Antigen-specific decidual CD8+ T cells include distinct effector memory and tissue-resident memory cells

Decidualization-associated recruitment of cytotoxic memory CD8+T cells to the maternal-fetal interface for immune defense

Decidual CD8+T (dCD8+T) cells are pivotal in the maintenance of the delicate balance between immune tolerance towards the fetus and immune resistance against pathogens. The endometrium and decidua represent the uterine environments before and during pregnancy, respectively, yet the composition and phenotypic alterations of uterine CD8+T cells in these tissues remain unclear. Using flow cytometry and analysis of transcriptome profiles, we demonstrated that human dCD8+T and endometrial CD8+T (eCD8+T) cells exhibited similar T cell differentiation statuses and phenotypes of tissue infiltrating or residency, compared to peripheral CD8+T (pCD8+T) cells. However, dCD8+T cells showed decreased expression of coinhibitory marker (PD-1), chemotaxis marker (CXCR3), and tissue-resident markers (CD69 and CD103), along with increased expression of granzyme B and granulysin, compared to eCD8+T cells. In vitro cytotoxicity assays further demonstrated that dCD8+T cells had greater effector functions than eCD8+T cells. Additionally, both in vitro and in vivo chemotaxis assays confirmed the recruitment of non-resident effector memory T cell subsets to the pregnant decidua, contributing to the dCD8+T cell-mediated anti-infection mechanism at the maternal-fetal interface. This work demonstrates dCD8+T cells replenished from the circulation retain their cytotoxic capacity, which may serve as an enhanced defense mechanism against infection during pregnancy.

Zika virus-induced fetal demise is driven by strain- and dose-specific RLR-driven activation of the interferon response in the decidua, placenta, and fetus in Ifnar1 -/- mice

Congenital Zika syndrome (CZS), the set of fetal and neonatal complications associated with Zika virus (ZIKV) infection in pregnancy, was first noted during the outbreak in the Americas in 2015-16. However, there was an unequal distribution of ZIKV cases and severe outcomes in all areas where ZIKV emerged in the Americas, demonstrating that the risk of CZS varied over space and time. Recently, we demonstrated that phenotypic heterogeneity existed between closely-related ZIKV strains. All ZIKV strains tested infected the placenta but varied in their capacity to cause overt fetal harm. Here, we further characterized the relative contributions of virus genotype and infecting dose of two phenotypically distinct ZIKV strains across multiple timepoints in gestation in pregnant mice that lack type-I interferon receptor function ( Ifnar1 -/- ). To better understand the underlying causes of adverse fetal outcomes, we used RNA sequencing to compare ZIKV-infected and uninfected tissues. We found that ZIKV infection triggers retinoic acid-inducible gene I (RIG-I)-like receptor-mediated activation of the interferon response at the maternal-fetal interface. However, modest chemical inhibition of RIG-I activation in the decidua and placenta did not protect against fetal demise. Instead, the fetal interferon response was significantly associated with fetal demise. Together, these findings suggest that the response to ZIKV at the maternal-fetal interface can vary depending on the infecting ZIKV genotype and dose, and that the fetal immune response is an important mediator of fetal harm.

IMPORTANCE

Previously, we used a mouse model of ZIKV infection during pregnancy to assess the pathogenic potential to the fetus of a panel of five, low-passage ZIKV strains representing the viral genetic diversity in the Americas. We found that phenotypic heterogeneity existed between these closely-related ZIKV strains. Here, we show that this heterogeneity is driven by retinoic acid-inducible gene I (RIG-I)-like receptor-mediated activation of the interferon response at the maternal-fetal interface. We used chemical inhibition of the RIG-I pathway and measured the transcriptional activity of interferon stimulated genes in fetuses to demonstrate that the fetal immune response may contribute to fetal demise.

Converging cytokine and metabolite networks shape asymmetric T cell fate at the term human maternal-fetal interface

Placentation presents immune conflict between mother and fetus, yet in normal pregnancy maternal immunity against infection is maintained without expense to fetal tolerance. This is believed to result from adaptations at the maternal-fetal interface (MFI) which affect T cell programming, but the identities (i.e., memory subsets and antigenic specificities) of T cells and the signals that mediate T cell fates and functions at the MFI remain poorly understood. We found intact recruitment programs as well as pro-inflammatory cytokine networks that can act on maternal T cells in an antigen-independent manner. These inflammatory signals elicit T cell expression of co-stimulatory receptors necessary for tissue retention, which can be engaged by local macrophages. Although pro-inflammatory molecules elicit T cell effector functions, we show that additional cytokine (TGF-β1) and metabolite (kynurenine) networks may converge to tune T cell function to those of sentinels. Together, we demonstrate an additional facet of fetal tolerance, wherein T cells are broadly recruited and restrained in an antigen-independent, cytokine/metabolite-dependent manner. These mechanisms provide insight into antigen-nonspecific T cell regulation, especially in tissue microenvironments where they are enriched.

Immunological regulation and the role of autophagy in preeclampsia

Autophagy is a bulk degradation system that maintains cellular homeostasis by producing energy and/or recycling excess proteins. During early placentation, extravillous trophoblasts invade the decidua and uterine myometrium, facing maternal immune cells, which participate in the immune suppression of paternal and fetal antigens. Regulatory T cells will likely increase in response to a specific antigen before and during early pregnancy. Insufficient expansion of antigen-specific Treg cells, which possess the same T cell receptor, is associated with the pathophysiology of preeclampsia, suggesting sterile systemic inflammation. Autophagy is involved in reducing inflammation through the degradation of inflammasomes and in the differentiation and function of regulatory T cells. Autophagy dysregulation induces protein aggregation in trophoblasts, resulting in placental dysfunction. In this review, we discuss the role of regulatory T cells in normal pregnancies. In addition, we discuss the association between autophagy and regulatory T cells in the development of preeclampsia based on reports on the role of autophagy in autoimmune diseases.