[Research advances in the development and function of macrophages and classical dendritic cells during resting and infection].

Macrophages (MACs) and classical dendritic cells (cDCs) represent the front line of immune defense, playing crucial roles in both innate and adaptive immunity due to their remarkable tissue specificity and precise adaptation to environmental cues. MACs contribute to maintaining tissue homeostasis and immune surveillance, while cDCs function as the most efficient antigen-presenting cells, playing a critical role in immune responses. These two cell types share similarities and interconnections. Both MACs and cDCs are capable of recognizing pathogens and tissue damage, secreting cytokines to activate other innate immune cells, and initiating or modulating adaptive immunity through interactions with T cells. In this review, we provide a comprehensive analysis of the research advances in the development and functions of MACs and cDCs during resting and infection processes, elucidate their interrelationships and interactions within the immune system, and offer a theoretical basis for in-depth studies of diseases.

Different species of Chiroptera: Immune cells and molecules.

The distinct composition and immune response characteristics of bats' innate and adaptive immune systems, which enable them to serve as host of numerous serious zoonotic viruses without falling ill, differ substantially from those of other mammals, it have garnered significant attention. In this article, we offer a systematic review of the names, attributes, and functions of innate and adaptive immune cells & molecules across different bat species. This includes descriptions of the differences shown by research between 71 bat species in 10 families, as well as comparisons between bats and other mammals. Studies of the immune cells & molecules of different bat species are necessary to understand the unique antiviral immunity of bats. By providing comprehensive information on these unique immune responses, it is hoped that new insights will be provided for the study of co-evolutionary dynamics between viruses and the bat immune system, as well as human antiviral immunity.

Kids' noses resist COVID-19.

Children resist COVID-19, and previous studies reported increased innate immunity in their upper airways. A new paper by Watkins et al. (https://doi.org/10.1084/jem.20230911) shows that the nasal mucosa of children is characterized by often asymptomatic viral and/or bacterial infections that dynamically regulate distinct innate immune programs.

Erythrocytes of the common carp are immune sentinels that sense pathogen molecular patterns, engulf particles and secrete pro-inflammatory cytokines against bacterial infection.

Introduction: Red blood cells (RBCs), also known as erythrocytes, are underestimated in their role in the immune system. In mammals, erythrocytes undergo maturation that involves the loss of nuclei, resulting in limited transcription and protein synthesis capabilities. However, the nucleated nature of non-mammalian RBCs is challenging this conventional understanding of RBCs. Notably, in bony fishes, research indicates that RBCs are not only susceptible to pathogen attacks but express immune receptors and effector molecules. However, given the abundance of RBCs and their interaction with every physiological system, we postulate that they act in surveillance as sentinels, rapid responders, and messengers. Methods: We performed a series of in vitro experiments with Cyprinus carpio RBCs exposed to Aeromonas hydrophila, as well as in vivo laboratory infections using different concentrations of bacteria. Results: qPCR revealed that RBCs express genes of several inflammatory cytokines. Using cyprinid-specific antibodies, we confirmed that RBCs secreted tumor necrosis factor alpha (TNFα) and interferon gamma (IFNγ). In contrast to these indirect immune mechanisms, we observed that RBCs produce reactive oxygen species and, through transmission electron and confocal microscopy, that RBCs can engulf particles. Finally, RBCs expressed and upregulated several putative toll-like receptors, including tlr4 and tlr9, in response to A. hydrophila infection in vivo. Discussion: Overall, the RBC repertoire of pattern recognition receptors, their secretion of effector molecules, and their swift response make them immune sentinels capable of rapidly detecting and signaling the presence of foreign pathogens. By studying the interaction between a bacterium and erythrocytes, we provide novel insights into how the latter may contribute to overall innate and adaptive immune responses of teleost fishes.

Life-history stage influences immune investment and oxidative stress in response to environmental heterogeneity in Antarctic fur seals.

Immune defenses are crucial for survival but costly to develop and maintain. Increased immune investment is therefore hypothesized to trade-off with other life-history traits. Here, we examined innate and adaptive immune responses to environmental heterogeneity in wild Antarctic fur seals. In a fully crossed, repeated measures design, we sampled 100 pups and their mothers from colonies of contrasting density during seasons of contrasting food availability. Biometric and cortisol data as well as blood for the analysis of 13 immune and oxidative status markers were collected at two key life-history stages. We show that immune responses of pups are more responsive than adults to variation in food availability, but not population density, and are modulated by cortisol and condition. Immune investment is associated with different oxidative status markers in pups and mothers. Our results suggest that early life stages show greater sensitivity to extrinsic and intrinsic effectors, and that immunity may be a strong target for natural selection even in low-pathogen environments such as Antarctica.

Unexpected regulatory functions of cyprinid Viperin on inflammation and metabolism.

BACKGROUND: Viperin, also known as radical S-adenosyl-methionine domain containing protein 2 (RSAD2), is an interferon-inducible protein that is involved in the innate immune response against a wide array of viruses. In mammals, Viperin exerts its antiviral function through enzymatic conversion of cytidine triphosphate (CTP) into its antiviral analog ddhCTP as well as through interactions with host proteins involved in innate immune signaling and in metabolic pathways exploited by viruses during their life cycle. However, how Viperin modulates the antiviral response in fish remains largely unknown. RESULTS: For this purpose, we developed a fathead minnow (Pimephales promelas) clonal cell line in which the unique viperin gene has been knocked out by CRISPR/Cas9 genome-editing. In order to decipher the contribution of fish Viperin to the antiviral response and its regulatory role beyond the scope of the innate immune response, we performed a comparative RNA-seq analysis of viperin-/- and wildtype cell lines upon stimulation with recombinant fathead minnow type I interferon. CONCLUSIONS: Our results revealed that Viperin does not exert positive feedback on the canonical type I IFN but acts as a negative regulator of the inflammatory response by downregulating specific pro-inflammatory genes and upregulating repressors of the NF-κB pathway. It also appeared to play a role in regulating metabolic processes, including one carbon metabolism, bone formation, extracellular matrix organization and cell adhesion.

Expression of ISG60 is induced by TLR3 signaling in BEAS­2B bronchial epithelial cells: Possible involvement in CXCL10 expression.

Viral infections in the respiratory tract are common, and, in recent years, severe acute respiratory syndrome coronavirus 2 outbreaks have highlighted the effect of viral infections on antiviral innate immune and inflammatory reactions. Specific treatments for numerous viral respiratory infections have not yet been established and they are mainly treated symptomatically. Therefore, understanding the details of the innate immune system underlying the airway epithelium is crucial for the development of new therapies. The present study aimed to investigate the function and expression of interferon (IFN)­stimulated gene (ISG)60 in non­cancerous bronchial epithelial BEAS­2B cells exposed to a Toll­like receptor 3 agonist. BEAS­2B cells were treated with a synthetic TLR3 ligand, polyinosinic­polycytidylic acid (poly IC). The mRNA and protein expression levels of ISG60 were analyzed using reverse transcription­quantitative PCR and western blotting, respectively. The levels of C­X­C motif chemokine ligand 10 (CXCL10) were examined using an enzyme­linked immunosorbent assay, and the effects of knockdown of IFN­ß, ISG60 and ISG56 were examined using specific small interfering RNAs. Notably, ISG60 expression was increased in proportion to poly IC concentration, and recombinant human IFN­ß also induced ISG60 expression. By contrast, knockdown of IFN­ß and ISG56 decreased ISG60 expression, and ISG60 knockdown reduced CXCL10 and ISG56 expression. These findings suggested that ISG60 is partly implicated in CXCL10 expression and that ISG60 may serve a role in the innate immune response of bronchial epithelial cells. The present study highlights ISG60 as a potential target for new therapeutic strategies against viral infections in the airway.

Hypoimmunogenic human iPSCs expressing HLA-G, PD-L1, and PD-L2 evade innate and adaptive immunity.

BACKGROUND: The human induced pluripotent stem cells (hiPSCs) can generate all the cells composing the human body, theoretically. Therefore, hiPSCs are thought to be a candidate source of stem cells for regenerative medicine. The major challenge of allogeneic hiPSC-derived cell products is their immunogenicity. The hypoimmunogenic cell strategy is allogenic cell therapy without using immune suppressants. Advances in gene engineering technology now permit the generation of hypoimmunogenic cells to avoid allogeneic immune rejection. In this study, we generated a hypoimmunogenic hiPSC (HyPSC) clone that had diminished expression of human leukocyte antigen (HLA) class Ia and class II and expressed immune checkpoint molecules and a safety switch. METHODS: First, we generated HLA class Ia and class II double knockout (HLA class Ia/II DKO) hiPSCs. Then, a HyPSC clone was generated by introducing exogenous ß-2-microglobulin (B2M), HLA-G, PD-L1, and PD-L2 genes, and the Rapamycin-activated Caspase 9 (RapaCasp9)-based suicide gene as a safety switch into the HLA class Ia/II DKO hiPSCs. The characteristics and immunogenicity of the HyPSCs and their derivatives were analyzed. RESULTS: We found that the expression of HLA-G on the cell surface can be enhanced by introducing the exogenous HLA-G gene along with B2M gene into HLA class Ia/II DKO hiPSCs. The HyPSCs retained a normal karyotype and had the characteristics of pluripotent stem cells. Moreover, the HyPSCs could differentiate into cells of all three germ layer lineages including CD45+ hematopoietic progenitor cells (HPCs), functional endothelial cells, and hepatocytes. The HyPSCs-derived HPCs exhibited the ability to evade innate and adaptive immunity. Further, we demonstrated that RapaCasp9 could be used as a safety switch in vitro and in vivo. CONCLUSION: The HLA class Ia/II DKO hiPSCs armed with HLA-G, PD-L1, PD-L2, and RapaCasp9 molecules are a potential source of stem cells for allogeneic transplantation.

From hit to vial: Precision discovery and development of an imidazopyrimidine TLR7/8 agonist adjuvant formulation.

Vaccination can help prevent infection and can also be used to treat cancer, allergy, and potentially even drug overdose. Adjuvants enhance vaccine responses, but currently, the path to their advancement and development is incremental. We used a phenotypic small-molecule screen using THP-1 cells to identify nuclear factor-κB (NF-κB)-activating molecules followed by counterscreening lead target libraries with a quantitative tumor necrosis factor immunoassay using primary human peripheral blood mononuclear cells. Screening on primary cells identified an imidazopyrimidine, dubbed PVP-037. Moreover, while PVP-037 did not overtly activate THP-1 cells, it demonstrated broad innate immune activation, including NF-κB and cytokine induction from primary human leukocytes in vitro as well as enhancement of influenza and SARS-CoV-2 antigen-specific humoral responses in mice. Several de novo synthesis structural enhancements iteratively improved PVP-037's in vitro efficacy, potency, species-specific activity, and in vivo adjuvanticity. Overall, we identified imidazopyrimidine Toll-like receptor-7/8 adjuvants that act in synergy with oil-in-water emulsion to enhance immune responses.

Pathophysiology and genomics of bronchiectasis.

Bronchiectasis is a complex and heterogeneous inflammatory chronic respiratory disease with an unknown cause in around 30-40% of patients. The presence of airway infection together with chronic inflammation, airway mucociliary dysfunction and lung damage are key components of the vicious vortex model that better describes its pathophysiology. Although bronchiectasis research has significantly increased over the past years and different endotypes have been identified, there are still major gaps in the understanding of the pathophysiology. Genomic approaches may help to identify new endotypes, as has been shown in other chronic airway diseases, such as COPD.Different studies have started to work in this direction, and significant contributions to the understanding of the microbiome and proteome diversity have been made in bronchiectasis in recent years. However, the systematic application of omics approaches to identify new molecular insights into the pathophysiology of bronchiectasis (endotypes) is still limited compared with other respiratory diseases.Given the complexity and diversity of these technologies, this review describes the key components of the pathophysiology of bronchiectasis and how genomics can be applied to increase our knowledge, including the study of new techniques such as proteomics, metabolomics and epigenomics. Furthermore, we propose that the novel concept of trained innate immunity, which is driven by microbiome exposures leading to epigenetic modifications, can complement our current understanding of the vicious vortex. Finally, we discuss the challenges, opportunities and implications of genomics application in clinical practice for better patient stratification into new therapies.

Protective interplay: Mycobacterium tuberculosis diminishes SARS-CoV-2 severity through innate immune priming.

At the beginning of the COVID-19 pandemic those with underlying chronic lung conditions, including tuberculosis (TB), were hypothesized to be at higher risk of severe COVID-19 disease. However, there is inconclusive clinical and preclinical data to confirm the specific risk SARS-CoV-2 poses for the millions of individuals infected with Mycobacterium tuberculosis (M.tb). We and others have found that compared to singly infected mice, mice co-infected with M.tb and SARS-CoV-2 leads to reduced SARS-CoV-2 severity compared to mice infected with SARS-CoV-2 alone. Consequently, there is a large interest in identifying the molecular mechanisms responsible for the reduced SARS-CoV-2 infection severity observed in M.tb and SARS-CoV-2 co-infection. To address this, we conducted a comprehensive characterization of a co-infection model and performed mechanistic in vitro modeling to dynamically assess how the innate immune response induced by M.tb restricts viral replication. Our study has successfully identified several cytokines that induce the upregulation of anti-viral genes in lung epithelial cells, thereby providing protection prior to challenge with SARS-CoV-2. In conclusion, our study offers a comprehensive understanding of the key pathways induced by an existing bacterial infection that effectively restricts SARS-CoV-2 activity and identifies candidate therapeutic targets for SARS-CoV-2 infection.

Histone demethylation tones down leukemia through innate immunity.

Histone demethylation by PHF8 initiates innate immune signaling in acute myeloid leukemia, elucidating a novel therapeutic strategy.

TRIM26 facilitates PRV infection through NDP52-mediated autophagic degradation of MAVS.

Pseudorabies virus (PRV) has evolved multiple strategies to evade host antiviral responses to benefit virus replication and establish persistent infection. Recently, tripartite motif 26 (TRIM26), a TRIM family protein, has been shown to be involved in a broad range of biological processes involved in innate immunity, especially in regulating viral infection. Herein, we found that the expression of TRIM26 was significantly induced after PRV infection. Surprisingly, the overexpression of TRIM26 promoted PRV production, while the depletion of this protein inhibited virus replication, suggesting that TRIM26 could positively regulate PRV infection. Further analysis revealed that TRIM26 negatively regulates the innate immune response by targeting the RIG-I-triggered type I interferon signalling pathway. TRIM26 was physically associated with MAVS independent of viral infection and reduced MAVS expression. Mechanistically, we found that NDP52 interacted with both TRIM26 and MAVS and that TRIM26-induced MAVS degradation was almost entirely blocked in NDP52-knockdown cells, demonstrating that TRIM26 degrades MAVS through NDP52-mediated selective autophagy. Our results reveal a novel mechanism by which PRV escapes host antiviral innate immunity and provide insights into the crosstalk among virus infection, autophagy, and the innate immune response.

Unconventional posttranslational modification in innate immunity.

Pattern recognition receptors (PRRs) play a crucial role in innate immunity, and a complex network tightly controls their signaling cascades to maintain immune homeostasis. Within the modification network, posttranslational modifications (PTMs) are at the core of signaling cascades. Conventional PTMs, which include phosphorylation and ubiquitination, have been extensively studied. The regulatory role of unconventional PTMs, involving unanchored ubiquitination, ISGylation, SUMOylation, NEDDylation, methylation, acetylation, palmitoylation, glycosylation, and myristylation, in the modulation of innate immune signaling pathways has been increasingly investigated. This comprehensive review delves into the emerging field of unconventional PTMs and highlights their pivotal role in innate immunity.

Functions and Clinical Relevance of Liver-Derived Immunoglobulins.

Liver is the largest internal organ of the body with vital functions. In addition to its endocrine and exocrine activities, liver also plays a pivotal role in the immune system, including haematopoietic functions. Liver parenchymal cells, which are epithelial cells, have been found to possess innate immune functions by expressing pattern-recognition receptors (PRRs), producing complement components, and secreting cytokines. Intriguingly, in recent years, it has been discovered that liver epithelial cells also produce immunoglobulins (Igs), which have long been thought to be produced exclusively by B cells. Notably, even liver epithelial cells from B lymphocyte-deficient mice, including SCID mice and µMT mice, could also produce Igs. Compelling evidence has revealed both the physiological and pathological functions of liver-derived Igs. For instance, liver epithelial cells-derived IgM can serve as a source of natural and specific antibodies that contribute to innate immune responses, while liver-produced IgG can act as a growth factor to promote cell proliferation and survival in normal hepatocytes and hepatocarcinoma. Similar to that in B cells, the toll-like receptor 9 (TLR9)-MyD88 signaling pathway is also actively involved in promoting liver epithelial cells to secrete IgM. Liver-derived Igs could potentially serve as biomarkers, prognostic indicators, and therapeutic targets in the clinical setting, particularly for liver cancers and liver injury. Nevertheless, despite significant advances, much remains unknown about the mechanisms governing Ig transcription in liver cells, as well as the detailed functions of liver-derived Igs and their involvement in diseases and adaptive immunity. Further studies are still needed to reveal these underlying, undefined issues related to the role of liver-derived Igs in both immunity and diseases.

High burden of viruses and bacterial pathobionts drives heightened nasal innate immunity in children.

Studies during the COVID-19 pandemic showed that children had heightened nasal innate immune responses compared with adults. To evaluate the role of nasal viruses and bacteria in driving these responses, we performed cytokine profiling and comprehensive, symptom-agnostic testing for respiratory viruses and bacterial pathobionts in nasopharyngeal samples from children tested for SARS-CoV-2 in 2021-22 (n = 467). Respiratory viruses and/or pathobionts were highly prevalent (82% of symptomatic and 30% asymptomatic children; 90 and 49% for children <5 years). Virus detection and load correlated with the nasal interferon response biomarker CXCL10, and the previously reported discrepancy between SARS-CoV-2 viral load and nasal interferon response was explained by viral coinfections. Bacterial pathobionts correlated with a distinct proinflammatory response with elevated IL-1ß and TNF but not CXCL10. Furthermore, paired samples from healthy 1-year-olds collected 1-2 wk apart revealed frequent respiratory virus acquisition or clearance, with mucosal immunophenotype changing in parallel. These findings reveal that frequent, dynamic host-pathogen interactions drive nasal innate immune activation in children.

Harnessing cGAS-STING axis for therapeutic benefits in systemic lupus erythematosus.

The cyclic GMP-AMP synthase (cGAS), a prominent intracellular DNA sensor in mammalian cells, controls the innate immune response and the stimulator of interferon genes (STING)-mediated synthesis of pro-inflammatory cytokines, such as type-I interferon (IFN-I). For decades, IFN-I has been hypothesized to be essential in the development of systemic lupus erythematosus (SLE), a chronic multisystem autoimmunity characterized by immune complex (IC) deposition in small vessels. Recent findings revealed that the activation of the cGAS-STING pathway by self-DNA would propagate the autoimmune responses via upregulating IFN-I production in SLE. In this review, we aimed to provide a comprehensive outlook of the role of the cGAS-STING pathway in SLE pathobiology, as well as, a better understanding of current therapeutic opportunities targeting this axis.

Microbiome-derived bacterial lipids regulate gene expression of proinflammatory pathway inhibitors in systemic monocytes.

How the microbiome regulates responses of systemic innate immune cells is unclear. In the present study, our purpose was to document a novel mechanism by which the microbiome mediates crosstalk with the systemic innate immune system. We have identified a family of microbiome Bacteroidota-derived lipopeptides-the serine-glycine (S/G) lipids, which are TLR2 ligands, access the systemic circulation, and regulate proinflammatory responses of splenic monocytes. To document the role of these lipids in regulating systemic immunity, we used oral gavage with an antibiotic to decrease the production of these lipids and administered exogenously purified lipids to increase the systemic level of these lipids. We found that decreasing systemic S/G lipids by decreasing microbiome Bacteroidota significantly enhanced splenic monocyte proinflammatory responses. Replenishing systemic levels of S/G lipids via exogenous administration returned splenic monocyte responses to control levels. Transcriptomic analysis demonstrated that S/G lipids regulate monocyte proinflammatory responses at the level of gene expression of a small set of upstream inhibitors of TLR and NF-κB pathways that include Trem2 and Irf4. Consistent with enhancement in proinflammatory cytokine responses, decreasing S/G lipids lowered gene expression of specific pathway inhibitors. Replenishing S/G lipids normalized gene expression of these inhibitors. In conclusion, our results suggest that microbiome-derived S/G lipids normally establish a level of buffered signaling activation necessary for well-regulated innate immune responses in systemic monocytes. By regulating gene expression of inflammatory pathway inhibitors such as Trem2, S/G lipids merit broader investigation into the potential dysfunction of other innate immune cells, such as microglia, in diseases such as Alzheimer's disease.

ILC2s induce Treg but not Th2-type immunity through IL-33/ST2 pathway in pulmonary tuberculosis.

INTRODUCTION: We investigated the function of type 2 innate lymphoid cells (ILC2s) and IL-33 in pulmonary tuberculosis (PTB). METHODOLOGY: Peripheral blood samples were collected from PTB patients and healthy controls. The cytometric bead array was used to detect plasma IL-33, TGF-ß, IL-4, IL-5, IL-6, IL-10, IL-13, and soluble ST2 (sST2). ILC2s, Th2, and Treg cells were detected with flow cytometry. Quantitative real-time PCR was used to measure mRNA levels. ILC2s were co-cultured with peripheral blood mononuclear cells and then intervened with IL-33 or anti-ST2 antibody + IL-33 in vitro. IL-4, IL-6, IL-5, IL-10, IL-13, and TGF-ß levels were measured by enzyme-linked immunosorbent assay. RESULTS: Compared with healthy controls, the levels of IL-33, sST2, TGF-ß, IL-10, and IL-6 in the plasma of PTB patients were significantly higher. No significant difference was found in the plasma IL-4, IL-5, and IL-13 levels. Patients with PTB had significantly increased ILC2s proportion and mRNA levels of RAR-related orphan receptor α and GATA binding protein 3. After 48 h of IL-33 stimulation in vitro, Treg cell proportion significantly increased and the IL-10 level was significantly elevated. Treatment with anti-ST2 abolished these effects. No significant difference was found in cytokines of IL-4, IL-6, IL-5, IL-13, and TGF-ß, or Th2 cells before and after IL-33 treatment. ILC2s proportion in peripheral blood was increased and plasma IL-33 was upregulated in PTB patients. CONCLUSIONS: IL-33 may promote the growth of ILC2s and the production of Treg-related cell cytokines, but not Th2-related cell cytokines, to participate in immune response to PTB.