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Background: Preeclampsia (PE) is a hypertensive disorder of pregnancy defined by new-onset hypertension occurring after 20 weeks of pregnancy, with end organ damage. Pro-inflammatory changes are also observed in these patients. Although the clinical features of PE are resolved soon after delivery, affected patients face a higher risk and earlier onset of cardiovascular disease (CVD). It is unknown what leads to this persistent elevated risk, and long-term alterations of the maternal immune system could be involved. Study objective: Our goal was to address the immune alterations and functional changes in the first year postpartum in PE as compared to normotensive (NT) pregnancies. Hypothesis: We hypothesize that the maternal immune profile is altered in the postpartum period in PE vs NT patients, with a proinflammatory bias and altered function in PE patients. Brief Statement of Methods: We prospectively followed 31 women (PE=15, NT=16) and collected blood 24 hours, and 3, 6, and 12 months postpartum. Plasma and peripheral blood mononuclear cells (PBMC) were isolated and stored for analysis. Inflammatory mediators were quantified through multiplex assays, and PBMCs profile were defined through flow cytometry as well as following inflammatory stimuli to assess their functional changes through intracellular cytokine staining and expression of activation markers. Summary of Results: PE patients had elevated CD3+ T cell frequencies at 3 and 12 months postpartum compared to NT patients. Both groups showed reduced CD14+ monocytes across postpartum timepoints compared with 24 hours. PE was also associated with increased amounts of pro-inflammatory cytokines (such as IL1α, IL9, IFNγ), chemokines and growth factors at multiple timepoints throughout the first year postpartum; NT patients had decreased amounts of pro-inflammatory cytokines. Intracellular staining showed altered immune cell functions in PE, with decreased IL-6 production following polyI:C stimulation and decreased IL-10+ monocytes after LPS and polyI:C at 3 months postpartum. At 3 months, PE patients had increased markers of activation (i.e. CD69+) in both NK cells and T cells, the latter following PMA/Ionomycin stimulation. Statement of Conclusions: Pregnancy itself induces lasting immune changes persisting to 12 months postpartum, even in NT patients, whilst PE complicated pregnancies have sustained inflammation and altered immune function in the postpartum period. Overall, this work will provide essential insight into an understudied period that many women experience and help to identify long lasting immunological changes that could impact long term maternal health. Future work will explore the impact of this sustained inflammation on epigenetic modifications in immune cells. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Abstract Description Preeclampsia (PE) is a complication of pregnancy characterized by de novo hypertension after 20 weeks of gestation with end-organ damage. Even though symptoms of PE rapidly resolve after delivery, patients have higher incidence of cardiovascular diseases in the years postpartum. Immunological changes have been observed in PE but it is unknown if these are sustained in the postpartum period. Our goal was to address the immune changes in the first year postpartum in PE as compared to normotensive (NT) as well as nulliparous women. We saw that both PE and NT pregnancies had altered immune system, especially decreased CD14+ monocytes and increased circulating pro-inflammatory cytokines when compared to nulliparous patients even one year after delivery. Furthermore, our intracellular cytokine staining analysis following stimulation suggest altered response in the postpartum period in PE with a predominant anti-inflammatory response vs NT. Overall this work suggest that the immune system remains different from nulliparous women at 1 year postpartum, even in cases of normotensive pregnancies, and is further altered following PE-complicated pregnancies. Although further analysis is ongoing, this shows that the immune system does not go back to pre-pregnancy levels in the postpartum period and that changes induced by pregnancy are at least in part sustained. We will further expand this work to address the functional changes in immune cells and the mechanisms underlying these changes. Topic Categories Mucosal and Regional Immunology (MUC)

Abstract Background and objective The placenta is crucial for fetal development; altered function is associated with complications and adverse neonatal outcomes. Our goal was to ascertain changes in the placental transcriptome in relation to neonatal outcome and fetal/placental sex. Study design Seventy-two mother-baby dyads were included. Demographic, obstetrical, neonatal, and infant health data were obtained through medical charts. Adverse neonatal outcome was defined as the presence of a pulmonary, cardiac, neurological or other health complication. Bulk RNA-sequencing of placental biopsies was obtained. P-value <0.05 was considered statistically significant. Results Neonates experiencing adverse outcomes were more likely to be premature or have lower birth weights. Analysis of the placental transcriptome revealed a predominant inflammatory profile in pregnancies associated with adverse neonatal outcomes with the top pathways being related to immune and inflammatory responses. Among differently expressed genes (DEGs), 1237 were upregulated and 239 were downregulated in adverse vs no adverse outcomes. Furthermore, sex-specific differences in gene expression were observed and indicated that male and female placentas displayed unique DEGs in association with adverse outcomes. Indeed, no DEG was observed in female placentas when comparing those without vs with adverse neonatal outcomes, as opposed to 1279 DEGs in male placentas, of which 91% were up-regulated in adverse subgroups. Conclusions These findings highlight that inflammatory pathways are upregulated in placentas in association with adverse neonatal outcomes, and showcase the importance of the fetal sex in understanding neonatal health. The placenta provides a unique tool for early identification of high-risk infants rapidly after delivery.

Abstract Pre-eclampsia (PE) affects 5–8% of pregnancies and has detrimental effects on maternal–fetal health. PE is characterized by de novo hypertension after 20 wk of gestation and end-organ damage. Systemic inflammatory imbalance has been associated with PE, but its contribution to the pathology is poorly understood. Our objective was to investigate maternal systemic immune changes in early-onset PE (EOPE) and late-onset PE (LOPE) versus uncomplicated pregnancies (control [CTRL]), and their contribution to endothelial activation, hallmark of hypertension. Blood samples were analyzed by flow cytometry, multiplex assay, intracellular cytokine staining, and single-cell RNA sequencing. We performed cocultures between circulating immune cells and HUVECs to assess endothelial activation. We found that EOPE had decreased regulatory T cells (4.64±0.33, p < 0.05) and monocytes (33.92±3.08, p < 0.01), whereas LOPE had decreased regulatory T cells (4.60±0.30, p < 0.05) and Th2 cells (7.50±0.62, p < 0.01) versus CTRL. Compared to CTRL, elevated cytokines/chemokines, and growth factors were observed in LOPE, whereas EOPE primarily showed decreased levels. Using intracellular cytokine staining, we observed more monocytes producing IL-12, TNF-α, and IL-1β (all p < 0.05) in LOPE versus CTRL. At the transcriptomic level, we found differentially expressed genes between EOPE and CTRL, predominantly related to upregulation of immune activation pathways. Lastly, EOPE PBMCs induced heightened endothelial activation in vitro observed by increased ICAM-1 and ET-1 (p < 0.05), whereas LOPE PBMCs required LPS stimulation. Although significant proteomic changes are observed in the LOPE group, the EOPE displayed changes mostly at the transcriptomic levels and could induce endothelial activation in vitro.

ABSTRACTProblemPreeclampsia (PE) and fetal growth restriction (FGR) are often associated with maternal inflammation and an increased risk of cardiovascular and metabolic disease in the affected mothers. The mechanism responsible for this increased risk of subsequent disease may involve reprogramming of innate immune cells, characterized by epigenetic modifications.Method of StudyCirculating monocytes from women with PE, FGR, or uncomplicated pregnancies (control) were isolated before labor. Cytokine release from monocytes following exposure to lipopolysaccharide (LPS) and the presence of lysine 4‐trimethylated histone 3 (H3K4me3) within TNF promoter sequences were evaluated. Single‐cell transcriptomic profiles of circulating monocytes from women with PE or uncomplicated pregnancies were assessed.ResultsMonocytes from women with PE or FGR exhibited increased IL‐10 secretion and decreased IL‐1β and GM‐CSF secretion in response to LPS. While TNFα secretion was not significantly different in cultures of control monocytes versus those from complicated pregnancies with or without LPS exposure, monocytes from complicated pregnancies had significantly decreased levels of H3K4me3 associated with TNF promoter sequences. Cluster quantification and pathway analysis of differentially expressed genes revealed an increased proportion of anti‐inflammatory myeloid cells and a lower proportion of inflammatory non‐classical monocytes among the circulating monocyte population in women with PE.ConclusionsMonocytes from women with PE and FGR exhibit an immune tolerance phenotype before initiation of labor. Further investigation is required to determine whether this tolerogenic phenotype persists after the affected pregnancy and contributes to increased risk of subsequent disease.

The dynamic immunological changes occurring throughout pregnancy are well-orchestrated and important for the success of the pregnancy. One of the key immune adaptations is the maternal immune tolerance towards the semi-allogeneic fetus. In this review, we provide a comprehensive overview of what is known about the innate and adaptive immunological changes in pregnancy and the role(s) of specific immune cells during physiological and pathological pregnancy. Alongside this, we provided details of remaining questions and challenges, as well as future perspectives for this growing field of research. Understanding the immunological changes that occur can inform potential strategies on treatments for the optimal health of the neonate and pregnant individual both during and after pregnancy.

AbstractProblemIt is now recognized that SARS‐CoV‐2 infection and pandemic‐related stress impacts maternal health. However, their effects at the maternal‐fetal interface are still debated.Method of studyWe recruited 199 women between March 2020 and July 2021, 79 SARS‐CoV‐2+ and 120 negative (the latter exposed to pandemic stress only). We also included 40 historic controls (i.e. pre‐pandemic uncomplicated pregnancies recruited before March 2020). Placental samples were collected for protein and histological analysis.ResultsThe majority of SARS‐CoV‐2+ women were multiethnic, had higher pre‐pregnancy BMI and elevated preterm birth rate (17%) vs SARS‐CoV‐2– or historic control. Placental inflammatory profile revealed increased IL‐1Ra and CRP, independently of SARS‐CoV‐2 status, whilst MCP‐1, IL‐6 and IFNγ were elevated in the negative, but pandemic stress‐exposed, group. These changes were predominant in placentas with inflammatory lesions on histopathological analysis. Furthermore, we observed elevated immune cells (CD45+) in placentas from SARS‐CoV‐2+ and negative pregnancies vs historic controls, even when individuals with pregnancy complications were excluded.ConclusionsPlacental inflammatory profiles differed between SARS‐CoV‐2 statuses, namely exposed to pandemic stress +/‐ SARS‐CoV‐2 infection. This highlights the need to understand the differences between the effects of pandemic‐related stress and the added burden of SARS‐CoV‐2 infection on placental health.

Pregnancy complications including preeclampsia, preterm birth, recurrent pregnancy loss, and fetal growth restriction affect over 12% of all pregnancies worldwide [...]