Immunosuppressive CD71+ erythroid cells compromise neonatal host defence against infection

What we know about alterations in immune cells during sepsis in veterinary animals?

Sepsis is still one of the most common causes of death of animals and humans. It is marked by an aberrant immune response to infection, resulting in extensive inflammation, organ dysfunction, and, in severe instances, organ failure. Recognizable symptoms and markers of sepsis encompass substantial elevations in body temperature, respiratory rate, hemoglobin levels, and alterations in immune cell counts, including neutrophils, monocytes, and basophils, along with increases in certain acute-phase proteins. In contrast to human medicine, veterinarians must take into account some species differences. This article provides a comprehensive overview of changes in the immune system during sepsis, placing particular emphasis on species variations and exploring potential future drugs and interventions. Hence, understanding the intricate balance of the immune responses during sepsis is crucial to develop effective treatments and interventions to improve the chances of recovery in animals suffering from this serious condition.

CD71 + erythroid cells promote intestinal symbiotic microbial communities in pregnancy and neonatal period

BACKGROUND

The establishment of microbial communities in neonatal mammals plays a pivotal role in shaping their immune responses to infections and other immune-related conditions. This process is influenced by a combination of endogenous and exogenous factors. Previously, we reported that depletion of CD71 + erythroid cells (CECs) results in an inflammatory response to microbial communities in newborn mice.

RESULTS

Here, we systemically tested this hypothesis and observed that the small intestinal lamina propria of neonatal mice had the highest frequency of CECs during the early days of life. This high abundance of CECs was attributed to erythropoiesis niches within the small intestinal tissues. Notably, the removal of CECs from the intestinal tissues by the anti-CD71 antibody disrupted immune homeostasis. This disruption was evident by alteration in the expression of antimicrobial peptides (AMPs), toll-like receptors (TLRs), inflammatory cytokines/chemokines, and resulting in microbial dysbiosis. Intriguingly, these alterations in microbial communities persisted when tested 5 weeks post-treatment, with a more notable effect observed in female mice. This illustrates a sex-dependent association between CECs and neonatal microbiome modulation. Moreover, we extended our studies on pregnant mice, observing that modulating CECs substantially alters the frequency and diversity of their microbial communities. Finally, we found a significantly lower proportion of CECs in the cord blood of pre-term human newborns, suggesting a potential role in dysregulated immune responses to microbial communities in the gut.

CONCLUSIONS

Our findings provide novel insights into pivotal role of CECs in immune homeostasis and swift adaptation of microbial communities in newborns. Despite the complexity of the cellular biology of the gut, our findings shed light on the previously unappreciated role of CECs in the dialogue between the microbiota and immune system. These findings have significant implications for human health. Video Abstract.

A subpopulation of human bone marrow erythroid cells displays a myeloid gene expression signature similar to that of classic monocytes

Erythroid cells, serving as progenitors and precursors to erythrocytes responsible for oxygen transport, were shown to exhibit an immunosuppressive and immunoregulatory phenotype. Previous investigations from our research group have revealed an antimicrobial gene expression profile within murine bone marrow erythroid cells which suggested a role for erythroid cells in innate immunity. In the present study, we focused on elucidating the characteristics of human bone marrow erythroid cells through comprehensive analyses, including NanoString gene expression profiling utilizing the Immune Response V2 panel, a BioPlex examination of chemokine and TGF-beta family proteins secretion, and analysis of publicly available single-cell RNA-seq data. Our findings demonstrate that an erythroid cell subpopulation manifests a myeloid-like gene expression signature comprised of antibacterial immunity and neutrophil chemotaxis genes which suggests an involvement of human erythroid cells in the innate immunity. Furthermore, we found that human erythroid cells secreted CCL22, CCL24, CXCL5, CXCL8, and MIF chemokines. The ability of human erythroid cells to express these chemokines might facilitate the restriction of immune cells in the bone marrow under normal conditions or contribute to the ability of erythroid cells to induce local immunosuppression by recruiting immune cells in their immediate vicinity in case of extramedullary hematopoiesis.

Targeting erythroid progenitor cells for cancer immunotherapy

Immunotherapy, especially immune checkpoint blockade therapy, represents a major milestone in the history of cancer therapy. However, the current response rate to immunotherapy among cancer patients must be improved; thus, new strategies for sensitizing patients to immunotherapy are urgently needed. Erythroid progenitor cells (EPCs), a population of immature erythroid cells, exert potent immunosuppressive functions. As a newly recognized immunosuppressive population, EPCs have not yet been effectively targeted. In this review, we summarize the immunoregulatory mechanisms of EPCs, especially for CD45+ EPCs. Moreover, in view of the regulatory effects of EPCs on the tumor microenvironment, we propose the concept of EPC-immunity, present existing strategies for targeting EPCs, and discuss the challenges encountered in both basic research and clinical applications. In particular, the impact of existing cancer treatments on EPCs is discussed, laying the foundation for combination therapies. The aim of this review is to provide new avenues for improving the efficacy of cancer immunotherapy by targeting EPCs.

Bipotential B-neutrophil progenitors are present in human and mouse bone marrow and emerge in the periphery upon stress hematopoiesis

Hematopoiesis is a tightly regulated process that gets skewed toward myelopoiesis. This restrains lymphopoiesis, but the role of lymphocytes in this process is not well defined. To unravel the intricacies of neutrophil responses in COVID-19, we performed bulk RNAseq on neutrophils from healthy controls and COVID-19 patients. Principal component analysis revealed distinguishing neutrophil gene expression alterations in COVID-19 patients. ICU and ward patients displayed substantial transcriptional changes, with ICU patients exhibiting a more pronounced response. Intriguingly, neutrophils from COVID-19 patients, notably ICU patients, exhibited an enrichment of immunoglobulin (Ig) and B cell lineage-associated genes, suggesting potential lineage plasticity. We validated our RNAseq findings in a larger cohort. Moreover, by reanalyzing single-cell RNA sequencing (scRNAseq) data on human bone marrow (BM) granulocytes, we identified the cluster of granulocyte-monocyte progenitors (GMP) enriched with Ig and B cell lineage-associated genes. These cells with lineage plasticity may serve as a resource depending on the host's needs during severe systemic infection. This distinct B cell subset may play a pivotal role in promoting myelopoiesis in response to infection. The scRNAseq analysis of BM neutrophils in infected mice further supported our observations in humans. Finally, our studies using an animal model of acute infection implicate IL-7/GM-CSF in influencing neutrophil and B cell dynamics. Elevated GM-CSF and reduced IL-7 receptor expression in COVID-19 patients imply altered hematopoiesis favoring myeloid cells over B cells. Our findings provide novel insights into the relationship between the B-neutrophil lineages during severe infection, hinting at potential implications for disease pathogenesis.

IMPORTANCE

This study investigates the dynamics of hematopoiesis in COVID-19, focusing on neutrophil responses. Through RNA sequencing of neutrophils from healthy controls and COVID-19 patients, distinct gene expression alterations are identified, particularly in ICU patients. Notably, neutrophils from COVID-19 patients, especially in the ICU, exhibit enrichment of immunoglobulin and B cell lineage-associated genes, suggesting potential lineage plasticity. Validation in a larger patient cohort and single-cell analysis of bone marrow granulocytes support the presence of granulocyte-monocyte progenitors with B cell lineage-associated genes. The findings propose a link between B-neutrophil lineages during severe infection, implicating a potential role for these cells in altered hematopoiesis favoring myeloid cells over B cells. Elevated GM-CSF and reduced IL-7 receptor expression in stress hematopoiesis suggest cytokine involvement in these dynamics, providing novel insights into disease pathogenesis.

Global Transcriptomic and Characteristics Comparisons between Mouse Fetal Liver and Bone Marrow Definitive Erythropoiesis

Erythropoiesis occurs first in the yolk sac as a transit "primitive" form, then is gradually replaced by the "definitive" form in the fetal liver (FL) during fetal development and in the bone marrow (BM) postnatally. While it is well known that differences exist between primitive and definitive erythropoiesis, the similarities and differences between FL and BM definitive erythropoiesis have not been studied. Here we performed comprehensive comparisons of erythroid progenitors and precursors at all maturational stages sorted from E16.5 FL and adult BM. We found that FL cells at all maturational stages were larger than their BM counterparts. We further found that FL BFU-E cells divided at a faster rate and underwent more cell divisions than BM BFU-E. Transcriptome comparison revealed that genes with increased expression in FL BFU-Es were enriched in cell division. Interestingly, the expression levels of glucocorticoid receptor Nr3c1, Myc and Myc downstream target Ccna2 were significantly higher in FL BFU-Es, indicating the role of the Nr3c1-Myc-Ccna2 axis in the enhanced proliferation/cell division of FL BFU-E cells. At the CFU-E stage, the expression of genes associated with hemoglobin biosynthesis were much higher in FL CFU-Es, indicating more hemoglobin production. During terminal erythropoiesis, overall temporal patterns in gene expression were conserved between the FL and BM. While biological processes related to translation, the tricarboxylic acid cycle and hypoxia response were upregulated in FL erythroblasts, those related to antiviral signal pathway were upregulated in BM erythroblasts. Our findings uncovered previously unrecognized differences between FL and BM definitive erythropoiesis and provide novel insights into erythropoiesis.

The heterogeneity of erythroid cells: insight at the single-cell transcriptome level

Erythroid cells, the most prevalent cell type in blood, are one of the earliest products and permeate through the entire process of hematopoietic development in the human body, the oxygen-transporting function of which is crucial for maintaining overall health and life support. Previous investigations into erythrocyte differentiation and development have primarily focused on population-level analyses, lacking the single-cell perspective essential for comprehending the intricate pathways of erythroid maturation, differentiation, and the encompassing cellular heterogeneity. The continuous optimization of single-cell transcriptome sequencing technology, or single-cell RNA sequencing (scRNA-seq), provides a powerful tool for life sciences research, which has a particular superiority in the identification of unprecedented cell subgroups, the analyzing of cellular heterogeneity, and the transcriptomic characteristics of individual cells. Over the past decade, remarkable strides have been taken in the realm of single-cell RNA sequencing technology, profoundly enhancing our understanding of erythroid cells. In this review, we systematically summarize the recent developments in single-cell transcriptome sequencing technology and emphasize their substantial impact on the study of erythroid cells, highlighting their contributions, including the exploration of functional heterogeneity within erythroid populations, the identification of novel erythrocyte subgroups, the tracking of different erythroid lineages, and the unveiling of mechanisms governing erythroid fate decisions. These findings not only invigorate erythroid cell research but also offer new perspectives on the management of diseases related to erythroid cells.

Deletion of the Mitochondrial Membrane Protein Fam210b Is Associated with the Development of Systemic Lupus Erythematosus

Mitochondrial dysfunction has been increasingly recognized as a trigger for systemic lupus erythematosus (SLE). Recent bioinformatics studies have suggested Fam210b as a significant candidate for the classification and therapeutic targeting of SLE. To experimentally prove the role of Fam210b in SLE, we constructed Fam210b knockout (Fam210b-/-) mice using the CRISPR-Cas9 method. We found that approximately 15.68% of Fam210b-/- mice spontaneously developed lupus-like autoimmunity, which was characterized by skin ulcerations, splenomegaly, and an increase in anti-double-stranded DNA (anti-dsDNA) IgG antibodies and anti-nuclear antibodies(ANA). Single-cell sequencing showed that Fam210b was mainly expressed in erythroid cells. Critically, the knockout of Fam210b resulted in abnormal erythrocyte differentiation and development in the spleens of mice. Concurrently, the spleens exhibited an increased number of CD71+ erythroid cells, along with elevated levels of reactive oxygen species (ROS) in the erythrocytes. The co-culture of CD71+ erythroid cells and lymphocytes resulted in lymphocyte activation and promoted dsDNA and IgG production. In summary, Fam210b knockout leads to a low probability of lupus-like symptoms in mice through the overproduction of ROS in CD71+ erythroid cells. Thus, Fam210b reduction may serve as a novel key marker that triggers the development of SLE.

Human erythroid progenitors express antigen presentation machinery

Early-life immune exposures can profoundly impact lifelong health. However, functional mechanisms underlying fetal immune development remain incomplete. Erythrocytes are not typically considered active immune mediators, primarily because erythroid precursors discard their organelles as they mature, thus losing the ability to alter gene expression in response to stimuli. Erythroid progenitors and precursors circulate in human fetuses and neonates. Although there is limited evidence that erythroid precursors are immunomodulatory, our understanding of the underlying mechanisms remains inadequate. To define the immunobiological role of fetal and perinatal erythroid progenitors and precursors, we analyzed single cell RNA-sequencing data and found that transcriptomics support erythroid progenitors as putative immune mediators. Unexpectedly, we discovered that human erythroid progenitors constitutively express Major Histocompatibility Complex (MHC) class II antigen processing and presentation machinery, which are hallmarks of specialized antigen presenting immune cells. Furthermore, we demonstrate that erythroid progenitors internalize and cleave foreign proteins into peptide antigens. Unlike conventional antigen presenting cells, erythroid progenitors express atypical costimulatory molecules and immunoregulatory cytokines that direct the development of regulatory T cells, which are critical for establishing maternal-fetal tolerance. Expression of MHC II in definitive erythroid progenitors begins during the second trimester, coinciding with the appearance of mature T cells in the fetus, and is absent in primitive progenitors. Lastly, we demonstrate physical and molecular interaction potential of erythroid progenitors and T cells in the fetal liver. Our findings shed light on a unique orchestrator of fetal immunity and provide insight into the mechanisms by which erythroid cells contribute to host defense.

Diverse immunological dysregulation, chronic inflammation, and impaired erythropoiesis in long COVID patients with chronic fatigue syndrome

A substantial number of patients recovering from acute SARS-CoV-2 infection present serious lingering symptoms, often referred to as long COVID (LC). However, a subset of these patients exhibits the most debilitating symptoms characterized by ongoing myalgic encephalomyelitis or chronic fatigue syndrome (ME/CFS). We specifically identified and studied ME/CFS patients from two independent LC cohorts, at least 12 months post the onset of acute disease, and compared them to the recovered group (R). ME/CFS patients had relatively increased neutrophils and monocytes but reduced lymphocytes. Selective T cell exhaustion with reduced naïve but increased terminal effector T cells was observed in these patients. LC was associated with elevated levels of plasma pro-inflammatory cytokines, chemokines, Galectin-9 (Gal-9), and artemin (ARTN). A defined threshold of Gal-9 and ARTN concentrations had a strong association with LC. The expansion of immunosuppressive CD71+ erythroid cells (CECs) was noted. These cells may modulate the immune response and contribute to increased ARTN concentration, which correlated with pain and cognitive impairment. Serology revealed an elevation in a variety of autoantibodies in LC. Intriguingly, we found that the frequency of 2B4+CD160+ and TIM3+CD160+ CD8+ T cells completely separated LC patients from the R group. Our further analyses using a multiple regression model revealed that the elevated frequency/levels of CD4 terminal effector, ARTN, CEC, Gal-9, CD8 terminal effector, and MCP1 but lower frequency/levels of TGF-β and MAIT cells can distinguish LC from the R group. Our findings provide a new paradigm in the pathogenesis of ME/CFS to identify strategies for its prevention and treatment.

Citrulline supplementation exacerbates sepsis severity in infected preterm piglets via early induced immunosuppression

Arginine (ARG)/Citrulline (CIT) deficiency is associated with increased sepsis severity after infection. Supplementation of CIT to susceptible patients with ARG/CIT deficiency such as preterm newborns with suspected infection might prevent sepsis, via maintaining immune and vascular function. Caesarean-delivered, parenterally nourished preterm pigs were treated with CIT (1g/kg bodyweight) via oral or continuous intravenous supplementation, then inoculated with live Staphylococcus epidermidis and clinically monitored for 14 h. Blood, liver, and spleen samples were collected for analysis. In vitro cord blood stimulation was performed to explore how CIT and ARG affect premature blood cell responses. After infection, oral CIT supplementation led to higher mortality, increased blood bacterial load, and systemic and hepatic inflammation. Intravenous CIT administration showed increased inflammation and bacterial burdens without significantly affecting mortality. Liver transcriptomics and data from in vitro blood stimulation indicated that CIT induces systemic immunosuppression in preterm newborns, which may impair resistance response to bacteria at the early stage of infection, subsequently causing later uncontrollable inflammation and tissue damage. The early stage of CIT supplementation exacerbates sepsis severity in infected preterm pigs, likely via inducing systemic immunosuppression.

Tumor-associated CD8+T cell tolerance induced by erythroid progenitor cells

Introduction

CD8+T cell tolerance plays an important role in tumor escape. Recent studies have shown that CD45+ erythroid progenitor cells (CD45+EPCs) generated through splenic extramedullary erythropoiesis suppress tumor immunity. However, the mechanism underlying how CD45+EPCs mediate CD8+T cell tolerance remains incompletely understood and requires further research.

Methods

In this study, the antigen-processing abilities of CD45+EPCs was verified through both in vitro and in vivo experiments. We have used the method of co-culture in vitro and adoptive transfer experiments in vivo to explore the effects of CD45+EPCs on CD8+T cell tolerance. RNA-sequencing analysis and blocking experiments were used to evaluate the role of ROS in the CD45+EPC mediated tolerance of CD8+T cells. Finally, we incorporated uric acid into the adoptive transfer experiments to rescue the CD45+EPC mediated tumor-promoting effect.

Results and discussion

We found that CD45+EPCs take up soluble proteins, present antigenic epitopes on their surface, and induce antigen-specific CD8+T cell anergy. In addition, we found that CD45+EPC directly nitrates tyrosine within the TCR/CD8 complex via the production of reactive oxygen species and peroxynitrite, preventing CD8+ T cells from responding to their specific peptide antigens. Furthermore, uric acid treatment effectively abolished the immunosuppressive effects of CD45+EPCs during CD8+T cell adoptive transfer, thereby enhancing the anti-tumor efficacy. These results demonstrated that CD8+T cell tolerance in tumor-bearing mice is induced by CD45+EPCs. The results of this study have direct implications for tumor immunotherapy.

Single-cell transcriptomic landscape of peripheral blood cells provides insights into adaptation of red-eared sliders (Trachemys scripta elegans)

Red-eared sliders (Trachemys scripta elegans), as one of the 100 most threatening aliens, have stronger immunity than the native species in response to environmental stress. Blood cells are an important component of immunity in the body. However, the blood cell researches of turtle are still in the traditional blood cell classification and morphological structure observation. Furthermore, turtle granulocytes cannot be accurately identified using traditional methods. Single-cell RNA sequencing techniques have been successfully implemented to study cells based on the mRNA expression patterns of each cell. The present study profiled the transcriptomes of peripheral blood cells in red-eared sliders to construct a single-cell transcriptional landscape of the different cell types and explored environmental adaptation mechanism from the perspective of hematology. All 14 transcriptionally distinct clusters (platelets, erythrocytes1, erythrocytes2, CSF1R monocytes, POF1B monocytes, neutrophils, GATA2high basophils, GATA2low basophils, CD4 T cells, CD7 T cells, B cells, ACKR4 cells, serotriflin cells, and ficolin cells) were identified in the peripheral blood cells of the red-eared sliders. In particular, a subtype of erythrocytes (erythrocytes1) that expressed immune signals was identified. Peripheral blood cells were grouped into three lineages: platelet, erythroid/lymphoid, and myeloid cell lineages. Furthermore, based on differentiation trajectory and up-regulated gene expression, ACKR4 cells were newly identified as lymphocytes, and serotriflin and ficolin cells as granulocytes. The single-cell transcriptional atlas of the peripheral blood cells in red-eared sliders provided in the present study will offer a comprehensive transcriptome reference for the exploration of physiological and pathological hematology in this species.

The immunosuppressive landscape in tumor microenvironment

Recent advances in cancer immunotherapy, especially immune checkpoint inhibitors (ICIs), have revolutionized the clinical outcome of many cancer patients. Despite the fact that impressive progress has been made in recent decades, the response rate remains unsatisfactory, and many patients do not benefit from ICIs. Herein, we summarized advanced studies and the latest insights on immune inhibitory factors in the tumor microenvironment. Our in-depth discussion and updated landscape of tumor immunosuppressive microenvironment may provide new strategies for reversing tumor immune evasion, enhancing the efficacy of ICIs therapy, and ultimately achieving a better clinical outcome.

Targeting Dectin-1 and or VISTA enhances anti-tumor immunity in melanoma but not colorectal cancer model

PURPOSE

Acquired resistance to immune checkpoint blockers (ICBs) is a major barrier in cancer treatment, emphasizing the need for innovative strategies. Dectin-1 (gene Clec7a) is a C-type lectin receptor best known for its ability to recognize β-glucan-rich structures in fungal cell walls. While Dectin-1 is expressed in myeloid cells and tumor cells, its significance in cancer remains the subject of controversy.

METHODS

Using Celc7a-/- mice and curdlan administration to stimulate Dectin-1 signaling, we explored its impact. VISTA KO mice were employed to assess VISTA's role, and bulk RNAseq analyzed curdlan effects on neutrophils.

RESULTS

Our findings reveal myeloid cells as primary Dectin-1 expressing cells in the tumor microenvironment (TME), displaying an activated phenotype. Strong Dectin-1 co-expression/co-localization with VISTA and PD-L1 in TME myeloid cells was observed. While Dectin-1 deletion lacked protective effects, curdlan stimulation significantly curtailed B16-F10 tumor progression. RNAseq and pathway analyses supported curdlan's role in triggering a cascade of events leading to increased production of pro-inflammatory mediators, potentially resulting in the recruitment and activation of immune cells. Moreover, we identified a heterogeneous subset of Dectin-1+ effector T cells in the TME. Similar to mice, human myeloid cells are the prominent cells expressing Dectin-1 in cancer patients.

CONCLUSION

Our study proposes Dectin-1 as a potential adjunctive target with ICBs, orchestrating a comprehensive engagement of innate and adaptive immune responses in melanoma. This innovative approach holds promise for overcoming acquired resistance to ICBs in cancer treatment, offering avenues for further exploration and development.

Unveiling the impact of maternal gestational diabetes mellitus on cord blood CD71+ erythroid cell transcriptome

IMPACT

This study reveals the effects of maternal gestational diabetes mellitus (GDM) on the transcriptome of CD71+ erythroid cells (CECs) in cord blood. It highlights the role of CECs in immunosuppressive function and identifies potential mechanisms linking GDM to adverse outcomes in offspring. This understanding might lead to improved strategies for managing and preventing adverse outcomes in infants born to mothers with GDM.

Life-threatening infections in human newborns: Reconciling age-specific vulnerability and interindividual variability

In humans, the interindividual variability of clinical outcome following exposure to a microorganism is immense, ranging from silent infection to life-threatening disease. Age-specific immune responses partially account for the high incidence of infection during the first 28 days of life and the related high mortality at population level. However, the occurrence of life-threatening disease in individual newborns remains unexplained. By contrast, inborn errors of immunity and their immune phenocopies are increasingly being discovered in children and adults with life-threatening viral, bacterial, mycobacterial and fungal infections. There is a need for convergence between the fields of neonatal immunology, with its in-depth population-wide characterization of newborn-specific immune responses, and clinical immunology, with its investigations of infections in patients at the cellular and molecular levels, to facilitate identification of the mechanisms of susceptibility to infection in individual newborns and the design of novel preventive and therapeutic strategies.

Anemia, Iron Supplementation, and the Brain

The developing brain is particularly vulnerable to extrinsic environmental events such as anemia and iron deficiency during periods of rapid development. Studies of infants with postnatal iron deficiency and iron deficiency anemia clearly demonstrated negative effects on short-term and long-term brain development and function. Randomized interventional trials studied erythropoiesis-stimulating agents and hemoglobin-based red blood cell transfusion thresholds to determine how they affect preterm infant neurodevelopment. Studies of red blood cell transfusion components are limited in preterm neonates. A biomarker strategy measuring brain iron status and health in the preanemic period is desirable to evaluate treatment options and brain response.

Kruppel-like factor 2+ CD4 T cells avert microbiota-induced intestinal inflammation

Intestinal colonization by antigenically foreign microbes necessitates expanded peripheral immune tolerance. Here we show commensal microbiota prime expansion of CD4 T cells unified by the Kruppel-like factor 2 (KLF2) transcriptional regulator and an essential role for KLF2+ CD4 cells in averting microbiota-driven intestinal inflammation. CD4 cells with commensal specificity in secondary lymphoid organs and intestinal tissues are enriched for KLF2 expression, and distinct from FOXP3+ regulatory T cells or other differentiation lineages. Mice with conditional KLF2 deficiency in T cells develop spontaneous rectal prolapse and intestinal inflammation, phenotypes overturned by eliminating microbiota or reconstituting with donor KLF2+ cells. Activated KLF2+ cells selectively produce IL-10, and eliminating IL-10 overrides their suppressive function in vitro and protection against intestinal inflammation in vivo. Together with reduced KLF2+ CD4 cell accumulation in Crohn's disease, a necessity for the KLF2+ subpopulation of T regulatory type 1 (Tr1) cells in sustaining commensal tolerance is demonstrated.

Transfusion of female blood in a rat model is associated with red blood cells entrapment in organs

Transfusion of red blood cells (RBCs) has been associated with adverse outcomes. Mechanisms may be related to donor sex and biological age of RBC. This study hypothesized that receipt of female blood is associated with decreased post-transfusion recovery (PTR) and a concomitant increased organ entrapment in rats, related to young age of donor RBCs. Donor rats underwent bloodletting to stimulate production of new, young RBCs, followed by Percoll fractionation for further enrichment of young RBCs based on their low density. Control donors did not undergo these procedures. Male rats received either a (biotinylated) standard RBC product or a product enriched for young RBCs, derived from either male or female donors. Controls received saline. Organs and blood samples were harvested after 24 hours. This study found no difference in PTR between groups, although only the group receiving young RBCs from females failed to reach a PTR of 75%. Receipt of both standard RBCs and young RBCs from females was associated with increased entrapment of donor RBCs in the lung, liver, and spleen compared to receiving blood from male donors. Soluble ICAM-1 and markers of hemolysis were higher in recipients of female blood compared to control. In conclusion, transfusing RBCs from female donors, but not from male donors, is associated with trapping of donor RBCs in organs, accompanied by endothelial activation and hemolysis.

Extramedullary hematopoiesis contributes to enhanced erythropoiesis during pregnancy via TGF-β signaling

Red blood cells are the predominant cellular component in human body, and their numbers increase significantly during pregnancy due to heightened erythropoiesis. CD71+ erythroid cells (CECs) are immature red blood cells, encompassing erythroblasts and reticulocytes, constitute a rare cell population primarily found in the bone marrow, although they are physiologically enriched in the neonatal mouse spleen and human cord blood. Presently, the mechanisms underlying the CECs expansion during pregnancy remain largely unexplored. Additionally, the mechanisms and roles associated with extramedullary hematopoiesis (EMH) of erythroid cells during pregnancy have yet to be fully elucidated. In this study, our objective was to examine the underlying mechanisms of erythroid-biased hematopoiesis during pregnancy. Our findings revealed heightened erythropoiesis and elevated CECs in both human and mouse pregnancies. The increased presence of transforming growth factor (TGF)-β during pregnancy facilitated the differentiation of CD34+ hematopoietic stem and progenitor cells (HSPCs) into CECs, without impacting HSPCs proliferation, ultimately leading to enhanced erythropoiesis. The observed increase in CECs during pregnancy was primarily attributed to EMH occurring in the spleen. During mouse pregnancy, splenic stromal cells were found to have a significant impact on splenic erythropoiesis through the activation of TGF-β signaling. Conversely, splenic macrophages were observed to contribute to extramedullary erythropoiesis in a TGF-β-independent manner. Our results suggest that splenic stromal cells play a crucial role in promoting extramedullary erythropoiesis and the production of CECs during pregnancy, primarily through TGF-β-dependent mechanisms.

Early-life interactions between the microbiota and immune system: impact on immune system development and atopic disease

Prenatal and early postnatal life represent key periods of immune system development. In addition to genetics and host biology, environment has a large and irreversible role in the immune maturation and health of an infant. One key player in this process is the gut microbiota, a diverse community of microorganisms that colonizes the human intestine. The diet, environment and medical interventions experienced by an infant determine the establishment and progression of the intestinal microbiota, which interacts with and trains the developing immune system. Several chronic immune-mediated diseases have been linked to an altered gut microbiota during early infancy. The recent rise in allergic disease incidence has been explained by the 'hygiene hypothesis', which states that societal changes in developed countries have led to reduced early-life microbial exposures, negatively impacting immunity. Although human cohort studies across the globe have established a correlation between early-life microbiota composition and atopy, mechanistic links and specific host-microorganism interactions are still being uncovered. Here, we detail the progression of immune system and microbiota maturation in early life, highlight the mechanistic links between microbes and the immune system, and summarize the role of early-life host-microorganism interactions in allergic disease development.

CD45- erythroid progenitor cells promote lymph node metastasis in gastric cancer by inducing a hybrid epithelial/mesenchymal state in lymphatic endothelial cells

BACKGROUND AND AIMS

Specific mechanisms of lymph node (LN) metastasis in early-stage gastric cancer (GC) have not been elucidated. The role of anemia, a vital clinical feature of GC, in LN metastasis is also unclear. Since the number of erythroid progenitor cells (EPCs) is increased in chronic anemia, we investigated its association with LN metastasis in GC.

METHODS

Flow cytometry and immunofluorescence analyses were performed to sort and study EPCs from the circulation and tumors of patients with stage I-III GC. The effect of these EPCs on the activation of T and B cells and on the functions of lymphatic endothelial cells (LECs) was determined, and their ability to promote LN metastasis was evaluated using a footpad-popliteal LN metastasis model based on two human adenocarcinoma GC cell lines in nude mice. The prognostic value of EPCs was also analyzed.

RESULTS

The proportion of CD45- EPCs was higher in the mononuclear cells in the circulation, tumors, and LNs of GC patients with LN metastasis (N+) than in those of GC patients without LN metastasis (N0). In N+ patients, CD45- EPCs were more abundant in metastatic LNs than in non-metastatic LNs. Lymphatic vessel endothelial hyaluronan receptor 1 immunoreactivity in tumors revealed that CD45- EPCs were positively associated with nodal stages and lymph vessel density. Furthermore, CD45- EPCs increased LEC proliferation and migration through their S100A8/A9 heterodimer-induced hybrid epithelial/mesenchymal (E/M) state; however, they did not influence the invasion and tubulogenesis of LECs or T and B cell proliferation. CD45- EPCs promoted LN metastasis in vivo; the S100A8/A9 heterodimer mimicked this phenomenon. Finally, CD45- EPCs predicted the overall and disease-free survival of stage I-III GC patients after radical resection.

CONCLUSIONS

The CD45- EPCs accumulated in GC tissues and metastatic LNs and promoted LN metastasis via the S100A8/9-induced hybrid E/M state of LECs, which was the specific mechanism of LN metastasis in the early stages of GC.

Murine Bone Marrow Erythroid Cells Have Two Branches of Differentiation Defined by the Presence of CD45 and a Different Immune Transcriptome Than Fetal Liver Erythroid Cells

Mouse erythropoiesis is a multifaceted process involving the intricate interplay of proliferation, differentiation, and maturation of erythroid cells, leading to significant changes in their transcriptomic and proteomic profiles. While the immunoregulatory role of murine erythroid cells has been recognized historically, modern investigative techniques have been sparingly applied to decipher their functions. To address this gap, our study sought to comprehensively characterize mouse erythroid cells through contemporary transcriptomic and proteomic approaches. By evaluating CD71 and Ter-119 as sorting markers for murine erythroid cells and employing bulk NanoString transcriptomics, we discerned distinctive gene expression profiles between bone marrow and fetal liver-derived erythroid cells. Additionally, leveraging flow cytometry, we assessed the surface expression of CD44, CD45, CD71, and Ter-119 on normal and phenylhydrazine-induced hemolytic anemia mouse bone marrow and splenic erythroid cells. Key findings emerged: firstly, the utilization of CD71 for cell sorting yielded comparatively impure erythroid cell populations compared to Ter-119; secondly, discernible differences in immunoregulatory molecule expression were evident between erythroid cells from mouse bone marrow and fetal liver; thirdly, two discrete branches of mouse erythropoiesis were identified based on CD45 expression: CD45-negative and CD45-positive, which had been altered differently in response to phenylhydrazine. Our deductions underscore (1) Ter-119's superiority over CD71 as a murine erythroid cell sorting marker, (2) the potential of erythroid cells in murine antimicrobial immunity, and (3) the importance of investigating CD45-positive and CD45-negative murine erythroid cells separately and in further detail in future studies.

Harnessing large language models (LLMs) for candidate gene prioritization and selection

BACKGROUND

Feature selection is a critical step for translating advances afforded by systems-scale molecular profiling into actionable clinical insights. While data-driven methods are commonly utilized for selecting candidate genes, knowledge-driven methods must contend with the challenge of efficiently sifting through extensive volumes of biomedical information. This work aimed to assess the utility of large language models (LLMs) for knowledge-driven gene prioritization and selection.

METHODS

In this proof of concept, we focused on 11 blood transcriptional modules associated with an Erythroid cells signature. We evaluated four leading LLMs across multiple tasks. Next, we established a workflow leveraging LLMs. The steps consisted of: (1) Selecting one of the 11 modules; (2) Identifying functional convergences among constituent genes using the LLMs; (3) Scoring candidate genes across six criteria capturing the gene's biological and clinical relevance; (4) Prioritizing candidate genes and summarizing justifications; (5) Fact-checking justifications and identifying supporting references; (6) Selecting a top candidate gene based on validated scoring justifications; and (7) Factoring in transcriptome profiling data to finalize the selection of the top candidate gene.

RESULTS

Of the four LLMs evaluated, OpenAI's GPT-4 and Anthropic's Claude demonstrated the best performance and were chosen for the implementation of the candidate gene prioritization and selection workflow. This workflow was run in parallel for each of the 11 erythroid cell modules by participants in a data mining workshop. Module M9.2 served as an illustrative use case. The 30 candidate genes forming this module were assessed, and the top five scoring genes were identified as BCL2L1, ALAS2, SLC4A1, CA1, and FECH. Researchers carefully fact-checked the summarized scoring justifications, after which the LLMs were prompted to select a top candidate based on this information. GPT-4 initially chose BCL2L1, while Claude selected ALAS2. When transcriptional profiling data from three reference datasets were provided for additional context, GPT-4 revised its initial choice to ALAS2, whereas Claude reaffirmed its original selection for this module.

CONCLUSIONS

Taken together, our findings highlight the ability of LLMs to prioritize candidate genes with minimal human intervention. This suggests the potential of this technology to boost productivity, especially for tasks that require leveraging extensive biomedical knowledge.

Short-term intensive fasting enhances the immune function of red blood cells in humans

BACKGROUND

Fasting is known to influence the immune functions of leukocytes primarily by regulating their mobilization and redistribution between the bone marrow and the peripheral tissues or circulation, in particular via relocalization of leukocytes back in the bone marrow. However, how the immune system responds to the increased risk of invasion by infectious pathogens with fewer leukocytes in the peripheral blood during fasting intervention remains an open question.

RESULTS

We used proteomic, biochemical and flow cytometric tools to evaluate the impact of short-term intensive fasting (STIF), known as beego, on red blood cells by profiling the cells from the STIF subjects before and after 6 days of fasting and 6 days of gradual refeeding. We found that STIF, by triggering the activation of the complement system via the complement receptor on the membrane of red blood cells, boosts fairly sustainable function of red blood cells in immune responses in close relation to various pathogens, including viruses, bacteria and parasites, particularly with the pronounced capacity to defend against SARS-CoV-2, without compromising their oxygen delivery capacity and viability.

CONCLUSION

STIF fosters the immune function of red blood cells and therefore, it may be considered as a nonmedical intervention option for the stronger capacity of red blood cells to combat infectious diseases.

Monocytes from Uninfected Neonates Born to Trypanosoma cruzi-Infected Mothers Display Upregulated Capacity to Produce TNF-α and to Control Infection in Association with Maternally Transferred Antibodies

Activated monocytes/macrophages that produce inflammatory cytokines and nitric oxide are crucial for controlling Trypanosoma cruzi infection. We previously showed that uninfected newborns from T. cruzi infected mothers (M+B- newborns) were sensitized to produce higher levels of inflammatory cytokines than newborns from uninfected mothers (M-B- newborns), suggesting that their monocytes were more activated. Thus, we wondered whether these cells might help limit congenital infection. We investigated this possibility by studying the activation status of M+B- cord blood monocytes and their ability to control T. cruzi in vitro infection. We showed that M+B- monocytes have an upregulated capacity to produce the inflammatory cytokine TNF-α and a better ability to control T. cruzi infection than M-B- monocytes. Our study also showed that T. cruzi-specific Abs transferred from the mother play a dual role by favoring trypomastigote entry into M+B- monocytes and inhibiting intracellular amastigote multiplication. These results support the possibility that some M+B- fetuses may eliminate the parasite transmitted in utero from their mothers, thus being uninfected at birth.

Erythroid-transdifferentiated myeloid cells promote portal vein tumor thrombus in hepatocellular carcinoma

Rationale: Hepatocellular carcinoma (HCC) is primarily characterized by a high incidence of vascular invasion. However, the specific mechanism underlying portal vein tumor thrombus (PVTT) in HCC remains unclear. As a consequence of myeloid cell developmental arrest, CD71+ erythroid progenitor cells (EPCs) and myeloid-derived suppressor cells play important roles in HCC; however, their roles in PVTT remain unclear. Methods: The role of CD71+ EPCs in the HCC tumor microenvironment (TME) was evaluated via morphological, RNA-sequencing, enzyme-linked immunosorbent assay, and flow cytometric analyses. Co-culture techniques were employed to assess the CD45+ EPCs and their vascular compromising effect. Additionally, the PVTT-promoting function of CD45+ EPCs was explored in vivo in a murine model. Results: The CD45+EPCs in HCC tissues exhibited increased myeloid cell features, including morphology, surface markers, transforming growth factor (TGF)-β generation, and gene expression, compared with those in circulation. Hence, a large proportion of CD45+EPCs, particularly those in TMEs, comprise erythroid-transdifferentiated myeloid cells (EDMCs). Additionally, the expression of C-C chemokine receptor type 2 (CCR2) mRNA was upregulated in CD45+EPCs within the TME. Tumor macrophages from HCC tissues induced substantial migration of CD45+EPCs in a dose-dependent manner. Meanwhile, results from immunofluorescence analyses revealed that these two cell types are positively associated in the TME and circulation. That is, EDMCs are chemoattracted by HCC macrophages mainly via CCR2 from CD45+ EPCs in the circulation. Additionally, the expressions of FX, FVII, FGB, C4b, CFB, and CFH were elevated in CD45+EPCs within the TME compared with those in the spleen. The CD45+EPCs from the HCC TME promoted vessel endothelial cell migration and compromised tube formation through TGF-β and FGB, respectively. Additionally, CD45+EPCs from the TME induced HCC cell migration. HCC macrophage-induced CD45+EPCs to exhibit higher levels of FX, FVII, FGB, and TGF-β. Meanwhile, upregulation of CCAAT/enhancer binding protein beta expression induced FGB and TGF-β generation in CD45+EPCs in the TME. WTAP, a major RNA m6A writer, stabilized FX and FVII mRNA and enhanced their nuclear export in CD45+EPCs from the TME. CD45+EPCs from the TME were positively associated with PVTT and poor prognosis. Splenectomy reduced the level of CD45+EPCs in the circulation and TME, as well as the incidence of microvascular invasion. The incidence of microvascular invasion increased following the transfer of HCC tissue CD45+EPCs to splenectomized HCC-bearing mice. Conclusions: The CD45+EPCs enriched in the HCC microenvironment are EDMCs, which are induced by HCC macrophages to migrate from the circulation to the TME. Subsequently, EDMCs promote PVTT by compromising the blood vessel endothelium, aggravating coagulation, and promoting HCC cell migration.

B lymphocytes transdifferentiate into immunosuppressive erythroblast-like cells

Recent studies have demonstrated that a particular group of nucleated cells that exhibit erythroid markers (TER119 in mice and CD235a in humans) possess the ability to suppress the immune system and promote tumor growth. These cells are known as CD45+ erythroid progenitor cells (EPCs). According to our study, it appears that a subset of these CD45+ EPCs originate from B lymphocytes. Under conditions of hypoxia, mouse B lymphoma cells are capable of converting to erythroblast-like cells, which display phenotypes of CD45+TER119+ cells, including immunosuppressive effects on CD8 T cells. Furthermore, non-neoplastic B cells have similar differentiation abilities and exert the same immunosuppressive effect under anemia or tumor conditions in mice. Similar B cells exist in neonatal mice, which provides an explanation for the potential origin of immunosuppressive erythroid cells in newborns. Additionally, CD19+CD235a+ double-positive cells can be identified in the peripheral blood of patients with chronic lymphocytic leukemia. These findings indicate that some CD45+ EPCs are transdifferentiated from a selective population of CD19+ B lymphocytes in response to environmental stresses, highlighting the plasticity of B lymphocytes. We anticipate a potential therapeutic implication, in that targeting a specific set of B cells instead of erythroid cells should be expected to restore adaptive immunity and delay cancer progression.

Tumor-associated myeloid cells in cancer immunotherapy

Tumor-associated myeloid cells (TAMCs) are among the most important immune cell populations in the tumor microenvironment, and play a significant role on the efficacy of immune checkpoint blockade. Understanding the origin of TAMCs was found to be the essential to determining their functional heterogeneity and, developing cancer immunotherapy strategies. While myeloid-biased differentiation in the bone marrow has been traditionally considered as the primary source of TAMCs, the abnormal differentiation of splenic hematopoietic stem and progenitor cells, erythroid progenitor cells, and B precursor cells in the spleen, as well as embryo-derived TAMCs, have been depicted as important origins of TAMCs. This review article provides an overview of the literature with a focus on the recent research progress evaluating the heterogeneity of TAMCs origins. Moreover, this review summarizes the major therapeutic strategies targeting TAMCs with heterogeneous sources, shedding light on their implications for cancer antitumor immunotherapies.

Understanding and targeting erythroid progenitor cells for effective cancer therapy

PURPOSE OF REVIEW

It is well described that tumor-directed aberrant myelopoiesis contributes to the generation of various myeloid populations with tumor-promoting properties. A growing number of recent studies have revealed the importance of the previously unappreciated roles of erythroid progenitor cells (EPCs) in the context of cancer, bringing the updated concept that altered erythropoiesis also facilitates tumor growth and progression. Better characterization of EPCs may provide attractive therapeutic opportunities.

RECENT FINDINGS

EPCs represent a heterogeneous population. They exhibit crucial pro-tumor activities by secreting growth factors and modulating the immune response. Cancers induce potent EPC expansion and suppress their differentiation. Recent single-cell transcriptome and lineage tracking analyses have provided novel insight that tumor-induced EPCs are able to be transdifferentiated into immunosuppressive myeloid cells to limit T-cell function and immunotherapy. Therapeutic strategies targeting key factors of EPC-driven immunosuppression, reducing the amount of EPCs, and promoting EPC differentiation and maturation have been extensively investigated.

SUMMARY

This review summarizes the current state of knowledge as to the fascinating biology of EPCs, highlights mechanisms by which they exert the tumor promoting activities, as well as the perspectives on future directions and strategies to target these cells for potential therapeutic benefit.

Dynamics of human hematopoietic stem and progenitor cell differentiation to the erythroid lineage

Erythropoiesis, the development of erythrocytes from hematopoietic stem cells, occurs through four phases: erythroid progenitor (EP) development, early erythropoiesis, terminal erythroid differentiation (TED), and maturation. According to the classical model that is based on immunophenotypic profiles of cell populations, each of these phases comprises multiple differentiation states that arise in a hierarchical manner. After segregation of lymphoid potential, erythroid priming begins during progenitor development and progresses through progenitor cell types that have multilineage potential. Complete separation of the erythroid lineage is achieved during early erythropoiesis with the formation of unipotent EPs: burst-forming unit-erythroid and colony-forming unit-erythroid. These erythroid-committed progenitors undergo TED and maturation, which involves expulsion of the nucleus and remodeling to form functional biconcave, hemoglobin-filled erythrocytes. In the last decade or so, many studies employing advanced techniques such as single-cell RNA-sequencing (scRNA-seq) as well as the conventional methods, including colony-forming cell assays and immunophenotyping, have revealed heterogeneity within the stem, progenitor, and erythroblast stages, and uncovered alternate paths for segregation of erythroid lineage potential. In this review, we provide an in-depth account of immunophenotypic profiles of all cell types within erythropoiesis, highlight studies that demonstrate heterogeneous erythroid stages, and describe deviations to the classical model of erythropoiesis. Overall, although scRNA-seq approaches have provided new insights, flow cytometry remains relevant and is the primary method for validation of novel immunophenotypes.

HIF-1α targeted deletion in myeloid cells decreases MDSC accumulation and alters microbiome in neonatal mice

The newborn's immune system is faced with the challenge of having to learn quickly to fight off infectious agents, but tolerating the colonization of the body surfaces with commensals without reacting with an excessive inflammatory response. Myeloid-derived suppressor cells (MDSC) are innate immune cells with suppressive activity on other immune cells that regulate fetal-maternal tolerance during pregnancy and control intestinal inflammation in neonates. Until now, nothing is known about the role of MDSC in microbiome establishment. One of the transcription factors regulating MDSC homeostasis is the hypoxia-inducible factor 1α (HIF-1α). We investigated the impact of HIF-1α on MDSC accumulation and microbiome establishment during the neonatal period in a mouse model with targeted deletion of HIF-1α in myeloid cells (Hif1a loxP/loxP LysMCre+). We show that in contrast to wildtype mice, where an extensive expansion of MDSC was observed, MDSC expansion in neonatal Hif1a loxP/loxP LysMCre+ mice was dramatically reduced both systemically and locally in the intestine. This was accompanied by an altered microbiome composition and intestinal T-cell homeostasis. Our results point toward a role of MDSC in inflammation regulation in the context of microbiome establishment and thus reveal a new aspect of the biological role of MDSC during the neonatal period.

Immunoregulatory properties of erythroid nucleated cells induced from CD34+ progenitors from bone marrow

CD 71+ erythroid nucleated cells have pronounced immunoregulatory properties in normal and pathological conditions. Many populations of cells with immunoregulatory properties are considered candidates for cellular immunotherapy for various pathologies. This study characterized the immunoregulatory properties of CD71+ erythroid cells derived from CD34-positive bone marrow cells under the influence of growth factors that stimulate differentiation into erythroid cells. CD34-negative bone marrow cells were used to isolate CD71+ erythroid nuclear cells. The resulting cells were used to assess the phenotype, determine the mRNA spectrum of the genes responsible for the main pathways and processes of the immune response, and obtain culture supernatants for the analysis of immunoregulatory factors. It was found that CD71+ erythroid cells derived from CD34+ cells carry the main markers of erythroid cells, but differ markedly from natural bone marrow CD71+ erythroid cells. The main differences are in the presence of the CD45+ subpopulation, distribution of terminal differentiation stages, transcriptional profile, secretion of certain cytokines, and immunosuppressive activity. The properties of induced CD71+ erythroid cells are closer to the cells of extramedullary erythropoiesis foci than to natural bone marrow CD71+ erythroid cells. Thus, when cultivating CD71+ erythroid cells for clinical experimental studies, it is necessary to take into account their pronounced immunoregulatory activity.

The Neonatal Immune System and Respiratory Pathogens

Neonates are more susceptible to some pathogens, particularly those that cause infection in the respiratory tract. This is often attributed to an incompletely developed immune system, but recent work demonstrates effective neonatal immune responses to some infection. The emerging view is that neonates have a distinctly different immune response that is well-adapted to deal with unique immunological challenges of the transition from a relatively sterile uterus to a microbe-rich world, tending to suppress potentially dangerous inflammatory responses. Problematically, few animal models allow a mechanistic examination of the roles and effects of various immune functions in this critical transition period. This limits our understanding of neonatal immunity, and therefore our ability to rationally design and develop vaccines and therapeutics to best protect newborns. This review summarizes what is known of the neonatal immune system, focusing on protection against respiratory pathogens and describes challenges of various animal models. Highlighting recent advances in the mouse model, we identify knowledge gaps to be addressed.

COVID-19 Vaccine Hesitancy among English-Speaking Pregnant Women Living in Rural Western United States

This mixed-method study investigated vaccine hesitancy among pregnant women living in rural western United States and their response to social media ads promoting COVID-19 vaccine uptake. Thirty pregnant or recently pregnant participants who live in rural zip codes in Washington, Oregon, California, and Idaho were interviewed between November 2022 and March 2023. Interviews were transcribed and coded, while the ad ratings were analyzed using linear mixed models. The study identified five main themes related to vaccine uptake, including perceived risk of COVID, sources of health information, vaccine hesitancy, and relationships with care providers. Participants rated ads most highly that used peer-based messengers and negative outcome-based content. Ads with faith-based and elder messengers were rated significantly lower than peer messengers (p = 0.04 and 0.001, respectively). An activation message was also rated significantly less favorably than negative outcome-based content (p = 0.001). Participants preferred evidence-based information and the ability to conduct their own research on vaccine safety and efficacy rather than being told to get vaccinated. Primary concerns of vaccine-hesitant respondents included the short amount of time the vaccine had been available and perceived lack of research on its safety during pregnancy. Our findings suggests that tailored messaging using peer-based messengers and negative outcome-based content can positively impact vaccine uptake among pregnant women living in rural areas of the Western United States.

Role of microbiota short-chain fatty acid chains in the pathogenesis of autoimmune diseases

There is emerging evidence that microbiota and its metabolites play an important role in helath and diseases. In this regard, gut microbiota has been found as a crucial component that influences immune responses as well as immune-related disorders such as autoimmune diseases. Gut bacterial dysbiosis has been shown to cause disease and altered microbiota metabolite synthesis, leading to immunological and metabolic dysregulation. Of note, microbiota in the gut produce short-chain fatty acids (SCFAs) such as acetate, butyrate, and propionate, and remodeling in these microbiota metabolites has been linked to the pathophysiology of a number of autoimmune disorders such as type 1 diabetes, multiple sclerosis, inflammatory bowel disease, rheumatoid arthritis, celiac disease, and systemic lupus erythematosus. In this review, we will address the most recent findings from the most noteworthy studies investigating the impact of microbiota SCFAs on various autoimmune diseases.

In utero priming of fetal immune activation: Myths and mechanisms

Mechanisms of fetal immune system development in utero remain incompletely elucidated. Protective immunity, the arm of reproductive immunology concerned with the progressive education of the fetal immune system as pregnancy advances, allows for programming of the immune system and immune maturation in utero and provides a responsive system to respond to rapid microbial and other antigenic exposure ex utero. Challenges in studying fetal tissues, immune system development, and the contributions of various endogenous and exogenous factors to this process are difficult to study as a progressive sampling of fetal biological samples is impractical during pregnancy, and animal models are limited. This review provides a summary of mechanisms of protective immunity and how it has been shaped, from transplacental transfer of immunoglobulins, cytokines, metabolites, as well as antigenic microchimeric cells to perhaps more controversial notions of materno-fetal transfer of bacteria that subsequently organize into microbiomes within the fetal tissues. This review will also provide a quick overview of future direction in the area of research on fetal immune system development and discusses methods to visualize fetal immune populations and determine fetal immune functions, as well as a quick look into appropriate models for studying fetal immunity.

Intratumoral erythroblastic islands restrain anti-tumor immunity in hepatoblastoma

Erythroblastic islands (EBIs) are the specialized structures for erythropoiesis, but they have never been found functional in tumors. As the most common pediatric liver malignancy, hepatoblastoma (HB) requires more effective and safer therapies to prevent progression and the lifelong impact of complications on young children. However, developing such therapies is impeded by a lack of comprehensive understanding of the tumor microenvironment. By single-cell RNA sequencing of 13 treatment-naive HB patients, we discover an immune landscape characterized by aberrant accumulation of EBIs, formed by VCAM1⁺ macrophages and erythroid cells, which is inversely correlated with survival of HB. Erythroid cells inhibit the function of dendritic cells (DCs) via the LGALS9/TIM3 axis, leading to impaired anti-tumor T cell immune responses. Encouragingly, TIM3 blockades relieve the inhibitory effect of erythroid cells on DCs. Our study provides an immune evasion mechanism mediated by intratumoral EBIs and proposes TIM3 as a promising therapeutic target for HB.

CD71+ RBCs: A potential immune mediator in transfusion

Donor - recipient sex - mismatched transfusion is associated with increased mortality. The mechanisms for this are not clear, but it may relate to transfusion-related immunomodulation. Recently, CD71⁺ erythroid cells (CECs), including reticulocytes (CD71⁺ RBCs) and erythroblasts, have been identified as potent immunoregulatory cells. The proportion of CD71⁺ RBCs in the peripheral blood is sufficient to play a potential immunomodulatory role. Differences in the quantity of CD71⁺ RBCs are dependent on blood donor sex. The total number of CD71⁺ RBCs in red cell concentrates is also affected by blood manufacturing methods, and storage duration. As a component of the total CECs, CD71⁺ RBCs can affect innate and adaptive immune cells. Phagocytosed CECs directly reduce TNF-α production from macrophages. CECs can also suppress the production of TNF-α production from antigen presenting cells. Moreover, CECs can suppress T cell proliferation thorough immune mediation and / or direct cell-to-cell interactions. Different in their biophysical features compared to mature RBCs, blood donor CD71⁺ RBCs may be preferential targets for the macrophages. This report summarizes the currently literature supporting an important role for CD71⁺ RBCs in adverse transfusion reactions including immune mediation and sepsis.

CD71+ erythroid cells suppress T-cell effector functions and predict immunotherapy outcomes in patients with virus-associated solid tumors

BACKGROUND

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of cancer. However, only a portion of patients respond to such treatments. Therefore, it remains a prevailing clinical need to identify factors associated with acquired resistance or lack of response to ICIs. We hypothesized that the immunosuppressive CD71⁺ erythroid cells (CECs) within the tumor and/or distant 'out-of-field' may impair antitumor response.

METHODS

We studied 38 patients with cancer through a phase II clinical trial investigating the effects of oral valproate combined with avelumab (anti-programmed death-ligand 1 (PD-L1)) in virus-associated solid tumors (VASTs). We quantified the frequency/functionality of CECs in blood and biopsies of patients. Also, we established an animal model of melanoma (B16-F10) to investigate the possible effects of erythropoietin (EPO) treatment on anti-PD-L1 therapy.

RESULTS

We found a substantial expansion of CECs in the blood of patients with VAST compared with healthy controls. We noted that the frequency of CECs in circulation was significantly higher at the baseline and throughout the study in non-responders versus responders to PD-L1 therapy. Moreover, we observed that CECs in a dose-dependent manner suppress effector functions of autologous T cells in vitro. The subpopulation of CD45⁺CECs appears to have a more robust immunosuppressive property compared with their CD45^- counterparts. This was illustrated by a stronger expression of reactive oxygen species, PD-L1/PD-L2, and V-domain Ig suppressor of T-cell activation in this subpopulation. Lastly, we found a higher frequency of CECs in the blood circulation at the later cancer stage and their abundance was associated with anemia, and a poor response to immunotherapy. Finally, we report the expansion of CECs in the spleen and tumor microenvironment of mice with melanoma. We found that although CECs in tumor-bearing mice secret artemin, this was not the case for VAST-derived CECs in humans. Notably, our results imply that EPO, a frequently used drug for anemia treatment in patients with cancer, may promote the generation of CECs and subsequently abrogates the therapeutic effects of ICIs (eg, anti-PD-L1).

CONCLUSIONS

Our results demonstrate that anemia by the expansion of CECs may enhance cancer progression. Notably, measuring the frequency of CECs may serve as a valuable biomarker to predict immunotherapy outcomes.

Mast cells-fetal mast cells crosstalk with maternal interfaces during pregnancy: Friend or foe?

Mast cells (MC) are hematopoietic immune cells that play a major role during allergic reactions in adults by releasing a myriad of vasoactive and inflammatory mediators. MC seed all vascularized tissues and are most prominent in organs with a barrier function such as skin, lungs, and intestines. These secreted molecules cause mild symptoms such as localized itchiness and sneezing to life-threatening symptoms (i.e., anaphylactic shock). Presently, despite the extensive research on Th2-mediated immune responses in allergic diseases in adults, we are still unable to determine the mechanisms of the role of MC in developing pediatric allergic (PA) disorders. In this review, we will summarize the most recent findings on the origin of MC and discuss the underappreciated contribution of MC in the sensitization phase to maternal antibodies during pregnancy in allergic reactions and other diseases such as infectious diseases. Then, we will lay out potential MC-dependent therapeutic strategies to be considered in future investigations to understand the remaining gaps in MC research for a better quality of life for these young patients.

LAG3+ erythroid progenitor cells inhibit HBsAg seroclearance during finite pegylated interferon treatment through LAG3 and TGF-β

HBsAg seroclearance, the ideal aim of anti-hepatitis B virus (HBV) treatment, cannot be achieved easily. Anemia is another common issue for chronic hepatitis B (CHB) patients, which leads to elevation of erythroid progenitor cells (EPCs) and immune suppression in cancer. This study investigated the role of EPCs in HBsAg seroclearance following PEGylated interferon-α (PEG-IFN) treatment. CD45⁺EPC accumulation in CHB patients and an AAV/HBV mice model was found in the circulation and liver by flow cytometry and immunofluorescence tests. Wright-Giemsa staining showed that these pathological CD45⁺EPCs presented elevated erythroid cells with relative immature morphologies and atypical cells compared with the control cells. CD45⁺EPCs were associated with immune tolerance and decreased HBsAg seroclearance during finite PEG-IFN treatment. CD45⁺EPCs suppressed antigen non-specific T cell activation and HBV-specific CD8⁺T cells, partially through transforming growth factor β (TGF-β). RNA-seq revealed that CD45⁺EPCs in patients with CHB presented a distinct gene expression profile compared with CD45^-EPCs and CD45⁺EPCs from cord blood. Notably, CD45⁺EPCs from patients with CHB expressed high level of Lymphocyte-activation gene 3 (LAG3), an immune checkpoint molecule, and were then defined as LAG3⁺EPCs. LAG3⁺EPCs diminished the function of antigen presenting cells through LAG3, which was another mechanism by which LAG3⁺EPCs' suppressed HBV-specific CD8⁺T cells. Anti-LAG3 and anti-TGF-β combination treatment decreased serum HBeAg, HBV DNA levels and HBsAg level, as well as HBsAg-expression in hepatocytes during PEG-IFN treatment in the AAV/HBV mice model. Conclusions: LAG3⁺EPCs inhibited the efficacy of PEG-IFN treatment on HBsAg seroclearance induced by LAG3 and TGF-β. Anti-LAG3, anti-TGF-β and PEG-IFN combination treatment might facilitate HBV clearance.

Clinical Signs of Kawasaki Disease from the Perspective of Epithelial-to-Mesenchymal Transition Recruiting Erythrocytes: A Literature Review

Kawasaki disease (KD) is a systemic vasculitis affecting children younger than 5 years of age. Early period in life is marked by rapid somatic growth with cell proliferation and immaturity of the immunity with dominant innate immune system. Coronary complications in KD are the most common acquired heart disease in children, yet the diagnosis of KD still depends on the clinical diagnostic criteria. Glossy red lips and conjunctival injection are characteristic signs enabling pediatricians to make the initial diagnosis of KD; however, little is known why these are so characteristic. The diagnostic criteria of KD seem to be scattered in seemingly irrelevant body systems such as the eyes, lips, skin, and heart. KD is classified as a connective tissue disease. Recently, red blood cells (RBCs) have emerged as important modulators in innate immune response. RBCs are reported to participate in extracellular matrix remodeling and upregulating matrix metalloproteinase (MMP) expression in dermal fibroblasts. Also, fibroblast growth factors and microRNAs associated with fibrosis are drawing attention in KD. The cardinal signs of KD appear at the border of muco-cutaneous junction. Head and neck regions are abundant in tissues undergoing epithelial-to-mesenchymal transition (EMT). Interstitial carditis and valve insufficiency as well as coronary arterial lesions may complicate KD, and these lesions present in tissues that originated from epicardial progenitor cells by EMT. Having reviewed the recent research on KD, we presume that the signs of KD present at borders between keratinized and non-keratinized stratified squamous epithelium where the EMT is still ongoing for the rapid somatic growth where RBCs are recruited as an innate immune response and to prevent excessive fibrosis in mucosa. KD presents scarcely in adults with somatic growth and immune maturation completed. In this review, we attempted to explain the reasons for the clinical manifestations of KD and to search for a link among the diagnostic clues in the perspective of EMT during the somatic growth and immune system maturation in children with KD.

Galectin-9 promotes natural killer cells activity via interaction with CD44

Natural killer (NK) cells are a potent innate source of cytokines and cytoplasmic granules. Their effector functions are tightly synchronized by the balance between the stimulatory and inhibitory receptors. Here, we quantified the proportion of NK cells and the surface presence of Galectin-9 (Gal-9) from the bone marrow, blood, liver, spleen, and lungs of adult and neonatal mice. We also examined the effector functions of Gal-9+NK cells compared with their Gal-9- counterparts. Our results revealed that Gal-9+NK cells are more abundant in tissues, in particular, in the liver than in the blood and bone marrow. We found Gal-9 presence was associated with enhanced cytotoxic effector molecules granzyme B (GzmB) and perforin expression. Likewise, Gal-9 expressing NK cells displayed greater IFN-γ and TNF-α expression than their negative counterparts under hemostatic circumstances. Notably, the expansion of Gal-9+NK cells in the spleen of mice infected with E. coli implies that Gal-9+NK cells may provide a protective role against infection. Similarly, we found the expansion of Gal-9+NK cells in the spleen and tumor tissues of melanoma B16-F10 mice. Mechanistically, our results revealed the interaction of Gal-9 with CD44 as noted by their co-expression/co-localization. Subsequently, this interaction resulted in enhanced expression of Phospho-LCK, ERK, Akt, MAPK, and mTOR in NK cells. Moreover, we found Gal-9+NK cells exhibited an activated phenotype as evidenced by increased CD69, CD25, and Sca-1 but reduced KLRG1 expression. Likewise, we found Gal-9 preferentially interacts with CD44high in human NK cells. Despite this interaction, we noted a dichotomy in terms of effector functions in NK cells from COVID-19 patients. We observed that the presence of Gal-9 on NK cells resulted in a greater IFN-γ expression without any changes in cytolytic molecule expression in these patients. These observations suggest differences in Gal-9+NK cell effector functions between mice and humans that should be considered in different physiological and pathological conditions. Therefore, our results highlight the important role of Gal-9 via CD44 in NK cell activation, which suggests Gal-9 is a potential new avenue for the development of therapeutic approaches to modulate NK cell effector functions.

The impact of biological age of red blood cell on in vitro endothelial activation markers

Introduction: Blood donor characteristics influence red blood cell transfusion outcomes. As donor sex affects the distribution of young to old RBCs in the circulation, we hypothesized that the amount of circulating young RBCs in the blood product are associated with immune suppression.

Materials and Methods: Blood samples were collected from healthy volunteers and density fractionated into young and old subpopulations. In an activated endothelial cell model, RBC adhesion to endothelium and secretion of endothelial activation markers were assessed. The impact of RBC biological age was also assessed in a T cell proliferation assay and in a whole blood stimulation assay.

Results: After Percoll fractionation, young RBCs contained more reticulocytes compared to old RBCs. Young RBCs associated with lower levels of E-selectin, ICAM-1, and vWF from activated endothelial cells compared to old RBCs. RBC subpopulations did not affect T cell proliferation or cytokine responses following whole blood stimulation.

Conclusion: Young RBCs contain more reticulocytes which are associated with lower levels of endothelial activation markers compared to old RBCs.

The Role of Immunity in the Pathogenesis of SARS-CoV-2 Infection and in the Protection Generated by COVID-19 Vaccines in Different Age Groups

This study aims to review the available data regarding the central role of immunity in combating SARS-CoV-2 infection and in the generation of protection by vaccination against COVID-19 in different age groups. Physiologically, the immune response and the components involved in it are variable, both functionally and quantitatively, in neonates, infants, children, adolescents, and adults. These immunological differences are mirrored during COVID-19 infection and in the post-vaccination period. The outcome of SARS-CoV-2 infection is greatly dependent on the reaction orchestrated by the immune system. This is clearly obvious in relation to the clinical status of COVID-19 infection, which can be symptomless, mild, moderate, or severe. Even the complications of the disease show a proportional pattern in relation to the immune response. On the contrary, the commonly used anti-COVID-19 vaccines generate protective humoral and cellular immunity. The magnitude of this immunity and the components involved in it are discussed in detail. Furthermore, many of the adverse effects of these vaccines can be explained on the basis of immune reactions against the different components of the vaccines. Regarding the appropriate choice of vaccine for different age groups, many factors have to be considered. This is a cornerstone, particularly in the following age groups: 1 day to 5 years, 6 to 11 years, and 12 to 17 years. Many factors are involved in deciding the route, doses, and schedule of vaccination for children. Another important issue in this dilemma is the hesitancy of families in making the decision about whether to vaccinate their children. Added to these difficulties is the choice by health authorities and governments concerning whether to make children's vaccination compulsory. In this respect, although rare and limited, adverse effects of vaccines in children have been detected, some of which, unfortunately, have been serious or even fatal. However, to achieve comprehensive control over COVID-19 in communities, both children and adults have to be vaccinated, as the former group represents a reservoir for viral transmission. The understanding of the various immunological mechanisms involved in SARS-CoV-2 infection and in the preparation and application of its vaccines has given the sciences a great opportunity to further deepen and expand immunological knowledge. This will hopefully be reflected positively on other diseases through gaining an immunological background that may aid in diagnosis and therapy. Humanity is still in continuous conflict with SARS-CoV-2 infection and will be for a while, but the future is expected to be in favor of the prevention and control of this disease.

Novel murine model reveals an early role for pertussis toxin in disrupting neonatal immunity to Bordetella pertussis

The increased susceptibility of neonates to specific pathogens has previously been attributed to an underdeveloped immune system. More recent data suggest neonates have effective protection against most pathogens but are particularly susceptible to those that target immune functions specific to neonates. Bordetella pertussis (Bp), the causative agent of "whooping cough", causes more serious disease in infants attributed to its production of pertussis toxin (PTx), although the neonate-specific immune functions it targets remain unknown. Problematically, the rapid development of adult immunity in mice has confounded our ability to study interactions of the neonatal immune system and its components, such as virtual memory T cells which are prominent prior to the maturation of the thymus. Here, we examine the rapid change in susceptibility of young mice and define a period from five- to eight-days-old during which mice are much more susceptible to Bp than mice even a couple days older. These more narrowly defined "neonatal" mice display significantly increased susceptibility to wild type Bp but very rapidly and effectively respond to and control Bp lacking PTx, more rapidly even than adult mice. Thus, PTx efficiently blocks some very effective form(s) of neonatal protective immunity, potentially providing a tool to better understand the neonatal immune system. The rapid clearance of the PTx mutant correlates with the early accumulation of neutrophils and T cells and suggests a role for PTx in disrupting their accumulation. These results demonstrate a striking age-dependent response to Bp, define an early age of extreme susceptibility to Bp, and demonstrate that the neonatal response can be more efficient than the adult response in eliminating bacteria from the lungs, but these neonatal functions are substantially blocked by PTx. This refined definition of "neonatal" mice may be useful in the study of other pathogens that primarily infect neonates, and PTx may prove a particularly valuable tool for probing the poorly understood neonatal immune system.

The association between exposure to antibiotics in the first week of life and later otitis media: The INCA study

Otitis media (OM) is one of the most common diagnoses in preschool-age children. Its pathophysiology is poorly understood, but is associated with changes in the nasopharyngeal microbiome, immune system, and presence of allergies. These, in turn, can be affected by early-life antibiotic exposure. Therefore, this study aimed to determine if antibiotic treatment in the first week of life in children born at term was associated with acute otitis media (AOM) and otitis media with effusion (OME) in the first 4-6 years of life.

METHODS

A prospective birth cohort of 436 term-born infants was followed up at 4-6 years of age. Parents reported (recurrent) AOM and OME through online questionnaires, sent to parents of 418 eligible children. Doctors' diagnoses of AOM and OME were collected after additional informed consent. Multivariate logistic regression analyses were used to study the association between antibiotic exposure and AOM and OME.

RESULTS

Of the 436 infants, 151 infants received antibiotics in the first week of life. In total, 341 (82%) questionnaires were collected. The parental-reported prevalence was 45% (155/341) for AOM. Of these 155 children, 33 children also had OME (10% of the total cohort). Doctor's diagnoses were obtained from 308 (74%) children, of which 30% (91/308) had AOM. Of these 91 children, 12 children also had OME and 8 children had OME without a diagnosis of AOM (6% of the total obtained diagnoses). Antibiotic treatment in the first week of life was not significantly associated with parent-reported nor doctor-diagnosed (recurrent) AOM and OME in the first 4-6 years of life in the regression models.

CONCLUSION

Antibiotic treatment in the first week of life was not associated with AOM and OME in the first 4-6 years of life in this prospective cohort of Dutch infants. More insight into the pathophysiology of OM is warranted to determine whether antibiotic-induced microbiome changes play a role in the susceptibility to OM.