Progesterone directly and indirectly affects perforin expression in cytolytic cells.

PROBLEM: Decidual lymphocytes (DL) expressing the cytolytic molecule perforin represent approximately 55% of DL in the first trimester of human pregnancy. Progesterone dominates this phase of pregnancy and controls the production of uterine cytokines and growth factors. The aim of this study was to investigate the role of progesterone and progesterone-induced blocking factor (PIBF) on perforin expression in DL and peripheral blood lymphocytes (PBL). METHOD OF STUDY: Perforin expression was analyzed in PBL and DL incubated either in culture medium or with decidual adherent cells (DAC) and peripheral blood adherent cells (PBAC) and their supernatants with or without progesterone or PIBF. Perforin was detected by flow cytometry in PB and in decidual first trimester pregnancy lymphocytes. RESULTS: Progesterone in high concentrations directly affects perforin expression in DL but not in PBL. Progesterone in a concentration dependent manner indirectly blocks perforin expression in DL and PBL cultured with adherent cells or their supernatants. PIBF blocked upregulation of perforin expression of DL cultured with DAC, but none of those cultured with PBAC. Similarly, PIBF was inefficient when PBL or DL were cultured with PBAC. CONCLUSION: Progesterone present in a high concentration locally at the maternal-fetal interface modulates perforin expression in the first trimester pregnancy DL.

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 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. METHOD OF STUDY: Review of literature and current data. RESULTS: In the decidua gamma/delta TCR positive cells significantly increase in number. A subset of gamma/delta T cells reacts with nonpolymorphic Class I or Class I like molecules. Trophoblast recognition is mediated by the V gamma 1 subset which recognize a conserved mammalian sequence on the trophoblast. Almost all gamma/delta T cells in the decidua are activated and use the V delta 1 chain, whereas the majority of human peripheral gamma/delta lymphocytes expresses V gamma 9/V delta 2 TCR. Peripheral gamma/delta T cells of healthy pregnant women preferentially use V gamma V delta 1 chains, on the other hand, those of recurrent aborters use the V gamma 9V delta 2 combination. Signaling via the V gamma 1.4V delta 1 receptor induces a Th2 type response, whereas activation of the lymphocytes via the V gamma 9V delta 2 receptor results in increased IL-12 production and natural killer (NK) activity. In the presence of progesterone, activated lymphocytes synthesize the progesterone induced blocking factor (PIBF), which inhibits NK activity and exerts an anti abortive effect in vivo. Decidual CD56+ and gamma delta+ cells are to a high extent the same population. CONCLUSION: All decidual CD56+ cells express PIBF, thus it cannot be excluded that local production of this substance contributes to low decidual NK activity and thus to the success of the pregnancy.

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 TNF alpha 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 TNF alpha than those from healthy pregnant women and PIBF expression on the lymphocytes was inversely related to serum concentration of TNF alpha. Increased NK activity of lymphocytes after neutralization of endogenous PIBF activity is corrected by anti-IL 2 treatment and PIBF inhibits IL 12 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 TNF alpha levels. Disturbances in this system might lead to the expression of the known synergistic effect of IL-12 and TNF alpha, resulting in a Th 1 type cytokine dominance and pregnancy termination.

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 on 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 n 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.