Early pregnancy decidual lymphocytes beside perforin use Fas ligand (FasL) mediated cytotoxicity

Innate Immunity in Autoimmune Thyroid Disease during Pregnancy

Autoimmune thyroid disease (AITD) is the most common organ-specific autoimmune disorder clinically presented as Hashimoto thyroiditis (HT) and Graves' disease (GD). The pathogenesis of AITD is caused by an inappropriate immune response related to genetic, non-genetic, and environmental factors. Pregnancy is one of the factors that have a great influence on the function of the thyroid gland because of the increased metabolic demand and the effects of hormones related to pregnancy. During pregnancy, an adaptation of the maternal immune system occurs, especially of the innate immune system engaged in maintaining adaptive immunity in the tolerant state, preventing the rejection of the fetus. Pregnancy-related hormonal changes (estrogen, progesterone, hCG) may modulate the activity of innate immune cells, potentially worsening the course of AITD during pregnancy. This especially applies to NK cells, which are associated with exacerbation of HD and GD. On the other hand, previous thyroid disorders can affect fertility and cause adverse outcomes of pregnancy, such as placental abruption, spontaneous abortion, and premature delivery. Additionally, it can cause fetal growth retardation and may contribute to impaired neuropsychological development of the fetus. Therefore, maintaining the thyroid equilibrium in women of reproductive age and in pregnant women is of the highest importance.

Functional prominence of natural killer cells and natural killer T cells in pregnancy and infertility: A comprehensive review and update

During pregnancy, complicated connections are formed between a mother and a fetus. In a successful pregnancy, the maternal-fetal interface is affected by dynamic changes, and the fetus is protected against the mother's immune system. Natural killer (NK) cells are one of the immune system cells in the female reproductive system that play an essential role in the physiology of pregnancy. NK cells not only exist in peripheral blood (PB) but also can exist in the decidua. Studies have suggested multiple roles for these cells, including decidualization, control of trophoblast growth and invasion, embryo acceptance and maintenance by the mother, and facilitation of placental development during pregnancy. Natural killer T (NKT) cells are another group of NK cells that play a crucial role in the maintenance of pregnancy and regulation of the immune system during pregnancy. Studies show that NK and NKT cells are not only effective in maintaining pregnancy but also can be involved in infertility-related diseases. This review focuses on NK and NKT cells biology and provides a detailed description of the functions of these cells in implantation, placentation, and immune tolerance during pregnancy and their role in pregnancy complications.

Reproductive immunology in viviparous mammals: evolutionary paradox of interactions among immune mechanisms and autologous or allogeneic gametes and semiallogeneic foetuses

Literally, reproductive immunology was born in bovine on-farm reproduction where seminal experiments intended for developing methods for embryo transfer in cattle were performed. Actually, these experiments led to two of major concepts and fundamental principles of reproductive immunology using the bovine species as a model for biomedical research, namely the concept of acquired immunological tolerance and the paradox of the semiallogeneic bovine foetus whereby such organism can develop within an immunologically competent host. Peter Medawar, a scientist who together with Frank Macfarlande Burnet shared the 1960 Nobel Prize in physiology or medicine for discovery of acquired immunological tolerance, while studying dizygotic cattle twins, thereby giving birth to reproductive immunology. Also, these findings significantly influenced development of organ transplants and showed that using farm animals as models for studying transplantation immunology had general relevance for mammalian biology and health including those of humans. However, the interest for further research of the fascinating maternal immune influences on pregnancy and perinatal outcomes and of the prevention and treatment of immunologically mediated reproductive disorders in viviparous mammals of veterinary relevance by veterinary immunologists and reproductive clinicians have been very scarce regarding the application of nonspecific immunomodulatory agents for prevention and treatment of subfertility and infertility in pigs and cattle, but still broadening knowledge in this area and hold great potential for improving such therapy in the future. The aim of the current overview is to provide up-to-date information and explaining/translating relevant immunology phenomena into veterinary practice for specialists and scientists/clinicians in reproduction of animals.

Altered Immune Response and Implantation Failure in Progesterone-Induced Blocking Factor-Deficient Mice

Earlier data suggest that progesterone-induced blocking factor (PIBF) is involved in implantation. The present study therefore aims to investigate the consequences of functional PIBF deficiency during the peri-implantation period. CD1 female mice were injected intraperitoneally with 2 μg anti-PIBF monoclonal antibody on days 1.5 and 4.5 of pregnancy. The number of implantation sites and resorption rates were recorded on day 10.5. PIBF+ decidual NK cells and B cells were detected by immunohistochemistry or immunofluorescence. Decidual and peripheral NK activity was assessed by flow cytometry. A prime PCR array was used for determining the differential expression of genes involved in lymphocyte activation and Th1 or Th2 differentiation in CD4+ and CD8+ spleen cells from pregnant anti-PIBF-treated and control mice. Anti-PIBF treatment in the peri-implantation period resulted in impaired implantation and increased resorption rates in later pregnancy. The number of PIBF+ decidual NK cells decreased, while both decidual and peripheral NK activity increased in the anti-PIBF-treated mice. B cells were absent from the resorbed deciduas of anti-PIBF-treated mice. The genes implicated in T cell activation were significantly downregulated in CD4+ and increased in CD8+ of the anti-PIBF-treated animals. The gene for IL-4 was significantly downregulated in CD4+ cells while that of IL-12A was upregulated in CD8+ cells of anti-PIBF-treated animals. These data suggest that the lack of PIBF results in an impaired T cell activation, together with Th1 differentiation and increased NK activity, resulting in implantation failure.

Progestogens and immunology

Fifty percent of fetal antigens are of paternal origin. These are recognized by the maternal immune system, thereby resulting in lymphocyte activation and the induction of progesterone receptors (PRs) in immune cells. Upon binding of progesterone to PRs on lymphocytes, a downstream mediator called progesterone-induced blocking factor (PIBF) is produced. The full-length PIBF is a 90 kDa protein; however, because of alternative splicing, several smaller isoforms are also produced. While the 90 kDa molecule plays a role in cell cycle regulation, the small isoforms are localized in the cytoplasm, and after secretion, they bind to their receptors on other cells and act in a cytokine-like manner. The communication between the embryo and the maternal immune system is established through PIBF-containing extracellular vesicles. PIBF induces an increased production of Th2 cytokines and inhibits degranulation of NK cells, and by regulating the maternal immune response, it contributes to successful implantation and maintenance of pregnancy.

The involvement of the progesterone receptor in PIBF and Gal-1 expression in the mouse endometrium

PROBLEM

The progesterone-regulated genes, PIBF and Gal-1, are key players in the feto-maternal immunological interaction. This study aims to investigate the expression of PIBF and Gal-1 in WT and progesterone receptor KO models as well as subsequent effects of PIBF on decidualization of stromal cells.

METHOD OF THE STUDY

PRAKO, PRBKO and PRKO BALB/c mice were used for assessing the role of PR isoforms in PIBF induction. PIBF- and Gal-1 mRNA expression in the uterus was tested by real-time PCR. The effect of PIBF on decidualization of endometrial stromal cells was verified by anti-desmin immunofluorescence. Immunohistochemistry was used for testing PIBF expression in the uterus. Gal-1, ERα and PR positive decidual NK cells were detected by immunofluorescence.

RESULTS

PIBF mRNA was significantly increased in progesterone-treated WT mice, but not in PRKO and PRAKO mice. PIBF protein expression was reduced in the endometria of PRKO and PRAKO, but not in PRBKO mice. During a 6-day culture, PIBF induced decidual transformation of endometrial stromal cells. PIBF expression in the mouse uterus was highest during the implantation window, while Gal-1 mRNA expression continuously increased between day 2.5 and day 11.5 of gestation. Decidual NK cells express Gal-1 and ERα, but not PR at day 7.5 murine pregnancy.

CONCLUSION

PIBF produced via engagement of PRA, is highly expressed in the endometrium during the implantation window, and plays a role in decidualization. The concerted action of PIBF and Gal-1 might contribute to the low cytotoxic activity of decidual NK cells.

The Role of Extracellular Vesicles and PIBF in Embryo-Maternal Immune-Interactions

Pregnancy represents a unique immunological situation. Though paternal antigens expressed by the conceptus are recognized by the immune system of the mother, the immune response does not harm the fetus. Progesterone and a progesterone induced protein; PIBF are important players in re-adjusting the functioning of the maternal immune system during pregnancy. PIBF expressed by peripheral pregnancy lymphocytes, and other cell types, participates in the feto-maternal communication, partly, by mediating the immunological actions of progesterone. Several splice variants of PIBF were identified with different physiological activity. The full length 90 kD PIBF protein plays a role in cell cycle regulation, while shorter splice variants are secreted and act as cytokines. Aberrant production of PIBF isoforms lead to the loss of immune-regulatory functions, resulting in and pregnancy failure. By up regulating Th2 type cytokine production and by down-regulating NK activity, PIBF contributes to the altered attitude of the maternal immune system. Normal pregnancy is characterized by a Th2-dominant cytokine balance, which is partly due to the action of the smaller PIBF isoforms. These bind to a novel form of the IL-4 receptor, and induce increased production of IL-3, IL-4, and IL-10. The communication between the conceptus and the mother is established via extracellular vesicles (EVs). Pre-implantation embryos produce EVs both in vitro, and in vivo. PIBF transported by the EVs from the embryo to maternal lymphocytes induces increased IL-10 production by the latter, this way contributing to the Th2 dominant immune responses described during pregnancy.

The Role of Progesterone in Feto-Maternal Immunological Cross Talk

This review aims to provide a brief historical overview of the feto-maternal immunological relationship, which profoundly influences the outcome of pregnancy. The initial question posed in the 1950s by Medawar [Symp Soc Exp Biol. 1953; 7: 320-338] was based on the assumption that the maternal immune system recognizes the fetus as an allograft. Indeed, based on the association between HLA-matching and spontaneous miscarriage, it became obvious that immunological recognition of pregnancy is required for a successful gestation. The restricted expression of polymorphic HLA antigens on the trophoblast, together with the presence of nonpolymorphic MHC products, excludes recognition by both T and NK cells of trophoblast-presented antigens; however, γδ T cells, which constitute the majority of decidual T cells, are likely candidates. Indeed, a high number of activated, progesterone receptor-expressing γδ T cells are present in the peripheral blood of healthy pregnant women and, in the presence of progesterone, these cells secrete an immunomodulatory protein called progesterone-induced blocking factor (PIBF). As early as in the peri-implantation period, the embryo communicates with the maternal immune system via PIBF containing extracellular vesicles. PIBF contributes to the dominance of Th2-type reactivity which characterizes normal pregnancy by inducing increased production of Th2 cytokines. The high expression of this molecule in the decidua might be one of the reasons for the low cytotoxic activity of decidual NK cells.

Dydrogesterone and the immunology of pregnancy

Progesterone is indispensable for the maintenance of pregnancy, both via its endocrine effects and its role in creating a favorable immunological environment for the fetus. This review focuses on the immunological effects of progesterone. Progestogens have been shown to have very interesting effects on cytokine production and decidual natural killer (NK) cell activity. The orally-administered progestogen, dydrogesterone, has the ability to modulate cytokine production patterns in a manner that could be conducive to successful pregnancy. The adverse effects of progesterone deficiency and the beneficial effects of progesterone supplementation in pregnancy pathologies will be discussed.

PIBF positive uterine NK cells in the mouse decidua

Though uterine NK cells (u NK cells) contain cytotoxic granules, and selectively over- express the genes of perforin and granzymes, during normal pregnancy, they are not cytotoxic. Progesterone is indispensable for the establishment and maintenance of pregnancy both in humans and in mice. Mouse uterine NK cells do not express the classical progesterone receptor, yet progesterone affects the recruitment and function of uterine NK cells, the latter partly via the Progesterone-Induced Blocking Factor (PIBF). We demonstrated PIBF positive granulated cells in the mouse decidua. The aim of this study was to characterize these cells by lectin immunohistochemistry and anti-perforin reactivity. PIBF+ granulated cells were absent from the deciduae of alymphoid mice, but appeared in the decidua of those that had been reconstituted with bone marrow from male BALB/c mice. PIBF+ granulated cells bound the DBA lectin, suggesting their NK cell nature, and also contained perforin, which co-localized with PIBF in the cytoplasmic granules. In anti-progesterone treated mice all of the PIBF+ cells were perforin positive at g. d. 12.5, in contrast to the 54% perforin positivity of PIBF+ cells in untreated mice.

CONCLUSION

The PIBF+ granulated cells in the decidua belong to the NK population, and PIPB co-localizes with perforin in the cytoplasmic granules.

Colocalization of Granulysin Protein Forms with Perforin and LAMP-1 in Decidual Lymphocytes During Early Pregnancy

PROBLEM

Granulysin (GNLY) occurs in two forms, which have molecular weights of 9 and 15 kDa. We analyzed the cytotoxic potential of decidual lymphocytes (DLs) and peripheral blood lymphocytes (PBLs) based on the forms of GNLY that colocalizes with perforin (PER) and LAMP-1 following activation.

METHODS

The forms of GNLY were detected by using confocal microscopy. We investigated the colocalization with PER and LAMP-1 in freshly isolated and activated DLs and PBLs.

RESULTS

Activation of DLs and PBLs by K-562 cells increased the colocalization of 9 kDa GNLY with PER and LAMP-1. K-562 cells transfected with HLA-C decreased 9 kDa GNLY colocalization with PER in DLs only. IL-15 in DLs decreased 9 kDa GNLY and LAMP-1 colocalization, but increased both 15 kDa GNLY and LAMP-1, and PER and LAMP-1 colocalization.

CONCLUSION

Activated DLs and PBLs show greater cytotoxic potential based on increased colocalization of 9 kDa GNLY and PER. HLA-C and IL-15 affect DLs, indicating their role in maintaining the pregnancy tolerance.

Granulysin Expression in Lymphocytes that Populate the Peripheral Blood and the Myocardium after an Acute Coronary Event

We aimed to analyse granulysin (GNLY)-mediated cytotoxicity in the peripheral blood of patients with non-ST-segment elevation myocardial infarction (NSTEMI) treated with anti-ischaemic drug therapy. Thirty-nine NSTEMI patients with a median age of 70 years and 28 age-matched healthy subjects were enrolled in this study. On day 7 after MI, the number of GNLY(+) lymphocytes in the peripheral blood increased approximately six-fold of that in the healthy subjects, measured by flow cytometry. On day 14, the number of GNLY(+) cells significantly decreased in T, NKT, and both CD56(+dim) and CD56(+bright) NK subsets. GNLY(+) CD3(+) and GNLY(+) CD56(+) cells infiltrated central zone of myocardial infarction (MI). In persons who died in the first week after MI, GNLY(+) cells were found within accumulation of apoptotic leucocytes and reached the apoptotic cardiomyocytes in border MI zones probably due to the influence of interleukin-15 in peri-necrotic cardiomyocytes, as it is was shown by immunohistology. By day 28, the percentage of GNLY(+) lymphocytes in peripheral blood returned to the levels similar to that of the healthy subjects. Anti-GNLY mAb decreased apoptosis of K562 targets using peripheral blood NK cells from days 7 and 28 after MI, while in assays using cells from days 1 and 21, both anti-GNLY and anti-perforin mAbs were required to significantly decrease apoptosis. Using NK cells from day 14, K562 apoptosis was nearly absent. In conclusion, it seems that GNLY(+) lymphocytes, probably attracted by IL-15, not only participate partially in myocardial cell apoptosis, but also hasten resolution of cardiac leucocyte infiltration in patients with NSTEMI.

Toxoplasma gondii infection of decidual CD1c(+) dendritic cells enhances cytotoxicity of decidual natural killer cells

There is crosstalk between decidual natural killer (dNK) cells and decidual dendritic cells (dDCs) that promotes tolerance of trophoblast cells carrying paternally derived antigens. In the present study, we report that infection of CD1c(+) dDCs with Toxoplasma gondii enhanced gamma interferon (IFN-γ) production by dNK cells in co-culture. The enhancement of IFN-γ production was induced by cytokine IL-12 which increased obviously in co-culture of dDCs with dNK cells following T. gondii infection, and this enhancement largely abrogated when cells were cultured in the presence of an anti-IL-12 antibody. The expression of KIR2DL4 and NKG2D on dNK cells was increased after T. gondii infection, and higher expression of NKG2D was induced by co-cultured dDCs. Neutralization of IL-12 decreased NKG2D expression on dNK cells. Furthermore, dDCs with T. gondii infection increased the cytotoxicity of co-cultured dNK cells against K562 target cells, which was mediated by activating receptor of NKG2D. Thus, T. gondii infection of dDCs enhanced dNK cell IFN-γ production and NKG2D expression, and then led to increased cytotoxicity of dNK cells. The up-regulated dNK cell cytotoxicity at the maternal-fetal interface may contribute to abnormal pregnancy outcomes caused by T. gondii infection in early pregnancy.

Human decidual NK cells: unique and tightly regulated effector functions in healthy and pathogen-infected pregnancies

NK cells present in the peripheral blood (PB) respond rapidly to pathogens or pathogen-infected cells by various means including cytotoxicity and release of cytokines and chemokines. In addition they modulate adaptive immunity via the interaction with dendritic cells. Decidual NK cells (dNK) are poorly cytotoxic in healthy pregnancy, both in humans and rodents, when compared to their PB counterparts. We will discuss recent findings that may contribute to answer the following questions: (i) Do dNK possess functional killing machinery in normal healthy pregnancy? (ii) If so, what are the regulatory mechanisms that negatively control this effector function? (iii) Have dNK from early pregnant uterus the intrinsic ability to kill pathogen-infected autologous maternal uterine cells and/or produce soluble factors that stimulate the anti-pathogen adaptive immune response? (iv) Do dNK undergo a receptor repertoire profile shift when they are in contact with pathogen-infected uterine cells? (v) Which pathogen-mediated signal(s) and molecular interactions subvert the inhibition of dNK cytolytic activity?

Granulysin expression and the interplay of granulysin and perforin at the maternal-fetal interface

Granulysin (GNLY) is a cytolytic/apoptotic molecule highly expressed in immune cells, particularly NK cells, at the maternal-fetal interface. The primary function of GNLY is to carry out lysis or apoptosis induction in target cells, tumor cells or cells infected by intracellular pathogens. To exert some of its functions GNLY needs to collaborate with perforin. The purpose of this study was to determine: (a) the expression of GNLY at the gene and protein levels at the maternal-fetal interface, (b) the relationship(s) between GNLY and perforin, and (c) GNLY secretion by NK cells stimulated by the NK-sensitive K562 cell line and its HLA-C and HLA-G transfectants. GNLY and perforin genes were found to be highly activated at the interface. GNLY mRNA was present at significantly higher levels compared with other cytolytic/apoptotic molecules. Confocal microscopy analysis showed that most first trimester pregnancy decidual lymphocytes simultaneously contained both GNLY and perforin protein in their cytoplasm, with a punctuate pattern consistent with granule localization. In contrast to peripheral blood, in unstimulated decidual lymphocytes GNLY and perforin rarely co-localized (10% of GNLY-positive cells and 20% of perforin-positive cells were positive for both proteins). Contact between decidual lymphocytes and K562 cells caused GNLY and perforin to be expressed in the same granules (approximately 50% co-localization), i.e., to attain the pattern seen in peripheral blood lymphocytes. The abundant GNLY secretion by decidual NK cells compared with peripheral blood NK cells after 2h of contact with the NK-sensitive K562 cells and K562 transfectants was striking.

Cell death mechanisms at the maternal-fetal interface: insights into the role of granulysin

During mammal pregnancy, a sensitive balance between hormones, cytokines, humoral factors, and local cellular interactions must be established. Cytotoxic cells infiltrating the decidua are heavily equipped with cytolytic molecules, in particular perforin and granulysin. Granulysin is especially abundant in NK cells which are able to spontaneously secrete high quantities of granulysin. Besides being a potent bactericidal and tumoricidal molecule, granulysin is also found to be a chemoattractant and a proinflammatory molecule. The precise role(s) of granulysin at the maternal-fetal interface has not been elucidated yet. It is possible that it behaves as a double-edged sword simultaneously acting as an immunomodulatory and a host defense molecule protecting both the mother and the fetus from a wide spectrum of pathogens, and on the other hand, in case of an NK cell activation, acting as an effector molecule causing the apoptosis of semiallograft trophoblast cells and consequently leading to various pregnancy disorders or pregnancy loss.

Perforin-mediated cytotoxicity in non-ST elevation myocardial infarction

The aim of this investigation was to examine the role of perforin (P)-mediated cytotoxicity in the dynamics of tissue damage in patients with non-ST-segment elevation myocardial infarction (NSTEMI) treated with anti-ischaemic drugs. We enrolled 48 patients with NSTEMI in this study [age, 71.5 years; 61.5/76 (median, 25th/75th percentiles)]. The percentage of total peripheral blood P(+) lymphocytes was elevated owing to the increased frequency of P(+) cells within natural killer (NK) subsets, T and NKT cells in patients on day 1 after NSTEMI when compared with healthy controls. Positive correlations were found between cardiac troponin I plasma concentrations and the frequency of P(+) cells, P(+) T cells, P(+) NK cells and their CD56(+dim) and CD56(+bright) subsets during the first week after the NSTEMI. The expression of P in NK cells was accompanied by P-mediated cytotoxicity against K-562 targets at all days examined, except day 21, when an anti-perforin monoclonal antibody did not completely abolish the killing. The percentage of P(+) T cells, P(+) NKT cells and P(+) NK subsets was the highest on the day 1 after NSTEMI and decreased in the post-infarction period. CD56(+) lymphocytes were found in damaged myocardium, suggesting their tissue recruitment. In conclusion, patients with NSTEMI have a strong and prolonged P-mediated systemic inflammatory reaction, which may sustain autoaggressive reactions towards myocardial tissue during the development of myocardial infarction.

Analysis of granulysin-mediated cytotoxicity in peripheral blood of patients with psoriatic arthritis

The objective of the present study was to investigate possible changes in granulysin (GNLY)-mediated cytotoxicity of peripheral blood lymphocytes in psoriatic arthritis (PsA) patients with respect to different phases of the disease. We prospectively enrolled 25 PsA patients in the active phase, 26 PsA patients in remission and 24 healthy controls. The simultaneous detection of intracellular GNLY and cell surface antigens (CD3 and CD56) was performed with flow cytometry. GNLY apoptotic protein was visualised by immunocytochemistry. Natural killer (NK) cell cytotoxicity was analysed with a cytotoxicity assay against human erythroleukaemia K-562 cells. The percentage of GNLY(+) cells did not differ significantly between PsA patients in the acute phase and those in remission; however, it was always higher than in healthy examinees due to the increased percentage of GNLY(+) cells within T cells, NKT cells, and both, and in the CD56(+dim) and CD56(+bright) NK subsets. The mean fluorescence intensity for GNLY was higher in all lymphocyte subpopulations in the acute phase than in remission and in healthy controls. Accordingly, GNLY-mediated NK cell cytotoxicity against K-562 cells of active phase PsA patients was significantly higher than that in patients in remission or in healthy controls. These findings demonstrated the involvement of GNLY in the worsening of PsA and suggested that GNLY mediated the development of joint lesions.

Recent advances in understanding immunology of reproductive failure

Aspects of the immunological relationship between mother and conceptus still remain a mystery, although the recent advances in molecular biology have enlightened some of the parameters that participate in fetomaternal cross-talk during implantation. The atypical expression of major histocompatibility complex (MHC), the specific role of some hormones and cytokines, as well as the temporal and spatial distributions of uterine natural killer cells, represent substantive parameters of fetomaternal immunotolerance during implantation. Although human maternal and fetal immunology is difficult to investigate, aberrant immune responses and an imbalanced cytokine network may be related to infertility, implantation failures after IVF and recurrent pregnancy losses. In this review, immunological and interacting factors involved in human reproductive failure are summarized and critically evaluated.

Progesterone-mediated immunomodulation in pregnancy: its relevance to leukocyte immunotherapy of recurrent miscarriage

Progesterone is crucial for the establishment and maintenance of pregnancy. Progesterone-regulated genes in the pregnant uterus control the development of endometrial receptivity as well as recruitment and differentiation of decidual NK cells, which in turn act on angiogenesis and trophoblast invasion. The link between progesterone and the immune system is established by lymphocyte progesterone receptors expressed in peripheral blood gammadelta T cells of pregnant women and in peripheral NK cells. Regulation of lymphocyte progesterone receptors is activation related, thus efficient recognition of fetal antigens is a requirement for the initiation of progesterone-dependent immunoregulatory mechanisms. Several immunological effects of progesterone are mediated by progesterone-induced blocking factor--the product of a progesterone-induced gene in lymphocytes. One part of unexplained recurrent miscarriages might have an immunological etiology. Immunization of the mothers with paternal or third-party leukocytes aims to correct the misregulated antifetal immune response. There are, however, serious concerns about this treatment, including the lack of information about the mode of action and possible adverse effects of the treatment, the failure to detect a significant effect of immunotherapy and the lack of a reliable generally accepted marker for patient selection. These concerns will be discussed in this review.

Progesterone in pregnancy; receptor-ligand interaction and signaling pathways

Progesterone is indispensable in creating a suitable endometrial environment for implantation, and also for the maintenance of pregnancy. Successful pregnancy depends on an appropriate maternal immune response to the fetus. Along with its endocrine effects, progesterone also acts as an "immunosteroid", by contributing to the establishment of a pregnancy protective immune milieu. Progesterone plays a role in uterine homing of NK cells and upregulates HLA-G gene expression, the ligand for NK inhibitory and activating receptors. At high concentrations, progesterone is a potent inducer of Th2-type cytokines as well as of LIF and M-CSF production by T cells. A protein called progesterone-induced blocking factor (PIBF), by inducing a Th2-dominant cytokine production mediates the immunological effects of progesterone. PIBF binds to a novel type of the IL-4 receptor and signals via the Jak/STAT pathway, to induce a number of genes, that not only affect the immune response, but might also play a role in trophoblast invasiveness.

Increased natural killer cells and decreased regulatory T cells are seen in complex atypical endometrial hyperplasia and well-differentiated carcinoma treated with progestins

Progestins are used to treat complex atypical hyperplasia and well-differentiated endometrial carcinoma in women who desire fertility preservation and those who are poor surgical candidates. Although sensitivity to progestins is thought to be associated with the presence of estrogen and progesterone receptors, it is known that receptor-negative tumors can also respond to the agent, suggesting that there is another direct antitumor action of progestin. Because tumor immune response is an additional predictor of survival in well-differentiated endometrial carcinoma, it is surprising that the role of progestins in tumor immunity has not been investigated. Regulatory T cells modulate the immune response, whereas cytotoxic T cells directly target tumor cells. In this study, we investigated the effect of progestins on regulatory T cells and cytotoxic T cells. The pre- and posttreatment endometrial samples of 15 progestin-treated patients with complex atypical hyperplasia or well-differentiated endometrial carcinoma were evaluated for therapeutic response and the presence of cytotoxic T cells and regulatory T cells. Immunohistochemical analysis was performed for FOXP3 to identify regulatory T cells and for granzyme B to identify activated cytotoxic T cells. To further characterize the cytotoxic T cell's subpopulations, we performed CD8 (cytotoxic T-cell marker) and CD56 (natural killer cells marker). Ten of 15 patients had normal morphology on follow-up endometrial samplings, and 4 patients had persistence or progression of the disease. Regulatory T-cell counts pretreatment were significantly higher in complex atypical hyperplasia and well-differentiated endometrial carcinoma than in posttreatment normal endometrium. Residual complex atypical hyperplasia and well-differentiated endometrial carcinoma present in posttreatment samples maintained high regulatory T cells and low number of cytotoxic T cells. Progestin treatment was associated with striking increase in cytotoxic T cells in areas with decidual reaction. Before treatment, most of the granzyme B+ cytotoxic T cells in complex atypical hyperplasia and well-differentiated endometrial carcinoma were CD8(+) T cells, whereas after treatment, up to 80% of cytotoxic T cells were natural killer cells. These results suggest that progestin treatment affects subpopulations of lymphocytes in the endometrium and may induce immune suppression of complex atypical hyperplasia and well-differentiated endometrial carcinoma.

Comparison of immune cell recruitment and function in endometrium during development of epitheliochorial (pig) and hemochorial (mouse and human) placentas

The role of maternal immune cells in early implantation sites has received special attention from reproductive biologists because immune cells participate in tissue transplant rejection. During normal pregnancy, endometrial immune cells differ from those in blood by subset distribution and appear to be activated but non-destructive of conceptuses. The immune system evolved well before placental mammals. By comparing the regulation and functions of endometrial immune cells between species in two phylogenetic clades that model differently evolved placental types (pig (Sus scrofa) versus mouse (Mus musculus) and human (Homo sapiens)), we seek to understand how "non-self" trophoblast cells thrive in most pregnancies. Our studies suggest recruitment of specific immune cells to conceptus-associated endometrium and immune cell-promoted endometrial angiogenesis are of key importance for mammalian conceptus well-being.

Human NK cells in pregnant uterus: why there?

Human Natural Killer (NK) cells are present in great number in pregnant uterine mucosa. They must be there for specialized functions, but which ones? This review discusses important recent observations that further contribute to this fascinating debate. Firstly, an array of corroborating findings indicates that uterine NK cell proliferation is synchronized with the cyclic surge of progesterone. Secondly, uterine NK cells are unlikely to exert a direct control on the embryo implantation. Thirdly, these NK cells influence the uterine vascular remodeling in early pregnancy but might not be the single key element that control trophoblast invasion. Finally, uterine NK cells are likely to be an important component of the local maternal immune response to pathogen infections.

Decidual natural killer cell tuning by autologous dendritic cells

PROBLEM

Dendritic cells (DC)/natural killer (NK) cells interactions in the deciduas of early human pregnancies were analyzed in vitro.

METHOD OF STUDY

Phenotype, cytokine expression and/or cytolytic mediators' expression were measured by flow cytometry in NK and DC from the freshly isolated decidual mononuclear cells or after their purification and co-culture in vitro. Proliferation of 5(6)-Carboxyfluorescein diacetate N-succinimidyl ester (CFSE)-labeled CD56(+) cells was analyzed by flow cytometry after the co-culture with CD1a(+) or CD83(+) DC.

RESULTS

Decidual CD1a(+) cells show less mature phenotype with no expression of CD197, lower expression of CD80 and CD86 and higher expression of CD206 and CD195 in comparison to CD83(+) cells. Interleukin (IL)-15, interferon-gamma and tumor necrosis factor-alpha productions were higher in immature than mature DC, whereas IL-10 and IL-18 were equally produced in both subpopulations. Immature DC increase perforin, FasL and TRAIL protein expression and proliferation of NK cells, but decrease their intracellular IL-15 production. Mature DC caused less efficient proliferation of NK cells, and did not affect cytokine and cytolytic mediator expression.

CONCLUSION

These results suggest that decidual CD1a(+) cells regulate and shape NK cell function more profoundly than CD83(+) cells in decidua.

Progesterone During Pregnancy: Endocrine?Immune Cross Talk in Mammalian Species and the Role of Stress

Progesterone is critical for the establishment and the maintenance of pregnancy, both by its endocrine and immunological effects. The genomic actions of progesterone are mediated by the intracellular progesterone receptors; A and B. A protein called P-induced blocking factor (PIBF), by inducing a T(H2) dominant cytokine production, mediates the immunological effects of progesterone. Progesterone plays a role in uterine homing of NK cells and up-regulates HLA-G gene expression, the ligand for various NK inhibitory receptors. At high concentrations progesterone is a potent inducer of Th2-type cytokines as well as of LIF and M-CSF production by T cells. Though a key role for progesterone in creating local immunosuppression has been conserved during the evolution of an epitheliochorial placenta, there has been some divergence in the pattern of endocrine-immunological cross talk in Bovidae. In sheep, uterine serpin, a progesterone-induced endometrial protein, mediates the immunosuppressive effects of progesterone. Epidemiological studies suggest the role of stress in premature pregnancy termination and exposure to stress induces abortion in mice via a significant reduction in progesterone levels, accompanied by reduced serum levels of PIBF. These effects are corrected by progesterone supplementation. These findings indicate the significance of a progesterone-dependent immuno-modulation in maternal tolerance of the fetus, which is discussed in this review.