Immunobiology of Acute Chorioamnionitis.

Acute chorioamnionitis is characterized by neutrophilic infiltration and inflammation at the maternal fetal interface. It is a relatively common complication of pregnancy and can have devastating consequences including preterm labor, maternal infections, fetal infection/inflammation, fetal lung, brain, and gastrointestinal tract injury. In this review, we will discuss current understanding of the pathogenesis, immunobiology, and mechanisms of this condition. Most commonly, acute chorioamnionitis is a result of ascending infection with relatively low-virulence organisms such as the Ureaplasma species. Furthermore, recent vaginal microbiome studies suggest that there is a link between vaginal dysbiosis, vaginal inflammation, and ascending infection. Although less common, microorganisms invading the maternal-fetal interface via hematogenous route (e.g., Zika virus, Cytomegalovirus, and Listeria) can cause placental villitis and severe fetal inflammation and injury. We will provide an overview of the knowledge gleaned from different animal models of acute chorioamnionitis and the role of different immune cells in different maternal-fetal compartments. Lastly, we will discuss how infectious agents can break the maternal tolerance of fetal allograft during pregnancy and highlight the novel future therapeutic approaches

In vivo activation of invariant natural killer T cells induces systemic and local alterations in Tâ cell subsets prior to preterm birth

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137689/1/cei12968.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137689/2/cei12968_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137689/3/cei12968-sup-0001-suppinfo1.pd

The Role Of Alarmins, Invariant Nkt Cells And Senescence In The Pathophysiology Of Sterile Intra-Amniotic Inflammation

Preterm birth is defined as the delivery of a live baby prior to the 37th week of gestation. It is the leading cause of neonatal mortality worldwide. Preterm neonates are at a higher risk for short- and long-term complications, and prematurity places significant burden on our society. Elucidation of the mechanisms that lead to spontaneous preterm labor will enable development of therapies to prevent this syndrome. We aimed to study pathological inflammation that is implicated in the pathophysiology of spontaneous preterm labor. Pathological inflammation can be initiated by the activation of innate immunity either by microorganisms or alarmins, which are endogenous danger signals derived cellular stress or injury. The inflammatory process initiated by alarmins in the amniotic cavity is referred to as sterile intraamniotic inflammation because it occurs in the absence of detectable microbial infection. Sterile intra-amniotic inflammation is more common than microbial-associated intra-amniotic inflammation in patients with intact chorioamniotic membranes who undergo spontaneous preterm labor, and administration of such alarmins as IL1α or HMGB1 was shown to induce preterm birth. Our major aim was to determine whether HMGB1 and three additional alarmins (S100A12, monosodium urate, and HSP70) are capable of inducing sterile inflammation of the chorioamniotic membranes and by what molecular mechanism. Our findings show that HMGB1, S100A12, monosodium urate, and HSP70 greatly increase secretion of pro-inflammatory cytokine IL-1β from the chorioamniotic membranes and up-regulate other pro-inflammatory pathways leading to collagen remodeling and synthesis of labor promoting enzyme prostaglandin synthase 2. We also found that activation of iNKT cells, which was shown to occur via stimulation with alarmins, induces preterm birth in mice by activating CD4+ and CD8+ T cells as well as innate immune cells and by establishing pro-inflammatory microenvironment at the maternal-fetal interface. We also identified rosiglitazone, an anti-inflammatory drug that dampens iNKT-dependent inflammation, as a potent treatment for preterm labor in mice. Finally, our data demonstrates that preterm labor is associated with dysregulated expression of senescence-associated genes and accumulation of senescence markers. Cellular senescence is characterized by release of pro-inflammatory mediators, including alarmins, and thus may provide a source of inflammatory signaling in a subset of patients who undergo preterm parturition

Macrophages exert homeostatic actions in pregnancy to protect against preterm birth and fetal inflammatory injury

Macrophages are commonly thought to contribute to the pathophysiology of preterm labor by amplifying inflammation — but a protective role has not previously been considered to our knowledge. We hypothesized that given their antiinflammatory capability in early pregnancy, macrophages exert essential roles in maintenance of late gestation and that insufficient macrophages may predispose individuals to spontaneous preterm labor and adverse neonatal outcomes. Here, we showed that women with spontaneous preterm birth had reduced CD209⁺CD206⁺ expression in alternatively activated CD45⁺CD14⁺ICAM3⁻ macrophages and increased TNF expression in proinflammatory CD45⁺CD14⁺CD80⁺HLA-DR⁺ macrophages in the uterine decidua at the materno-fetal interface. In Cd11b(DTR/DTR) mice, depletion of maternal CD11b⁺ myeloid cells caused preterm birth, neonatal death, and postnatal growth impairment, accompanied by uterine cytokine and leukocyte changes indicative of a proinflammatory response, while adoptive transfer of WT macrophages prevented preterm birth and partially rescued neonatal loss. In a model of intra-amniotic inflammation–induced preterm birth, macrophages polarized in vitro to an M2 phenotype showed superior capacity over nonpolarized macrophages to reduce uterine and fetal inflammation, prevent preterm birth, and improve neonatal survival. We conclude that macrophages exert a critical homeostatic regulatory role in late gestation and are implicated as a determinant of susceptibility to spontaneous preterm birth and fetal inflammatory injury.Nardhy Gomez-Lopez, Valeria Garcia-Flores, Peck Yin Chin, Holly M. Groome, Melanie T. Bijland, Kerrilyn R. Diener, Roberto Romero, and Sarah A. Robertso

The Role of Type I and Type II NKT Cells in Materno-Fetal Immunity

NKT cells represent a small but significant immune cell population as being a part of and bridging innate and adaptive immunity. Their ability to exert strong immune responses via cytotoxicity and cytokine secretion makes them significant immune effectors. Since pregnancy requires unconventional maternal immunity with a tolerogenic phenotype, investigation of the possible role of NKT cells in materno-fetal immune tolerance mechanisms is of particular importance. This review aims to summarize and organize the findings of previous studies in this field. Data and information about NKT cells from mice and humans will be presented, focusing on NKT cells characteristics during normal pregnancy in the periphery and at the materno-fetal interface and their possible involvement in female reproductive failure and pregnancy complications with an immunological background

Decidual Neutrophil Infiltration Is Not Required for Preterm Birth in a Mouse Model of Infection-Induced Preterm Labor

Parturition is associated with a leukocyte influx into the intrauterine tissues; however, the exact role these leukocytes play in the onset of labor remains unclear. Neutrophil infiltration of the uteroplacental tissues has been particularly associated with infection-associated preterm labor (PTL) in both women and mouse models. In this study, we investigated the role of neutrophils in a mouse model of infection-induced PTL. Intrauterine administration of LPS on day 17 of gestation resulted in a 7-fold increase in the number of decidual neutrophils compared with control mice receiving PBS (p < 0.01; n = 8–11). We hypothesized that neutrophil influx is necessary for PTL and that neutrophil depletion would abolish preterm birth. To test this hypothesis, mice were depleted of neutrophils by treatment with anti–Gr-1, anti–Ly-6G, or the appropriate IgG control Ab on day 16 of gestation prior to LPS on day 17 (n = 6–7). Successful neutrophil depletion was confirmed by flow cytometry and immunohistochemistry. Neutrophil depletion with Gr-1 resulted in reduced uterine and placental Il-1β expression (p < 0.05). Neutrophil depletion with Ly-6G reduced uterine Il-1β and Tnf-α expression (p < 0.05). However, neutrophil depletion with either Ab did not delay LPS-induced preterm birth. Collectively, these data show that decidual neutrophil infiltration is not essential for the induction of infection-induced PTL in the mouse, but that neutrophils contribute to the LPS-induced inflammatory response of the uteroplacental tissues

Targeting Toll-like receptor-4 to tackle preterm birth and fetal inflammatory injury

Every year, 15 million pregnancies end prematurely, resulting in more than 1 million infant deaths and long-term health consequences for many children. The physiological processes of labour and birth involve essential roles for immune cells and pro-inflammatory cytokines in gestational tissues. There is compelling evidence that the mechanisms underlying spontaneous preterm birth are initiated when a premature and excessive inflammatory response is triggered by infection or other causes. Exposure to pro-inflammatory mediators is emerging as a major factor in the 'fetal inflammatory response syndrome' that often accompanies preterm birth, where unscheduled effects in fetal tissues interfere with normal development and predispose to neonatal morbidity. Toll-like receptors (TLRs) are critical upstream gatekeepers of inflammatory activation. TLR4 is prominently involved through its ability to sense and integrate signals from a range of microbial and endogenous triggers to provoke and perpetuate inflammation. Preclinical studies have identified TLR4 as an attractive pharmacological target to promote uterine quiescence and protect the fetus from inflammatory injury. Novel small-molecule inhibitors of TLR4 signalling, specifically the non-opioid receptor antagonists (+)-naloxone and (+)-naltrexone, are proving highly effective in animal models for preventing preterm birth induced by bacterial mimetic LPS, heat-killed Escherichia coli, or the TLR4-dependent pro-inflammatory lipid, platelet-activating factor (PAF). Here, we summarise the rationale for targeting TLR4 as a master regulator of inflammation in fetal and gestational tissues, and the potential utility of TLR4 antagonists as candidates for preventative and therapeutic application in preterm delivery and fetal inflammatory injury.Sarah A Robertson, Mark R Hutchinson, Kenner C Rice, Peck-Yin Chin, Lachlan M Moldenhauer, Michael J Stark, David M Olson, Jeffrey A Keela

The role of innate lymphoid cells in mucosal inflammation in paediatric viral bronchiolitis

Background Human respiratory syncytial virus (RSV) is the most common cause of bronchiolitis and acute lower respiratory tract infections (LRTI) among children worldwide. RSV is the leading cause of childhood hospitalisation and a financial burden on national health systems. No vaccine that protects against RSV infection is available. Children with bronchiolitis are at high risk of developing wheeze and asthma later in childhood. Recent data suggest that innate immunity plays a vital role in childhood, especially when maternal antibodies' levels are low and adaptive immune responses are immature. Innate lymphoid cells (ILCs) are among the most recently discovered innate immune cell types that could play a pivotal role in innate responses to RSV bronchiolitis. ILCs have been classified into three groups: ILC1, ILC2 and ILC3 depending on their function, transcription factor expression and phenotype. Although ILC2 numbers have been found to be elevated in bronchiolitis, the phenotypic and functional differences between ILCs from healthy infants and those with bronchiolitis have not been explored. Hypothesis I propose that ILC frequencies and function are associated with disease severity and aetiology in children with acute lower respiratory tract infection. Sub-hypothesis 1 ILCs from neonates are functionally different from healthy adult subjects. Sub-hypothesis 2 Alterations in ILC frequencies and numbers in blood and airway samples are associated with disease severity, pathogen type and load. Sub-hypothesis 3 Alterations in ILC function are associated with disease severity, pathogen type and load. Methods To determine differences in ILCs in early life, lymphocyte populations, including ILC subset frequencies and numbers in blood samples collected from adults and neonates were investigated by flow cytometry. To study ILCs in bronchiolitis, blood and upper and lower airway samples were collected from infants with and without a respiratory viral infection. An optimised multicolour immunophenotyping panel (OMIP), intracellular staining panels (ICS) and other systems of analytical approach such as UMAP (Uniform Manifold Approximation and Projection), heatmaps, correlograms and principal component analysis (PCA) were used. ILCs were defined using the following gating strategy: live, single, CD45+, lineage negative (CD3, CD14, CD16, CD56, CD1a, CD123 FcεR1α)- and CD127+ cells. ILC1 cells were defined as CD117−CRTH2−, ILC2 cells were defined as CRTH2+ CD117int and ILC3s were defined as CD117+CRTH2−. At the same time, other lymphocyte and granulocyte populations were enumerated. Alongside cellular work, using the Meso Scale Discovery (MSD) platform, 29 immune mediators and cytokines were measured in airway samples. Results I successfully optimised flow cytometry panels to determine frequencies and function of ILCs in small volumes of difficult to obtain clinical samples. Results suggest that ILC numbers were higher in whole blood obtained from neonates compared to healthy adults (P=0.0032), however, they produced significantly less IFN-γ (P=0.0015). Furthermore, there were significantly lower numbers of NKT (P=0.0001) and MAIT cells (P=0.0031) in neonates compared to healthy adults. In bronchiolitis, ILC numbers were significantly decreased in peripheral blood (P=0.005) and airways samples (P=0.025) obtained from bronchiolitic compared to control subjects; however, their capacity for IFN-γ production was similar between those groups. Interestingly, there was a significantly decreased production of IFN-γ in CD4+ (P=0.042) and CD8+ T cells (P=0.006) from bronchiolitic compared to control patients. Finally, levels of almost all mediators were higher in bronchiolitic babies than controls, including both type-1, type-2 and type-17 associated cytokines. Only IL-4 production in lower and upper airways was increased in rhinovirus- (RV) but not RSV-associated bronchiolitis (P=0.006). Conclusions Small volumes of whole blood and paediatric respiratory samples can be used for enumerating ILCs (NK cells, ILC1, ILC2, ILC3), granulocytes (eosinophils and neutrophils), T – cells (CD4+ and CD8+), MAIT cells and NKT-like cells. The comparison of neonate and adult functional responses suggests that innate lymphoid cells are mature in early life and might play a pivotal role in the neonatal type-2 bias via the production of IL-13. Bronchiolitis was characterised not only by CD3+ T cell but also by CD3- lymphopenia. ILCs numbers were much lower in infants with bronchiolitis compared to healthy controls; however, ILC had the ability to produce IFN-γ. My data suggest that RSV and RV can lead to different phenotypes of bronchiolitis. Finally, I demonstrated the importance of studying the lower and upper airways simultaneously, discovering that inflammatory signatures were different between these two compartments. For the first time all members of the ILC family were studied in viral bronchiolitis. Determining why some infants develop bronchiolitis and the pathogenesis of lower airway disease in infants could lead to a better understanding of early life immunity and the development of new biomarkers and clinical prophylactics.Open Acces