Immunogenesis of preeclampsia: lessons from donor gametes

Immunologic aspects of preeclampsia

Preeclampsia is a syndrome with multiple etiologies. The diagnosis can be made without proteinuria in the presence of dysfunction of at least 1 organ associated with hypertension. The common pathophysiological pathway includes endothelial cell activation, intravascular inflammation, and syncytiotrophoblast stress. There is evidence to support, among others, immunologic causes of preeclampsia. Unlike defense immunology, reproductive immunology is not based on immunologic recognition systems of self/non-self and missing-self but on immunotolerance and maternal-fetal cellular interactions. The main mechanisms of immune escape from fetal to maternal immunity at the maternal-fetal interface are a reduction in the expression of major histocompatibility complex molecules by trophoblast cells, the presence of complement regulators, increased production of indoleamine 2,3-dioxygenase, activation of regulatory T cells, and an increase in immune checkpoints. These immune protections are more similar to the immune responses observed in tumor biology than in allograft biology. The role of immune and nonimmune decidual cells is critical for the regulation of trophoblast invasion and vascular remodeling of the uterine spiral arteries. Regulatory T cells have been found to play an important role in suppressing the effectiveness of other T cells and contributing to local immunotolerance. Decidual natural killer cells have a cytokine profile that is favored by the presence of HLA-G and HLA-E and contributes to vascular remodeling. Studies on the evolution of mammals show that HLA-E, HLA-G, and HLA-C1/C2, which are expressed by trophoblasts and their cognate receptors on decidual natural killer cells, are necessary for the development of a hemochorial placenta with vascular remodeling. The activation or inhibition of decidual natural killer cells depends on the different possible combinations between killer cell immunoglobulin-like receptors, expressed by uterine natural killer cells, and the HLA-C1/C2 antigens, expressed by trophoblasts. Polarization of decidual macrophages in phenotype 2 and decidualization of stromal cells are also essential for high-quality vascular remodeling. Knowledge of the various immunologic mechanisms required for adequate vascular remodeling and their dysfunction in case of preeclampsia opens new avenues of research to identify novel biological markers or therapeutic targets to predict or prevent the onset of preeclampsia.

The placenta and preeclampsia: villain or victim?

Preeclampsia is a disease whose characterization has not changed in the 150 years since the cluster of signs associated with the disorder were first described. Although our understanding of the pathophysiology of preeclampsia has advanced considerably since then, there is still little consensus regarding the true etiology of preeclampsia. As a consequence, preeclampsia has earned the moniker "disease of theories," predominantly because the underlying biological mechanisms linking clinical epidemiologic findings to observed organ dysfunction in preeclampsia are far from clear. Despite the lack of cohesive evidence, expert consensus favors the hypothesis that preeclampsia is a primary placental disorder. However, there is now emerging evidence that suboptimal maternal cardiovascular performance resulting in uteroplacental hypoperfusion is more likely to be the cause of secondary placental dysfunction in preeclampsia. Preeclampsia and cardiovascular disease share the same risk factors, preexisting cardiovascular disease is the strongest risk factor (chronic hypertension, congenital heart disease) for developing preeclampsia, and there are now abundant data from maternal echocardiography and angiogenic marker studies that cardiovascular dysfunction precedes the development of preeclampsia by several weeks or months. Importantly, cardiovascular signs and symptoms (hypertension, cerebral edema, cardiac dysfunction) predominate in preeclampsia at clinical presentation and persist into the postnatal period with a 30% risk of chronic hypertension in the decade after birth. Placental malperfusion caused by suboptimal maternal cardiovascular performance may lead to preeclampsia, thereby explaining the preponderance of cardiovascular drugs (aspirin, calcium, statins, metformin, and antihypertensives) in preeclampsia prevention strategies. Despite the seriousness of the maternal and fetal consequences, we are still developing sensitive screening, reliable diagnostic, effective therapeutic, or improvement strategies for postpartum maternal cardiovascular legacy in preeclampsia. The latter will only become clear with an acceptance and understanding of the cardiovascular etiology of preeclampsia.

Outcomes of pregnancies using donor sperm compared with those using partner sperm: systematic review and meta-analysis

BACKGROUND

Registry data from the Human Fertilisation and Embryology Authority (HFEA) show an increase of 40% in IUI and 377% in IVF cases using donor sperm between 2006 and 2016.

OBJECTIVE AND RATIONALE

The objective of this study was to establish whether pregnancies conceived using donor sperm are at higher risk of obstetric and perinatal complications than those conceived with partner sperm. As more treatments are being carried out using donor sperm, attention is being given to obstetric and perinatal outcomes, as events in utero and at delivery have implications for long-term health. There is a need to know if there is any difference in the outcomes of pregnancies between those conceived using donor versus partner sperm in order to adequately inform and counsel couples.

SEARCH METHODS

We performed a systematic review and meta-analysis of the outcomes of pregnancies conceived using donor sperm compared with partner sperm. Searches were performed in the OVID MEDLINE, OVID Embase, CENTRAL and CINAHL databases, including all studies published before 11 February 2019. The search strategy involved search terms for pregnancy, infant, donor sperm, heterologous artificial insemination, donor gametes, pregnancy outcomes and perinatal outcomes. Studies were included if they assessed pregnancies conceived by any method using, or infants born from, donor sperm compared with partner sperm and described early pregnancy, obstetric or perinatal outcomes. The Downs and Black tool was used for quality and bias assessment of studies.

OUTCOMES

Of 3391 studies identified from the search, 37 studies were included in the review and 36 were included in the meta-analysis. For pregnancies conceived with donor sperm, versus partner sperm, there was an increase in the relative risk (RR) (95% CI) of combined hypertensive disorders of pregnancy: 1.44 (1.17-1.78), pre-eclampsia: 1.49 (1.05-2.09) and small for gestational age (SGA): 1.42 (1.17-1.79) but a reduced risk of ectopic pregnancy: 0.69 (0.48-0.98). There was no difference in the overall RR (95% CI) of miscarriage: 0.94 (0.80-1.11), gestational diabetes: 1.49 (0.62-3.59), pregnancy-induced hypertension (PIH): 1.24 (0.87-1.76), placental abruption: 0.65 (0.04-10.37), placenta praevia: 1.19 (0.64-2.21), preterm birth: 0.98 (0.88-1.08), low birth weight: 0.97 (0.82-1.15), high birthweight: 1.28 (0.94-1.73): large for gestational age (LGA): 1.01 (0.84-1.22), stillbirth: 1.23 (0.97-1.57), neonatal death: 0.79 (0.36-1.73) and congenital anomaly: 1.15 (0.86-1.53).

WIDER IMPLICATIONS

The majority of our findings are reassuring, except for the mild increased risk of hypertensive disorders of pregnancy and SGA in pregnancies resulting from donor sperm. However, the evidence for this is limited and should be interpreted with caution because the evidence was based on observational studies which varied in their quality and risk of bias. Further high-quality population-based studies reporting obstetric outcomes in detail are required to confirm these findings.

The role of lymphocytic cells in infertility and reproductive failures in women with antiphospholipid antibodies

Background: The problem of pregnancy losses and infertility in autoimmune pathology is one of the most urgent problems of modern reproductive medicine. Antiphospholipid antibodies (aPL) are very often connected with reproductive failures such as miscarriage, antenatal fetal death, preeclampsia and even infertility and failure of in vitro fertilization (IVF) program.Aim: To evaluate the difference in immune status of aPL-positive women with infertility compared to healthy women and explain the possible mechanism of pathological effects of aPL, a correlation analysis between the level of aPL and the lymphocytes subpopulation was performed.Study design: We observed 280 women of reproductive age. Of these, 191 who met the inclusion and exclusion criteria were included in the study. All 191 women were tested for lupus anticoagulant (LA), antibodies (isotypes IgG, IgM) to cardiolipin (aCL), ß2-glycoprotein-1 (b2-GpI). Of these, 128 women had high level of aPL. The subpopulation of lymphocyte in aPL-positive women was compared with healthy women without reproductive pathology.Results: In women with aPL, the absolute number of CD3⁺ lymphocytes, cytotoxic lymphocytes CD3⁺CD8⁺, T helpers CD3⁺CD4⁺, and the absolute levels of NK-cells and NK T-cells were significantly lower. In women with infertility and aPL circulation, we found the significantly higher absolute and relative level of CD19⁺ lymphocytes compared with healthy women.Conclusion: T-regulatory cells play an important role in inducing tolerance to fetal alloantigens and limiting the intensity of the immune response. NK cells play an important role in processes of trophoblast invasion and spiral artery remodeling. Significantly reduced level of T-cells found in women with aPL may be associated with insufficient decidualization of endometrium for embryo invasion, which is clinically manifested by IVF failure.

Preeclampsia: Acute Complications and Management Priorities

Acute complications of preeclampsia contribute substantially to maternal and fetal morbidity and mortality. The considerable variation in onset, clinical presentation, and severity of this hypertensive disease that is unique to pregnancy creates challenges in identifying risk factors for clinical deterioration. Delivery of the fetus remains the only definitive treatment for preeclampsia. Surveillance of signs and symptoms and laboratory parameters consistent with progression in severity requires an appreciation of the dynamic and progressive nature of the disease. This article provides a comprehensive overview of the pathophysiology of preeclampsia, setting the foundation for discussion of management priorities for acute complications that pose the greatest risks to maternal health.

Immunological Tolerance, Pregnancy, and Preeclampsia: The Roles of Semen Microbes and the Father

Although it is widely considered, in many cases, to involve two separable stages (poor placentation followed by oxidative stress/inflammation), the precise originating causes of preeclampsia (PE) remain elusive. We have previously brought together some of the considerable evidence that a (dormant) microbial component is commonly a significant part of its etiology. However, apart from recognizing, consistent with this view, that the many inflammatory markers of PE are also increased in infection, we had little to say about immunity, whether innate or adaptive. In addition, we focused on the gut, oral and female urinary tract microbiomes as the main sources of the infection. We here marshall further evidence for an infectious component in PE, focusing on the immunological tolerance characteristic of pregnancy, and the well-established fact that increased exposure to the father's semen assists this immunological tolerance. As well as these benefits, however, semen is not sterile, microbial tolerance mechanisms may exist, and we also review the evidence that semen may be responsible for inoculating the developing conceptus (and maybe the placenta) with microbes, not all of which are benign. It is suggested that when they are not, this may be a significant cause of PE. A variety of epidemiological and other evidence is entirely consistent with this, not least correlations between semen infection, infertility and PE. Our view also leads to a series of other, testable predictions. Overall, we argue for a significant paternal role in the development of PE through microbial infection of the mother via insemination.