Corrigendum: Dynamics of host immune response development during Schistosoma mansoni infection.

[This corrects the article DOI: 10.3389/fimmu.2022.906338.].

Comparative phenotype of circulating versus tissue immune cells in human lung and blood compartments during health and disease.

The lung is a dynamic mucosal surface constantly exposed to a variety of immunological challenges including harmless environmental antigens, pollutants, and potentially invasive microorganisms. Dysregulation of the immune system at this crucial site is associated with a range of chronic inflammatory conditions including asthma and Chronic Pulmonary Obstructive Disease (COPD). However, due to its relative inaccessibility, our fundamental understanding of the human lung immune compartment is limited. To address this, we performed flow cytometric immune phenotyping of human lung tissue and matched blood samples that were isolated from 115 donors undergoing lung tissue resection. We provide detailed characterization of the lung mononuclear phagocyte and T cell compartments, demonstrating clear phenotypic differences between lung tissue cells and those in peripheral circulation. Additionally, we show that CD103 expression demarcates pulmonary T cells that have undergone recent TCR and IL-7R signalling. Unexpectedly, we discovered that the immune landscape from asthmatic or COPD donors was broadly comparable to controls. Our data provide a much-needed expansion of our understanding of the pulmonary immune compartment in both health and disease.

Dynamics of Host Immune Response Development During Schistosoma mansoni Infection.

Schistosomiasis is a disease of global significance, with severity and pathology directly related to how the host responds to infection. The immunological narrative of schistosomiasis has been constructed through decades of study, with researchers often focussing on isolated time points, cell types and tissue sites of interest. However, the field currently lacks a comprehensive and up-to-date understanding of the immune trajectory of schistosomiasis over infection and across multiple tissue sites. We have defined schistosome-elicited immune responses at several distinct stages of the parasite lifecycle, in three tissue sites affected by infection: the liver, spleen, and mesenteric lymph nodes. Additionally, by performing RNA-seq on the livers of schistosome infected mice, we have generated novel transcriptomic insight into the development of schistosome-associated liver pathology and fibrosis across the breadth of infection. Through depletion of CD11c+ cells during peak stages of schistosome-driven inflammation, we have revealed a critical role for CD11c+ cells in the co-ordination and regulation of Th2 inflammation during infection. Our data provide an updated and high-resolution account of how host immune responses evolve over the course of murine schistosomiasis, underscoring the significance of CD11c+ cells in dictating host immunopathology against this important helminth infection.

Mapping the Influence of the Gut Microbiota on Small Molecules across the Microbiome Gut Brain Axis.

Microbes exert influence across the microbiome-gut-brain axis through neurotransmitter production, induction of host immunomodulators, or the release or induction of other microbial or host molecules. Here, we used mass spectrometry imaging (MSI), a label-free imaging tool, to map molecular changes in the gut and brain in germ-free, antibiotic-treated and control mice. We determined spatial distribution and relative quantification of neurotransmitters and their precursors in response to the microbiome. Using untargeted MSI, we detected a significant change in the levels of four identified small molecules in the brains of germ-free animals compared to controls. However, antibiotic treatment induced no significant changes in these same metabolites in the brain after 1 week of treatment. This work exemplifies the utility of MSI as a tool for the study of known and discovery of novel, mediators of microbiome-gut-brain axis communication.

Plasmacytoid Dendritic Cells Facilitate Th Cell Cytokine Responses throughout Schistosoma mansoni Infection.

Plasmacytoid dendritic cells (pDCs) are potent producers of type I IFN (IFN-I) during viral infection and respond to IFN-I in a positive feedback loop that promotes their function. IFN-I shapes dendritic cell responses during helminth infection, impacting their ability to support Th2 responses. However, the role of pDCs in type 2 inflammation is unclear. Previous studies have shown that pDCs are dispensable for hepatic or splenic Th2 responses during the early stages of murine infection with the trematode Schistosoma mansoni at the onset of parasite egg laying. However, during S. mansoni infection, an ongoing Th2 response against mature parasite eggs is required to protect the liver and intestine from acute damage and how pDCs participate in immune responses to eggs and adult worms in various tissues beyond acute infection remains unclear. We now show that pDCs are required for optimal Th2 cytokine production in response to S. mansoni eggs in the intestinal-draining mesenteric lymph nodes throughout infection and for egg-specific IFN-γ at later time points of infection. Further, pDC depletion at chronic stages of infection led to increased hepatic and splenic pathology as well as abrogated Th2 cell cytokine production and activation in the liver. In vitro, mesenteric lymph node pDCs supported Th2 cell responses from infection-experienced CD4+ T cells, a process dependent on pDC IFN-I responsiveness, yet independent of Ag. Together, these data highlight a previously unappreciated role for pDCs and IFN-I in maintaining and reinforcing type 2 immunity in the lymph nodes and inflamed tissue during helminth infection.

Women's engagement, views and experiences of postnatal follow-up after gestational diabetes mellitus in pregnancy.

BACKGROUND: The evidence base relating to women's engagement and experiences of postnatal care following Gestational Diabetes Mellitus in the United Kingdom is limited. Additionally, the uptake of a postnatal fasting blood glucose testing following Gestational Diabetes Mellitus appears to be poor. OBJECTIVE: This study aimed to explore women's engagement, views and experiences of postnatal care following Gestational Diabetes Mellitus in the United Kingdom. DESIGN AND PARTICIPANTS: An online survey of participants that had Gestational Diabetes Mellitus was undertaken to gather mixed-methods data regarding women's engagement, views and experiences of postnatal care. Demographic data were also collected. FINDINGS: A total of 31 participants completed the online survey; respondents were from two countries in the United Kingdom only (England and Wales). Some respondents indicated positive postnatal experiences following Gestational Diabetes Mellitus (such as good family support) with effective communication by some healthcare teams and screening coinciding with engagement with the routine six week follow-up appointment. Overall, findings indicated a general dissatisfaction with the care provided, mostly due to the inconsistency of information and advice in relation to the type of screening test and the timing, location and organisation of blood glucose screening and follow up care. CONCLUSION: This study provides an insight into ways that may improve women's engagement, views and experiences of postnatal care following Gestational Diabetes Mellitus in England and Wales. IMPLICATIONS FOR PRACTICE: Findings indicate a lack of consistent adherence to national guidance. A clear care pathway facilitating continuity of care for women in the postnatal period following Gestational Diabetes Mellitus, along with further education and support for health professionals, may improve the provision of postnatal care. The authors recognise the limitations of this small standalone study however, findings highlight the need for further exploration of postnatal follow up following Gestational Diabetes Mellitus in the UK.

Defined Intestinal Regions Are Drained by Specific Lymph Nodes That Mount Distinct Th1 and Th2 Responses Against Schistosoma mansoni Eggs.

The balance of type 1 and type 2 immune responses plays a crucial role in anti-helminth immunity and can either support chronic infection or drive type 2 mediated expulsion of the parasite. Helminth antigens and secreted molecules directly influence this balance and induce a favorable immunological environment for the parasite's survival. However, less is known if the site of infection also influences the balance of type 1 and type 2 immunity. Here, we report that tissue-specific immune responses are mounted against helminth antigens, which elicited strong IL-4 responses when injected into the skin, while the same antigen, delivered into the intestinal subserosa, induced increased IFN-γ and reduced Th2 responses. Immune responses in individual mesenteric lymph nodes that drain defined regions of the intestine furthermore displayed a site-specific pattern of type 1 and type 2 immunity after Schistosoma mansoni or Heligmosomoides polygyrus infection. S. mansoni egg-specific Th2 responses were detectable in all mesenteric lymph nodes but Th1 responses were only present in those draining the colon, while H. polygyrus infection elicited mixed Th1 and Th2 responses in the lymph nodes associated with the site of infection. Similar site-specific type 1 and type 2 immune responses were observed in the draining lymph nodes after the controlled delivery of S. mansoni eggs into different segments of the small and large intestine using microsurgical techniques. Different subsets of intestinal dendritic cells were hereby responsible for the uptake and priming of Th1 and Th2 responses against helminth antigens. Migratory CD11b+CD103- and especially CD11b+CD103+ DC2s transported S. mansoni egg antigens to the draining lymph nodes to induce Th1 and Th2 responses, while CD103+ DC1s induced only IFN-γ responses. In contrast, H. polygyrus antigens were predominantly transported by CD11b+CD103- DC2s and CD103+ DC1s and all DC subsets induced similar Th1 but weaker Th2 responses, compared to S. mansoni egg antigens. The development of adaptive anti-helminth immune responses is therefore influenced by the antigen itself, the uptake and priming characteristics of antigen-positive dendritic cell subsets and the site of infection, which shape the level of Th1 and Th2 responses in order to create a favorable immunological environment for the parasite.

Improving Evaluation and Treatment of Hyperbilirubinemia in Late Preterm Infants.

Late preterm (LPT) infants are at an increased risk for hyperbilirubinemia. Accurate identification and early treatment are needed for optimal health outcomes. In a newborn nursery at an academic medical center, bilirubin levels were drawn at 24 hours of life, per protocol. These infants were rarely treated at this time. Rather, predischarge bilirubin levels (at about 48 hours of life) would indicate treatment, often leading to increased length of hospital stay. The practice change evaluation was conducted using retrospective medical record review. Practice change to test serum bilirubin levels at 36 hours of life rather than 24 hours of life. Compliance with the practice change was achieved (P < .05). More LPT infants were identified and treated for hyperbilirubinemia without an increase in length of stay. Readmissions for hyperbilirubinemia and blood draw rates also declined. Although more LPT infants were identified and treated for hyperbilirubinemia, there is room for improvement, and increased adherence to the policy might yield an even greater impact on quality and safety of care surrounding bilirubin management.

Microbiome-derived carnitine mimics as previously unknown mediators of gut-brain axis communication.

Alterations to the gut microbiome are associated with various neurological diseases, yet evidence of causality and identity of microbiome-derived compounds that mediate gut-brain axis interaction remain elusive. Here, we identify two previously unknown bacterial metabolites 3-methyl-4-(trimethylammonio)butanoate and 4-(trimethylammonio)pentanoate, structural analogs of carnitine that are present in both gut and brain of specific pathogen-free mice but absent in germ-free mice. We demonstrate that these compounds are produced by anaerobic commensal bacteria from the family Lachnospiraceae (Clostridiales) family, colocalize with carnitine in brain white matter, and inhibit carnitine-mediated fatty acid oxidation in a murine cell culture model of central nervous system white matter. This is the first description of direct molecular inter-kingdom exchange between gut prokaryotes and mammalian brain cells, leading to inhibition of brain cell function.

The Methyl-CpG-Binding Protein Mbd2 Regulates Susceptibility to Experimental Colitis via Control of CD11c+ Cells and Colonic Epithelium.

Methyl-CpG-binding domain-2 (Mbd2) acts as an epigenetic regulator of gene expression, by linking DNA methylation to repressive chromatin structure. Although Mbd2 is widely expressed in gastrointestinal immune cells and is implicated in regulating intestinal cancer, anti-helminth responses and colonic inflammation, the Mbd2-expressing cell types that control these responses are incompletely defined. Indeed, epigenetic control of gene expression in cells that regulate intestinal immunity is generally poorly understood, even though such mechanisms may explain the inability of standard genetic approaches to pinpoint the causes of conditions like inflammatory bowel disease. In this study we demonstrate a vital role for Mbd2 in regulating murine colonic inflammation. Mbd2-/- mice displayed dramatically worse pathology than wild type controls during dextran sulfate sodium (DSS) induced colitis, with increased inflammatory (IL-1ß+) monocytes. Profiling of mRNA from innate immune and epithelial cell (EC) populations suggested that Mbd2 suppresses inflammation and pathology via control of innate-epithelial cell crosstalk and T cell recruitment. Consequently, restriction of Mbd2 deficiency to CD11c+ dendritic cells and macrophages, or to ECs, resulted in increased DSS colitis severity. Our identification of this dual role for Mbd2 in regulating the inflammatory capacity of both CD11c+ cells and ECs highlights how epigenetic control mechanisms may limit intestinal inflammatory responses.

The major secreted protein of the whipworm parasite tethers to matrix and inhibits interleukin-13 function.

Infection by soil transmitted parasitic helminths, such as Trichuris spp, are ubiquitous in humans and animals but the mechanisms determining persistence of chronic infections are poorly understood. Here we show that p43, the single most abundant protein in T. muris excretions/secretions, is non-immunogenic during infection and has an unusual sequence and structure containing subdomain homology to thrombospondin type 1 and interleukin (IL)-13 receptor (R) α2. Binding of p43 to IL-13, the key effector cytokine responsible for T. muris expulsion, inhibits IL-13 function both in vitro and in vivo. Tethering of p43 to matrix proteoglycans presents a bound source of p43 to facilitate interaction with IL-13, which may underpin chronic intestinal infection. Our results suggest that exploiting the biology of p43 may open up new approaches to modulating IL-13 function and control of Trichuris infections.

The lung environment controls alveolar macrophage metabolism and responsiveness in type 2 inflammation.

Fine control of macrophage activation is needed to prevent inflammatory disease, particularly at barrier sites such as the lungs. However, the dominant mechanisms that regulate the activation of pulmonary macrophages during inflammation are poorly understood. We found that alveolar macrophages (AlvMs) were much less able to respond to the canonical type 2 cytokine IL-4, which underpins allergic disease and parasitic worm infections, than macrophages from lung tissue or the peritoneal cavity. We found that the hyporesponsiveness of AlvMs to IL-4 depended upon the lung environment but was independent of the host microbiota or the lung extracellular matrix components surfactant protein D (SP-D) and mucin 5b (Muc5b). AlvMs showed severely dysregulated metabolism relative to that of cavity macrophages. After removal from the lungs, AlvMs regained responsiveness to IL-4 in a glycolysis-dependent manner. Thus, impaired glycolysis in the pulmonary niche regulates AlvM responsiveness during type 2 inflammation.

Dynamics of Colon Monocyte and Macrophage Activation During Colitis.

Background: Macrophages are pivotal in coordinating a range of important processes in the intestines, including controlling intracellular infections and limiting damaging inflammation against the microbiota. However, it is not clear how gut macrophages, relative to recruited blood monocytes and other myeloid cells, contribute to the intestinal inflammatory milieu, nor how macrophages and their monocyte precursors mediate recruitment of other immune cells to the inflamed intestine. Methods: Myeloid cell populations isolated from colonic inflammatory bowel disease (IBD) or murine dextran sulphate sodium (DSS) induced colitis were assessed using flow cytometry and compared to healthy controls. In addition, mRNA expression profiles in human and murine colon samples, and in macrophages and monocytes from healthy and inflamed murine colons, were analysed by quantitative PCR (qPCR) and mRNA microarray. Results: We show that the monocyte:macrophage balance is disrupted in colon inflammation to favour recruitment of CD14+HLA-DRInt cells in humans, and Ly6CHi monocytes in mice. In addition, we identify that murine blood monocytes receive systemic signals enabling increased release of IL-1ß prior to egress from the blood into the colon. Further, once within the colon and relative to other myeloid cells, monocytes represent the dominant local source of both IL-1ß and TNF. Finally, our data reveal that, independent of inflammation, murine colon macrophages act as a major source of Ccl7 and Ccl8 chemokines that trigger further recruitment of their pro-inflammatory monocyte precursors. Conclusions: Our work suggests that strategies targeting macrophage-mediated monocyte recruitment may represent a promising approach for limiting the chronic inflammation that characterises IBD.

The circadian regulator BMAL1 programmes responses to parasitic worm infection via a dendritic cell clock.

Resistance to the intestinal parasitic helminth Trichuris muris requires T-helper 2 (TH2) cellular and associated IgG1 responses, with expulsion typically taking up to 4 weeks in mice. Here, we show that the time-of-day of the initial infection affects efficiency of worm expulsion, with strong TH2 bias and early expulsion in morning-infected mice. Conversely, mice infected at the start of the night show delayed resistance to infection, and this is associated with feeding-driven metabolic cues, such that feeding restriction to the day-time in normally nocturnal-feeding mice disrupts parasitic expulsion kinetics. We deleted the circadian regulator BMAL1 in antigen-presenting dendritic cells (DCs) in vivo and found a loss of time-of-day dependency of helminth expulsion. RNAseq analyses revealed that IL-12 responses to worm antigen by circadian-synchronised DCs were dependent on BMAL1. Therefore, we find that circadian machinery in DCs contributes to the TH1/TH2 balance, and that environmental, or genetic perturbation of the DC clock results in altered parasite expulsion kinetics.

Circadian clock component REV-ERBα controls homeostatic regulation of pulmonary inflammation.

Recent studies reveal that airway epithelial cells are critical pulmonary circadian pacemaker cells, mediating rhythmic inflammatory responses. Using mouse models, we now identify the rhythmic circadian repressor REV-ERBα as essential to the mechanism coupling the pulmonary clock to innate immunity, involving both myeloid and bronchial epithelial cells in temporal gating and determining amplitude of response to inhaled endotoxin. Dual mutation of REV-ERBα and its paralog REV-ERBß in bronchial epithelia further augmented inflammatory responses and chemokine activation, but also initiated a basal inflammatory state, revealing a critical homeostatic role for REV-ERB proteins in the suppression of the endogenous proinflammatory mechanism in unchallenged cells. However, REV-ERBα plays the dominant role, as deletion of REV-ERBß alone had no impact on inflammatory responses. In turn, inflammatory challenges cause striking changes in stability and degradation of REV-ERBα protein, driven by SUMOylation and ubiquitination. We developed a novel selective oxazole-based inverse agonist of REV-ERB, which protects REV-ERBα protein from degradation, and used this to reveal how proinflammatory cytokines trigger rapid degradation of REV-ERBα in the elaboration of an inflammatory response. Thus, dynamic changes in stability of REV-ERBα protein couple the core clock to innate immunity.

Intravitreal Dexamethasone Implant (Ozurdex) to Control Recurrent Severe Idiopathic Uveitis Leads to Improvement in Steroid-Induced Diabetes Mellitus.

Steroid-induced diabetes mellitus (SIDM) poses a unique challenge for the physician and ophthalmologist when faced with chronic recurrent uveitis controlled only with systemic steroids. We report a unique case where SIDM improved significantly following administration of intravitreal dexamethasone. A 53-year-old female had a history of recurrent idiopathic anterior uveitis that required oral steroids for control despite orbital floor steroids and systemic immunosuppression. After 9 years of oral steroid treatment she was diagnosed with SIDM necessitating insulin therapy. Following intravitreal dexamethasone implant, her oral steroid use was tapered with subsequent improvement in her diabetes and eventual cessation of insulin. In uveitis, steroid sparing immunosuppression may be used to minimize systemic steroid exposure. In this case, we demonstrated that an intravitreal dexamethasone implant achieved this goal. We recommend considering the use of such implants in patients with recurrent uveitis, particularly when there are significant steroid-induced side effects.

Type I interferon is required for T helper (Th) 2 induction by dendritic cells.

Type 2 inflammation is a defining feature of infection with parasitic worms (helminths), as well as being responsible for widespread suffering in allergies. However, the precise mechanisms involved in T helper (Th) 2 polarization by dendritic cells (DCs) are currently unclear. We have identified a previously unrecognized role for type I IFN (IFN-I) in enabling this process. An IFN-I signature was evident in DCs responding to the helminth Schistosoma mansoni or the allergen house dust mite (HDM). Further, IFN-I signaling was required for optimal DC phenotypic activation in response to helminth antigen (Ag), and efficient migration to, and localization with, T cells in the draining lymph node (dLN). Importantly, DCs generated from Ifnar1-/- mice were incapable of initiating Th2 responses in vivo These data demonstrate for the first time that the influence of IFN-I is not limited to antiviral or bacterial settings but also has a central role to play in DC initiation of Th2 responses.

Heterogeneity of Phenotype and Function Reflects the Multistage Development of T Follicular Helper Cells.

T follicular helper cells (Tfh) provide crucial signals for germinal center (GC) formation, but Tfh populations are heterogeneous. While PD1hi Tfh are important in the GC response, the function of the PD1lo Tfh-like subset is unknown. We show that these cells, like the PD1hi GC-Tfh, depend upon B cells; however, their entry to follicles is independent of CXCR5 or cognate interactions with B cells. The differentiation into PD1hi Tfh is dependent on MHC class II interactions with B cells and requires CXCR5. Our data suggest a Tfh differentiation pathway that is initially B cell-independent, then dependent on non-cognate B cell interactions, and finally following cognate interaction with B cells and CXCR5-ligands allows the formation of GC-Tfh. The PD1lo Tfh-like cells make early cytokine responses and may represent precursors of CD4 memory cells.

Immune Tolerance to Apoptotic Self Is Mediated Primarily by Regulatory B1a Cells.

The chronic autoimmune inflammatory diseases, systemic lupus erythematosus and Sjogren's syndrome, develop when tolerance to apoptotic cells (ACs) is lost. We have previously reported that this tolerance is maintained by innate-like, IL-10 secreting regulatory B cells. Two questions remained. First, do these regulatory B cells belong predominantly to a single subset of steady-state B cells and second, what is their specificity? We report here that innate-like B cells with markers characteristic for B1a cells (CD43+veCD19hiCD5+veIgMhiIgDlo) constitute 80% of splenic and 96% of peritoneal B cells that respond to ACs by secreting IL-10. AC responsive B1a cells secrete self-reactive natural antibodies (NAbs) and IL-10, which is augmented by toll-like receptor (TLR) 7 or TLR9 stimulation. In so doing, they both accelerate the clearance of dying cells by macrophages and inhibit their potential to mount proinflammatory immune responses. While B1a cells make prolonged contact with ACs, they do not require TIM1 or complement to mediate their regulatory function. In an animal model of neural inflammation (experimental autoimmune encephalomyelitis), just 105 activated B1a B cells was sufficient to restrain inflammation. Activated B1a B cells also induced antigen-specific T cells to secrete IL-10. Hence, regulatory B1a cells specifically recognize and augment tolerance to apoptotic self via IL-10 and NAbs; but once activated, can also prevent autoimmune mediated inflammation.

A central role for hepatic conventional dendritic cells in supporting Th2 responses during helminth infection.

Dendritic cells (DCs) are the key initiators of T-helper (Th) 2 immune responses against the parasitic helminth Schistosoma mansoni. Although the liver is one of the main sites of antigen deposition during infection with this parasite, it is not yet clear how distinct DC subtypes in this tissue respond to S. mansoni antigens in vivo, or how the liver microenvironment might influence DC function during establishment of the Th2 response. In this study, we show that hepatic DC subsets undergo distinct activation processes in vivo following murine infection with S. mansoni. Conventional DCs (cDCs) from schistosome-infected mice upregulated expression of the costimulatory molecule CD40 and were capable of priming naive CD4(+) T cells, whereas plasmacytoid DCs (pDCs) upregulated expression of MHC class II, CD86 and CD40 but were unable to support the expansion of either naive or effector/memory CD4(+) T cells. Importantly, in vivo depletion of pDCs revealed that this subset was dispensable for either maintenance or regulation of the hepatic Th2 effector response during acute S. mansoni infection. Our data provides strong evidence that S. mansoni infection favors the establishment of an immunogenic, rather than tolerogenic, liver microenvironment that conditions cDCs to initiate and maintain Th2 immunity in the context of ongoing antigen exposure.