bims-reprim Biomed News
on Reproductive immunology
Issue of 2020‒12‒20
six papers selected by
Iva Filipovic
Karolinska Institutet

  1. Front Immunol. 2020 ;11 551707
      Innate lymphoid cells (ILCs) are a new set of cells considered to be a part of the innate immune system. ILCs are classified into five subsets (according to their transcription factors and cytokine profile) as natural killer cells (NK cells), group 1 ILCs, group 2 ILCs, group 3 ILCs, and lymphoid tissue inducers (LTi). Functionally, these cells resemble the T helper population but lack the expression of recombinant genes, which is essential for the formation of T cell receptors. In this work, the authors address the distinction between peripheral and decidual NK cells, highlighting their diversity in ILC biology and its relevance to human pregnancy. ILCs are effector cells that are important in promoting immunity, inflammation, and tissue repair. Recent studies have directed their attention to ILC actions in pregnancy. Dysregulation or expansion of pro-inflammatory ILC populations as well as abnormal tolerogenic responses may directly interfere with pregnancy, ultimately resulting in pregnancy loss or adverse outcomes. In this review, we characterize these cells, considering recent findings and addressing knowledge gaps in perinatal medicine in the context of ILC biology. Moreover, we discuss the relevance of these cells not only to the process of immune tolerance, but also in disease.
    Keywords:  inflammation; innate immune response; innate lymphoid cells; pregnancy; preterm birth
  2. Cells. 2020 Dec 16. pii: E2699. [Epub ahead of print]9(12):
      The immune system plays a critical role during pregnancy, but the specific mechanisms and immune cell function needed to support pregnancy remain incompletely understood. Despite decades of research efforts, it is still unclear how the immune system maintains tolerance of fetal-derived tissues, which include most cells of the placenta and of course the fetus itself, without forfeiting the ability to protect against harmful infections. T cells recognize antigen in the context of major histocompatibility complex (MHC) encoded proteins, but classical MHC class I and II expression are diminished in fetal-derived cells. Can T cells present at the maternal-fetal interface (MFI) protect these cells from infection? Here we review what is known in regard to tissue-resident memory T (Trm) cells at the MFI. We mainly focus on how Trm cells can contribute to protection in the context of the unique features of the MFI, such as limited MHC expression as well as the temporary nature of the MFI, that are not found in other tissues.
    Keywords:  MHC class I/II; maternal–fetal interface; placenta; tissue-resident memory T cells
  3. Hum Reprod. 2020 Dec 12. pii: deaa318. [Epub ahead of print]
      STUDY QUESTION: What are the detailed endometrial tissue specific and systemic dendritic cell (DC) subset disturbances in endometriosis?SUMMARY ANSWER: This study confirms myeloid DC (mDC) and plasmacytoid DC subsets are readily identified in endometrial tissue and shows both endometrial and circulating differences in DC populations in women with endometriosis, with disease stage-specific relationships evident locally in the endometrium.
    WHAT IS KNOWN ALREADY: Immune factors in the uterus, the peritoneal environment and systemically are implicated in the pathogenesis and progression of both endometriosis and infertility. While there is some evidence that endometrial DC populations are altered in endometriosis, DC subset involvement in both the endometrium and peripheral blood have not been comprehensively investigated so the functional consequences have been unknown.
    STUDY DESIGN, SIZE, DURATION: This prospective cross-sectional cohort study compares circulating and endometrial DC populations in women of reproductive age with and without endometriosis (n = 55 and 30, respectively), wherein each participant donated samples at a single time point. Study participants were surveyed for menstrual cycle phase, American Society for Reproductive Medicine (ASRM) endometriosis disease stage and fertility status (where possible).
    PARTICIPANTS/MATERIALS, SETTING, METHODS: Peripheral blood samples were processed into mononuclear cells for analysis by flow cytometry, and endometrial samples were analysed by immunohistochemistry and dissociated into single-cell suspension for flow cytometry.
    MAIN RESULTS AND THE ROLE OF CHANCE: In the endometrium of women with endometriosis, IRF-8+ cells were increased during the proliferative phase (P = 0.014), total DC proportions increased in the secretory phase (P = 0.038) and normal menstrual cyclical fluctuations in CD1c+ and IRF-8+ cells blunted; indicative of a consistently inflammatory tissue environment. The inflammatory changes in CD141+ and IRF-8+ populations in the endometrium of women with endometriosis were particularly evident in more advanced ASRM stages of the disease (respective P-values 0.032 and 0.045). There was also evidence of systemic inflammation in women with endometriosis, with increased circulating CD141+ mDC proportions (overall P = 0.040, secretory phase P = 0.021).
    LIMITATIONS, REASONS FOR CAUTION: As is common in this type of study, one of the main limitations was small sample numbers, particularly during the menstrual phase of the cycle.
    WIDER IMPLICATIONS OF THE FINDINGS: Further phenotyping of local and circulating immune cell subtypes is critical to improving understanding of endometriosis pathogenesis and immune contributions to infertility associated with the disease.
    STUDY FUNDING/COMPETING INTEREST(S): This research was financially supported by a Sydney Medical School and Balnaves Foundation Kick Start Grant and the Department of Obstetrics, Gynaecology and Neonatology at The University of Sydney. The authors have no conflicts of interest to declare.
    Keywords:  blood; dendritic cells; endometriosis; endometrium; flow cytometry; immunohistochemistry; inflammation; menstrual cycle
  4. Am J Reprod Immunol. 2020 Dec 14. e13386
      PROBLEM: The Reduced Uterine Perfusion Pressure (RUPP) rat model of placental ischemia recapitulates many characteristics of preeclampsia including maternal hypertension, intrauterine growth restriction (IUGR), and increased cytolytic natural killer cells (cNKs). While we have previously shown a 5-fold higher cytotoxicity of RUPP NKs vs normal pregnant NKs, their role in RUPP pathophysiology remains unclear. In this study, we tested the hypotheses that (1) adoptive transfer of RUPP-stimulated NKs will induce maternal hypertension and IUGR in normal pregnant control (Sham) rats and (2) adoptive transfer of Sham NKs will attenuate maternal hypertension and IUGR in RUPP rats.METHOD OF STUDY: On gestation day (GD)14, vehicle or 5x106 RUPP NKs were infused i.v. into a subset of Sham rats (Sham+RUPP NK), and vehicle or 5x106 Sham NKs were infused i.v. into a subset of RUPP rats (RUPP+Sham NK; n=12/group). On GD18, Uterine Artery Resistance Index (UARI) was measured. On GD19 mean arterial pressure (MAP) was measured, animals were sacrificed, and blood and tissues were collected for analysis.
    RESULTS: Adoptive transfer of RUPP NK cells into Sham rats resulted in elevated NK activation, UARI, placental oxidative stress, and preproendothelin expression as well as reduced circulating nitrate/nitrite. This led to maternal hypertension and IUGR. RUPP recipients of Sham NK cells demonstrated normalized NK activation, sFlt-1, circulating and placental VEGF, and UARI, which led to improved maternal blood pressure and normal fetal growth.
    CONCLUSIONS: These data suggest a direct role for cNKs in causing preeclampsia pathophysiology and a role for normal NKs to improve maternal outcomes and IUGR during late gestation.
    Keywords:  Hypertension; Natural Killer Cells; Preeclampsia; Pregnancy
  5. J Vis Exp. 2020 Nov 24.
      Endometriosis is a leading cause of pelvic pain and infertility. It is defined by the presence of endometrial tissue in extrauterine locations. The development of novel therapies and diagnostic tools for endometriosis has been limited due in part to challenges in studying the disease. Outside of primates, few mammals menstruate, and none develop spontaneous endometriosis. Rodent models are popular but require artificial induction of endometriosis, with many utilizing either immunocompromised mice or surgically induced disease. Recently, more attention has been given to models involving intraperitoneal injection. We present a murine model of endometriosis that integrates several features of existing endometriosis models into a novel, simplified system that relies on microscopic quantification in lieu of subjective grading. In this model, we perform hormonal stimulation of donor mice, intraperitoneal injection, systematic abdominal survey and tissue harvest, and histologic quantification that can be performed and verified at any time after necropsy. This model requires minimal resources and training; does not require expertise by lab technicians in murine survival surgery or in the identification of gross endometriotic lesions; can be used in immunocompromised, immunocompetent, and/or mutant mice; and reliably creates endometriotic lesions that are histologically consistent with human endometriotic disease.
  6. Transplantation. 2020 Dec 10.
      Uterine transplantation (UTx) is a fertility restoring treatment for women with absolute uterine factor infertility. At a time when there is no question of the procedure's feasibility, and as the number of livebirths begins to increase exponentially, various important reproductive, fetal and maternal medicine implications have emerged. Detailed outcomes from 17 livebirths following UTx are now available, which are reviewed herein, along with contextualized extrapolation from pregnancy outcomes in other solid organ transplants. Differences in recipient demographics and reproductive aspirations between UTx and other transplant recipients make extrapolating management strategies and outcomes in other solid organ transplants inappropriate. Whereas preterm delivery remains prominent, small for gestational age or hypertensive disorders do not appear to be as prevalent following UTx when compared to other solid organ transplants. Given the primary objective of undertaking UTx is to achieve a livebirth, publication of reproductive outcomes is essential at this early stage, to reflect upon and optimize the management of future cases.