Human Lung Conventional Dendritic Cells Orchestrate Lymphoid Neogenesis during Chronic Obstructive Pulmonary Disease

The therapeutic potential of vitamin D supplementation in asthma

Recent years have seen a search for more effective forms of asthma therapy, with one possible option being vitamin D supplementation. The main objective of this study was to present the current state of knowledge on the effect of vitamin D supplementation on the course of asthma in children and adults; it also reviews the existing literature on prenatal vitamin D supplementation and asthma status. The search comprised articles, mostly randomized controlled trials (RCTs), included in the PubMed database and published after 2018. Most RCTs conducted on children indicate that vitamin supplementation did not affect the course of the disease, its control, or exacerbations; however, several trials in adults confirm it to have beneficial effects, with an important role being played by vitamin D deficiency. Unfortunately, the studies demonstrated considerable heterogeneity concerning the age and number of participants, dose, duration, and use of guidelines for pharmaceutical drugs, making it difficult to draw clear conclusions. Further, properly designed, large-scale studies with long-term follow-ups are needed.

Exploring a pico-well based scRNA-seq method (HIVE) for simplified processing of equine bronchoalveolar lavage cells

Single-cell RNA sequencing (scRNA-seq) is a valuable tool for investigating cellular heterogeneity in diseases such as equine asthma (EA). This study evaluates the HIVE™ scRNA-seq method, a pico-well-based technology, for processing bronchoalveolar lavage (BAL) cells from horses with EA. The HIVE method offers practical advantages, including compatibility with both field and clinical settings, as well as a gentle workflow suited for handling sensitive cells. Our results show that the major cell types in equine BAL were successfully identified; however, the proportions of T cells and macrophages deviated from cytological expectations, with macrophages being overrepresented and T cells underrepresented. Despite these limitations, the HIVE method confirmed previously identified T cell and macrophage subpopulations and defined other BAL cell subsets. However, compared to previous studies T helper subsets were less clearly defined. Additionally, consistent with previous scRNA-seq studies, the HIVE method detected fewer granulocytes and mast cells than anticipated in the total BAL samples. Nevertheless, applying the method to purified mast cells recovered an expected number of cells. A small set of eosinophils were also detected which have not been characterized in earlier studies. In summary these findings suggest that while the HIVE method shows promise for certain applications, further optimization is needed to improve the accuracy of cell type representation, particularly for granulocytes and mast cells, in BAL samples.

Global DNA Methylation and DNA Methyltransferase Status Among Cigarette Smokers in Saudi

Smoking is a serious public health concern worldwide. It is a common environmental factor causing epigenetic alterations. This study aimed to explore the effect of smoking on DNA methylation by quantifying global DNA methylation, measuring the concentrations of plasma DNA methyltransferases (DNMT1, DNMT3A, and DNMT3B) among cigarette smokers in Saudi, and comparing these results with those of nonsmokers. Whole blood specimens were collected from Saudi cigarette smokers (n = 36) and non-smokers as controls (n = 36). Global DNA alteration was determined by a 5-methylation Cytosine (5-mC) colorimetric assay, and the concentration of DNMT proteins was measured by enzyme-linked immunosorbent assay (ELISA). DNA hypomethylation was found in smokers compared with controls (p < 0.001). Cigarette smokers showed significantly increased DNMT concentrations (DNM-1, DNMT-3A, and DNMT-3B) (p < 0.005). Global DNA hypomethylation correlated significantly with smoking duration (r = -0.854, p = 0.040) but not with other clinical parameters. In addition, DNMTs also were significantly correlated with smoking duration DNMT1 (r = 0.033, p = 0.002), DNMT3A (r = 0.431, p < 0.001), and DNMT3B (r = 0.553, p = 0.015). Our findings suggest that cigarette smoke induces epigenetic dysregulation, a principal player in cancer and various diseases through global DNA hypomethylation and high concentrations of DNMTs among cigarette smokers compared with nonsmokers.

The role of dendritic cells in tertiary lymphoid structures: implications in cancer and autoimmune diseases

Tertiary Lymphoid Structures (TLS) are organized aggregates of immune cells such as T cells, B cells, and Dendritic Cells (DCs), as well as fibroblasts, formed postnatally in response to signals from cytokines and chemokines. Central to the function of TLS are DCs, professional antigen-presenting cells (APCs) that coordinate the adaptive immune response, and which can be classified into different subsets, with specific functions, and markers. In this article, we review current data on the contribution of different DC subsets to TLS function in cancer and autoimmunity, two opposite sides of the immune response. Different DC subsets can be found in different tumor types, correlating with cancer prognosis. Moreover, DCs are also present in TLS found in autoimmune and inflammatory conditions, contributing to disease development. Broadly, the presence of DCs in TLS appears to be associated with favorable clinical outcomes in cancer while in autoimmune pathologies these cells are associated with unfavorable prognosis. Therefore, it is important to analyze the complex functions of DCs within TLS in order to enhance our fundamental understanding of immune regulation but also as a possible route to create innovative clinical interventions designed for the specific needs of patients with diverse pathological diseases.

Immunologic aspects of asthma: from molecular mechanisms to disease pathophysiology and clinical translation

In the present review, we focused on recent translational and clinical discoveries in asthma immunology, facilitating phenotyping and stratified or personalized interventions for patients with this condition. The immune processes behind chronic inflammation in asthma exhibit marked heterogeneity, with diverse phenotypes defining discernible features and endotypes illuminating the underlying molecular mechanisms. In particular, two primary endotypes of asthma have been identified: "type 2-high," characterized by increased eosinophil levels in the airways and sputum of patients, and "type 2-low," distinguished by increased neutrophils or a pauci-granulocytic profile. Our review encompasses significant advances in both innate and adaptive immunities, with emphasis on the key cellular and molecular mediators, and delves into innovative biological and targeted therapies for all the asthma endotypes. Recognizing that the immunopathology of asthma is dynamic and continuous, exhibiting spatial and temporal variabilities, is the central theme of this review. This complexity is underscored through the innumerable interactions involved, rather than being driven by a single predominant factor. Integrated efforts to improve our understanding of the pathophysiological characteristics of asthma indicate a trend toward an approach based on disease biology, encompassing the combined examination of the clinical, cellular, and molecular dimensions of the disease to more accurately correlate clinical traits with specific disease mechanisms.

Impairment of Gal-9 and Tim-3 crosstalk between Tregs and Th17 cells drives tobacco smoke-induced airway inflammation

Overexpression of T-cell immunoglobulin and mucin-domain containing-3 (TIM-3) on T cells has been observed in smokers. However, whether and how galectin-9 (Gal-9)/TIM-3 signal between T-regulatory cells (Tregs) and type 17 helper (Th17) cells contributes to tobacco smoke-induced airway inflammation remains unclear. Here, we aimed to explore the role of the Gal-9/TIM-3 signal between Tregs and Th17 cells during chronic tobacco smoke exposure. Tregs phenotype and the expression of TIM-3 on CD4+ T cells were detected in a mouse model of experimental emphysema. The role of TIM-3 in CD4+ T cells was explored in a HAVCR2-/- mouse model and in mice that received recombinant anti-TIM3. The crosstalk between Gal-9 and Tim-3 was evaluated by coculture Tregs with effector CD4+ T cells. We also invested the expression of Gal-9 in Tregs in patients with COPD. Our study revealed that chronic tobacco smoke exposure significantly reduces the frequency of Tregs in the lungs of mice and remarkably shapes the heterogeneity of Tregs by downregulating the expression of Gal-9. We observed a pro-inflammatory but restrained phenotypic transition of CD4+ T cells after tobacco smoke exposure, which was maintained by TIM-3. The restrained phenotype of CD4+ T cells was perturbed when TIM-3 was deleted or neutralised. Tregs from the lungs of mice with emphysema displayed a blunt ability to inhibit the differentiation and proliferation of Th17 cells. The inhibitory function of Tregs was partially restored by using recombinant Gal-9. The interaction between Gal-9 and TIM-3 inhibits the differentiation of Th17 cells and promotes apoptosis of CD4+ T cells, possibly by interfering with the expression of retinoic acid receptor-related orphan receptor gamma t. The expression of Gal-9 in Tregs was reduced in patients with COPD, which was associated with Th17 response and lung function. These findings present a new paradigm that impairment of Gal-9/Tim-3 crosstalk between Tregs and Th17 cells during chronic tobacco smoke exposure promotes tobacco smoke-induced airway/lung inflammation.

Tertiary lymphoid structures in diseases: immune mechanisms and therapeutic advances

Tertiary lymphoid structures (TLSs) are defined as lymphoid aggregates formed in non-hematopoietic organs under pathological conditions. Similar to secondary lymphoid organs (SLOs), the formation of TLSs relies on the interaction between lymphoid tissue inducer (LTi) cells and lymphoid tissue organizer (LTo) cells, involving multiple cytokines. Heterogeneity is a distinguishing feature of TLSs, which may lead to differences in their functions. Growing evidence suggests that TLSs are associated with various diseases, such as cancers, autoimmune diseases, transplant rejection, chronic inflammation, infection, and even ageing. However, the detailed mechanisms behind these clinical associations are not yet fully understood. The mechanisms by which TLS maturation and localization affect immune function are also unclear. Therefore, it is necessary to enhance the understanding of TLS development and function at the cellular and molecular level, which may allow us to utilize them to improve the immune microenvironment. In this review, we delve into the composition, formation mechanism, associations with diseases, and potential therapeutic applications of TLSs. Furthermore, we discuss the therapeutic implications of TLSs, such as their role as markers of therapeutic response and prognosis. Finally, we summarize various methods for detecting and targeting TLSs. Overall, we provide a comprehensive understanding of TLSs and aim to develop more effective therapeutic strategies.

Reciprocal regulation of T follicular helper cells and dendritic cells drives colitis development

The immunological mechanisms underlying chronic colitis are poorly understood. T follicular helper (TFH) cells are critical in helping B cells during germinal center reactions. In a T cell transfer colitis model, a lymphoid structure composed of mature dendritic cells (DCs) and TFH cells was found within T cell zones of colonic lymphoid follicles. TFH cells were required for mature DC accumulation, the formation of DC-T cell clusters and colitis development. Moreover, DCs promoted TFH cell differentiation, contributing to colitis development. A lineage-tracing analysis showed that, following migration to the lamina propria, TFH cells transdifferentiated into long-lived pathogenic TH1 cells, promoting colitis development. Our findings have therefore demonstrated the reciprocal regulation of TFH cells and DCs in colonic lymphoid follicles, which is critical in chronic colitis pathogenesis.

Causal Involvement of Immune Cells in Chronic Obstructive Pulmonary Disease: A Mendelian Randomization Study

Background

The immune cells play a substantial role in the development and progression of chronic obstructive pulmonary disease (COPD). We aim to investigate the causal involvement of immune cells in COPD via a Mendelian randomization (MR) analysis.

Methods

Published genome-wide association studies (GWAS) statistics on immune cells were analyzed, with genetic variants identified as instrumental variables (IVs). Inverse-variance weighting (IVW), weighted median, and MR-Egger regression methods were employed, along with simple mode and weighted mode adopted in the two-sample MR analysis. Sensitivity analysis was conducted to examine the heterogeneity, horizontal pleiotropy, and stability of the causal relationship.

Results

IVW results suggested that CCR2 on CD62L+ plasmacytoid dendritic cells (DC), CCR2 on plasmacytoid DC, CD11b on CD66b++ myeloid cells, CD19 on CD20- CD38- CD24+ memory B cell subset, CD25 on transitional B cells, and CD25++CD8br %CD8br T cells were risk factors for the development of COPD. Besides, CD127 on effector memory-like cytotoxic T lymphocytes lacking expression of co-stimulatory molecule 28 (CD28-EM CTLs) and HLA DR+ NK ACs expressing human leukocyte antigen DR molecules while being natural killer cells (%NK ACs) were protective factors for COPD.

Conclusion

This study unveiled a causal relationship between immune cell phenotype and COPD. These findings offer new insights for the prevention and treatment of COPD using COPD-associated immune cells.

A model of dysregulated crosstalk between dendritic, natural killer, and regulatory T cells in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is characterized by infiltration of the airways and lung parenchyma by inflammatory cells. Lung pathology results from the cumulative effect of complex and aberrant interactions between multiple cell types. However, three cell types, natural killer cells (NK), dendritic cells (DCs), and regulatory T cells (Tregs), are understudied and underappreciated. We propose that their mutual interactions significantly contribute to the development of COPD. Here, we highlight recent advances in NK, DC, and Treg biology with relevance to COPD, discuss their pairwise bidirectional interactions, and identify knowledge gaps that must be bridged to develop novel therapies. Understanding their interactions will be crucial for therapeutic use of autologous Treg, an approach proving effective in other diseases with immune components.

Combined analysis of bulk RNA and single-cell RNA sequencing to identify pyroptosis-related markers and the role of dendritic cells in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is characterized by dyspnea caused by airflow limitation. Further development may lead to decreased lung function and other lung diseases. Pyroptosis is a type of programmed cell death that involves multiple pathways. For example, the pathway induced by the NLR family pyrin domain containing 3 (NLRP3) inflammasome is closely associated with COPD exacerbation. Therefore, in this study, various machine learning algorithms were applied to screen for diagnostically relevant pyroptosis-related genes from the GEO dataset, and the results were verified using external datasets. The results showed that deep neural networks and logistic regression algorithms had the highest AUC of 0.91 and 0.74 in the internal and external test sets, respectively. Here, we explored the immune landscape of COPD using diagnosis-related genes. We found that the infiltrating abundance of dendritic cells significantly differed between the COPD and control groups. Finally, the communication patterns of each cell type were explored based on scRNA-seq data. The critical role of significant pathways involved in communication between DCS and other cell populations in the occurrence and progression of COPD was identified.

Effectiveness of Immunotherapy in Non-Small Cell Lung Cancer Patients with a Diagnosis of COPD: Is This a Hidden Prognosticator for Survival and a Risk Factor for Immune-Related Adverse Events?

The interplay between the immune system and chronic obstructive pulmonary disease (COPD) and non-small cell lung cancer (NSCLC) is complex and multifaceted. In COPD, chronic inflammation and oxidative stress can lead to immune dysfunction that can exacerbate lung damage, further worsening the respiratory symptoms. In NSCLC, immune cells can recognise and attack the cancer cells, which, however, can evade or suppress the immune response by various mechanisms, such as expressing immune checkpoint proteins or secreting immunosuppressive cytokines, thus creating an immunosuppressive tumour microenvironment that promotes cancer progression and metastasis. The interaction between COPD and NSCLC further complicates the immune response. In patients with both diseases, COPD can impair the immune response against cancer cells by reducing or suppressing the activity of immune cells, or altering their cytokine profile. Moreover, anti-cancer treatments can also affect the immune system and worsen COPD symptoms by causing lung inflammation and fibrosis. Immunotherapy itself can also cause immune-related adverse events that could worsen the respiratory symptoms in patients with COPD-compromised lungs. In the present review, we tried to understand the interplay between the two pathologies and how the efficacy of immunotherapy in NSCLC patients with COPD is affected in these patients.

The differentiation courses of the Tfh cells: a new perspective on autoimmune disease pathogenesis and treatment

The follicular helper T cells are derived from CD4+T cells, promoting the formation of germinal centers and assisting B cells to produce antibodies. This review describes the differentiation process of Tfh cells from the perspectives of the initiation, maturation, migration, efficacy, and subset classification of Tfh cells, and correlates it with autoimmune disease, to provide information for researchers to fully understand Tfh cells and provide further research ideas to manage immune-related diseases.

Straight to the point: targeted mRNA-delivery to immune cells for improved vaccine design

With the deepening of our understanding of adaptive immunity at the cellular and molecular level, targeting antigens directly to immune cells has proven to be a successful strategy to develop innovative and potent vaccines. Indeed, it offers the potential to increase vaccine potency and/or modulate immune response quality while reducing off-target effects. With mRNA-vaccines establishing themselves as a versatile technology for future applications, in the last years several approaches have been explored to target nanoparticles-enabled mRNA-delivery systems to immune cells, with a focus on dendritic cells. Dendritic cells (DCs) are the most potent antigen presenting cells and key mediators of B- and T-cell immunity, and therefore considered as an ideal target for cell-specific antigen delivery. Indeed, improved potency of DC-targeted vaccines has been proved in vitro and in vivo. This review discusses the potential specific targets for immune system-directed mRNA delivery, as well as the different targeting ligand classes and delivery systems used for this purpose.

Single-cell transcriptomics delineates the immune cell landscape in equine lower airways and reveals upregulation of FKBP5 in horses with asthma

Equine asthma (EA) is a heterogenous, complex disease, with a significant negative impact on horse welfare and performance. EA and human asthma share fundamental similarities, making EA a useful model for studying the disease. One relevant sample type for investigating chronic lung inflammation is bronchoalveolar lavage fluid (BALF), which provides a snapshot of the immune cells present in the alveolar space. To investigate the immune cell landscape of the respiratory tract in horses with mild-to-moderate equine asthma (mEA) and healthy controls, single-cell RNA sequencing was conducted on equine BALF cells. We characterized the major immune cell populations present in equine BALF, as well as subtypes thereof. Interestingly, the most significantly upregulated gene discovered in cases of mEA was FKBP5, a chaperone protein involved in regulating the activity of the glucocorticoid receptor.

Tertiary Lymphoid Structures Are Related to Inflammatory Progression and Bone Loss in Human Apical Periodontitis

INTRODUCTION

Bone loss is strongly associated with the immunologic milieu in apical periodontitis (AP). Tertiary lymphoid structures (TLSs) are organized lymphoid cell aggregates that form in nonlymphoid tissues under persistent inflammatory circumstances. To date, there has been no relevant report of TLSs in periapical lesions. This work aimed to investigate the formation and potential function of TLSs in AP.

METHODS

Tissues from human apical lesions (n = 61) and healthy oral mucosa (n = 5) were collected. Immunohistochemistry and multiplex immunofluorescence were used to detect the formation of TLSs. Correlation analyses were performed between clinical variables and TLSs. In addition, immunohistochemistry was used to evaluate the expression of interleukin-1 beta, interleukin-6, receptor activator of nuclear factor kappa-B ligand, and macrophage subsets in the apical lesions.

RESULTS

Periapical granulomas (n = 24) and cysts (n = 37) were identified by histologic evaluation. TLSs, composed of B-cell and T-cell clusters, developed in periapical granulomas and radicular cysts. The CXC-chemokine ligand 13, its receptor CXC-chemokine receptor 5, follicular dendritic cells, and high endothelial venules were localized in TLSs. The quantity and size of TLSs were positively associated with bone loss in AP. Moreover, proinflammatory cytokines and macrophage subsets were also substantially elevated in TLS regions of apical lesions.

CONCLUSIONS

The formation of TLSs in periapical granulomas and cysts was closely associated with persistent immune responses and bone loss in apical lesions. TLSs provide an updated insight into the complicated immune response process in AP.

Valaciclovir for Epstein-Barr Virus Suppression in Moderate-to-Severe COPD: A Randomized Double-Blind Placebo-Controlled Trial

BACKGROUND

Epstein-Barr virus (EBV) frequently is measured at high levels in COPD using sputum quantitative polymerase chain reaction, whereas airway immunohistochemistry analysis has shown EBV detection to be common in severe disease.

RESEARCH QUESTION

Is valaciclovir safe and effective for EBV suppression in COPD?

STUDY DESIGN AND METHODS

The Epstein-Barr Virus Suppression in COPD (EViSCO) trial was a randomized double-blind placebo-controlled trial conducted at the Mater Hospital Belfast, Northern Ireland. Eligible patients had stable moderate-to-severe COPD and sputum EBV (measured using quantitative polymerase chain reaction) and were assigned randomly (1:1) to valaciclovir (1 g tid) or matching placebo for 8 weeks. The primary efficacy outcome was sputum EBV suppression (defined as ≥ 90% sputum viral load reduction) at week 8. The primary safety outcome was the incidence of serious adverse reactions. Secondary outcome measures were FEV1 and drug tolerability. Exploratory outcomes included changes in quality of life, sputum cell counts, and cytokines.

RESULTS

From November 2, 2018, through March 12, 2020, 84 patients were assigned randomly (n = 43 to valaciclovir). Eighty-one patients completed trial follow-up and were included in the intention-to-treat analysis of the primary outcome. A greater number of participants in the valaciclovir group achieved EBV suppression (n = 36 [87.8%] vs n = 17 [42.5%]; P < .001). Valaciclovir was associated with a significant reduction in sputum EBV titer compared with placebo (-90,404 copies/mL [interquartile range, -298,000 to -15,200 copies/mL] vs -3,940 copies/mL [interquartile range, -114,400 to 50,150 copies/mL]; P = .002). A statistically nonsignificant 24-mL numerical FEV1 increase was shown in the valaciclovir group (difference, -44 mL [95% CI, -150 to 62 mL]; P = .41). However, a reduction in sputum white cell count was noted in the valaciclovir group compared with the placebo group (difference, 2.89 [95% CI, 1.5 × 106-7.4 × 106]; P = .003).

INTERPRETATION

Valaciclovir is safe and effective for EBV suppression in COPD and may attenuate the sputum inflammatory cell infiltrate. The findings from the current study provide support for a larger trial to evaluate long-term clinical outcomes.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT03699904; URL: www.

CLINICALTRIALS

gov.

Modulation of Human Dendritic Cell Functions by Phosphodiesterase-4 Inhibitors: Potential Relevance for the Treatment of Respiratory Diseases

Inhibitors of phosphodiesterase-4 (PDE4) are small-molecule drugs that, by increasing the intracellular levels of cAMP in immune cells, elicit a broad spectrum of anti-inflammatory effects. As such, PDE4 inhibitors are actively studied as therapeutic options in a variety of human diseases characterized by an underlying inflammatory pathogenesis. Dendritic cells (DCs) are checkpoints of the inflammatory and immune responses, being responsible for both activation and dampening depending on their activation status. This review shows evidence that PDE4 inhibitors modulate inflammatory DC activation by decreasing the secretion of inflammatory and Th1/Th17-polarizing cytokines, although preserving the expression of costimulatory molecules and the CD4+ T cell-activating potential. In addition, DCs activated in the presence of PDE4 inhibitors induce a preferential Th2 skewing of effector T cells, retain the secretion of Th2-attracting chemokines and increase the production of T cell regulatory mediators, such as IDO1, TSP-1, VEGF-A and Amphiregulin. Finally, PDE4 inhibitors selectively induce the expression of the surface molecule CD141/Thrombomodulin/BDCA-3. The result of such fine-tuning is immunomodulatory DCs that are distinct from those induced by classical anti-inflammatory drugs, such as corticosteroids. The possible implications for the treatment of respiratory disorders (such as COPD, asthma and COVID-19) by PDE4 inhibitors will be discussed.

Mechanisms of organ fibrosis: Emerging concepts and implications for novel treatment strategies

Fibrosis, or tissue scarring, develops as a pathological deviation from the physiological wound healing response and can occur in various organs such as the heart, lung, liver, kidney, skin, and bone marrow. Organ fibrosis significantly contributes to global morbidity and mortality. A broad spectrum of etiologies can cause fibrosis, including acute and chronic ischemia, hypertension, chronic viral infection (e.g., viral hepatitis), environmental exposure (e.g., pneumoconiosis, alcohol, nutrition, smoking) and genetic diseases (e.g., cystic fibrosis, alpha-1-antitrypsin deficiency). Common mechanisms across organs and disease etiologies involve a sustained injury to parenchymal cells that triggers a wound healing response, which becomes deregulated in the disease process. A transformation of resting fibroblasts into myofibroblasts with excessive extracellular matrix production constitutes the hallmark of disease, however, multiple other cell types such as immune cells, predominantly monocytes/macrophages, endothelial cells, and parenchymal cells form a complex network of profibrotic cellular crosstalk. Across organs, leading mediators include growth factors like transforming growth factor-β and platelet-derived growth factor, cytokines like interleukin-10, interleukin-13, interleukin-17, and danger-associated molecular patterns. More recently, insights into fibrosis regression and resolution of chronic conditions have deepened our understanding of beneficial, protective effects of immune cells, soluble mediators and intracellular signaling. Further in-depth insights into the mechanisms of fibrogenesis can provide the rationale for therapeutic interventions and the development of targeted antifibrotic agents. This review gives insight into shared responses and cellular mechanisms across organs and etiologies, aiming to paint a comprehensive picture of fibrotic diseases in both experimental settings and in human pathology.

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

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

Catching Our Breath: Updates on the Role of Dendritic Cell Subsets in Asthma

Dendritic cells (DCs), as potent antigen presenting cells, are known to play a central role in the pathophysiology of asthma. The understanding of DC biology has evolved over the years to include multiple subsets of DCs with distinct functions in the initiation and maintenance of asthma. Furthermore, asthma is increasingly recognized as a heterogeneous disease with potentially diverse underlying mechanisms. The goal of this review is to summarize the role of DCs and the various subsets therein in the pathophysiology of asthma and highlight some of the crucial animal models shaping the field today. Potential future avenues of investigation to address existing gaps in knowledge are discussed.

Macrophages-derived Factor XIII links coagulation to inflammation in COPD

Background

The local, extravascular, activation of the coagulation system in response to injury is a key factor mediating the resulting inflammatory response. Coagulation Factor XIIIA (FXIIIA) found in alveolar macrophages (AM) and dendritic cells (DC), by influencing fibrin stability, might be an inflammatory modifier in COPD.

Aims

To study the expression of FXIIIA in AM and Langerin+DC (DC-1) and their relation to the inflammatory response and disease progression in COPD.

Methods

In 47 surgical lungs, 36 from smokers (22 COPD and 14 no-COPD) and 11 from non-smokers we quantified by immunohistochemistry FXIIIA expression in AM and DC-1 along with numbers of CD8+Tcells and CXCR3 expression in lung parenchyma and airways. Lung function was measured prior to surgery.

Results

The percentage of AM expressing FXIII (%FXIII+AM) was higher in COPD than no-COPD and non-smokers. DC-1 expressed FXIIIA and their numbers were higher in COPD than no-COPD and non-smokers. DC-1 positively correlated with %FXIII+AM (r=0.43; p<0.018). CD8+Tcells, which were higher in COPD than in no-COPD, were correlated with DC-1 (p<0.01) and %FXIII+AM. CXCR3+ cells were increased in COPD and correlated with %FXIII+AM (p<0.05). Both %FXIII+AM (r=-0.6; p=0.001) and DC-1 (r=-0.7; p=0.001) correlated inversely with FEV1.

Conclusion

FXIIIA, an important link between the extravascular coagulation cascade and inflammatory response, is significantly expressed in alveolar macrophages and dendritic cells of smokers with COPD, suggesting that it could play an important role in the adaptive inflammatory reaction characteristic of the disease.

Contribution of adaptive immunity to human COPD and experimental models of emphysema

The pathophysiology of chronic obstructive pulmonary disease (COPD) and the undisputed role of innate immune cells in this condition have dominated the field in the basic research arena for many years. Recently, however, compelling data suggesting that adaptive immune cells may also contribute to the progressive nature of lung destruction associated with COPD in smokers have gained considerable attention. The histopathological changes in the lungs of smokers can be limited to the large or small airways, but alveolar loss leading to emphysema, which occurs in some individuals, remains its most significant and irreversible outcome. Critically, however, the question of why emphysema progresses in a subset of former smokers remained a mystery for many years. The recognition of activated and organized tertiary T- and B-lymphoid aggregates in emphysematous lungs provided the first clue that adaptive immune cells may play a crucial role in COPD pathophysiology. Based on these findings from human translational studies, experimental animal models of emphysema were used to determine the mechanisms through which smoke exposure initiates and orchestrates adaptive autoreactive inflammation in the lungs. These models have revealed that T helper (Th)1 and Th17 subsets promote a positive feedback loop that activates innate immune cells, confirming their role in emphysema pathogenesis. Results from genetic studies and immune-based discoveries have further provided strong evidence for autoimmunity induction in smokers with emphysema. These new findings offer a novel opportunity to explore the mechanisms underlying the inflammatory landscape in the COPD lung and offer insights for development of precision-based treatment to halt lung destruction.

Maternal diet modulates the infant microbiome and intestinal Flt3L necessary for dendritic cell development and immunity to respiratory infection

Poor maternal diet during pregnancy is a risk factor for severe lower respiratory infections (sLRIs) in the offspring, but the underlying mechanisms remain elusive. Here, we demonstrate that in mice a maternal low-fiber diet (LFD) led to enhanced LRI severity in infants because of delayed plasmacytoid dendritic cell (pDC) recruitment and perturbation of regulatory T cell expansion in the lungs. LFD altered the composition of the maternal milk microbiome and assembling infant gut microbiome. These microbial changes reduced the secretion of the DC growth factor Flt3L by neonatal intestinal epithelial cells and impaired downstream pDC hematopoiesis. Therapy with a propionate-producing bacteria isolated from the milk of high-fiber diet-fed mothers, or supplementation with propionate, conferred protection against sLRI by restoring gut Flt3L expression and pDC hematopoiesis. Our findings identify a microbiome-dependent Flt3L axis in the gut that promotes pDC hematopoiesis in early life and confers disease resistance against sLRIs.

Human dendritic cell subsets: An updated view of their ontogeny and functional specialization

Human DCs have been divided into several subsets based on their phenotype and ontogeny. Recent high throughput single-cell methods have revealed additional heterogeneity within human DC subsets, and new subpopulations have been proposed. In this review, we provide an updated view of the human DC subsets and of their ontogeny supported by recent clinical studies . We also summarize their main characteristics including their functional specialization.

Screening and identification of tissue-infiltrating immune cells and genes for patients with emphysema phenotype of COPD

Objective

To study the tissue-infiltrating immune cells of the emphysema phenotype of chronic obstructive pulmonary disease (COPD) and find the molecular mechanism related to the development of emphysema to offer potential targets for more precise treatment of patients with COPD.

Methods

Combined analyses of COPD emphysema phenotype lung tissue-related datasets, GSE47460 and GSE1122, were performed. CIBERSORT was used to assess the distribution of tissue-infiltrating immune cells. Weighted gene co-expression network analysis (WGCNA) was used to select immune key genes closely related to clinical features. Rt-qPCR experiments were used for the validation of key genes. Emphysema risk prediction models were constructed by logistic regression analysis and a nomogram was developed.

Results

In this study, three immune cells significantly associated with clinical features of emphysema (FEV1 post-bronchodilator % predicted, GOLD Stage, and DLCO) were found. The proportion of neutrophils (p=0.025) infiltrating in the emphysema phenotype was significantly increased compared with the non-emphysema phenotype, while the proportions of M2 macrophages (p=0.004) and resting mast cells (p=0.01) were significantly decreased. Five immune-related differentially expressed genes (DEGs) were found. WGCNA and clinical lung tissue validation of patients with emphysema phenotype were performed to further screen immune-related genes closely related to clinical features. A key gene (SERPINA3) was selected and included in the emphysema risk prediction model. Compared with the traditional clinical prediction model (AUC=0.923), the combined prediction model, including SERPINA3 and resting mast cells (AUC=0.941), had better discrimination power and higher net benefit.

Conclusion

This study comprehensively analyzed the tissue-infiltrating immune cells significantly associated with emphysema phenotype, including M2 macrophages, neutrophils, and resting mast cells, and identified SERPINA3 as a key immune-related gene.

Role of Cholinergic Anti-Inflammatory Pathway in Protecting Sepsis-Induced Acute Lung Injury through Regulation of the Conventional Dendritic Cells

BACKGROUND

The cholinergic anti-inflammatory pathway connects the immune response system and the nervous system via the vagus nerve. The key regulatory receptor is the α7-subtype of the nicotinic acetylcholine receptor (α7nAChR). Cholinergic anti-inflammatory pathway has been proved to be effective in suppressing the inflammation responses in acute lung injury (ALI). Dendritic cells (DCs), the important antigen-presenting cells, also express the α7nAChR. Past studies have indicated that reducing the quantity of mature conventional DCs and inhibiting the maturation of pulmonary DCs may prove effective for the treatment of ALI. However, the effects of cholinergic anti-inflammatory pathway on maturation, function, and quantity of DCs and conventional DCs in ALI remain unclear.

OBJECTIVE

It was hypothesized that cholinergic anti-inflammatory pathway may inhibit the inflammatory response of ALI by regulating maturation, phenotype, and quantity of DCs and conventional DCs.

METHODS

GTS-21 (GTS-21 dihydrochloride), an α7nAchR agonist, was prophylactically administered in sepsis-induced ALI mouse model and LPS-primed bone marrow-derived dendritic cells. The effects of GTS-21 were observed with respect to maturation, phenotype, and quantity of DCs, conventional DCs, and conventional DCs2 (type 2 conventional DCs) and the release of DC-related proinflammatory cytokines in vivo and in vitro.

RESULTS

The results of the present study revealed that GTS-21 treatment decreased the maturation of DCs and the production of DC-related proinflammatory cytokines in vitro and in sepsis-induced ALI mouse model; it reduced the quantity of CD11c+MHCII+ conventional DCs and CD11c+CD11b+ conventional DCs2 in vivo experiment.

CONCLUSIONS

Cholinergic anti-inflammatory pathway contributes to the reduction in the inflammatory response in ALI by regulating maturation, phenotype, and quantity of DCs, conventional DCs, and conventional DCs2.

Human lung cDC1 drive increased perforin-mediated NK cytotoxicity in Chronic Obstructive Pulmonary Disease

In chronic obstructive pulmonary disease (COPD), lung natural killer cells (NKs) lyse autologous lung epithelial cells in vitro, but underlying mechanisms and their relationship to epithelial cell apoptosis in vivo are undefined. Although this cytolytic capacity of lung NKs depends on priming by dendritic cells (DC), whether priming correlates with DC maturation or is limited to a specific DC subset are also unknown. We recruited ever-smokers (≥10 pack-years) (n=96) undergoing clinically-indicated lung resections. We analyzed lung NKs for cytotoxic molecule transcripts and for cytotoxicity, which we correlated with in situ detection of activated Caspase-3/7+ airway epithelial cells. To investigate DC priming, we measured lung DC expression of CCR2, CCR7, and CX3CR1, and co-cultured peripheral blood NKs with autologous lung DC, either matured using LPS (non-obstructed smokers) or separated into conventional DC type-1 (cDC1) versus cDC type-2 (cDC2) (COPD). Lung NKs in COPD expressed more perforin (p<0.02) and granzyme B (p<0.03) transcripts; inhibiting perforin blocked in vitro killing by lung NKs. Cytotoxicity in vitro correlated significantly (S_r=0.68, p=0.0043) with numbers of apoptotic epithelial cells per airway. In non-obstructed smokers, LPS-induced maturation enhanced DC-mediated priming of blood NKs, reflected by greater epithelial cell death. Although CCR7 expression was greater in COPD in both cDC1 (p<0.03) and cDC2 (p=0.009), only lung cDC1 primed NK killing. Thus, rather than being intrinsic to those with COPD, NK priming is a capacity of human lung DC that is inducible by recognition of bacterial (and possibly other) danger signals and restricted to the cDC1 subset.

Conventional type 2 lung dendritic cells are potent inducers of follicular helper T cells in the asthmatic lung

BACKGROUND

Follicular helper T (Tfh) cells represent a unique subset of helper CD4⁺ T cells in lymphoid follicles. Recently, Tfh cells were shown to play an important role in asthma through B cell differentiation. Conventional lung DCs are classified into two major subsets: conventional type 1 (cDC1) and type 2 (cDC2). Although the two subsets are different in driving particular T cell responses, the subset that induces Tfh cells in the asthmatic lung primarily has yet to be fully elucidated.

METHODS

We evaluated Tfh cells, defined by the expression of CD4 and CXCR5, in HDM-challenged mice. Next, we characterized cDC1 and cDC2 purified from antigen-primed lung and examined their Tfh cell-inducing capacity. Additionally, the ability of lung DC-induced Tfh cells to cause germinal center B (GCB) cells to produce antigen-specific IgE was assessed.

RESULTS

In HDM-challenged mice, Bcl-6-expressing Tfh cells were significantly increased in the mediastinal lymph nodes. Lung cDC2, but not lung cDC1, increased after HDM priming, and cDC2 secreted larger amounts of IL-6 with higher ICOS-L expression than cDC1. In the co-cultures with OVA-specific naïve CD4⁺ T cells, cDC2 from OVA-primed lung induced Bcl-6-expressing Tfh cells more efficiently, together with larger amounts of IL-6 and IL-21, than cDC1. Blockage of IL-6 or ICOS-L significantly reduced Tfh cell induction. Finally, cDC2-induced Tfh cells enabled GCB cells to produce OVA-specific IgE.

CONCLUSIONS

In asthmatic lung, cDC2 is the primary DC subset responsible for Tfh cell differentiation and plays an important role in humoral immunity in asthma by inducing Tfh cells.

Tumor-Associated Tertiary Lymphoid Structures: From Basic and Clinical Knowledge to Therapeutic Manipulation

The tumor microenvironment is a complex ecosystem almost unique to each patient. Most of available therapies target tumor cells according to their molecular characteristics, angiogenesis or immune cells involved in tumor immune-surveillance. Unfortunately, only a limited number of patients benefit in the long-term of these treatments that are often associated with relapses, in spite of the remarkable progress obtained with the advent of immune checkpoint inhibitors (ICP). The presence of “hot” tumors is a determining parameter for selecting therapies targeting the patient immunity, even though some of them still do not respond to treatment. In human studies, an in-depth analysis of the organization and interactions of tumor-infiltrating immune cells has revealed the presence of an ectopic lymphoid organization termed tertiary lymphoid structures (TLS) in a large number of tumors. Their marked similarity to secondary lymphoid organs has suggested that TLS are an “anti-tumor school” and an “antibody factory” to fight malignant cells. They are effectively associated with long-term survival in most solid tumors, and their presence has been recently shown to predict response to ICP inhibitors. This review discusses the relationship between TLS and the molecular characteristics of tumors and the presence of oncogenic viruses, as well as their role when targeted therapies are used. Also, we present some aspects of TLS biology in non-tumor inflammatory diseases and discuss the putative common characteristics that they share with tumor-associated TLS. A detailed overview of the different pre-clinical models available to investigate TLS function and neogenesis is also presented. Finally, new approaches aimed at a better understanding of the role and function of TLS such as the use of spheroids and organoids and of artificial intelligence algorithms, are also discussed. In conclusion, increasing our knowledge on TLS will undoubtedly improve prognostic prediction and treatment selection in cancer patients with key consequences for the next generation immunotherapy.

Identification of Inflammation-Related Biomarker Lp-PLA2 for Patients With COPD by Comprehensive Analysis

Purpose

Chronic obstructive pulmonary disease (COPD) is a complex and persistent lung disease and lack of biomarkers. The aim of this study is to screen and verify effective biomarkers for medical practice.

Methods

Differential expressed genes analysis and weighted co-expression network analysis were used to explore potential biomarker. Gene Ontology (GO) enrichment, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and Gene set enrichment analysis (GSEA) analysis were used to explore potential mechanism. CIBERSORTx website was used to evaluate tissue-infiltrating immune cells. Enzyme-linked immunosorbent assay (ELISA) was used to assess the concentrations of the Lp-PLA2 in serum.

Results

Ten genes were selected via combined DEGs and WGCNA. Furthermore, PLA2G7 was choose based on validation from independent datasets. Immune infiltrate and enrichment analysis suggest PLA2G7 may regulate immune pathway via macrophages. Next, Lp-PLA2(coded by PLA2G7 gene) level was upregulated in COPD patients, increased along with The Global Average of COPD (GOLD) stage. In additional, Lp-PLA2 level was significant correlate with FEV1/FVC, BMI, FFMI, CAT score, mMRC score and 6MWD of COPD patients. Finally, the predictive efficiency of Lp-PLA2 level (AUC:0.796) and derived nomogram model (AUC:0.884) in exercise tolerance was notably superior to that of the sit-to-stand test and traditional clinical features.

Conclusion

Lp-PLA2 is a promising biomarker for COPD patients and is suitable for assessing exercise tolerance in clinical practice.

Dendritic Cells Are the Intriguing Players in the Puzzle of Idiopathic Pulmonary Fibrosis Pathogenesis

Idiopathic pulmonary fibrosis (IPF) is the most devastating progressive interstitial lung disease that remains refractory to treatment. Pathogenesis of IPF relies on the aberrant cross-talk between injured alveolar cells and myofibroblasts, which ultimately leads to an aberrant fibrous reaction. The contribution of the immune system to IPF remains not fully explored. Recent evidence suggests that both innate and adaptive immune responses may participate in the fibrotic process. Dendritic cells (DCs) are the most potent professional antigen-presenting cells that bridge innate and adaptive immunity. Also, they exert a crucial role in the immune surveillance of the lung, where they are strategically placed in the airway epithelium and interstitium. Immature DCs accumulate in the IPF lung close to areas of epithelial hyperplasia and fibrosis. Conversely, mature DCs are concentrated in well-organized lymphoid follicles along with T and B cells and bronchoalveolar lavage of IPF patients. We have recently shown that all sub-types of peripheral blood DCs (including conventional and plasmacytoid DCs) are severely depleted in therapy naïve IPF patients. Also, the low frequency of conventional CD1c⁺ DCs is predictive of a worse prognosis. The purpose of this mini-review is to focus on the main evidence on DC involvement in IPF pathogenesis. Unanswered questions and opportunities for future research ranging from a better understanding of their contribution to diagnosis and prognosis to personalized DC-based therapies will be explored.

Airspace Macrophages and Monocytes Exist in Transcriptionally Distinct Subsets in Healthy Adults

Rationale: Macrophages are the most abundant immune cell in the alveoli and small airways and are traditionally viewed as a homogeneous population during health. Whether distinct subsets of airspace macrophages are present in healthy humans is unknown. Single-cell RNA sequencing allows for examination of transcriptional heterogeneity between cells and between individuals. Understanding the conserved repertoire of airspace macrophages during health is essential to understanding cellular programing during disease.Objectives: We sought to determine the transcriptional heterogeneity of human cells obtained from BAL of healthy adults.Methods: Ten subjects underwent bronchoscopy with BAL. Cells from lavage were subjected to single-cell RNA sequencing. Unique cell populations and putative functions were identified. Transcriptional profiles were compared across individuals.Measurements and Main Results: We identify two novel subgroups of resident airspace macrophages-defined by proinflammatory and metallothionein gene expression profiles. We define subsets of monocyte-like cells and compare them with peripheral blood mononuclear cells. Finally, we compare global macrophage and monocyte programing between males and females.Conclusions: Healthy human airspaces contain multiple populations of myeloid cells that are highly conserved between individuals and between sexes. Resident macrophages make up the largest population and include novel subsets defined by inflammatory and metal-binding profiles. Monocyte-like cells within the airspaces are transcriptionally aligned with circulating blood cells and include a rare population defined by expression of cell-matrix interaction genes. This study is the first to delineate the conserved heterogeneity of airspace immune cells during health and identifies two previously unrecognized macrophage subsets.

The basic immunology of asthma

In many asthmatics, chronic airway inflammation is driven by IL-4-, IL-5-, and IL-13-producing Th2 cells or ILC2s. Type 2 cytokines promote hallmark features of the disease such as eosinophilia, mucus hypersecretion, bronchial hyperresponsiveness (BHR), IgE production, and susceptibility to exacerbations. However, only half the asthmatics have this "type 2-high" signature, and "type 2-low" asthma is more associated with obesity, presence of neutrophils, and unresponsiveness to corticosteroids, the mainstay asthma therapy. Here, we review the underlying immunological basis of various asthma endotypes by discussing results obtained from animal studies as well as results generated in clinical studies targeting specific immune pathways.

Inflammatory Type 2 cDCs Acquire Features of cDC1s and Macrophages to Orchestrate Immunity to Respiratory Virus Infection

The phenotypic and functional dichotomy between IRF8⁺ type 1 and IRF4⁺ type 2 conventional dendritic cells (cDC1s and cDC2s, respectively) is well accepted; it is unknown how robust this dichotomy is under inflammatory conditions, when additionally monocyte-derived cells (MCs) become competent antigen-presenting cells (APCs). Using single-cell technologies in models of respiratory viral infection, we found that lung cDC2s acquired expression of the Fc receptor CD64 shared with MCs and of IRF8 shared with cDC1s. These inflammatory cDC2s (inf-cDC2s) were superior in inducing CD4⁺ T helper (Th) cell polarization while simultaneously presenting antigen to CD8⁺ T cells. When carefully separated from inf-cDC2s, MCs lacked APC function. Inf-cDC2s matured in response to cell-intrinsic Toll-like receptor and type 1 interferon receptor signaling, upregulated an IRF8-dependent maturation module, and acquired antigens via convalescent serum and Fc receptors. Because hybrid inf-cDC2s are easily confused with monocyte-derived cells, their existence could explain why APC functions have been attributed to MCs.

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Type I interferon drives differentiation of inf-cDC2s that closely resemble MCs

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Inf-cDC2s prime CD4⁺ and CD8⁺ T cells, whereas MCs lack APC function

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Inf-cDC2s internalize antibody-complexed antigen via Fc receptors

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IRF8 controls maturation gene module in inf-cDC2s