Aliz Barakonyi

Progesterone as an immunomodulatory molecule

Increased progesterone sensitivity of pregnancy lymphocytes is due to activation-induced appearance of progesterone binding sites in the lymphocytes. Following recognition of fetally derived antigens gamma/delta TCR+ cells develop progesterone receptors. Progesterone binding results in the synthesis of a mediator protein named the progesterone-induced blocking factor (PIBF). PIBF by acting on the phospholipase A2 enzyme interferes with arachidonic acid metabolism, induces a Th2 biased immune response, and by controlling NK activity exerts an anti-abortive effect.

The role of γ/δ T cells in progesterone-mediated immunomodulation during pregnancy: A review

PROBLEM: To determine if pregnancy is recognized by the immune system and if inadequate recognition of fetal antigens might result in failed pregnancy.

The role of γ/δ T cell receptor positive cells in pregnancy

PROBLEM: Due to the lack of classical HLA antigens on the trophoblast, fetal antigens are possibly presented in a non major histocompatibility complex (MHC) restricted way. Decidual γδ T cells, which significantly increase in number during pregnancy, might play a role in recognition of fetal antigens and also in determining the quality of the response to these antigens. Our study was aimed at investigating the role of this cell population in progesterone‐dependent immunomodulation.

Recognition of Nonclassical HLA Class I Antigens by γδ T Cells During Pregnancy

The healthy trophoblast does not express classical HLA-A and HLA-B products; therefore, an MHC-restricted recognition of trophoblast-presented Ags is unlikely. In the decidua and also in peripheral blood of healthy pregnant women, γδ T cells significantly increase in number. We investigated the possible role of γδ T cells in recognition of trophoblast-presented Ags. PBL and isolated γδ T cells from healthy pregnant women as well as from those at risk for premature pregnancy termination were conjugated to choriocarcinoma cells (JAR) transfected with nonclassical HLA Ags (HLA-E, HLA-G). To investigate the involvement of killer-inhibitory/killer-activatory receptors in trophoblast recognition, we tested the effect of CD94 block on cytotoxic activity of Vδ2+ enriched γδ T cells to HLA-E- and/or HLA-G-transfected targets. Lymphocytes from healthy pregnant women preferentially recognized HLA− choriocarcinoma cells, whereas those from pathologically pregnant patients did not discriminate between HLA+ and HLA− cells. Normal pregnancy Vδ2+ T cells conjugated at a significantly increased rate to HLA-E transfectants, whereas Vδ2+ lymphocytes from pathologically pregnant women did not show a difference between those and HLA− cells. Blocking of the CD94 molecule of Vδ2+ lymphocytes from healthy pregnant women resulted in an increased cytotoxic activity to HLA-E-transfected target cells. These data indicate that Vδ2+ lymphocytes of healthy pregnant women recognize HLA-E on the trophoblast, whereas Vδ1 cells react with other than HLA Ags. In contrast to Vδ2+ lymphocytes from healthy pregnant women, those from women with pathological pregnancies do not recognize HLA-E via their killer-inhibitory receptors and this might account for their high cytotoxic activity.

The role of γ/δ T-cell receptor-positive cells in pregnancy : Part II

PROBLEM: We have previously demonstrated a significantly increased ratio of γ/δ T‐cell receptor (TCR)‐positive progesterone receptor(PR)‐positive cells in the peripheral blood of healthy pregnant women compared to that of recurrent aborters or non‐pregnant individuals. Treatment of pregnancy lymphocytes with a pan anti‐γ/δ TCR antibody inhibits progesterone‐induced blocking factor (PIBF) production, increases natural killer (NK) activity, and alters the cytokine profile. The present study was aimed at investigating the role of the different γ/δ subpopulations in these phenomena.

Immunoactivation in preeclampsia: Vδ2+ and regulatory T cells during the inflammatory stage of disease

Recent data suggest a dominant role of the innate, rather than the adaptive immune system in pregnancy-related immunoregulation. gamma/delta T cells, that comprise a minor subpopulation of human peripheral blood lymphocytes, represent a link between the innate and the acquired immune systems. However little is known about how they function in preeclampsia, which is suggested to be associated with a Th1 predominant immune response. The aim of our study was to investigate the presence and phenotype of Vdelta2+ cells and of regulatory T cells in the pathogenesis of preeclampsia. Since Vdelta2+ T cell function has been shown to be altered in patients with preeclampsia we investigated the expression of perforin, Fas and TIM-3 by Vdelta2+ T cells and the possible role of activating and inhibitory NK cell receptors as well as of regulatory T cells. Vdelta2+ T cells of preeclamptic patients demonstrated an increased perforin and IFNgamma production, which could be explained by dysregulation of NK cell receptor expression. These Th1 polarized cells were less susceptible to apoptosis than Vdelta2+ T cells from healthy pregnant women. Our data suggest that activated Vdelta2+ T cells of preeclamptic women have an increased cytotoxic potential, which may be due to altered expression of NK cell inhibitory and activating receptors. In this study we report a series of observations, which taken together suggest the role of multiple pathways in generating an exaggerated systemic inflammatory response observed in the clinical stage of preeclampsia.

Possible role of natural killer and natural killer T-like cells in implantation failure after IVF

During implantation, maternal immunoactivation and tolerance are not only limited to the decidua but are also observed in the periphery, predominantly affecting the innate immune system. Since unexplained female infertility, as well as recurrent spontaneous abortion and implantation failure, are thought to be associated with pathological maternal immunotolerance mechanisms, this study focused on immune profile analysis of IVF candidates. Previous studies on peripheral natural killer (NK) cell characteristics of IVF patients have been limited to the comparison of blood samples taken prior to the IVF procedure. This study performed a follow-up study and compared patients data obtained on the day of oocyte collection with the data 1 week after embryo transfer. The aim was to investigate phenotypic (subpopulations, CD69, T-cell immunoglobulin mucin 3 and NK-activating receptor expression) and functional (perforin and CD107a expression) changes in the peripheral NK and NK T (NKT)-like cell populations. During this short period of time around the IVF procedure, women with failed IVF reflected unfavourable Th1-oriented changes of NK and NKT-like cells. In comparison the follow-up data for women with successful conception remained principally constant. The observed peripheral changes during early pregnancy in the same individual may also have importance in successful embryo implantation.

Involvement of Galectin-9/TIM-3 Pathway in the Systemic Inflammatory Response in Early-Onset Preeclampsia

Background Preeclampsia is a common obstetrical disease affecting 3-5% of pregnancies and representing one of the leading causes of both maternal and fetal mortality. Maternal symptoms occur as an excessive systemic inflammatory reaction in response to the placental factors released by the oxidatively stressed and functional impaired placenta. The T-cell immunoglobulin domain and mucin domain (TIM) family is a relatively newly described group of molecules with a conserved structure and important immunological functions. Identification of Galectin-9 as a ligand for TIM-3 has established the Galectin-9/TIM-3 pathway as an important regulator of Th1 immunity and tolerance induction. Methods The aim of our study was to investigate the expression and function of Galectin-9 and TIM-3 molecules by peripheral blood mononuclear cells and the possible role of Galectin-9/TIM-3 pathway in the immunoregulation of healthy pregnancy and early-onset preeclampsia. We determined TIM-3 and Gal-9 expression and cytotoxicicty of peripheral lymphocytes of early-onset preeclamptic women and healthy pregnant woman using flow cytometry. Results Investigating peripheral lymphocytes of women with early-onset preeclampsia, our results showed a decreased TIM-3 expression by T cells, cytotoxic T cells, NK cells and CD56dim NK cells compared to healthy pregnant women. Interestingly, we found a notably increased frequency of Galectin-9 positive cells in each investigated lymphocyte population in the case of early-onset preeclamptic patients. We further demonstrated increased cytotoxic activity by cytotoxic T and CD56dim NK cells in women with early-onset preeclampsia. Our findings showed that the strongest cellular cytotoxic response of lymphocytes occurred in the TIM-3 positive subpopulations of different lymphocytes subsets in early-onset preeclampsia. Conclusion These data suggest that Gal-9/TIM-3 pathway could play an important role in the immune regulation during pregnancy and the altered Galectin-9 and TIM-3 expression could result an enhanced systemic inflammatory response including the activation of Th1 lymphocytes in preeclampsia.

The Role of Invariant NKT Cells in Pre-Eclampsia

Problem  Recent data suggest a dominant role of the innate, rather than the adaptive immune system in pregnancy‐related immunoregulation. Invariant NKT (iNKT) cells represent a link between the innate and the acquired immune systems; however, little is known about how they function in pre‐eclampsia. The aim of our study was to investigate the possible role of iNKT cells in the pathogenesis of pre‐eclampsia.

γ/δT-cell subsets, NKG2A expression and apoptosis of Vδ2+ T cells in pregnant women with or without risk of premature pregnancy termination

Problem:  Potentially cytotoxic Vδ2+ T lymphocytes recognize human leukocyte antigen‐E on the trophoblast via their CD94/NKG2A receptors. This study aims at determing the percentage of γ/δ T‐cell subsets, their NKG2A and Annexin V positivity in peripheral blood of healthy pregnant women and women at risk of premature pregnancy termination.