated from term placentae (i.e. successful pregnancies). CD9- trophoblasts were isolated by affinity column and stained for intracellular cytokeratin, and surface CD200 using PE-anti-human CD200 monoclonal antibody. mRNA was extracted from CD9+ and CD9- cells and tested by reverse transcription-polymerase chain reaction for CD200 mRNA. CD9- placental cells were separated by velocity sedimentation and test for CD200-dependent suppression of an allogeneic human mixed lymphocyte culture where cytotoxic T cell (CTL) generation, and Thl --> Th2 cytokine production shift were measured.

RESULTS

CD9- but not CD9+ placental cell populations contained cells with mRNA for CD200, both a normal length transcript and a truncated transcript. Flow cytometry showed a CD200+ cytokeratin+ moderate-to-large-sized cell population compatible with trophoblasts and a smaller subset of cytokeratin- cells that expressed CD200 at normal and at high levels. The moderate-sized population proved most potent at inhibiting CTL generation and caused a Th1 --> Th2 cytokine shift. These effects were blocked by monoclonal anti-CD200.

CONCLUSIONS

A subpopulation of cytokeratin+ placental trophoblasts express bioactive CD200 able to alter maternal immune responses in a favorable (Th2 > Th1) direction. Two populations of CD200+ small- and medium-small-sized cytokeratin- placental cells remain to be identified. Studies of karyotyped first trimester elective termination and spontaneous miscarriage tissues are needed.

Preeclampsia: a multifactorial disease resulting from the interaction of the feto-maternal HLA genotype and HCMV infection

PROBLEM

To clarify the possible influence of human leukocyte antigen (HLA) mother-child genotypes and human cytomegalo virus (HCMV) presence on the development of preeclampsia.

METHODS OF STUDY

One hundred and four DNA samples from mothers with preeclampsia, mothers with a normal history of pregnancies and their neonates were tested by polymerase chain reaction-sequence specific oligonucleotide probes (PCR-SSOP) for HLA-A, -G, -DRB1, -DQA1, -DQB1 alleles. The HCMV sequences were analyzed using a PCR-SSOP method and the four primers described by Chou (Chou S: J Clin Microb 1992; 30:2307-2310).

RESULTS

Compared with their respective controls, a significant increase of DRB1*07 among neonates (P(c) = 0.05) and of DRB1*07 and/or DRB1*06 among pre-eclamptic mothers (P(c) = 0.003, RR = 8,5) was found. When HCMV sequences were detected in pre-eclamptic mothers carrying those phenotypes the RR increased up to 40. Furthermore, the fetal inheritance of a maternal HLA-G*0104 increased the risk for the appearance of the disease (RR = 30; P = 0.025).

CONCLUSION

The results suggest that the presence of alleles HLA-G*0104, DRB1*07/06, HCMV sequences and the fetal inheritance of maternal G*0104, should be considered as conditioning factors for the development of preeclampsia.

Transcriptional control of MHC genes in fetal trophoblast cells

Tight control of MHC expression is essential for the outcome of a successful pregnancy. The lack of MHC class II and class I mediated antigen presentation by fetal trophoblast cells is an important mechanism to evade maternal immune recognition. Interestingly, the deficient expression of MHC class II molecules (HLA-DR, -DQ and -DP) and of the classical MHC class I molecules HLA-A and HLA-B is also noted after IFN-gamma treatment in trophoblast-derived cell lines. Our studies show that in trophoblast cell lines the IFN-gamma induced transactivation of HLA-A and HLA-B promoters is repressed. Furthermore, it was found that trophoblast cells lacked IFN-gamma mediated induction of the class II transactivator (CIITA). This lack of CIITA expression in trophoblast cells is due to CIITA promoter hypermethylation. In addition to lack of CIITA expression, trophoblast cells also displayed a repressed expression of RFX5. Together, these observations reveal a silencing of multiple activation pathways that are critical to the transcriptional control of MHC class II and class I antigen presentation functions by trophoblast cells.

Chronic chorioamnionitis: a clinicopathologic and immunohistochemical study

Lymphocytic inflammation of the fetal membranes is unusual and has been termed chronic chorioamnionitis. We report the clinicopathologic and immunohistochemical findings in 31 placentas with chronic chorioamnionitis. The most common histopathologic association was chronic villitis of unknown etiology, which was identified in 22 (71%) of the 31 placentas. The severity of the chronic villitis did not correlate with the severity of chronic chorioamnionitis. Additional placental findings included chronic intervillositis in two, fetal vessel thrombosis in five, hemorrhagic endovasculitis in four, decidual chronic vasculitis in three, and atherosis in one. Maternal history included pregnancy-induced hypertension in six and diabetes in one. Twelve infants were preterm, and five had intrauterine growth retardation. There was no neonatal sepsis or death. Immunohistochemical staining in areas of chronic chorioamnionitis showed CD3+ and CD8+ cells present in moderate numbers, and CD4+ cells in smaller numbers. CD20+ and CD56+ cells were rare or absent. Chronic chorioamnionitis is commonly associated with chronic villitis of unknown etiology, shares similar clinical associations, and may have a related cause, possibly immunologic.