Progesterone Induced Blocking Factor Seen in Pregnancy Lymphocytes Soon After Implantation

PROBLEM: The immunomodulatory effect of progesterone (P) in pregnancy manifested via a protein named the P-induced blocking factor (PIBF) was previously reported. The goal of this study was to measure and compare the PIBF expression on lymphocytes between pregnant and non-pregnant women especially in early pregnancy. METHODS: PIBF expression was determined by immunocytochemistry using a PIBF-specific polyclonal antibody. Levels were assessed during the mid-cycle, luteal phase, and first trimester of pregnancy. RESULTS: PIBF expression was found in 24.9% of mid-cycle sera, 49% of luteal phase sera of women who failed to conceive, and 75% of luteal phase sera of women who conceived. CONCLUSIONS: These data indicate that the percentage of PIBF expressing lymphocytes increases as a result of pregnancy and that the stimulus for PIBF induction occurs soon after implantation. These data support the concept that PIBF may play an important role in early implantation possibly by inhibiting the destructive function of natural killer lymphocytes.     

Expression of an Immunomodulatory Protein Known as Progesterone Induced Blocking Factor (PIBF) Does Not Correlate With First Trimester Spontaneous Abortions in Progesterone Supplemented Women

PROBLEM: An immunomodulatory protein known as the progesterone induced blocking factor (PIBF) has been found to positively correlate with early pregnancy beta human chorionic gonadotropin (B-hCG) levels. The study presented herein evaluated PIBF levels from conception to the end of the first trimester to determine if lower levels will correlate with first trimester spontaneous abortions (SAB). METHOD: Progesterone induced blocking factor expression by lymphocytes measured using an immunocytochemistry method was compared in pregnant women with ongoing vs. failed pregnancies. RESULTS: There were no differences in the proportion of women having lymphocytes expressing PIBF or in the median numbers when comparing ongoing vs. failed pregnancies. There was no B-hCG interval where failed pregnancies were found to have lower frequency of PIBF expressing lymphocytes. CONCLUSION: Inadequate PIBF expression independent of low P levels does not appear to be an etiologic factor for first trimester SABs; thus measuring this protein in pregnant women lacks practical usefulness.     

Expression of kisspeptin/GPR54 and PIBF/PR in the first trimester trophoblast and decidua of women with recurrent spontaneous abortion

Kisspeptin and its receptor GPR54 play a major role in trophoblast invasion, and progesterone-induced blocking factor (PIBF) is needed for maintaining pregnancy. The expression of kisspeptin/GPR54 and PIBF/progesterone receptor (PR) in trophoblasts and deciduas and the relationship between kisspeptin and PIBF were investigated in the same women with recurrent spontaneous abortion (RSA). Trophoblastic and decidual tissues were collected from 32 RSA women who miscarried a genetically normal fetus, and 35 women who had voluntary abortion. Kisspeptin, GPR54, PIBF and PR were investigated using immunohistochemistry. Kisspeptin, GPR54 and PIBF expressions in syncytiotrophoblasts and cytotrophoblasts were decreased in RSA women as compared to controls (P < 0.05). Kisspeptin, PIBF and PR expressions in deciduas were significantly decreased in RSA women as compared to controls (P < 0.01). GPR54 expression in deciduas nearly showed no difference between the RSA group and the control group (P = 0.958). Kisspeptin and PIBF expressions in syncytiotrophoblasts, cytotrophoblasts and deciduas were correlated with each other in the RSA group (Kappa = 0.602, P = 0.001; Kappa = 0.590, P = 0.001; Kappa = 0.392, P = 0.011). These data support the hypothesis that decreased kisspeptin and PIBF expressions in trophoblasts and deciduas are associated with RSA.     

The Expression of a Progesterone-Induced Immunomodulatory Protein in Pregnancy Lymphocytes

PROBLEM : The immunological effects of progesterone are mediated by a protein, named the progesterone-induced blocking factor (PIBF). The PIBF blocks NK activity in vitro and therefore prevents the abortive effect of high NK activity in mice. Increased NK activity has been suggested to play a role in pregnancy termination; thus NK inhibitory effect of the PIBF should contribute to the maintenance of normal gestation. This study was designed to investigate the relationship between in vivo PIBF-producing capacity and in vitro cytotoxic activity of pregnancy lymphocytes, as well as the clinical status or the outcome of pregnancy. METHOD : Lymphocytes of 168 pregnant women (96 normal pregnancies, 16 showing clinical symptoms of threatened preterm pregnancy termination, 46 recurrent aborters, and 10 women sampled at the onset of spontaneous abortion or preterm delivery) were isolated on Ficoll-Paque gradient. The lymphocytes were tested for reactivity with a PIBF-specific antibody by immunocytochemistry, and simultaneously for cytotoxic activity to human embryonic fibroblast targets. RESULTS : The percentage of PIBF-positive lymphocytes in peripheral blood of healthy pregnant women was significantly higher than in that of women at risk for premature pregnancy termination. In peripheral blood of patients undergoing spontaneous pregnancy termination at the time of sampling, and in those of women showing symptoms of premature pregnancy termination we found lower than normal percentage of PIBF-positive cells. PIBF expression of the lymphocytes showed an inverse correlation with NK activity, and the rate of PIBF positive lymphocytes was related to the outcome of pregnancy. CONCLUSION : These data suggest a strong relationship between PIBF producing capacity as well as NK activity of the lymphocytes and the success of gestation.     

Progesterone induced blocking factor (PIBF) mediates progesterone induced suppression of decidual lymphocyte cytotoxicity

PROBLEM: Progesterone induced blocking factor (PIBF) is a mediator of progesterone that blocks peripheral blood lytic natural killer (NK) activity. Progesterone or PIBF stimulated decidual macrophages block up-regulation of perforin expression in decidual lymphocytes (DL). Therefore, we investigated whether progesterone regulates cytotoxicity of DL. METHOD OD STUDY: Decidual mononuclear cells were cultured with progesterone. PIBF, progesterone and anti-PIBF antibody or in the medium only. Cytolytic activity of non-adherent DL was measured by PKH-26 (red) 2 hr cytolytic assay and flow cytometry. Perforin positive DL were detected by immunofluorescency and PIBF-positive cells by immunohistology. RESULTS: Progesterone and PIBF, in a dose-dependent manner decreased cytotoxicity of DL against K-562 targets, and perforin egzocytosys was blocked. Anti-PIBF antibodies reversed the progesterone mediated reduction in cytolytic activity of DL. PIBF positive cells were found in first trimester pregnancy decidua. CONCLUSION: The results indicate possible role for PIBF, as a mediator of progesterone in regulation of DL cytolytic activity at the maternal-foetal (M-F) interface.     

Evidence that the Expression of Progesterone-Induced Blocking Factor by Maternal T-Lymphocytes Is Positively Correlated with Conception

PROBLEM: To compare the expression by T-lymphocytes of an immunomodulatory protein known as progesterone-induced blocking factor (PIBF) in conception versus non-conception cycles even when there has been definite fertilization and embryo formation. METHOD: PIBF expression on T lymphocytes was measured using an immunohistochemical method with a PIBF-specific polyclonal antibody. These levels were determined in patients undergoing three types of therapy: non-in vitro fertilization (IVF), IVF-embryo transfer (ET), and frozen ET. Sera were drawn 12 days from ovulation in non-IVF cycles or 9 days after ET and were assayed for PIBF and beta human chorionic gonadotropin. Comparison of the frequency of lymphocyte expression of PIBF in pregnant versus non-pregnant women were made. RESULTS: PIBF was detected in 29.5% of non-pregnant women and 52.5% of pregnant women. There were no differences in PIBF levels by therapy used in non-pregnant cases or in the pregnant group. CONCLUSION: These data are consistent with the hypothesis that maternal expression of PIBF in T-lymphocytes soon after trophoblast invasion may depend on successful implantation.     

Progesterone as an immunomodulator

In the presence of progesterone, lymphocytes of healthy pregnant women produce a 34-kDa protein, which, because of its immunomodulatory effects has been called progesterone induced blocking factor (PIBF). PIBF is a secreted molecule and thus appears in biological fluids. Urinary PIBF concentrations in healthy pregnant women are significantly higher than in recurrent aborters, or in women showing clinical symptoms of threatened abortion. Recent data suggest, that PIBF production is not exclusively a pregnancy-related phenomenon. PIBF is present in most undifferentiated tissues, e.g. malignant tumors. The possible role of PIBF in tumor development will be discussed.     

Correlations of the expression of γδ T cells and their co‐stimulatory molecules TIGIT,PD‐1, ICOS and BTLA with PR and PIBF in the peripheral blood and decidual tissues of women with unexplained recurrent spontaneous abortion

Semi‐allogeneic embryos are not rejected by the maternal immune system due to maternal–fetal immune tolerance. Progesterone (P) receptor (PR)‐expressing γδ T cells are present in healthy pregnant women. In the presence of P, these cells secrete an immunomodulatory protein called progesterone‐induced blocking factor (PIBF), which can facilitate immune escape and is important in preventing embryonic rejection. This work investigated the correlations of the expression of γδ T cells and their co‐stimulatory molecules T cell immunoglobulin and ITIM domain (TIGIT), programmed cell death 1 (PD‐1), inducible co‐stimulator (ICOS) and B and T lymphocyte attenuator (BTLA) with progesterone receptor (PR) and progesterone‐induced blocking factor (PIBF) in peripheral blood and decidual tissue in women with unexplained recurrent spontaneous abortion (URSA) and normal pregnant (NP) women. We confirmed that γδ T cell proportions and PIBF expression in the peripheral blood and decidua of URSA women decreased significantly, while PR expression in decidua decreased. However, TIGIT, PD‐1, ICOS and BTLA expression in γδ T cells in peripheral blood did not change, while TIGIT and PD‐1 expression in γδ T cells in decidua increased significantly. Under the action of PHA‐P (10 µg/ml), co‐blocking of TIGIT (15 µg/ml) and PD‐1 (10 µg/ml) antibodies further induced γδ T cell proliferation, but PIBF levels in the culture medium supernatant did not change. At 10^?10 M P, γδ T cells proliferated significantly, and PIBF concentrations in the culture medium supernatant increased. γδ T cells co‐cultured with P, TIGIT and PD‐1 blocking antibodies showed the most significant proliferation, and PIBF concentrations in the culture medium supernatant were the highest. These results confirm that P is necessary for PIBF production. The TIGIT and PD‐1 pathways participate in γδ T cell proliferation and activation and PIBF expression and play important roles in maintaining pregnancy.     

PIBF: The Double Edged Sword. Pregnancy and Tumor

Citation Szekeres‐Bartho J, Polgar B. PIBF: The Double Edged Sword. Pregnancy and Tumor. Am J Reprod Immunol 2010; 64: 77–86 Problem The role of progesterone‐dependent immunomodulation in the maintenance of normal pregnancy. Methods In vitro and in vivo data on the effect that progesterone and its mediator progesterone‐induced blocking factor (PIBF) exert on the immune functions of pregnant women are reviewed, together with clinical findings. Results Activated pregnancy lymphocytes express progesterone receptors, which enable progesterone to induce a protein called PIBF. PIBF increases Th2 type cytokine production by signaling via a novel type of IL‐4 receptor and activating the Jak/STAT pathway. PIBF inhibits phosholipase A2, thus reduces prostaglandin synthesis. PIBF inhibits perforin release in human decidual lymphocytes and reduces the deleterious effect of high NK activity on murine pregnancy. PIBF production is a characteristic feature of normal human pregnancy, and its concentration is reduced in threatened pregnancies. PIBF mRNA and protein are expressed in a variety of malignant tumors. Inhibition of PIBF synthesis increases survival rates of leukemic mice. Conclusion Progesterone‐induced blocking factor is produced by pregnancy lymphocytes and also by malignant tumors. The PIBF‐induced Th2‐dominant immune response is favorable during pregnancy but might facilitate tumor growth by suppressing local antitumor immune responses.     

Fertility Among Women With Recurrent Spontaneous Abortions—The Effect of Paternal Cell Immunization Treatment

PROBLEM : The risk of women whose chief complaint is recurrent spontaneous abortions (RSA) for secondary infertility (infecundability) has not been evaluated prospectively. The effect of paternal mononuclear cell immunization on conception rates is unknown. METHOD : Two hundred women whose chief complaint was RSA were randomly assigned to be immunized with paternal mononuclear cells either before or after (up to 6 postmenstrual weeks) conception. Fertility rates (both conception and live birth) were evaluated for the group immunized before conception and compared to those for the control group, who were not immunized until after conception, using life table and multiple logistic regression analyses. RESULTS : Prospectively ascertained, age-related conception rates for nonimmunized RSA controls appeared to be similar to those for general populations. Immunization before pregnancy had no significant effect (power ± 14%) on rates of conception (66% before, 77% after) or time to conceive (median weeks before 19.5, after 27.0). Live birth rates (before 59%, after 63%) were also similar for both groups (P = 0.7). CONCLUSION : Women whose only prior complaint was RSA were not at high risk for secondary infecundability, and immunization did not alter either conception rates or time to conceive. Postponement of immunization until after conception did not affect live birth rates for women selected for study because they did not have a history of prior infecundability or early repeated miscarriages.     

Cytokine Production by Lymphocytes in Pregnancy

PROBLEM: In the presence of progesterone lymphocytes of pregnant women release a 34- kDa protein named the progesterone-induced blocking factor (PIBF). PIBF mediates the immunomodulatory and anti-abortive effects of progesterone and its presence is related to the outcome of pregnancy. PIBF induces production of Th2 type cytokines by activated lymphocytes. The in vivo relationship between PIBF- and cytokine production of pregnancy lymphocytes and the outcome of pregnancy was investigated. METHOD OF STUDY: Interleukin (IL)-12 and IL-10 production and PIBF expression in peripheral lymphocytes of 111 healthy pregnant women and 120 women at risk for premature pregnancy termination were detected by immunocytochemistry. RESULTS: We found increased IL-12 and low PIBF and IL-10 expression on lymphocytes of “risk” patients, and a high rate of IL-10 and PIBF positivity on lymphocytes from healthy pregnant women. The cytokine production pattern of the lymphocytes was related to the presence or absence of previous abortions as well as to the outcome of pregnancy. CONCLUSION: These data suggest the involvement of an altered cytokine production pattern in the immunologic effects of progesterone.     

The Immunological Pregnancy Protective Effect of Progesterone Is Manifested via Controlling Cytokine Production

PROBLEM: This study was aimed at investigating the involvement of an altered cytokine pattern in the immunomodulatory and anti-abortive effects of a progesterone-induced immunomodulatory protein (PIBF). METHOD: PIBF expression on lymphocytes of healthy pregnant women and from women at risk for premature pregnancy termination was determined. In sera of the same women TNFα was quantified by a bioassay using L929 cells. NK activity was determined by a single cell cytotoxicity assay. Cytokine production of the lymphocytes or murine spleen cells was measured by ELISA or detected by immunocytochemistry. In pregnant mice endogenous PIBF activity was neutralized by anti-PIBF IgG. RESULTS: Sera of women at risk for premature pregnancy termination contained significantly higher concentrations of TNFα than those from healthy pregnant women and PIBF expression on the lymphocytes was inversely related to serum concentration of TNFα. Increased NK activity of lymphocytes after neutralization of endogenous PIBF activity is corrected by anti-IL2 treatment and PIBF inhibits IL12 expression on activated lymphocytes. PIBF increases IL-10 production by activated spleen cells. In pregnant mice, neutralization of endogenous PIBF activity by specific antibody results in increased resorption rate and reduced splenic IL-10 production. CONCLUSIONS: Our data allow the assumption that via blocking IL-12 production PIBF inhibits NK activation with a concomitant reduction of TNFα levels. Disturbances in this system might lead to the expression of the known synergistic effect of IL-12 and TNFα, resulting in a Th1 type cytokine dominance and pregnancy termination.     

Progesterone regulates IL12 expression in pregnancy lymphocytes by inhibiting phospholipase A2

PROBLEM: Progesterone-induced blocking factor (PIBF) is one of the pathways that mediate the immunological effects of progesterone. PIBF inhibits natural killer (NK) cytotoxic activity. Recently we showed that neutralization of PIBF results in an increased interleukin (IL)-12 expression, which is corrected by cyclooxygenase inhibitors. As exogenous arachidonic acid (AA) voids the NK blocking effect of PIBF, it is likely that PIBF acts before the level of the cyclooxygenase enzyme. Therefore in this study we investigated the effect of PIBF neutralizing antibody and simultaneous phospholipase A2 inhibitor quinacrine (Q) treatment on IL-12 production. METHODS: Pregnancy lymphocytes were treated with anti-PIBF antibody or lipopolysaccharide (LPS) as a positive control, in the presence or absence of Q. IL-12 expression by PBMC was detected by immunocytochemistry. RESULTS: Neutralization of PIBF as well as LPS treatment resulted in an increased IL-12 expression, which was corrected by simultaneous Q treatment. Pre-treatment of lymphocytes with progesterone prevented the stimulating effect of LPS on IL-12 production. CONCLUSION: Progesterone binding of the lymphocytes is followed by the release of PIBF that inhibits AA release. The subsequent block of prostaglandin synthesis reduces IL-12 production and results in a lowered cytotoxic NK activity, which may contribute to a normal pregnancy outcome.     

Asymmetric Antibodies and Pregnancy

PROBLEM: Asymmetric IgG antibodies (AAb) possess a mannose-rich oligosaccharide residue bound to one of the Fab regions, making them unable to activate immunoeffector mechanisms. The proportion of asymmetric antibodies is increased after prolonged immunization with particulate antigens like cellular spleen cells. During pregnancy, AAb were found in serum and bound to placenta with specific activity to paternal antigens. No previous reports about the status of AAb in recurrent spontaneous abortion (RSA) patients have been published to date. Therefore, the aim of the present study was to analyze the percentage of asymmetric IgG molecules in serum samples of (a) healthy pregnant and non-pregnant women, (b) pregnant women with a history of RSA, and (c) non-pregnant RSA patients receiving paternal lymphocyte immunotherapy (LIT) or intravenous gammaglobulin therapy (IVIgs). METHOD OF STUDY: A previously-described differential ELISA technique was used to determine the percentage of IgG that was of the asymmetric type. RESULTS: During normal pregnancy, there was an increase in the percentage of high ConA affinity IgG serum molecules with a major increase at the second trimester. Pregnant RSA patients at the second trimester had lower values. When evaluating non-pregnant RSA patients who received LIT, it was observed that the immunized patients expressed a higher percentage of asymmetric IgG antibodies. The pregnant patients who received IVIgs had a percentage of AAbs comparable to normal pregnant patients. Additionally, the presence of IgG asymmetric molecules was confirmed in commercial gammaglobulin preparations. CONCLUSION: Results suggest a protective role of AAb during pregnancy.     

Progesterone and Non-specific Immunologic Mechanisms in Pregnancy

PROBLEM: Progesterone-dependent immunomodulation is one of the mechanisms that enables pregnancy to proceed to term. Immunologic effects of progesterone are mediated by a protein named the progesterone-induced blocking factor (PIBF). Among other effects this protein inhibits natural killer (NK) activity and displays an anti-abortive effect in mice. Recently we have shown that PIBF induces a Th2 shift in vitro. The present study was aimed at investigating the in vivo effect of PIBF on cytokine production, as well as the relationship between cytokine production, NK activity, and pregnancy loss. METHOD OF STUDY: Balb-c mice on day 8.5 of pregnancy were injected intraperitoneally with 0.5 mg of rabbit anti-PIBF immunoglobulin G (IgG). Another group of mice was simultaneously treated with anti-NK monoclonal antibodies. Mice treated with the same amount of normal rabbit serum or untreated mice of similar gestational age were used as controls. The animals were sacrificed on day 10.5, and their uteri were inspected. The ratio of living and resorbed embryos was determined. NK activity as well as cytokine expression on the spleen cells were determined by immunocytochemistry and enzyme-linked immunoadsorbent assay (ELISA). RESULTS: Mitogen-activated spleen cells from anti-PIBF-treated mice produced significantly (P < 0.001) less IL-10 than those of pregnant control mice. A significantly higher percentage (P < 0.001) of spleen cells from anti-PIBF-treated mice expressed interferon-γ (IFNγ) as determined by immunocytochemistry, than those of untreated pregnant mice. There was a positive relationship between the percentage of IFNγ-positive spleen cells and resorption rates, and an inverse relationship between the latter and interleukin-10 (IL-10) production. All these effects were corrected by treatment with anti-NK antibodies. CONCLUSION: Our data suggest that PIBF contributes to the success of gestation via eytokine-mediated inhibition of NK activity.     

The progesterone-induced blocking factor modulates the balance of PKC and intracellular Ca

PROBLEM: Progesterone-induced blocking factor (PIBF) induces Th2 biased cytokine production; therefore, this study investigates the effects of PIBF on the protein kinase C (PKC)/Ca(++) system - which plays a key role in Th1/Th2 differentiation. METHOD OF STUDY: Proteins from PIBF-treated cells were reacted on Western blots with phospho-specific antibodies recognizing different PKC izoforms. Intracellular free calcium was measured by flow cytometry. RESULTS: Both interleukin (IL)-4 and PIBF induced PKC phosphorylation, which was abrogated by anti-IL-4Ralpha or anti-PIBF immunoglobulin G pre-treatment. PIBF treatment did not alter intracellular Ca(++) levels. Inhibition of PKCzeta or PKCtheta phosphorylation, but not that of PKCalpha/beta resulted in the loss of STAT6 and Jak1 phosphorylation by PIBF. CONCLUSIONS: Our data show that PIBF phosphorylates PKC via binding to the IL-4R, without affecting intracellular Ca(++). Phosphorylation of PKCzeta and PKCtheta is required for Jak1 and STAT6 activation, whereas PKCalpha/beta is not involved. These findings explain the mechanism by which PIBF supports a Th2 dominant cytokine pattern.     

孕激素诱导的封闭因子在先兆流产患者血清中的表达

目的通过检测先兆流产患者血清中孕酮及孕激素诱导的封闭因子（PIBF）的表达水平,探讨PIBF与先兆流产的关系及临床意义。方法先兆流产患者72例为观察组,同期健康早孕妇女40例为对照组,采用酶联免疫吸附方法（ELISA）检测血清中孕酮及PIBF水平并进行对比分析。结果两组孕妇的年龄、妊娠时间和血清孕酮水平比较差异无统计学意义（P〉0.05）;观察组PIBF水平为（103.91±25.12）ng/ml,明显低于对照组的（117.62±24.33）ng/ml,差异有统计学意义（P〈0.05）。观察组血清孕酮水平与PIBF之间不存在相关关系（P〉0.05）,对照组血清孕酮水平与PIBF之间存在相关关系（P〈0.05）。结论 PIBF表达降低与自然流产的发生有关系,妊娠早期血清PIBF水平降低是引起自然流产的原因之一。     

Progesterone-Induced Blocking Factor and Cytokine Profile in Women with Threatened Pre-Term Delivery

Problem  The objective of this study was to compare serum concentrations of progesterone-induced blocking factor (PIBF), anti-inflammatory (IL-10), and pro-inflammatory (IL-6, TNFα, and IFNγ) cytokines of women with threatened pre-term delivery, with those of women with normal pregnancy and to evaluate the impact of PIBF on the outcome of pregnancy.
Method of study  A prospective study was conducted on a sample of 30 women with threatened pre-term delivery (study group) and 20 healthy pregnant women (control group) between the 24th and 37th gestational weeks. Serum PIBF, anti-inflammatory (IL-10), and pro-inflammatory (IL-6, TNFα, and IFNγ) cytokine concentrations were measured by enzyme-linked immunosorbent assay (ELISA).
Results  Thirteen of 30 patients (43.3%) with symptoms of threatened pre-term delivery, and one of 20 patients (5%) in the control group delivered before the 37th week of gestation. Mean PIBF concentrations in serum samples of patients with threatened pre-term delivery were significantly lower than in those of healthy pregnant women (171.12 ± 162.06 ng/mL versus 272.85 ± 114.87 ng/mL; P  < 0.05). Women with symptoms of threatened pre-term delivery had significantly lower serum levels of IL-10, and higher levels of IL-6 as well as IFNγ compared with healthy controls.
Conclusion  Our results indicate that measuring PIBF and cytokine concentrations in serum during pregnancy is feasible and may be important for understanding immunological causes of pre-term delivery.     

Progesterone-induced blocking factor inhibits degranulation of natural killer cells.

PROBLEM: During the first trimester of pregnancy, nonclassical (CD3-, CD56+, CD16-, perforin [P]bright+) natural killer (NK) cells comprise the major decidual lymphocyte population. These cells, in spite of their high perforin content, exert a low cytolytic activity. Peripheral blood lymphocytes of healthy pregnant women produce progesterone-induced blocking factor (PIBF), which inhibits NK activity. PIBF-producing cells are likely to be present in decidua and might contribute to low decidual NK activity. METHOD OF STUDY: Decidual cells obtained from elective pregnancy termination were double labeled for CD56 and PIBF. We tested the effect of PIBF on perforin liberation by activated peripheral blood NK cells. RESULTS: Sixty percent of decidual lymphocytes were CD56 + and expressed PIBF at the same time. PIBF-treated and untreated peripheral blood NK cells were incubated with K-562 cells, and perforin content of target conjugated NK cells was detected with immunocytochemistry. PIBF treatment of peripheral blood lymphocytes significantly reduced lysis of K-562 cells. Among target bound lymphocytes in PIBF-treated samples, we found a significantly (P < 0.01) higher rate of P+ cells than in untreated samples. CONCLUSIONS: These data suggest that PIBF inhibits cytotoxicity of NK cells via a block of degranulation, and since decidual NK cells are PIBF+, it cannot be ruled out that this effect of PIBF contributes to low decidual NK activity.     

The role of gamma/delta 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 gammadelta 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. METHOD OF STUDY: Peripheral lymphocytes from healthy pregnant women and from habitual aborters were tested by immunocytochemistry for the presence of gamma/delta T cell receptor (TCR) and progesterone receptor. To investigate the effect of treatment with a pan anti gamma/delta antibody, lymphocytes were incubated for 3 hr with the antibody, and then interleukin (IL)-10, IL-12 and progesterone-induced blocking factor (PIBF) expression (by immuno-cytochemistry) as well as natural killer (NK) cell activity were determined. RESULTS: In peripheral blood of healthy pregnant women the percentage of gamma/delta TCR+ cells was significantly higher (P < 0.001) than in that of recurrent aborters or of non-pregnant individuals. Ninety-seven percent of gamma/delta TCR+ pregnancy lymphocytes expressed progesterone receptor. Binding of a specific antibody to the gamma/delta TCR inhibited PIBF- as well as IL-10 production, whereas it increased NK activity and IL-12 expression. CONCLUSIONS: These data suggest the role of gamma/delta TCR-bearing lymphocytes in progesterone-dependent immunomodulation.