Biotinylated anti-progesterone monoclonal antibodies specifically target the uterine epithelium and block implantation in the mouse

Hormones, cytokines and fetal anomalies in habitual abortion

Recurrent miscarriage may be due to an inherently abnormal embryo (e.g. chromosomal aberrations), or maternal factors (e.g. uterine anomalies or antiphospholipid antibodies). However, there may be another mechanism; fetuses may have anomalies induced by toxic maternal factors. Early ultrasound scanning has revealed structural anomalies in karyotypically normal embryos in pregnancies that have terminated in first-trimester missed abortion. The serum of recurrently miscarrying women is toxic to blastocysts, embryos and fetuses. Teratogens such as cyclophosphamide or toxins such as lipopolysaccharide cause fetal demise by excessive apoptosis. Excessive apoptosis may be mediated by tumor necrosis factor-alpha and other cytokines. Both immunomodulation and hormonal support (progesterone or human chorionic gonadotropin supplements) have been used to improve the live birth rate in recurrently aborting women. Each may modulate the balance between Th1 and Th2 cytokines. Th2 cytokines are thought to benefit the developing embryo by enhancing placental growth and function, and possibly by preventing inappropriate apoptosis. Although neither hormonal support nor immunopotentiation have proved to be beneficial, no trial has limited itself to pregnancies that are karyotypically normal. This review assesses fetal structural anomalies in humans and laboratory animals as causes of pregnancy loss, the role of cytokines in those anomalies and the role of immunomodulation and hormones in modifying these effects.

Defective production of both leukemia inhibitory factor and type 2 T-helper cytokines by decidual T cells in unexplained recurrent abortions

Leukemia inhibitory factor is essential for embryo implantation, and a shift from type 1 T-helper to type 2 T-helper response at the fetal-maternal interface may contribute to successful pregnancy. We show that LIF production is associated with type 2 T-helper cells, is upregulated by IL-4 and progesterone and is downregulated by IL-12, IFN-gamma and IFN-alpha. We also show a decreased production of LIF, IL-4 and IL-10 by decidual T cells of women with unexplained recurrent abortions in comparison with that of women with normal gestation. The defective production of LIF and/or type 2 T-helper cytokines may contribute to the development of unexplained recurrent abortions.

Regulation of fetal allograft survival by a hormone-controlled Th1- and Th2-type cytokines

There is clear evidence to suggest that the maternal immune system during pregnancy can enhance or inhibit the development of the fetoplacental unit. Recent data support the view that some cytokines produced by both T cells and non-T cells (IL-3, GM-CSF, TGF-beta, IL-4, IL-10), favor fetal survival and growth. In contrast, other cytokines, such as IFN-gamma, TNF-beta and TNF-alpha, can rather compromise pregnancy. Accordingly, we show here that T-cell clones generated from the decidua of women with unexplained recurrent abortion produced significantly lower concentrations of IL-4 than clones derived from the decidua of voluntary abortions or the endometrium of nonpregnant women. Thus, despite the complexity of the cytokine network, it appears that cytokines favoring the maintenance of fetal survival mainly belong to the Th2 pathway, whereas the failure of pregnancy rather associates with the predominance of Th1-type cytokines and/or the absence of Th2-type cytokines. Interestingly, we also found that, at least in vitro, progesterone promotes the preferential development of Th2-like cells and induces transient IL-4 production by established Th1 cells, whereas relaxin, another corpus luteum-derived hormone, mainly promotes the development of Th1-like cells. These data provide an excellent basis for investigating the relationship between the endocrine and the immune system in the regulation of the maternal-fetal interaction.

Proto-oncogene erbA expression and increased abundance of progesterone receptors in the mouse uterus after passive immunisation against progesterone before implantation

Passive immunisation with a monoclonal anti-progesterone antibody (DB3) prevents pregnancy in the mouse, and antibody is localised in the endometrium before the onset of implantation. BALB/c female mice were injected intraperitoneally with 9 nmol of DB3 (a dose known to cause 100% infertility) 32 h post coitum, and the uterus was removed at various times after injection. Using a monoclonal anti-progesterone receptor antibody (PR6), expression of progesterone receptors was found to be abundant in uterine tissue of DB3-treated mice; this was associated with substantial progesterone receptor mRNA levels and with maximum localisation of DB3 antibody as detected by anti-idiotype antibody. Control animals treated with an equal amount of the mouse myeloma protein P3 showed very low levels of progesterone receptor in the uterus. DB3 treatment also affected uterine expression of the proto-oncogene erbA product (which shows primary sequence homology with the progesterone receptor) as revealed by specific antiserum to the ERBA protein and by in situ hybridisation with a cDNA probe to v-erbA. Time-course studies indicated that the erbA gene was expressed at a high level before progesterone receptor expression increased, that its expression was dependent on the presence of the embryo and that erbA expression persisted longer in DB3-treated females. The observations suggest that anti-progesterone immunisation has a direct effect within the uterus, involving persistence of proto-oncogene erbA expression (which itself may represent an early maternal response to pregnancy) and increased progesterone receptor levels resulting from an unopposed oestrogen effect derived from local ligand withdrawal.