The lymphoid-associated interleukin 7 receptor (IL7R) regulates tissue-resident macrophage development

IL-7 in autoimmune diseases: mechanisms and therapeutic potential

Interleukin-7 (IL-7) is a pleiotropic cytokine that plays a crucial role in the development, homeostasis, and function of the immune system. Growing evidence has demonstrated that IL-7 is involved in the pathogenesis of various autoimmune diseases including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), type 1 diabetes (T1D) and multiple sclerosis (MS). This review aims to summarize the current understanding of the role of IL-7 in autoimmune diseases, focusing on its mechanisms of action, implications for disease progression, and potential therapeutic applications. Produced by stromal cells, IL-7 binds to IL-7 receptor (IL-7R) on diverse immune cells. It is crucial for T cell development, survival, and proliferation. In autoimmune diseases, it activates and expands autoreactive T cells and influences B cell function, potentially leading to autoantibody production. The review further delves into the role of IL-7 in different autoimmune diseases. In RA, elevated IL-7/IL-7R promotes memory T cell survival, cytokine production, and influences B cells and monocytes to contribute to inflammation and joint damage. In SLE, elevated soluble form of IL-7R is associated with disease activity, promoting the survival of autoreactive T cells and enhancing the production of pro-inflammatory cytokines. In MS, genetic variations in the IL-7R gene are linked to disease susceptibility, and IL-7 impacts the survival and differentiation of T cell subsets involved in multiple sclerosis pathogenesis. For T1D, IL-7 affects the function of immune cells that attack pancreatic β cells. Given its central role in autoimmune processes, targeting the IL-7/IL-7R axis holds great therapeutic potential. By modulating IL-7 signaling, it may be possible to restore immune tolerance, reduce the activation of autoreactive immune cells, and alleviate disease symptoms. Understanding the complex mechanisms of IL-7 in autoimmune diseases is essential for the development of effective and targeted therapies.

Postprandial parasympathetic signals promote lung type 2 immunity

Lung type 2 immunity protects against pathogenic infection, but its dysregulation causes asthma. Although it has long been observed that symptoms of asthmatic patients often become exaggerated following food intake, the pathophysiological mechanism underlying this postprandial phenomenon is incompletely understood. Here, we report that lung type 2 immunity in mice is enhanced after feeding, which correlates with parasympathetic activation. Also, local parasympathetic innervations exhibit spatial engagement with such immune responses mediated by group 2 innate lymphoid cells (ILC2s). Pharmacologic or surgical blockage of parasympathetic signals diminishes lung type 2 immunity. Conversely, chemogenetic manipulation of parasympathetic inputs and their upstream neurocircuit is sufficient to modulate those immune responses. We then show that the cholinergic receptor muscarinic 4 (Chrm4) for the parasympathetic neurotransmitter acetylcholine is expressed in mouse or human lung ILC2s, and the Chrm4 deletion mitigates ILC2-mediated lung inflammation. These results have revealed a critical neuroimmune function of the gut-brain-lung reflex.

IL-7 Immunotherapies: Current Applications and Engineering Opportunities

BACKGROUND

IL-7 is a cytokine that plays a critical role in the development and proliferation of many different immune cells. IL-7 is notably important for the proper development and activity of T cells and B cells. Additionally, the cytokine plays a role in the function of natural killer cells and dendritic cells. Because of this innate biological activity, IL-7 has gained traction as a potential immunotherapy for multiple applications.

METHODS

We conducted a comprehensive literature review to explore the physiological role of IL-7 and current applications harnessing the biology of IL-7 as a therapeutic. We also investigated the ways in which IL-7 is being engineered to enhance its therapeutic potential.

RESULTS

Notably, IL-7 has demonstrated efficacy in adoptive cell therapy models and as a vaccine adjuvant. The cytokine has also been used as a treatment for sepsis and other chronic infections. To further enhance its therapeutic efficacy, IL-7 has been engineered by fusing the cytokine to antibody fragments or other bioactive or targeting molecules. These engineered IL-7 therapeutics seek to improve the cytokine's pharmacokinetic and immunological properties and reduce off-target effects.

CONCLUSION

IL-7 immunotherapies largely remain at the preclinical stage, but there is growing interest in IL-7's many therapeutic applications and increasing opportunities to further engineer the molecule for future clinical translation.

Single-cell analysis reveals the loss of FABP4-positive proliferating valvular endothelial cells relates to functional mitral regurgitation

BACKGROUND

Functional mitral regurgitation (MR) is a common form of mitral valve dysfunction that often persists even after surgical intervention, requiring reoperation in some cases. To advance our understanding of the pathogenesis of functional MR, it is crucial to characterize the cellular composition of the mitral valve leaflet and identify molecular changes in each cell subtype within the mitral valves of MR patients. Therefore, we aimed to comprehensively examine the cellular and molecular components of mitral valves in patients with MR.

METHODS

We conducted a single-cell RNA sequencing (scRNA-seq) analysis of mitral valve leaflets extracted from six patients who underwent heart transplantation. The cohort comprised three individuals with moderate-to-severe functional MR (MR group) and three non-diseased controls (NC group). Bioinformatics was applied to identify cell types, delineate cell functions, and explore cellular developmental trajectories and interactions. Key findings from the scRNA-seq analysis were validated using pathological staining to visualize key markers in the mitral valve leaflets. Additionally, in vitro experiments with human primary valvular endothelial cells were conducted to further support our results.

RESULTS

Our study revealed that valve interstitial cells are critical for adaptive valve remodelling, as they secrete extracellular matrix proteins and promote fibrosis. We discovered an abnormal decrease in a subpopulation of FABP4 (fatty acid binding protein 4)-positive proliferating valvular endothelial cells. The trajectory analysis identifies this subcluster as the origin of VECs. Immunohistochemistry on the expanded cohort showed a reduction of FABP4-positive VECs in patients with functional MR. Intervention experiments with primary cells indicated that FABP4 promotes proliferation and migration in mitral valve VECs and enhances TGFβ-induced differentiation.

CONCLUSIONS

Our study presented a comprehensive assessment of the mitral valve cellular landscape of patients with MR and sheds light on the molecular changes occurring in human mitral valves during functional MR. We found a notable reduction in the proliferating endothelial cell subpopulation of valve leaflets, and FABP4 was identified as one of their markers. Therefore, FABP4 positive VECs served as proliferating endothelial cells relates to functional mitral regurgitation. These VECs exhibited high proliferative and differentiative properties. Their reduction was associated with the occurrence of functional MR.

A rare HSC-derived megakaryocyte progenitor accumulates via enhanced survival and contributes to exacerbated thrombopoiesis upon aging

Distinct routes of cellular production from hematopoietic stem cells (HSCs) have defined our current view of hematopoiesis. Recently, we challenged classical views of platelet generation, demonstrating that megakaryocyte progenitors (MkPs), and ultimately platelets, can be specified via an alternate and additive route of HSC-direct specification specifically during aging. This "shortcut" pathway generates hyperactive platelets likely to contribute to age-related platelet-mediated morbidities. Here, we used single-cell RNA/CITEseq to demonstrate that these age-unique, non-canonical (nc)MkPs can be prospectively defined and experimentally isolated from wild type mice. Surprisingly, this revealed that a rare population of ncMkPs also exist in young mice. Young and aged ncMkPs are functionally distinct from their canonical (c)MkP counterparts, with aged ncMkPs paradoxically and uniquely exhibiting enhanced survival and platelet generation capacity. We further demonstrate that aged HSCs generate significantly more ncMkPs than their younger counterparts, yet this is accomplished without strict clonal restriction. Together, these findings reveal significant phenotypic, functional, and aging-dependent heterogeneity among the MkP pool and uncover unique features of megakaryopoiesis throughout life, potentially offering cellular and molecular targets for mitigation of age-related adverse thrombotic events.

Blocking IL-17a Signaling Decreases Lung Inflammation and Improves Alveolarization in Experimental Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease of preterm infants that is associated with life-long morbidities. Inflammatory insults contribute to BPD pathogenesis. Although the proinflammatory cytokine, IL-17a, plays a role in various neonatal inflammatory disorders, its role in BPD pathogenesis is unclear. To test the hypothesis that blocking IL-17a signaling decreases lipopolysaccharide (LPS)-mediated experimental BPD in neonatal mice, wild-type mice were injected intraperitoneally with phosphate-buffered saline or LPS during the saccular lung developmental phase. Pulmonary IL-17a expression was determined by enzyme-linked immunosorbent assay and by flow cytometry. LPS-injected mice had higher pulmonary IL-17a protein levels and IL-17a+ and IL-22+ cells. γδ T cells, followed by non-T lymphoid cells, were the primary producers of IL-17a. Wild-type mice were then injected intraperitoneally with isotype antibody (Ab) or IL-17a Ab, while they were treated with phosphate-buffered saline or LPS, followed by quantification of lung inflammatory markers, alveolarization, vascularization, cell proliferation, and apoptosis. LPS-mediated alveolar simplification, apoptosis, and cell proliferation inhibition were significantly greater in mice treated with isotype Ab than in those treated with IL-17a Ab. Furthermore, STAT1 activation and IL-6 levels were significantly greater in LPS-exposed mice treated with isotype Ab than in those treated with IL-17a Ab. The study results indicate that blocking IL-17a signaling decreases LPS-mediated experimental BPD.

Mouse monocytes express CD127 by immune cells, not LPS

The essential role of interleukin 7 (IL-7) signaling via its receptor (IL-7Rα; CD127) in T cell development and function has been well documented. However, CD127 expression and function in myeloid cells, including monocytes, are less clear, especially in mice. In the present study we report an inducible CD127 expression in mouse monocytes/macrophages. This induction is dependent on the presence of other immune cells, highlighting that regulation of CD127 expression on monocytes differs in mice and humans. We demonstrate that CD127 is functional, as IL-7 downregulated its expression. We also saw decreased CD127 expression during inflammation in vivo. Overall, upregulation of CD127 expression in vitro and its downregulation in vivo confirm that CD127 is an inducible marker on mouse monocyte/macrophage cells, in contrast to findings recently published by others. Characterizing the role of CD127 signaling in myeloid cells in inflammatory disorders would be worthwhile in future study.

CD163+ macrophages in mantle cell lymphoma induce activation of prosurvival pathways and immune suppression

ABSTRACT

Mantle cell lymphoma (MCL) is dependent on a supportive tumor immune microenvironment (TIME) in which infiltration of CD163+ macrophages has a negative prognostic impact. This study explores how abundance and spatial localization of CD163+ cells are associated with the biology of MCL, using spatial multiomic investigations of tumor and infiltrating CD163+ and CD3+ cells. A total of 63 proteins were measured using GeoMx digital spatial profiling in tissue microarrays from 100 diagnostic MCL tissues. Regions of interest were selected in tumor-rich and tumor-sparse tissue regions. Molecular profiling of CD163+ macrophages, CD20+ MCL cells, and CD3+ T-cells was performed. To validate protein profiles, 1811 messenger RNAs were measured in CD20+ cells and 2 subsets of T cells. Image analysis was used to extract the phenotype and position of each targeted cell, thereby allowing the exploration of cell frequencies and cellular neighborhoods. Proteomic investigations revealed that CD163+ cells modulate their immune profile depending on their localization and that the immune inhibitory molecules, V-domain immunoglobulin suppressor of T-cell activation and B7 homolog 3, have higher expression in tumor-sparse than in tumor-rich tissue regions and that targeting should be explored. We showed that MCL tissues with more abundant infiltration of CD163+ cells have a higher proteomic and transcriptional expression of key components of the MAPK pathway. Thus, the MAPK pathway may be a feasible therapeutic target in patients with MCL with CD163+ cell infiltration. We further showed the independent and combined prognostic values of CD11c and CD163 beyond established risk factors.

Single-cell atlas of the small intestine throughout the human lifespan demonstrates unique features of fetal immune cells

Proper development of mucosal immunity is critical for human health. Over the past decade, it has become evident that in humans, this process begins in utero. However, there are limited data on the unique features and functions of fetal mucosal immune cells. To address this gap, we integrated several single-cell ribonucleic acid sequencing datasets of the human small intestine (SI) to create an SI transcriptional atlas throughout the human life span, ranging from the first trimester to adulthood, with a focus on immune cells. Fetal SI displayed a complex immune landscape comprising innate and adaptive immune cells that exhibited distinct transcriptional programs from postnatal samples, especially compared with pediatric and adult samples. We identified shifts in myeloid populations across gestation and progression of memory T-cell states throughout the human lifespan. In particular, there was a marked shift of memory T cells from those with stem-like properties in the fetal samples to fully differentiated cells with a high expression of activation and effector function genes in adult samples, with neonatal samples containing both features. Finally, we demonstrate that the SI developmental atlas can be used to elucidate improper trajectories linked to mucosal diseases by implicating developmental abnormalities underlying necrotizing enterocolitis, a severe intestinal complication of prematurity. Collectively, our data provide valuable resources and important insights into intestinal immunity that will facilitate regenerative medicine and disease understanding.

An age-progressive platelet differentiation path from hematopoietic stem cells causes exacerbated thrombosis

Platelet dysregulation is drastically increased with advanced age and contributes to making cardiovascular disorders the leading cause of death of elderly humans. Here, we reveal a direct differentiation pathway from hematopoietic stem cells into platelets that is progressively propagated upon aging. Remarkably, the aging-enriched platelet path is decoupled from all other hematopoietic lineages, including erythropoiesis, and operates as an additional layer in parallel with canonical platelet production. This results in two molecularly and functionally distinct populations of megakaryocyte progenitors. The age-induced megakaryocyte progenitors have a profoundly enhanced capacity to engraft, expand, restore, and reconstitute platelets in situ and upon transplantation and produce an additional platelet population in old mice. The two pools of co-existing platelets cause age-related thrombocytosis and dramatically increased thrombosis in vivo. Strikingly, aging-enriched platelets are functionally hyper-reactive compared with the canonical platelet populations. These findings reveal stem cell-based aging as a mechanism for platelet dysregulation and age-induced thrombosis.

From Hematopoietic Stem Cells to Platelets: Unifying Differentiation Pathways Identified by Lineage Tracing Mouse Models

Platelets are the terminal progeny of megakaryocytes, primarily produced in the bone marrow, and play critical roles in blood homeostasis, clotting, and wound healing. Traditionally, megakaryocytes and platelets are thought to arise from multipotent hematopoietic stem cells (HSCs) via multiple discrete progenitor populations with successive, lineage-restricting differentiation steps. However, this view has recently been challenged by studies suggesting that (1) some HSC clones are biased and/or restricted to the platelet lineage, (2) not all platelet generation follows the "canonical" megakaryocytic differentiation path of hematopoiesis, and (3) platelet output is the default program of steady-state hematopoiesis. Here, we specifically investigate the evidence that in vivo lineage tracing studies provide for the route(s) of platelet generation and investigate the involvement of various intermediate progenitor cell populations. We further identify the challenges that need to be overcome that are required to determine the presence, role, and kinetics of these possible alternate pathways.

The emerging family of RORγt+ antigen-presenting cells

Antigen-presenting cells (APCs) are master regulators of the immune response by directly interacting with T cells to orchestrate distinct functional outcomes. Several types of professional APC exist, including conventional dendritic cells, B cells and macrophages, and numerous other cell types have non-classical roles in antigen presentation, such as thymic epithelial cells, endothelial cells and granulocytes. Accumulating evidence indicates the presence of a new family of APCs marked by the lineage-specifying transcription factor retinoic acid receptor-related orphan receptor-γt (RORγt) and demonstrates that these APCs have key roles in shaping immunity, inflammation and tolerance, particularly in the context of host-microorganism interactions. These RORγt+ APCs include subsets of group 3 innate lymphoid cells, extrathymic autoimmune regulator-expressing cells and, potentially, other emerging populations. Here, we summarize the major findings that led to the discovery of these RORγt+ APCs and their associated functions. We discuss discordance in recent reports and identify gaps in our knowledge in this burgeoning field, which has tremendous potential to advance our understanding of fundamental immune concepts.

The Impact of Juvenile Microglia Transcriptomics on the Adult Brain Regeneration after Cerebral Ischemia

Microglial cells play a pivotal role in the brain's health and operation through all stages of life and in the face of illness. The contributions of microglia during the developmental phase of the brain markedly contrast with their contributions in the brain of adults after injury. Enhancing our understanding of the pathological mechanisms that involve microglial activity in brains as they age and in cerebrovascular conditions is crucial for informing the creation of novel therapeutic approaches. In this work we provide results on microglia transcriptomics in the juvenile vs injured adult brain and its impact on adult brain regeneration after cerebral ischemia. During fetal brain development, microglia cells are involved in gliogenesis, angiogenesis, axonal outgrowth, synaptogenesis, neurogenesis and synaptic reorganization by engulfing neuronal extensions. Within the mature, intact brain, microglial cells exhibit reduced movement of their processes in response to minimal neuronal activity, while they continuously monitor their surroundings and clear away cellular debris. Following a stroke in the adult brain, inflammation, neurodegeneration, or disruptions in neural equilibrium trigger alterations in both the genetic blueprint and the structure and roles of microglia, a state often described as "activated" microglia. Such genetic shifts include a notable increase in the pathways related to phagosomes, lysosomes, and the presentation of antigens, coupled with a rise in the expression of genes linked to cell surface receptors. We conclude that a comparison of microglia transcriptomic activity during brain development and post-stroke adult brain might provide us with new clues about how neurodegeneration occurs in the adult brain. This information could very useful to develop drugs to slow down or limit the post-stroke pathology and improve clinical outcome.

Induced pluripotent and CD34+ stem cell derived myeloid cells display differential responses to particle and dust mite exposure

Myeloid cells form an essential component of initial responses to environmental hazards and toxic exposures. The ability to model these responses in vitro is central to efforts tasked with identifying hazardous materials and understanding mechanisms of injury and disease. Induced pluripotent stem cell (iPSC) derived cells have been suggested as alternatives to more established primary cell testing systems for these purposes. iPSC derived macrophage and dendritic like cells were compared to CD34+ haematopoietic stem cell derived populations using transcriptomic analysis. Using single cell sequencing-based characterisation of iPSC derived myeloid cells, we identified transitional, mature and M2 like macrophages as well as dendritic like antigen presenting cells and fibrocytes. Direct transcriptomic comparisons between iPSC and CD34+ cell derived populations revealed higher expression of myeloid differentiation genes such as MNDA, CSF1R and CSF2RB in CD34+ cells, while iPSC populations had higher fibroblastic and proliferative markers. Exposure of differentiated macrophage populations to nanoparticle alone or in combination with dust mite, resulted in differential gene expression on combination only, with responses markedly absent in iPSC compared to CD34+ derived cells. The lack of responsiveness in iPSC derived cells may be attributable to lower levels of dust mite component receptors CD14, TLR4, CLEC7A and CD36. In summary, iPSC derived myeloid cells display typical characteristics of immune cells but may lack a fully mature phenotype to adequately respond to environmental exposures.

Neuroglia Cells Transcriptomic in Brain Development, Aging and Neurodegenerative Diseases

Glia cells are essential for brain functioning during development, aging and disease. However, the role of astroglia plays during brain development is quite different from the role played in the adult lesioned brain. Therefore, a deeper understanding of pathomechanisms underlying astroglia activity in the aging brain and cerebrovascular diseases is essential to guide the development of new therapeutic strategies. To this end, this review provides a comparison between the transcriptomic activity of astroglia cells during development, aging and neurodegenerative diseases, including cerebral ischemia. During fetal brain development, astrocytes and microglia often affect the same developmental processes such as neuro-/gliogenesis, angiogenesis, axonal outgrowth, synaptogenesis, and synaptic pruning. In the adult brain astrocytes are a critical player in the synapse remodeling by mediating synapse elimination while microglia activity has been associated with changes in synaptic plasticity and remove cell debris by constantly sensing the environment. However, in the lesioned brain astrocytes proliferate and play essential functions with regard to energy supply to the neurons, neurotransmission and buildup of a protective scar isolating the lesion site from the surroundings. Inflammation, neurodegeneration, or loss of brain homeostasis induce changes in microglia gene expression, morphology, and function, generally referred to as "primed" microglia. These changes in gene expression are characterized by an enrichment of phagosome, lysosome, and antigen presentation signaling pathways and is associated with an up-regulation of genes encoding cell surface receptors. In addition, primed microglia are characterized by upregulation of a network of genes in response to interferon gamma. Conclusion. A comparison of astroglia cells transcriptomic activity during brain development, aging and neurodegenerative disorders might provide us with new therapeutic strategies with which to protect the aging brain and improve clinical outcome.

IL-7 and IL-7R in health and disease: An update through COVID times

The role of IL-7 and IL-7R for normal lymphoid development and an adequately functioning immune system has been recognized for long, with severe immune deficiency and lymphoid leukemia as extreme examples of the consequences of deregulation of the IL-7-IL-7R axis. In this review, we provide an update (focusing on the past couple of years) on IL-7 and IL-7R in health and disease. We highlight the findings on IL-7/IL-7R signaling mechanisms and the, sometimes controversial, impact of IL-7 and its receptor on leukocyte biology, COVID-19, acute lymphoblastic leukemia, and different solid tumors, as well as their relevance as therapeutic tools or targets.

SILAC-based quantitative proteomics to investigate the eicosanoid associated inflammatory response in activated macrophages

BACKGROUND

Macrophages play a central role in inflammation by phagocytosing invading pathogens, apoptotic cells and debris, as well as mediating repair of tissues damaged by trauma. In order to do this, these dynamic cells generate a variety of inflammatory mediators including eicosanoids such as prostaglandins, leukotrienes and hydroxyeicosatraenoic acids (HETEs) that are formed through the cyclooxygenase, lipoxygenase and cytochrome P450 pathways. The ability to examine the effects of eicosanoid production at the protein level is therefore critical to understanding the mechanisms associated with macrophage activation.

RESULTS

This study presents a stable isotope labelling with amino acids in cell culture (SILAC) -based proteomics strategy to quantify the changes in macrophage protein abundance following inflammatory stimulation with Kdo2-lipid A and ATP, with a focus on eicosanoid metabolism and regulation. Detailed gene ontology analysis, at the protein level, revealed several key pathways with a decrease in expression in response to macrophage activation, which included a promotion of macrophage polarisation and dynamic changes to energy requirements, transcription and translation. These findings suggest that, whilst there is evidence for the induction of a pro-inflammatory response in the form of prostaglandin secretion, there is also metabolic reprogramming along with a change in cell polarisation towards a reduced pro-inflammatory phenotype.

CONCLUSIONS

Advanced quantitative proteomics in conjunction with functional pathway network analysis is a useful tool to investigate the molecular pathways involved in inflammation.

Midkine expression by stem-like tumor cells drives persistence to mTOR inhibition and an immune-suppressive microenvironment

mTORC1 is hyperactive in multiple cancer types1,2. Here, we performed integrative analysis of single cell transcriptomic profiling, paired T cell receptor (TCR) sequencing, and spatial transcriptomic profiling on Tuberous Sclerosis Complex (TSC) associated tumors with mTORC1 hyperactivity, and identified a stem-like tumor cell state (SLS) linked to T cell dysfunction via tumor-modulated immunosuppressive macrophages. Rapamycin and its derivatives (rapalogs) are the primary treatments for TSC tumors, and the stem-like tumor cells showed rapamycin resistance in vitro, reminiscent of the cytostatic effects of these drugs in patients. The pro-angiogenic factor midkine (MDK) was highly expressed by the SLS population, and associated with enrichment of endothelial cells in SLS-dominant samples. Inhibition of MDK showed synergistic benefit with rapamycin in reducing the growth of TSC cell lines in vitro and in vivo. In aggregate, this study suggests an autocrine rapamycin resistance mechanism and a paracrine tumor survival mechanism via immune suppression adopted by the stem-like state tumor cells with mTORC1 hyperactivity.

IL7Rα, but not Flk2, is required for hematopoietic stem cell reconstitution of tissue-resident lymphoid cells

Tissue-resident lymphoid cells (TLCs) span the spectrum of innate-to-adaptive immune function. Unlike traditional, circulating lymphocytes that are continuously generated from hematopoietic stem cells (HSCs), many TLCs are of fetal origin and poorly generated from adult HSCs. Here, we sought to further understand murine TLC development and the roles of Flk2 and IL7Rα, two cytokine receptors with known function in traditional lymphopoiesis. Using Flk2- and Il7r-Cre lineage tracing, we found that peritoneal B1a cells, splenic marginal zone B (MZB) cells, lung ILC2s and regulatory T cells (Tregs) were highly labeled. Despite high labeling, loss of Flk2 minimally affected the generation of these cells. In contrast, loss of IL7Rα, or combined deletion of Flk2 and IL7Rα, dramatically reduced the number of B1a cells, MZBs, ILC2s and Tregs, both in situ and upon transplantation, indicating an intrinsic and essential role for IL7Rα. Surprisingly, reciprocal transplants of wild-type HSCs showed that an IL7Rα^−/− environment selectively impaired reconstitution of TLCs when compared with TLC numbers in situ. Taken together, our data defined Flk2- and IL7Rα-positive TLC differentiation paths, and revealed functional roles of Flk2 and IL7Rα in TLC establishment.

Summary: Tissue-resident lymphoid cells develop via IL7Rα-positive progenitors and are repopulated by transplanted adult hematopoietic stem cells; however, such TLC lymphopoiesis cannot be fully rescued in IL7Rα^−/− recipient mice.

IL7R Is Correlated With Immune Cell Infiltration in the Tumor Microenvironment of Lung Adenocarcinoma

Tumor microenvironment plays an important role in the development, progression, and prognosis of lung adenocarcinoma. Exploring new biomarkers based on the immune microenvironment of lung adenocarcinoma can effectively predict the prognosis and provide effective clinical treatment. In this study, we used the ESTIMATE algorithm to score the immune and stromal components in lung adenocarcinoma data downloaded from the TCGA database. The result showed that the immune/stromal score was associated with clinical features and prognosis of lung adenocarcinoma patients. Interleukin-7 receptor (IL7R) is an important prognostic biomarker identified by intersection analysis of protein-protein interaction networks and Cox regression survival analysis. According to TCGA and Oncomine database analysis, IL7R expression in adenocarcinoma tissues was significantly lower than that in normal lung tissues and was further verified in clinical tissue samples. Survival analysis showed IL7R was an independent prognostic factor of lung adenocarcinoma. IL7R expression was positively correlated with the overall survival and progression-free survival of lung adenocarcinoma patients and negatively correlated with tumor size. Our results suggest that IL7R inhibits tumor growth by regulating the proportion of immune infiltrating cells in the tumor immune microenvironment. IL7R could be a beneficial prognostic marker in patients with lung adenocarcinoma and has great potential in immune therapy.

Analyzing Prognostic Hub Genes in the Microenvironment of Cutaneous Melanoma by Computer Integrated Bioinformatics

Cutaneous melanoma (CM) is attracting increasing attention due to high mortality. In response to this, we synthetically analyze the CM dataset from the TCGA database and explore microenvironment-related genes that effectively predict patient prognosis. Immune/stromal scores of cases are calculated using the ESTIMATE algorithm and are significantly associated with overall patient survival. Then, differentially expressed genes are identified by comparing the immune score and stromal score, also prognostic genes are subsequently screened. Functional analysis shows that these genes are enriched in different activities of immune system. Moreover, 19 prognosis-related hub genes are extracted from the protein-protein interaction network, of which four unreported genes (IL7R, FLT3, C1QC, and HLA-DRB5) are chosen for validation. A significant negative relationship is found between the expression levels of the 4 genes and pathological stages, notably T grade. Furthermore, the K-M plots and TIMER results show that these genes have favorable value for CM prognosis. In conclusion, these results give a novel insight into CM and identify IL7R, FLT3, C1QC, and HLA-DRB5 as crucial roles for the diagnosis and treatment of CM.

New transgenic mouse models enabling pan-hematopoietic or selective hematopoietic stem cell depletion in vivo

Hematopoietic stem cell (HSC) multipotency and self-renewal are typically defined through serial transplantation experiments. Host conditioning is necessary for robust HSC engraftment, likely by reducing immune-mediated rejection and by clearing limited HSC niche space. Because irradiation of the recipient mouse is non-specific and broadly damaging, there is a need to develop alternative models to study HSC performance at steady-state and in the absence of radiation-induced stress. We have generated and characterized two new mouse models where either all hematopoietic cells or only HSCs can be specifically induced to die in vivo or in vitro. Hematopoietic-specific Vav1-mediated expression of a loxP-flanked diphtheria-toxin receptor (DTR) renders all hematopoietic cells sensitive to diphtheria toxin (DT) in “Vav-DTR” mice. Crossing these mice to Flk2-Cre mice results in “HSC-DTR” mice which exhibit HSC-selective DT sensitivity. We demonstrate robust, rapid, and highly selective cell ablation in these models. These new mouse models provide a platform to test whether HSCs are required for long-term hematopoiesis in vivo, for understanding the mechanisms regulating HSC engraftment, and interrogating in vivo hematopoietic differentiation pathways and mechanisms regulating hematopoietic homeostasis.

CD127 imprints functional heterogeneity to diversify monocyte responses in inflammatory diseases

Inflammatory monocytes are key mediators of acute and chronic inflammation; yet, their functional diversity remains obscure. Single-cell transcriptome analyses of human inflammatory monocytes from COVID-19 and rheumatoid arthritis patients revealed a subset of cells positive for CD127, an IL-7 receptor subunit, and such positivity rendered otherwise inert monocytes responsive to IL-7. Active IL-7 signaling engaged epigenetically coupled, STAT5-coordinated transcriptional programs to restrain inflammatory gene expression, resulting in inverse correlation between CD127 expression and inflammatory phenotypes in a seemingly homogeneous monocyte population. In COVID-19 and rheumatoid arthritis, CD127 marked a subset of monocytes/macrophages that retained hypoinflammatory phenotypes within the highly inflammatory tissue environments. Furthermore, generation of an integrated expression atlas revealed unified features of human inflammatory monocytes across different diseases and different tissues, exemplified by those of the CD127high subset. Overall, we phenotypically and molecularly characterized CD127-imprinted functional heterogeneity of human inflammatory monocytes with direct relevance for inflammatory diseases.

Transcriptomic and Lipidomic Mapping of Macrophages in the Hub of Chronic Beta-Adrenergic-Stimulation Unravels Hypertrophy-, Proliferation-, and Lipid Metabolism-Related Genes as Novel Potential Markers of Early Hypertrophy or Heart Failure

Sympathetic nervous system overdrive with chronic release of catecholamines is the most important neurohormonal mechanism activated to maintain cardiac output in response to heart stress. Beta-adrenergic signaling behaves first as a compensatory pathway improving cardiac contractility and maladaptive remodeling but becomes dysfunctional leading to pathological hypertrophy and heart failure (HF). Cardiac remodeling is a complex inflammatory syndrome where macrophages play a determinant role. This study aimed at characterizing the temporal transcriptomic evolution of cardiac macrophages in mice subjected to beta-adrenergic-stimulation using RNA sequencing. Owing to a comprehensive bibliographic analysis and complementary lipidomic experiments, this study deciphers typical gene profiles in early compensated hypertrophy (ECH) versus late dilated remodeling related to HF. We uncover cardiac hypertrophy- and proliferation-related transcription programs typical of ECH or HF macrophages and identify lipid metabolism-associated and Na⁺ or K⁺ channel-related genes as markers of ECH and HF macrophages, respectively. In addition, our results substantiate the key time-dependent role of inflammatory, metabolic, and functional gene regulation in macrophages during beta-adrenergic dependent remodeling. This study provides important and novel knowledge to better understand the prevalent key role of resident macrophages in response to chronically activated beta-adrenergic signaling, an effective diagnostic and therapeutic target in failing hearts.

Clearing the Haze: How Does Nicotine Affect Hematopoiesis before and after Birth?

Hematopoiesis is a tightly regulated process orchestrated by cell-intrinsic and cell-extrinsic cues. Over the past several decades, much effort has been focused on understanding how these cues regulate hematopoietic stem cell (HSC) function. Many endogenous key regulators of hematopoiesis have been identified and extensively characterized. Less is known about the mechanisms of long-term effects of environmental toxic compounds on hematopoietic stem and progenitor cells (HSPCs) and their mature immune cell progeny. Research over the past several decades has demonstrated that tobacco products are extremely toxic and pose huge risks to human health by causing diseases like cancer, respiratory illnesses, strokes, and more. Recently, electronic cigarettes have been promoted as a safer alternative to traditional tobacco products and have become increasingly popular among younger generations. Nicotine, the highly toxic compound found in many traditional tobacco products, is also found in most electronic cigarettes, calling into question their purported "safety". Although it is known that nicotine is toxic, the pathophysiology of disease in exposed people remains under investigation. One plausible contributor to altered disease susceptibility is altered hematopoiesis and associated immune dysfunction. In this review, we focus on research that has addressed how HSCs and mature blood cells respond to nicotine, as well as identify remaining questions.

CFU-S assay: a historical single-cell assay that offers modern insight into clonal hematopoiesis

Hematopoietic stem cells (HSCs) have been studied extensively since their initial functional description in 1961 when Dr. James Till and Dr. Ernest McCulloch developed the first in vivo clonal strategy, termed the spleen colony-forming unit (CFU-S) assay, to assess the functional capacity of bone marrow-derived hematopoietic progenitors at the single-cell level. Through transplantation of bone marrow cells and analysis of the resulting cellular nodules in the spleen, the CFU-S assay revealed both the self-renewal and clonal differentiation capacity of hematopoietic progenitors. Further development and use of this assay have identified highly proliferative, self-renewing, and differentiating HSCs that possess clonal, multilineage differentiation. The CFU-S strategy has also been adapted to interrogating single purified hematopoietic stem and progenitor cell populations, advancing our knowledge of the hematopoietic hierarchy. In this review, we explore the major discoveries made with the CFU-S assay, consider its modern use and recent improvements, and compare it with commonly used long-term transplantation assays to determine the continued value of the CFU-S assay for understanding HSC biology and hematopoiesis.

Acute and endothelial-specific Robo4 deletion affect hematopoietic stem cell trafficking independent of VCAM1

Hematopoietic stem cell (HSC) trafficking is regulated by a number of complex mechanisms. Among them are the transmembrane protein Robo4 and the vascular cell adhesion molecule, VCAM1. Endothelial VCAM1 is a well-known regulator of hematopoietic cell trafficking, and our previous studies revealed that germline deletion of Robo4 led to impaired HSC trafficking, with an increase in vascular endothelial cell (VEC) numbers and downregulation of VCAM1 protein on sinusoidal VECs. Here, we utilized two Robo4 conditional deletion models in parallel with Robo4 germline knockout mice (R4KO) to evaluate the effects of acute and endothelial cell-specific Robo4 deletion on HSC trafficking. Strikingly similar to the R4KO, the acute deletion of Robo4 resulted in altered HSC distribution between the bone marrow and blood compartments, despite normal numbers of VECs and wild-type levels of VCAM1 cell surface protein on sinusoidal VECs. Additionally, consistent with the R4KO mice, acute loss of Robo4 in the host perturbed long-term engraftment of donor wild-type HSCs and improved HSC mobilization to the peripheral blood. These data demonstrate the significant role that endothelial Robo4 plays in directional HSC trafficking, independent of alterations in VEC numbers and VCAM1 expression.

Megakaryocyte progenitor cell function is enhanced upon aging despite the functional decline of aged hematopoietic stem cells

Age-related morbidity is associated with a decline in hematopoietic stem cell (HSC) function, but the mechanisms of HSC aging remain unclear. We performed heterochronic HSC transplants followed by quantitative analysis of cell reconstitution. Although young HSCs outperformed old HSCs in young recipients, young HSCs unexpectedly failed to outcompete the old HSCs of aged recipients. Interestingly, despite substantial enrichment of megakaryocyte progenitors (MkPs) in old mice in situ and reported platelet (Plt) priming with age, transplanted old HSCs were deficient in reconstitution of all lineages, including MkPs and Plts. We therefore performed functional analysis of young and old MkPs. Surprisingly, old MkPs displayed unmistakably greater regenerative capacity compared with young MkPs. Transcriptome analysis revealed putative molecular regulators of old MkP expansion. Collectively, these data demonstrated that aging affects HSCs and megakaryopoiesis in fundamentally different ways: whereas old HSCs functionally decline, MkPs gain expansion capacity upon aging.

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Reconstitution deficit by old HSCs was observed by chimerism and absolute cell numbers

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Young HSCs did not outcompete resident HSCs in aged recipient mice

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Old MkPs display remarkable capacity to engraft, expand, and reconstitute platelets

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Aging is associated with changes in MkP genome-wide expression signatures

Data mining of immune-related prognostic genes in metastatic melanoma microenvironment

Skin cutaneous melanoma (SKCM) is one of the most deadly malignancies. Although immunotherapies showed the potential to improve the prognosis for metastatic melanoma patients, only a small group of patients can benefit from it. Therefore, it is urgent to investigate the tumor microenvironment in melanoma as well as to identify efficient biomarkers in the diagnosis and treatments of SKCM patients. A comprehensive analysis was performed based on metastatic melanoma samples from the Cancer Genome Atlas (TCGA) database and ESTIMATE algorithm, including gene expression, immune and stromal scores, prognostic immune‐related genes, infiltrating immune cells analysis and immune subtype identification. Then, the differentially expressed genes (DEGs) were obtained based on the immune and stromal scores, and a list of prognostic immune‐related genes was identified. Functional analysis and the protein–protein interaction network revealed that these genes enriched in multiple immune-related biological processes. Furthermore, prognostic genes were verified in the Gene Expression Omnibus (GEO) databases and used to predict immune infiltrating cells component. Our study revealed seven immune subtypes with different risk values and identified T cells as the most abundant cells in the immune microenvironment and closely associated with prognostic outcomes. In conclusion, the present study thoroughly analyzed the tumor microenvironment and identified prognostic immune‐related biomarkers for metastatic melanoma.

A wave of bipotent T/ILC-restricted progenitors shapes the embryonic thymus microenvironment in a time-dependent manner

During embryonic development, multiple waves of hematopoietic progenitors with distinct lineage potential are differentially regulated in time and space. Two different waves of thymic progenitors colonize the fetal thymus where they contribute to thymic organogenesis and homeostasis. The origin, the lineage differentiation potential of the first wave, and their relative contribution in shaping the thymus architecture, remained, however, unclear. Here, we show that the first wave of thymic progenitors comprises a unique population of bipotent T and innatel lymphoid cells (T/ILC), generating a lymphoid tissue inducer cells (LTi's), in addition to invariant Vγ5+ T cells. Transcriptional analysis revealed that innate lymphoid gene signatures and, more precisely, the LTi-associated transcripts were expressed in the first, but not in the second, wave of thymic progenitors. Depletion of early thymic progenitors in a temporally controlled manner showed that the progeny of the first wave is indispensable for the differentiation of autoimmune regulator-expressing medullary thymic epithelial cells (mTECs). We further show that these progenitors are of strict hematopoietic stem cell origin, despite the overlap between lymphopoiesis initiation and the transient expression of lymphoid-associated transcripts in yolk sac (YS) erythromyeloid-restricted precursors. Our work highlights the relevance of the developmental timing on the emergence of different lymphoid subsets, required for the establishment of a functionally diverse immune system.

EKLF/KLF1 expression defines a unique macrophage subset during mouse erythropoiesis

Erythroblastic islands are a specialized niche that contain a central macrophage surrounded by erythroid cells at various stages of maturation. However, identifying the precise genetic and transcriptional control mechanisms in the island macrophage remains difficult due to macrophage heterogeneity. Using unbiased global sequencing and directed genetic approaches focused on early mammalian development, we find that fetal liver macrophages exhibit a unique expression signature that differentiates them from erythroid and adult macrophage cells. The importance of erythroid Krüppel-like factor (EKLF)/KLF1 in this identity is shown by expression analyses in EKLF-/- and in EKLF-marked macrophage cells. Single-cell sequence analysis simplifies heterogeneity and identifies clusters of genes important for EKLF-dependent macrophage function and novel cell surface biomarkers. Remarkably, this singular set of macrophage island cells appears transiently during embryogenesis. Together, these studies provide a detailed perspective on the importance of EKLF in the establishment of the dynamic gene expression network within erythroblastic islands in the developing embryo and provide the means for their efficient isolation.

Environmental signals rather than layered ontogeny imprint the function of type 2 conventional dendritic cells in young and adult mice

Conventional dendritic cells (cDC) are key activators of naive T cells, and can be targeted in adults to induce adaptive immunity, but in early life are considered under-developed or functionally immature. Here we show that, in early life, when the immune system develops, cDC2 exhibit a dual hematopoietic origin and, like other myeloid and lymphoid cells, develop in waves. Developmentally distinct cDC2 in early life, despite being distinguishable by fate mapping, are transcriptionally and functionally similar. cDC2 in early and adult life, however, are exposed to distinct cytokine environments that shape their transcriptional profile and alter their ability to sense pathogens, secrete cytokines and polarize T cells. We further show that cDC2 in early life, despite being distinct from cDC2 in adult life, are functionally competent and can induce T cell responses. Our results thus highlight the potential of harnessing cDC2 for boosting immunity in early life.

Chromatin accessibility maps provide evidence of multilineage gene priming in hematopoietic stem cells

Hematopoietic stem cells (HSCs) have the capacity to differentiate into vastly different types of mature blood cells. The epigenetic mechanisms regulating the multilineage ability, or multipotency, of HSCs are not well understood. To test the hypothesis that cis-regulatory elements that control fate decisions for all lineages are primed in HSCs, we used ATAC-seq to compare chromatin accessibility of HSCs with five unipotent cell types. We observed the highest similarity in accessibility profiles between megakaryocyte progenitors and HSCs, whereas B cells had the greatest number of regions with de novo gain in accessibility during differentiation. Despite these differences, we identified cis-regulatory elements from all lineages that displayed epigenetic priming in HSCs. These findings provide new insights into the regulation of stem cell multipotency, as well as a resource to identify functional drivers of lineage fate.

IRF5 guides monocytes toward an inflammatory CD11c+ macrophage phenotype and promotes intestinal inflammation

Mononuclear phagocytes (MNPs) are vital for maintaining intestinal homeostasis but, in response to acute microbial stimulation, can also trigger immunopathology, accelerating recruitment of Ly6C^hi monocytes to the gut. The regulators that control monocyte tissue adaptation in the gut remain poorly understood. Interferon regulatory factor 5 (IRF5) is a transcription factor previously shown to play a key role in maintaining the inflammatory phenotype of macrophages. Here, we investigate the impact of IRF5 on the MNP system and physiology of the gut at homeostasis and during inflammation. We demonstrate that IRF5 deficiency has a limited impact on colon physiology at steady state but ameliorates immunopathology during Helicobacter hepaticus-induced colitis. Inhibition of IRF5 activity in MNPs phenocopies global IRF5 deficiency. Using a combination of bone marrow chimera and single-cell RNA-sequencing approaches, we examined the intrinsic role of IRF5 in controlling colonic MNP development. We demonstrate that IRF5 promotes differentiation of Ly6C^hi monocytes into CD11c⁺ macrophages and controls the production of antimicrobial and inflammatory mediators by these cells. Thus, we identify IRF5 as a key transcriptional regulator of the colonic MNP system during intestinal inflammation.

Distinct developmental pathways from blood monocytes generate human lung macrophage diversity

The study of human macrophages and their ontogeny is an important unresolved issue. Here, we use a humanized mouse model expressing human cytokines to dissect the development of lung macrophages from human hematopoiesis in vivo. Human CD34⁺ hematopoietic stem and progenitor cells (HSPCs) generated three macrophage populations, occupying separate anatomical niches in the lung. Intravascular cell labeling, cell transplantation, and fate-mapping studies established that classical CD14⁺ blood monocytes derived from HSPCs migrated into lung tissue and gave rise to human interstitial and alveolar macrophages. In contrast, non-classical CD16⁺ blood monocytes preferentially generated macrophages resident in the lung vasculature (pulmonary intravascular macrophages). Finally, single-cell RNA sequencing defined intermediate differentiation stages in human lung macrophage development from blood monocytes. This study identifies distinct developmental pathways from circulating monocytes to lung macrophages and reveals how cellular origin contributes to human macrophage identity, diversity, and localization in vivo.

Interleukin 7 receptor is required for myeloid cell homeostasis and reconstitution by hematopoietic stem cells

Respiratory diseases are a leading cause of death worldwide, with vulnerability to disease varying greatly between individuals. The reasons underlying disease susceptibility are unknown, but there is often a variable immune response in lungs often. Recently, we identified a surprising novel role for the interleukin 7 receptor (IL7R), a primarily lymphoid-associated regulator, in fetal-specified, lung-resident macrophage development. Here, we report that traditional, hematopoietic stem cell-derived myeloid cells in the adult lung, peripheral blood, and bone marrow also depend on IL7R expression. Using single- and double-germline knockout models, we found that eosinophil numbers were reduced on deletion of IL7Rα. We then employed two Cre recombinase models in lineage tracing experiments to test whether these cells developed through an IL7Rα+ pathway. Despite the impact of IL7Rα deletion, IL7R-Cre labeled only a minimal fraction of eosinophils. We therefore examined the intrinsic versus extrinsic requirement for IL7R in the production of eosinophils using reciprocal hematopoietic stem cell transplantation assays. These assays revealed that extrinsic, but not eosinophil-intrinsic, IL7R is required for eosinophil reconstitution by HSCs in the adult lung. To determine which external factors may be influencing eosinophil development and survival, we performed a cytokine array analysis between wild-type and IL7Rα-deficient mice and found several differentially regulated proteins. These findings expand on our previous report that IL7R is required not only for proper lymphoid cell development and homeostasis, but also for myeloid cell homeostasis in tissues.

Identifying the pattern of immune related cells and genes in the peripheral blood of ischemic stroke

Background

Ischemic stroke (IS) is the second leading cause of death worldwide which is a serious hazard to human health. Evidence suggests that the immune system plays a key role in the pathophysiology of IS. However, the precisely immune related mechanisms were still not been systematically understood.

Methods

In this study, we aim to identify the immune related modules and genes that might play vital role in the occurrence and development of IS by using the weighted gene co-expression network analysis (WGCNA). Meanwhile, we applied a kind of deconvolution algorithm to reveal the proportions of 22 subsets of immune cells in the blood samples.

Results

There were total 128 IS patients and 67 healthy control samples in the three Gene Expression Omnibus (GEO) datasets. Under the screening criteria, 1082 DEGs (894 up-regulated and 188 down-regulated) were chosen for further analysis. A total of 11 clinically significant modules were identified, from which immune-related hub modules and hub genes were further explored. Finally, 16 genes were selected as real hub genes for further validation analysis. Furthermore, these CIBERSORT results suggest that detailed analysis of the immune subtype distribution pattern has the potential to enhance clinical prediction and to identify candidates for immunotherapy. More specifically, we identified that neutrophil emerge as a promising target for IS therapies.

Conclusions

In the present study, we investigated the immune related gene expression modules, in which the SLAMF1, IL7R and NCF4 may be novel therapeutic targets to promote functional and histological recovery after ischemic stroke. Furthermore, these hub genes and neutrophils may become important biological targets in the drug screening and drug designing.

Ubiquitous overexpression of CXCL12 confers radiation protection and enhances mobilization of hematopoietic stem and progenitor cells

C-X-C motif chemokine ligand 12 (CXCL12; aka SDF1α) is a major regulator of a number of cellular systems, including hematopoiesis, where it influences hematopoietic cell trafficking, proliferation, and survival during homeostasis and upon stress and disease. A variety of constitutive, temporal, ubiquitous, and cell-specific loss-of-function models have documented the functional consequences on hematopoiesis upon deletion of Cxcl12. Here, in contrast to loss-of-function experiments, we implemented a gain-of-function approach by generating a doxycycline-inducible transgenic mouse model that enables spatial and temporal overexpression of Cxcl12. We demonstrated that ubiquitous CXCL12 overexpression led to an increase in multipotent progenitors in the bone marrow and spleen. The CXCL12+ mice displayed reduced reconstitution potential as either donors or recipients in transplantation experiments. Additionally, we discovered that Cxcl12 overexpression improved hematopoietic stem and progenitor cell mobilization into the blood, and conferred radioprotection by promoting quiescence. Thus, this new CXCL12+ mouse model provided new insights into major facets of hematopoiesis and serves as a versatile resource for studying CXCL12 function in a variety of contexts.

Immune serum-activated human macrophages coordinate with eosinophils to immobilize Ascaris suum larvae

Helminth infection represents a major health problem causing approximately 5 million disability-adjusted life years worldwide. Concerns that repeated anti-helminthic treatment may lead to drug resistance render it important that vaccines are developed but will require increased understanding of the immune-mediated cellular and antibody responses to helminth infection. IL-4 or antibody-activated murine macrophages are known to immobilize parasitic nematode larvae, but few studies have addressed whether this is translatable to human macrophages. In the current study, we investigated the capacity of human macrophages to recognize and attack larval stages of Ascaris suum, a natural porcine parasite that is genetically similar to the human helminth Ascaris lumbricoides. Human macrophages were able to adhere to and trap A suum larvae in the presence of either human or pig serum containing Ascaris-specific antibodies and other factors. Gene expression analysis of serum-activated macrophages revealed that CCL24, a potent eosinophil attractant, was the most upregulated gene following culture with A suum larvae in vitro, and human eosinophils displayed even greater ability to adhere to, and trap, A suum larvae. These data suggest that immune serum-activated macrophages can recruit eosinophils to the site of infection, where they act in concert to immobilize tissue-migrating Ascaris larvae.

Macrophages represent the major pool of IL-7Rα expressing cells in patients with myocarditis

Myocarditis is characterized by infiltration and activation of cytokine as well as chemokine receptors frequently producing heart failure. Causes are often infections triggering inflammatory and immune responses but these initial lines of defense might be finally disastrous. To identify mediators we screened various receptors by confocal microscopy and identified cardiac interleukin-7 (IL-7) receptor-α (IL-7Rα) expressing cells in patients with myocarditis. IL-7Rα+ cells were analyzed by markers for leukocytes (CD45), B cells (CD19), T cells (CD3, CD4, CD8) and macrophages (CD68, CD163, CD206). Immune cells were hardly detected in controls. In patients with myocarditis main inflammatory populations consisted of macrophages and T cells. B cells were hardly present. 90% of CD68+ macrophages but less than 20% of CD3+ T cells were IL-7Rα+. This was surprising since T and B lymphocytes are generally regarded as the major IL-7Rα+ cells. Since IL-7 acts as a chemokine, the expression of its receptor might orchestrate cardiac macrophage infiltration. In contrast, consumption of IL-7 by IL-7Rα+ cardiac macrophages might potentially prevent a certain overshooting immune reaction and sepsis by reducing proliferation and survival of lymphocytes. Our data suggest a participation of IL-7Rα+ macrophages in the development of myocarditis and heart failure.

Chronic Inflammation: A Common Promoter in Tertiary Lymphoid Organ Neogenesis

Tertiary lymphoid organs (TLOs) frequently develop locally in adults in response to non-resolving inflammation. Chronic inflammation leads to the differentiation of stromal fibroblast cells toward lymphoid tissue organizer-like cells, which interact with lymphotoxin α1β2+ immune cells. The interaction initiates lymphoid neogenesis by recruiting immune cells to the site of inflammation and ultimately leads to the formation of TLOs. Mature TLOs harbor a segregated T-cell zone, B-cell follicles with an activated germinal center, follicular dendritic cells, and high endothelial venules, which architecturally resemble those in secondary lymphoid organs. Since CXCL13 and LTα₁β₂ play key roles in TLO neogenesis, they might constitute potential biomarkers of TLO activity. The well-developed TLOs actively regulate local immune responses and influence disease progression, and they are thereby regarded as the powerhouses of local immunity. In this review, we recapitulated the determinants for TLOs development, with great emphasis on the fundamental role of chronic inflammation and tissue-resident stromal cells for TLO neogenesis, hence offering guidance for therapeutic interventions in TLO-associated diseases.

Flip the coin: IL-7 and IL-7R in health and disease

The cytokine IL-7 and its receptor, IL-7R, are critical for T cell and, in the mouse, B cell development, as well as differentiation and survival of naive T cells, and generation and maintenance of memory T cells. They are also required for innate lymphoid cell (ILC) development and maintenance, and consequently for generation of lymphoid structures and barrier defense. Here we discuss the central role of IL-7 and IL-7R in the lymphoid system and highlight the impact of their deregulation, placing a particular emphasis on their 'dark side' as promoters of cancer development. We also explore therapeutic implications and opportunities associated with either positive or negative modulation of the IL-7-IL-7R signaling axis.

Viagra Enables Efficient, Single-Day Hematopoietic Stem Cell Mobilization

Hematopoietic stem cell (HSC) transplantation is a curative treatment for a variety of blood and immune disorders. Currently available methods to obtain donor HSCs are suboptimal, and the limited supply of donor HSCs hampers the success and availability of HSC transplantation therapies. We recently showed that manipulation of vascular integrity can be employed to induce HSC mobilization from the bone marrow to the blood stream, facilitating non-invasive collection of HSCs. Here, we tested whether FDA-approved vasodilators are capable of mobilizing HSCs. We found that a rapid, 2-h regimen of a single oral dose of Viagra (sildenafil citrate) combined with a single injection of the CXCR4 antagonist AMD3100 leads to efficient HSC mobilization at levels rivaling the standard-of-care 5-day regimen of granulocyte-colony stimulating factor (G-CSF/Filgrastim/Neupogen). Our findings solidify vascular integrity as an essential regulator of HSC trafficking and provide an attractive, single-day regimen for HSC mobilization using already FDA-approved drugs.

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Viagra enhances AMD3100-mediated HSC mobilization

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Extremely rapid and efficient HSC mobilization with two FDA-approved drugs

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Vascular integrity regulates HSC trafficking

Prognostic genes of melanoma identified by weighted gene co-expression network analysis and drug repositioning using a network-based method

Melanoma is one of the most malignant types of skin cancer. However, the efficacy and utility of available drug therapies for melanoma are limited. The objective of the present study was to identify potential genes associated with melanoma progression and to explore approved therapeutic drugs that target these genes. Weighted gene co-expression network analysis was used to construct a gene co-expression network, explore the associations between genes and clinical characteristics and identify potential biomarkers. Gene expression profiles of the GSE65904 dataset were obtained from the Gene Expression Omnibus database. RNA-sequencing data and clinical information associated with melanoma obtained from The Cancer Genome Atlas were used for biomarker validation. A total of 15 modules were identified through average linkage hierarchical clustering. In the two significant modules, three network hub genes associated with melanoma prognosis were identified: C-X-C motif chemokine receptor 4 (CXCR4), interleukin 7 receptor (IL7R) and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit γ (PIK3CG). The receiver operating characteristic curve indicated that the mRNA levels of these genes exhibited excellent prognostic efficiency for primary and metastatic tumor tissues. In addition, the proximity between candidate genes associated with melanoma progression and drug targets obtained from DrugBank was calculated in the protein interaction network, and the top 15 drugs that may be suitable for treating melanoma were identified. In summary, co-expression network analysis led to the selection of CXCR4, IL7R and PIK3CG for further basic and clinical research on melanoma. Utilizing a network-based method, 15 drugs that exhibited potential for the treatment of melanoma were identified.