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Stress is known to induce abortions in mice and humans, putatively via increased levels of abortogenic Th1 cytokines and a decrease of progesterone. Adequate levels of progesterone exert an antiabortive response through binding to the progesterone-receptor, which induces the release of progesterone-induced blocking factor (PIBF) from lymphocytes. PIBF is highly pregnancy-protective by induction of a Th2 biased immune activity. The aim of this study was to investigate the effect of the progesterone derivative dydrogesterone (6-dehydro-retroprogesterone) in stress-triggered murine abortion. DBA/2J-mated CBA/J female mice were randomized in different groups: two groups were treated with different dydrogesterone dosages in a single injection before exposure to sound stress on Day 5 of pregnancy, one group was exposed to stress without dydrogesterone treatment, the fourth group received no stress and no dydrogesterone. On gestation Day 13, a highly elevated abortion rate was detected in stressed mice compared to control mice. Stressed animals presented lower levels of progesterone and PIBF in plasma and a reduced staining intensity of progesterone receptor at the feto-maternal interface. Injection of dydrogesterone abrogated the effect of stress on the abortion rate. Further, dydrogesterone increased levels of plasma PIBF in stressed mice, but did not affect progesterone levels. Interestingly, dydrogesterone dramatically increased the percentage of IL-4 positive decidual immune cells in stressed mice. Our data suggest that dydrogesterone abrogates stress-triggered abortion by inducing a Th2 biased local immune response.

Polymorphic MHC is absent from the trophoblast, therefore, it resists NK as well as CTL-mediated lysis in vitro. Activated gamma / delta TCR positive cells are significantly enriched in the decidua as well as in peripheral blood of healthy pregnant women. Human peripheral gamma / delta lymphocytes preferentially express the V gamma 9/V delta 2 TCR, whereas those of the decidua use the V delta 1 chain. These subpopulations are functionally polarized, the former being Th1, the latter Th2. Potentially cytotoxic V delta 2+ lymphocytes recognize HLA-E on the trophoblast via the CD94/NKG2A receptor, which induces an inhibitory signal, thus potentially inhibiting Th1 type cytokine production., (Copyright 2001 Academic Press.)

Problem: We have previously demonstrated a significantly increased ratio of gamma/delta 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-gamma/delta 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 gamma/delta subpopulations in these phenomena., Method of Study: Peripheral blood lymphocytes from healthy pregnant women were incubated with either anti-gamma1.4 and delta1, or anti-gamma9 and delta2 antibodies. The effect of these treatments on PR induction and interleukin (IL)-10 and IL-12 expression were tested by immunocytochemistry. NK activity of anti-gamma/delta treated lymphocytes was also determined., Results: In peripheral blood of healthy pregnant women, the most frequently occurring chain combination was gamma1.4/delta1, whereas in recurrent aborters, the gamma9/delta2 combination was predominant. Treatment of normal pregnancy lymphocytes with a mixture of gamma1.4 and delta1 antibodies resulted in a significantly reduced NK activity and increased PR and IL-10 expression, whereas treatment with a mixture of gamma9 and delta2 antibodies significantly reduced IL-10 production and slightly increased IL-12 production and NK activity. These data suggest the presence of two functionally distinct subpopulations in the peripheral blood of pregnant women.

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.

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.