HLA G: at the interface

HLA-G - evolvement from a trophoblast specific marker to a checkpoint molecule in cancer, a narrative review about the specific role in breast- and gynecological cancer

Human leukocyte antigen G (HLA-G) is known as a non-classical molecule of the major histocompatibility complex class Ib and downregulates the mother's immune response against the fetus during pregnancy, thereby generating immune tolerance. Due to the latter effect, HLA-G is also referred to as an immune checkpoint molecule. Originally identified on extravillous trophoblasts, HLA-G is already known to induce immune tolerance at various stages of the immune response, for example through cell differentiation and proliferation, cytolysis and cytokine secretion. Because of these functions, HLA-G is involved in various processes of cancer progression, but a comprehensive review of the role of HLA-G in gynecologic cancers is lacking. Therefore, this review focuses on the existing knowledge of HLA-G in ovarian cancer, endometrial cancer, cervical cancer and breast cancer. HLA-G is predominantly expressed in cancer tissues adjacent to the extravillous trophoblast. Therefore, modulating its expression in the cancer target tissues of cancer patients could be a potential therapeutic approach to treat these diseases.

New insights on folliculogenesis and follicular placentation in marine viviparous fish black rockfish (Sebastes schlegelii)

In viviparous fish, a considerable degree of variation in placental structures have been described. However, no distinct structures are reported in Scorpaenidae. In this study, we demonstrate a new type of folliculogenesis and follicular placentation in Sebastes schlegelii. Before copulation, the germinal epithelium gradually surrounds the oocytes and develops into individually follicles with a stalk-like structure hanging on the ovigerous lamella, which ensures each follicle have access to spermatozoa after copulation. From V to early gestation stage, the cyp17-I highly expressesaccompanied by cyp19a1a signals disappearance, and 11-ketotestosterone level keeps rising and peaks at blastula stage, while 17β-estradiol declines to the bottom. Meanwhile, the theca cells rapidly proliferate and invade outwards forming a highly hypertrophied and folded microvillous placenta. This unbalance of hormone might be an important factor driving the theca cells proliferation and invasion. Additionally, some conserved genes related to mammalian placentation are significantly high expression in follicular placenta suggesting the high convergence in vertebrate placenta evolution.

PLAC8, a new marker for human interstitial extravillous trophoblast cells, promotes their invasion and migration

Proper differentiation of trophoblast cells in the human placenta is a prerequisite for a successful pregnancy, and dysregulation of this process may lead to malignant pregnancy outcomes, such as preeclampsia. Finding specific markers for different types of trophoblast cells is essential for understanding trophoblast differentiation. Here, we report that placenta-specific protein 8 (PLAC8) is specifically expressed in the interstitial extravillous trophoblast cells (iEVTs) on the fetomaternal interface. Using model systems, including placental villi-decidua co-culture, iEVTs induction by using primary trophoblast cells or explants, etc., we found that PLAC8 promotes invasion and migration of iEVTs. Mechanistically, time-lapse imaging, GTPase activity assay, co-immunoprecipitation and RNA-seq studies show that PLAC8 increases the Cdc42 and Rac1 activities, and further induces the formation of filopodia at the leading edge of the migratory trophoblast cells. More interestingly, PLAC8 is significantly upregulated under hypoxia and expression of PLAC8 is higher in iEVTs from preeclamptic placentas when compared with those from the normal control placentas. Together, PLAC8 is a new marker for iEVTs and plays an important role in promoting trophoblast invasion and migration.

Highlighted Article: Oxygen tension-dependent expression of placenta-specific protein 8 positively regulates trophoblast invasion and migration partially through upregulating the activation of Rac1 and Cdc42.

Correlation of serum sHLA-G levels with cyst stage in patients with cystic echinococcosis: is it an immune evasion strategy?

Patients with cystic echinococcosis (CE) can harbour cysts for years or even decades, apparently without effect of the immune system on the metacestode. Although several immune evasion mechanisms by echinococcal cysts have been described, it is unclear whether the human leucocyte antigen (HLA) system plays a role in the susceptibility or resistance to CE in humans. HLA-G molecules are known to exert a suppressive action on dendritic cells maturation and on natural killer (NK) cells functions, therefore hampering T-cell responses and NK cytolysis. HLA-G plays an important role in immune tolerance, is involved in foetus and in allotransplant tolerance, and may be involved in tumoral and viral immune evasion. In this study, we assessed the presence and levels of soluble HLA-G (sHLA-G) in patients with CE using a commercial ELISA kit to determine whether host's HLA-G may have a role in the course of human CE.

Soluble monomers, dimers and HLA-G-expressing extracellular vesicles: the three dimensions of structural complexity to use HLA-G as a clinical biomarker

The HLA-G molecule belongs to the family of nonclassical human leukocyte antigen (HLA) class I. At variance to classical HLA class I, HLA-G displays (i) a low number of nucleotide variations within the coding region, (ii) a high structural diversity, (iii) a restricted peptide repertoire, (iv) a limited tissue distribution and (v) strong immune-suppressive properties. The physiological HLA-G surface expression is restricted to the maternal-fetal interface and to immune-privileged adult tissues. Soluble forms of HLA-G (sHLA-G) are detectable in various body fluids. Cellular activation and pathological processes are associated with an aberrant or a neo-expression of HLA-G/sHLA-G. Functionally, HLA-G and its secreted forms are considered to be key players in the induction of short- and long-term tolerance. Thus, its unique expression profile and tolerance-inducing functions render HLA-G/sHLA-G an attractive biomarker to monitor the systemic health/disease status and disease activity/progression for clinical approaches in disease management and treatments. Here, we place emphasis on (i) the current status of the tolerance-inducing functions by HLA-G/sHLA-G, (ii) the current complexity to implement this molecule as a meaningful clinical biomarker regarding the three dimensions of structural diversity (monomers, dimers and HLA-G-expressing extracellular vesicles) with its functional implications, and (iii) novel and future approaches to detect and quantify sHLA-G structures and functions.

Cytokine knockouts in reproduction: the use of gene ablation to dissect roles of cytokines in reproductive biology

Cytokines play many diverse and important roles in reproductive biology, and dissecting the complex interactions between these proteins and the different reproductive organs is a difficult task. One approach is to use gene ablation, or 'knockout', to analyse the effect of deletion of a single cytokine on mouse reproductive function. This review summarizes the essential roles of cytokines in reproductive biology that have been revealed by gene knockout studies, including development and regulation of the hypothalamo-pituitary-gondal axis, ovarian folliculogenesis, implantation and immune system modulation during pregnancy. However, successful utilization of this approach must consider the caveats associated with gene ablation studies, e.g. embryonic lethality, systemic effects of cytokine ablation on local reproductive processes and the limited exposure to pathogens in mice housed in laboratory conditions. New sophisticated technology that temporally or spatially regulates gene ablation can overcome some of these limitations. Discoveries on the roles of cytokines in reproductive function uncovered by gene ablation studies can now be applied to improve in vitro fertilization for infertile couples and in the development of contraceptive therapies.

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

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

Soluble HLA-G1 at the materno-foetal interface--a review

HLA-G differs from the other MHC class I genes. This includes a unique promoter region, a restricted constitutive tissular distribution, the translation of different membrane-bound and soluble isoforms, a shortened cytoplasmic tail and a minimal polymorphim. Soluble HLA-G1 is an immunosuppressive molecule inducing apoptosis of activated CD8(+) T cells and down-modulating CD4(+) T cell proliferation. Soluble HLA-G1 may also contribute to the control of implantation.

Interferon-tau stimulates granulocyte-macrophage colony-stimulating factor gene expression in bovine lymphocytes and endometrial stromal cells

Interferon-tau (IFN-tau), the antiluteolytic signal produced by the trophoblast prior to implantation in ruminants, exhibits immunomodulatory properties. It stimulates the production of prostaglandin (PG) E(2) in bovine endometrial cells via the induction of cyclooxygenase-2 (COX-2). We previously demonstrated that preconditioning lymphocytes with PGE(2) increases the expression of granulocyte-macrophage colony-stimulating factor (GM-CSF), a cytokine that promotes conceptus growth and survival. Our goal in the present study was to evaluate the impact of IFN-tau on the expression of GM-CSF in bovine peripheral blood lymphocytes (PBL) and endometrial epithelial and stromal cells. Changes in PGE(2) production and mRNA levels of COX-2 were also studied in PBL in response to IFN-tau. Gene expression was estimated by semiquantitative reverse transcription-polymerase chain reaction and Northern analysis. The expression of GM-CSF in PBL was stimulated by treatment with IFN-tau. Furthermore, GM-CSF mRNA levels were increased after preconditioning PBL for 3 days with IFN-tau, followed by a 12-h restimulation without IFN-tau. Inhibition rather than stimulation of PGE(2) production and COX-2 expression in PBL during treatment with IFN-tau suggests a direct effect on GM-CSF expression. Moreover, GM-CSF expression was stimulated in uterine stromal cells in response to IFN-tau. This study provides the first evidence for stimulation of GM-CSF expression by IFN-tau in both leukocytes and endometrial stromal cells. In view of the role of GM-CSF on fetal growth and survival, these results support the hypothesis that the conceptus mediates accommodation mechanisms in the uterus during early pregnancy by modulating the expression of beneficial cytokines at the fetomaternal interface.

Human lymphocytes obtained from decidual tissue express killer activatory receptors as well as killer inhibitory receptors: analysis using a single strand conformation polymorphism method

PROBLEM

The objective was to clarify whether lymphocytes in decidual tissue express only killer inhibitory receptors (KIRs) or both KIRs and killer activatory receptors (KARs).

METHOD OF STUDY

A polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) analysis method, using cDNA as a template, was applied to detect as many natural killer receptors (NKRs) expressed on natural killer (NK) cells as possible and to distinguish between KIRs and KARs. Using this method, we analyzed NKRs on lymphocytes in decidual tissue and maternal peripheral blood mononuclear cells (PBMCs) (n = 10) from the same individuals.

RESULTS

More than 20 SSCP bands were detected for NKRs on both the lymphocytes in decidual tissue and the maternal PBMCs. The SSCP band patterns were different for each individual. KARs mRNA was detected in lymphocytes in decidual tissue according to the SSCP analysis results.

CONCLUSION

Lymphocytes in decidual tissue express not only KIRs but also KARs; this finding suggests their roles in placentation and the maintenance of pregnancy.

Effect of rat placental culture supernatants on cellular and humoral immune responses

PROBLEM

To evaluate the effect of rat placental culture supernatants (PS) on spontaneous, mitogen- and alloantigen-induced lymphoproliferation, antibody synthesis regulation, and symmetric/asymmetric antibody ratio.

METHOD OF STUDY

The effect of PS was determined: (a) on cell proliferation of murine hybridoma cells and on spontaneous or ConA-induced proliferation of murine and rat splenocytes by thymidine incorporation; (b) on rat or mouse cell-mediated cytotoxicity (CMC) by 51Cr release; and (c) on antibody synthesis by enzyme-linked immunoadsorbent assay (ELISA).

RESULTS

With 20% PS, hybridoma cell inhibition was 37% and that of splenocytes up to 60%, whereas it was 75 and 43%, respectively, in the presence of ConA. Despite marked cell death, hybridoma proliferation index increased significantly. There was a drop in total antidinitrophenylated (DNP) immunoglobulin G1 (IgG1) antibody production and an increase in asymmetric antibody percentage, correlating with placental supernatant concentration.

CONCLUSIONS

Rat placental culture supernatants inhibit cell proliferation in all cases, diminish total antibody production, and increase the percentage of asymmetric antibodies by the hybridoma, and they increase antibody production by rat splenocytes.

Human cytotrophoblastic cells absorb the NK blocking activity of monoclonal BA11

PROBLEM

R80K is a polymorphic alloantigeneic protein present on human placental trophoblast and on paternal B lymphocytes and monocytes. This protein, unlike the former candidate TLX antigen, stimulates a protective maternal immune response in vivo. A murine monoclonal BA11 antibody, directed against R80K, prevents abortion in three murine pregnancy-failure models and inhibits human and murine NK activity. We attempted to define the target of BA11 in the human NK assay system.

METHODS

A CELISA method was used to detect R80K antigen on the surface of different cells using the BA11 antibody. The effect, on human peripheral blood NK activity against K562, by BA11 before and after absorption by different cells, including the K562 target, was determined.

RESULTS

R80K was detected on term placental syncytio and cytotrophoblast and on BeWo cells, by CELISA. BA11 suppressed NK lysis of K562 cell sin a dose-dependent manner. Absorption of the BA11 by BeWo and by cytotrophoblastic cells significantly decreased the NK-inhibitory activity. There was minimal absorption by K562 and BA11-pretreateed K562 cells remained susceptible to NK lysis. By contrast, BA11-pretreated peripheral blood cells lost all NK activity.

CONCLUSIONS

The inhibition of NK killing of K562 cells by BA11 is more complex than simple masking of a trophoblast cell-associated molecule in K562 necessary for recognition in NK cells.

Immunoactive products of placenta. V. Immunoregulatory properties of a low molecular weight compound obtained from human placental cultures

PROBLEM

We have previously shown that supernatants from short-term cultures of human placental explants (HPS) are immunosuppressive in vitro as well as in vivo. They contain a low M.W. factor endowed with immunoregulatories activities (Filtrate of such with a 5 kDa cut off). In this paper, we wanted to assess whether this low M.W. material accounts for most, if not all, of the immunosuppressive properties of crude HPS and begin to investigate its mode of action.

RESULTS

The filtrate is active across species barrier and inhibits human and murine PHA driven lymphocyte proliferation, Mixed Lymphocyte Reaction, and Natural Killer activity as did crude HPS. It does not affect CTL lytic function at effector stage. Its cross species activity allowed us to study its effects in vivo. It corrects resorbtions in the CBA x DBA/2 murine spontaneous abortion model, and suppresses local and general GVH reactions in a model (A cells into irradiated A x B Fls) relevant to a clinical use e.g., bone marrow transplantation. To ensure that such survival of the recipients was due to donor cells in the latter, surviving experimental animals were analysed by FACS for repopulating lymphocytes phenotype, which was indeed of donor origin. To elucidate the mechanism(s) of action of the active HPS moiety, we first tested various malignant cell lines for the minimal incubation time required for maximal lymphocyte inhibition. In the same vein, we verified that lymphocytes stimulated by PHA and simultaneously treated with filtrate were unresponsive to a second PHA challenge. The effects of the material was reversible if cells were washed out of it early enough before otherwise entering a cycle leading ultimately to cell death in vitro. Finally, we tested several second messenger pathways, none of which were modified.

CONCLUSION

These data suggest that the filtrate contains an entity that represents the main, if not all, the immunosuppressive molecules present in HPS. In addition, they suggest that the material acts only on activated T cells and requires to be present early in the replication activation cycle. Altogether, the in vitro data strongly suggest that the material is acting by inducing clonal deletion in activated (T) cells.

Placental expression of HLA class I genes

This article presents an overview of the more recent data dealing with the constitutive, transcriptional, and translational expression of classical class Ia and nonclassical HLA-E and -G class Ib products in the different trophoblast cell subpopulations that constitute the maternofetal interface during human pregnancy. Of particular interest is the expression of alternatively spliced HLA-G transcriptional isoforms that may be translated in membrane-bound or soluble protein products. Molecular regulatory mechanisms that may control the differential expression of class Ia and class Ib molecules, according to the cell types, state of differentiation, and stages of gestation are also examined. They may operate at the levels of transcription, translation and/or transport of proteins to the cell surface. Functional significance of the absence of detectable cell surface expression of class Ia molecules in all trophoblast cell subpopulations, and of the presence of membrane-bound HLA-G products in extravillous cytotrophoblast cells is finally questioned.

HLA-G expression during preimplantation human embryo development

HLA-G is a nonclassical class I major histocompatibility complex molecule with a restricted pattern of expression that includes the placental extravillus cytotrophoblast cells in direct contact with maternal tissues. Circumstantial evidence suggests that HLA-G may play a role in protection of the semiallogeneic human fetus. We examined whether HLA-G is expressed during the critical period of preimplantation human development and whether expression of this molecule could be correlated with the cleavage rate of embryos. Using reverse transcription PCR on surplus human embryos and unfertilized oocytes from patients undergoing in vitro fertilization we detected HLA-G heavy chain mRNA in 40% of 148 of blastocysts tested. The presence of HLA-G mRNA was also detected in unfertilized oocytes and in early embryos, but not in control cumulus oophorus cells. beta 2-Microglobulin mRNA was also found in those embryos expressing HLA-G. In concordance with our mRNA data, a similar proportion of embryos stained positive for HLA-G utilizing a specific monoclonal antibody. Interestingly, expression of HLA-G mRNA was associated with an increased cleavage rate, as compared to embryos lacking HLA-G transcript. Thus, HLA-G could be a functional homologue of the mouse Qa-2 antigen, which has been implicated in differences in the rate of preimplantation embryo development. To our knowledge, the presence of HLA-G mRNA and protein in human preimplantation embryos and oocytes has not been reported previously. The correlation of HLA-G mRNA expression with cleavage rate suggests that this molecule may play an important role in human pre-embryo development.

Alloimmunization against well defined polymorphic major histocompatibility or class I MHC transfected L cells antigens can prevent poly IC induced fetal death in mice

METHOD

It is possible to induce increased fetal resorption in a number of inbred murine matings by injecting Poly (I) Poly (C12U) 3.5 days postconception, a maneuver associated with natural killer-mediated damage to the feto placental unit such as occurs in spontaneous fetal resorptions.

RESULTS

We show here that alloimmunization can block this effect. In addition, maternal immune responses induced by alloimmunization against isolated mutant class I or class II, as well as by immunization with class I MHC alloantigens (Kd) transfected L cells are sufficient to restore normal fetal viability. It is not necessary that the maternal immune response be specifically directed against paternal alloantigens fr the fetal protection to ensue, since the effect occurs in inbred matings when the mother is immunized against unrelated class I or class II alloantigens. As in previous studies conducted in the murine species, not all MHC alloimmunizations are protective. In addition, as control, immunization with a monomorphic class I MHC molecular (37), transfected L cells, sheep red blood cells or hen egg lysozyme is without effect.

CONCLUSION

These results indicate that defined MHC antigens can mediate fetal protection from induced fetal resorption, and suggest that one driving force in promoting MHC antigen polymorphism in mammals is their capacity to confer protection from NK mediated fetal demise.

Granulated metrial gland cells--not part of the natural killer cell lineage?

The relationship of rodent granulated metrial gland (GMG) cells to the natural killer (NK) cell lineage is reviewed. The antigenic profile of GMG cells provides insufficient evidence to indicate that these cells form part of the NK cell lineage. No good evidence is found that GMG cells are cytotoxic to the NK cytotoxicity target, Yac-1. In Beige mice, which have a defect in the lytic pathway of NK cells, GMG cells were found to kill labyrinthine cytotrophoblast. It is concluded that GMG cells are not a type of NK cell but a novel member of the leucocyte population.

Fetal-maternal immune interaction: blocking antibody and survival of the fetus

In the late 1940s it became clear that the homograft reaction was essentially the result of an immune response. Subsequently, Medawar commented on the apparent paradox of the survival of the mammalian fetus in the face of such a potential (cell-mediated) immune response. In an outbred population the fetal-placental unit will be antigenically different to the mother by virtue of its complement of paternal genes and additionally there may be developmental or stage-specific gene products that are immunogenic. Many mechanisms have been proposed to account for the survival of the fetus in the face of a potential immune attack and, while many of these have been investigated in considerable detail, there has been no clear-cut indication that any one plays a predominant role. Either control of immune rejection of the fetus is exercised by an as yet undiscovered mechanism or, more probably, by a combination of some or all of the mechanisms that have been proposed by many workers over the last three decades. Potential controlling processes, which will be reviewed briefly, include: systemic and local modification of maternal responsiveness; altered expression of MHC antigens on extra-embryonic tissues; the placenta as a barrier; and blocking antibody responses. We discuss some of our recent studies in which we have started to look for potential blocking antibodies in a mouse model system. Cells secreting immunoglobulins M and G, characterized in hemolytic plaque assays, have been mapped to areas close to the midgestation mouse embryo, using an immunocryohistological technique. A scaled-down version of hybridoma technology has been used as an analytical probe of the specificity and isotype of immunoglobulin secreted by cells originating either from close to the embryo/fetus or from the para-aortic lymph nodes (PALN). So far monoclonal (IgG1) antibodies with specificity for embryonic cells have been derived together with some monoclonal immunoglobulins with as yet uncharacterized antibody specificity.

The number of cells used for immunotherapy of repeated spontaneous abortion influences pregnancy outcome

One hundred and sixty-eight women were immunized on a single occasion with paternal mononuclear cells (MNC) for recurrent spontaneous abortion (RSA) and pregnancy outcomes were analysed with respect to the number of MNC given. The study was done in a prospective sequential fashion using all MNC recoverable from a unit of the spouse's blood and both patients and investigators were blinded as to the number of cells injected. Women receiving low and mid-range doses of MNC (58-305 x 10(6) and 308-567 x 10(6), respectively) had a significantly higher pregnancy success rate (57%) than those receiving the high (568-2677 x 10(6)) dose of MNC (41%). In 77 consecutive patients the diameter of the largest immediate skin flare reaction at the site of subcutaneous injection was recorded. No correlation was found between the skin flare response and the number of MNC injected. Our data suggest that a blinded trial of paternal MNC immunization comparing what appears to be optimum numbers of cells (100-550 million) to a low dose inoculum (e.g., 10 million), again noting the sizes of the skin flare reactions, might answer questions about efficacy and placebo effects of immunotherapy for RSA.

Immunological aspects of pre-eclampsia

The first pregnancy preponderance and apparent partner specificity of pre-eclampsia suggest that it might have an immune aetiology. The pathogenesis of pre-eclampsia is undefined although it is clear that it is a placental disorder. The maternal syndrome appears to be mediated by placental ischaemia secondary to spiral artery insufficiency. This leads to a hypothesis that pre-eclampsia is a two-stage disease. The first comprises processes that limit the size of the spiral arteries (poor placentation) or obstruct them (acute atherosis). Either or both may have immunological causes although there is no direct evidence. Factors limiting placentation could involve maternal immune intolerance of the fetal allograft, which in their most extreme expression could lead to immunologically mediated abortion. Thus pre-eclampsia may be part of a wider spectrum of pregnancy loss secondary to poor maternal immune accommodation of her genetically disparate fetus. The second stage involves the consequences of the ensuing placental ischaemia. The syndrome is currently tentatively ascribed to diffuse maternal endothelial dysfunction. There is less reason to invoke immunological mechanisms in the second stage although neutrophil activation could explain generalized endothelial damage. It should be clear that these conclusions are provisional and that the greatest need is for more investigation to eliminate the uncertainty which clouds our concepts.

Flow-cytometric analysis of immune cell populations in human decidua from various types of first-trimester pregnancy

We undertook an investigation in which flow cytometry was used to characterize immune cell populations in the decidua of first-trimester normal pregnancies, spontaneous abortions, and ectopic pregnancies in comparison to the nonpregnant endometrium to demonstrate how the proportions of immunocompetent cell populations at the fetomaternal interface are influenced by the presence and state of a fetoplacental allograft. No significant differences were found in the decidua of the different types of first-trimester pregnancy in the proportions of the CD45+, CD14+, CD3+, CD4+, CD8+, CD19+, CD3-/CD16+ and/or CD56+, CD3+/CD16+ and/or CD56+, CD4+/Leu-8+, CD4+/Leu-8-, CD8+/CD11b+, CD8+/CD11b-, and CD3+/HLA-DR- decidual leukocyte subsets. However, the percentage of decidual CD3+/HLA-DR+ cells, which are characteristic of activated T cells, was significantly higher in spontaneous abortions than in normal pregnancies (p less than 0.05). This suggests that the accumulation of decidual leukocytes may be regulated mainly by hormones and/or cytokines rather than by the presence and state of an intrauterine conceptus and that on/off-switching of activation of decidual T cells may be associated with successful maintenance of the implanted embryo.

Localization of major histocompatibility complex class I and II mRNA in human first-trimester chorionic villi by in situ hybridization

Maternal immune recognition of pregnancy occurs despite the nonexpression of classical major histocompatibility complex (MHC) antigenic determinants by chorionic villous trophoblast, which comprise the major surface area where maternal blood contacts fetal-derived cells. cDNA-mRNA in situ hybridization was used to probe expression of transcripts corresponding to nonpolymorphic MHC determinants in first-trimester chorionic villus samples. The HLA-B7 probe hybridization signals were localized to syncytiotrophoblast and to cells of the mesenchyme but not to villous cytotrophoblast. HLA-G mRNA was found only in syncytiotrophoblast. A DR beta clone hybridized to both villous cytotrophoblast and syncytiotrophoblast. The results suggest that expression of trophoblast class I and class II determinants early in gestation (10 wk) may be regulated by posttranscriptional events. This also suggests the potential for maternal antifetal alloimmune responses.

The role of immunization treatment in preventing recurrent abortion

Published reports of controlled studies of immunization treatment in recurrent abortion have not shown any ability of either third-party cells or the husband's cells to prevent further abortions, whereas preliminary results of ongoing studies speak in favor of a beneficial effect of third-party cells. However, the lack of significant differences so far does not prove that immunotherapy in habitual abortion is ineffective, because all of these studies include too few patients in each group to give any conclusive results. Only a mega-trial could evaluate the efficacy and side effects of leukocyte immunotherapy. Such controlled studies are needed to clarify the true benefits, risks, and limitations of immunization treatment in recurrent abortion. Factors such as appropriate inclusion criteria, the time relationship between immunization and the next pregnancy, the number of immunizations required, the cell source and cell doses need to be established. Until this additional information is available this treatment should not be considered routinely indicated. This approach should be restricted to a few centers in order to provide maximal possibilities for collection and evaluation of the data.

On the nature and function of human uterine granular lymphocytes

The 'foetal allograft' concept of the maternal-foetal relationship is currently being questioned. This is partly due to the increasing awareness of uterine large granular lymphocytes, a subset of natural killer cells found in the human endometrium at the time of placentation. Analogous cells are present in several species. The possible role of these cells in the regulation of the trophoblast-maternal interface is discussed here by Ashley King and Yung Wai Loke.