Successful embryo implantation requires the synchronization of embryo development and uterine preparation. The embryo must have developed to the blastocyst stage and the endometrium must be in a receptive phase. Wilcox et al1 have estimated that 65% of conceptions end in unrecognized losses....

During pregnancy some cells traffic between the fetus and mother and recent studies indicate low levels persist in the respective hosts decades later. Microchimerism (Mc) refers to a small population of cells or DNA harbored by one individual that derive from a genetically distinct individual....

The hypothalamic neuropeptide corticotropin-releasing hormone (CRH), as well as its receptors, have been identified in several reproductive organs, including the endometrial glands, the decidualized endometrial stroma and the placental trophoblast, synctiotrophoblast and decidua.1-9...

The unusual tolerance against fetal antigens is still one of the greatest miracles of pregnancy. Dealing with reproductive immunology, the question arises as to how the maternal immune system handles the foreign fetal antigens leading to that tolerance. Focussing on the various subsets of...

The mechanisms of acceptance of the fetus by the maternal immune system are mediated in part by immunomodulatory proteins expressed by placental cells. The recent discovery of novel members of the B7 family of immunomodulators has prompted much excitement among the scientific community because...

Infertility and pregnancy wastage affect one of every nine couples in Western Europe and in the United States. The molecular events of embryonic attachment to the endometrial epithelium and subsequent invasion and nidation into the stroma have long been of interest, scientifically to...

Phylogenetic analysis suggests that the internalization of reproduction and the develop ment of hemochorial placentation have been accompanied by conservation of primitive genitourinary genes. The products include the renin-angiotensin system and the innate immune system. This explains what...

Pregnancy loss is the one of the most common obstetrical complications. The majority of pregnancy losses are random or isolated incidences that in many cases are related to genetic abnormalities. However, 2-5 % of reproductive age women experience recurrent miscarriages.1,2 Recurrent pregnancy...

The maternal-fetal interface represents an immunologically unique site that must promote tolerance to the allogenic fetus, whilst maintaining host defense against a diverse array of possible pathogens. Clinical studies have shown a strong association between certain pregnancy complications and...

Apoptosis occurs in the villous trophoblast of normal placentas throughout pregnancy, but with higher frequency near term in comparison to the first trimester. In pregnancies complicated by preeclampsia or intrauterine growth restriction (IUGR), a greater incidence of villous and extravillous...

During implantation, apoptosis is critical for the appropriate tissue remodeling of the maternal decidua and invasion of the developing embryo. Yet the regulation of apoptosis is also imperative for a successful pregnancy. The quick and effective removal of apoptotic cells by tissue...

Although the etiology of intrauterine growth restriction (IUGR) and preeclampsia (PE) remains unclear, most investigators attribute the initial “insult” to poor utero-placental perfusion due to defective trophoblast invasion that ultimately compromises fetal well-being.1-3 The resultant...

Maternal immune tolerance to paternal allo-antigens expressed by the fetus is a precondition of successful pregnancy in viviparous mammals. This occurs despite exposure of the maternal immune system to potentially immunogenic fetal tissue. Local immune evasion mechanisms are thought to prevent...

All sexually reproducing organisms produce gametes that must be protected from immune challenge. Recent data indicates that the majority of the carbohydrate sequences that coat the murine zona pellucida are also upregulated on activated lymphocytes, and some participate in gamete binding. This...

The immunological paradox of mammalian pregnancy is the acceptance of the fetus, a semiallogeneic allograft that normally should provoke an immune response of the maternal T cells leading to fetal rejection. In this chapter the current understanding of decidual T-cell immunobiology is...

The mechanisms of protection of the allogeneic fetus from the maternal immune response during pregnancy remain mysterious more than fifty years after the paradox of maternal tolerance was first raised by Peter Medawar. Preimplantation embryos express paternal antigens early in development....

Soon after the principles of nonself immunological recognition were discovered, it was realized that the state of pregnancy seemingly presents a paradox. In an outbreed popula tion, half of the fetal genes are paternal, thus the fetus may be considered a semi-allograft. Yet, unlike the outcome...

To describe the clinical findings and implications of leukemia inhibitory factor (LIF) in human reproduction. Leukemia inhibitory factor (LIF) is a pleiotropic cytokine of the interleukin-6 family and has different biological actions in various tissue systems. Although named for its ability to...

Embryo implantation is critically dependent on a supportive uterine environment. Uter ine receptivity is the culmination of a cellular and molecular transformation mediated locally by paracrine signals under the governance of ovarian steroid hormones, with cells and cytokines of the immune...

Viviparity remains an immunological paradox despite increased knowledge of immunological processes that occur during mammalian pregnancy. The maternal immune system protects both mother and fetus from invading pathogens during gestation, but also has to maintain immunological tolerance towards...

Natural killer cells are found in large numbers in the endometrium and decidua, and data suggest that NK cell functions and interactions with fetal-derived trophoblasts can have a profound impact on pregnancy. Altered NK cell numbers and activity have been associated with a variety of clinical...

Inherited thrombophilias are a heterogeneous group of conditions which have been associated with a variety of pregnancy complications, including early and late fetal loss, intrauterine growth restriction, abruptio placentae, and preeclampsia.1 As the functional significance of the burgeoning...

Cases of recurrent abortions, preeclampsia or babies born with hemolytic diseases of the new born, still puzzle us with the question “Why did your mother reject you?” Although, after looking at the complexity of the maternal-fetal immune interaction and the cases of successful pregnancies,...