The role of the IL23/IL17 axis in bronchiolitis obliterans syndrome after lung transplantation

Relationship between immune cells and the development of chronic lung allograft dysfunction

A major cause of death for lung transplant recipients (LTRs) is the advent of chronic lung allograft dysfunction (CLAD), which has long plagued the long-term post-transplant prognosis and quality of survival of transplant patients. The intricacy of its pathophysiology and the irreversibility of its illness process present major obstacles to the clinical availability of medications. Immunotherapeutic medications are available, but they only aim to slow down the course of CLAD rather than having any therapeutic impact on the disease's development. For this reason, understanding the pathophysiology of CLAD is essential for both disease prevention and proven treatment. The immunological response in particular, in relation to chronic lung allograft dysfunction, has received a great deal of interest recently. Innate immune cells like natural killer cells, eosinophils, neutrophils, and mononuclear macrophages, as well as adaptive immunity cells like T and B cells, play crucial roles in this process through the release of chemokines and cytokines. The present review delves into changes and processes within the immune microenvironment, with a particular focus on the quantity, subtype, and characteristics of effector immune cells in the peripheral and transplanted lungs after lung transplantation. We incorporate and solidify the documented role of immune cells in the occurrence and development of CLAD with the advancements in recent years.

A Critical Review on the Role of Probiotics in Lung Cancer Biology and Prognosis

Lung cancer remains the leading cause of cancer-related deaths worldwide. According to the American Cancer Society (ACS), it ranks as the second most prevalent type of cancer globally. Recent findings have highlighted bidirectional gut-lung interactions, known as the gut-lung axis, in the pathophysiology of lung cancer. Probiotics are live microorganisms that boost host immunity when consumed adequately. The immunoregulatory mechanisms of probiotics are thought to operate through the generation of various metabolites that impact both the gut and distant organs (e.g., the lungs) through blood. Several randomized controlled trials have highlighted the pivotal role of probiotics in gut health especially for the prevention and treatment of malignancies, with a specific emphasis on lung cancer. Current research indicates that probiotic supplementation positively affects patients, leading to a suppression in cancer symptoms and a shortened disease course. While clinical trials validate the therapeutic benefits of probiotics, their precise mechanism of action remains unclear. This narrative review aims to provide a comprehensive overview of the present landscape of probiotics in the management of lung cancer.

Donor IL-17 receptor A regulates LPS-potentiated acute and chronic murine lung allograft rejection

Chronic lung allograft dysfunction (CLAD) is a major complication after lung transplantation that results from a complex interplay of innate inflammatory and alloimmune factors, culminating in parenchymal and/or obliterative airway fibrosis. Excessive IL-17A signaling and chronic inflammation have been recognized as key factors in these pathological processes. Herein, we developed a model of repeated airway inflammation in mouse minor alloantigen-mismatched single-lung transplantation. Repeated intratracheal LPS instillations augmented pulmonary IL-17A expression. LPS also increased acute rejection, airway epithelial damage, and obliterative airway fibrosis, similar to human explanted lung allografts with antecedent episodes of airway infection. We then investigated the role of donor and recipient IL-17 receptor A (IL-17RA) in this context. Donor IL-17RA deficiency significantly attenuated acute rejection and CLAD features, whereas recipient IL-17RA deficiency only slightly reduced airway obliteration in LPS allografts. IL-17RA immunofluorescence positive staining was greater in human CLAD lungs compared with control human lung specimens, with localization to fibroblasts and myofibroblasts, which was also seen in mouse LPS allografts. Taken together, repeated airway inflammation after lung transplantation caused local airway epithelial damage, with persistent elevation of IL-17A and IL-17RA expression and particular involvement of IL-17RA on donor structural cells in development of fibrosis.

Identification of Hub Genes in the Pathogenesis of Bronchiolitis Obliterans via Bioinformatic Analysis and Experimental Verification

Background

Bronchiolitis obliterans (BO) is a chronic disease that can arise as a complication of severe childhood pneumonia and can also impact the long-term survival of patients after lung transplantation. However, the precise molecular mechanism underlying BO remains unclear. We aimed to identify BO-associated hub genes and their molecular mechanisms.

Methods

BO-associated transcriptome datasets (GSE52761, GSE137169, and GSE94557) were downloaded from the Gene Expression Omnibus (GEO) database to identify differentially expressed genes (DEGs). Additional bioinformatics analyses, such as Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Protein-Protein Interaction (PPI) analyses, were performed to determine functional roles and DEG-associated regulatory networks. Prediction of hub genes using the 12 algorithms available in the Cytohubba plugin of Cytoscape software was also performed. Verification was performed using the BO mouse model.

Results

Our results revealed 57 DEGs associated with BO, of which 18 were down-regulated and 39 were up-regulated. The Cytohubba plugin data further narrowed down the 57 DEGs into 9 prominent hub genes (CCR2, CD1D, GM2A, TFEC, MPEG1, CTSS, GPNMB, BIRC2, and CTSZ). Genes such as CCR2, TFEC, MPEG1, CTSS, and CTSZ were dysregulated in 2,3-butanedione-induced BO mice, whereas TFEC, CTSS, and CTSZ were dysregulated in nitric acid-induced BO mouse models.

Conclusion

Our study identified and validated four novel BO biomarkers, which may allow further investigation into the development of distinct BO diagnostic markers and novel therapeutic avenues.

Insight on immune cells in rejection and infection postlung transplant

OBJECTIVE

The aim of this study is to provide a concise overview of the role of immune cells in rejection and infection after lung transplantation.

METHODS

Based on previous clinical and basic studies, the role of various types of immune cells in the development of rejection and infection after lung transplantation is summarized.

RESULTS

Immune cell functional status is strongly associated with common complications after lung transplantation, such as primary graft dysfunction, infection and occlusive bronchitis syndrome. Targeted balancing of immune cell tolerance and rejection is an important tool for successful lung transplantation.

CONCLUSION

A comprehensive understanding of immune cell function and the mechanisms that balance immune tolerance and immune rejection may be a crucial factor in improving survival after lung transplantation.

[Chronic lung allograft dysfunction in 2022, past and updates]

INTRODUCTION

While short-term results of lung transplantation have improved considerably, long-term survival remains below that achieved for other solid organ transplants.

CURRENT KNOWLEDGE

The main cause of late mortality is chronic lung allograft dysfunction (CLAD), which affects nearly half of the recipients 5 years after transplantation. Immunological and non-immune risk factors have been identified. These factors activate the innate and adaptive immune system, leading to lesional and altered wound-healing processes, which result in fibrosis affecting the small airways or interstitial tissue. Several phenotypes of CLAD have been identified based on respiratory function and imaging pattern. Aside from retransplantation, which is possible for only small number of patients, no treatment can reverse the CLAD process.

PERSPECTIVES

Current therapeutic research is focused on anti-fibrotic treatments and photopheresis. Basic research has identified numerous biomarkers that could prove to be relevant as therapeutic targets.

CONCLUSION

While the pathophysiological mechanisms of CLAD are better understood than before, a major therapeutic challenge remains.

JAK-STAT activation contributes to cytotoxic T cell-mediated basal cell death in human chronic lung allograft dysfunction

Chronic lung allograft dysfunction (CLAD) is the leading cause of death in lung transplant recipients. CLAD is characterized clinically by a persistent decline in pulmonary function and histologically by the development of airway-centered fibrosis known as bronchiolitis obliterans. There are no approved therapies to treat CLAD, and the mechanisms underlying its development remain poorly understood. We performed single-cell RNA-Seq and spatial transcriptomic analysis of explanted tissues from human lung recipients with CLAD, and we performed independent validation studies to identify an important role of Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling in airway epithelial cells that contributes to airway-specific alloimmune injury. Specifically, we established that activation of JAK-STAT signaling leads to upregulation of major histocompatibility complex 1 (MHC-I) in airway basal cells, an important airway epithelial progenitor population, which leads to cytotoxic T cell-mediated basal cell death. This study provides mechanistic insight into the cell-to-cell interactions driving airway-centric alloimmune injury in CLAD, suggesting a potentially novel therapeutic strategy for CLAD prevention or treatment.

Systems prediction of chronic lung allograft dysfunction: Results and perspectives from the Cohort of Lung Transplantation and Systems prediction of Chronic Lung Allograft Dysfunction cohorts

Background

Chronic lung allograft dysfunction (CLAD) is the leading cause of poor long-term survival after lung transplantation (LT). Systems prediction of Chronic Lung Allograft Dysfunction (SysCLAD) aimed to predict CLAD.

Methods

To predict CLAD, we investigated the clinicome of patients with LT; the exposome through assessment of airway microbiota in bronchoalveolar lavage cells and air pollution studies; the immunome with works on activation of dendritic cells, the role of T cells to promote the secretion of matrix metalloproteinase-9, and subpopulations of T and B cells; genome polymorphisms; blood transcriptome; plasma proteome studies and assessment of MSK1 expression.

Results

Clinicome: the best multivariate logistic regression analysis model for early-onset CLAD in 422 LT eligible patients generated a ROC curve with an area under the curve of 0.77. Exposome: chronic exposure to air pollutants appears deleterious on lung function levels in LT recipients (LTRs), might be modified by macrolides, and increases mortality. Our findings established a link between the lung microbial ecosystem, human lung function, and clinical stability post-transplant. Immunome: a decreased expression of CLEC1A in human lung transplants is predictive of the development of chronic rejection and associated with a higher level of interleukin 17A; Immune cells support airway remodeling through the production of plasma MMP-9 levels, a potential predictive biomarker of CLAD. Blood CD9-expressing B cells appear to favor the maintenance of long-term stable graft function and are a potential new predictive biomarker of BOS-free survival. An early increase of blood CD4 + CD57 + ILT2+ T cells after LT may be associated with CLAD onset. Genome: Donor Club cell secretory protein G38A polymorphism is associated with a decreased risk of severe primary graft dysfunction after LT. Transcriptome: blood POU class 2 associating factor 1, T-cell leukemia/lymphoma domain, and B cell lymphocytes, were validated as predictive biomarkers of CLAD phenotypes more than 6 months before diagnosis. Proteome: blood A2MG is an independent predictor of CLAD, and MSK1 kinase overexpression is either a marker or a potential therapeutic target in CLAD.

Conclusion

Systems prediction of Chronic Lung Allograft Dysfunction generated multiple fingerprints that enabled the development of predictors of CLAD. These results open the way to the integration of these fingerprints into a predictive handprint.

Cytokines in Lung Transplantation

Lung transplantation has developed significantly in recent years, but post-transplant care and patients' survival still need to be improved. Moreover, organ shortage urges novel modalities to improve the quality of unsuitable lungs. Cytokines, the chemical mediators of the immune system, might be used for diagnostic and therapeutic purposes in lung transplantation. Cytokine monitoring pre- and post-transplant could be applied to the prevention and early diagnosis of injurious inflammatory events including primary graft dysfunction, acute cellular rejection, bronchiolitis obliterans syndrome, restrictive allograft syndrome, and infections. In addition, preoperative cytokine removal, specific inhibition of proinflammatory cytokines, and enhancement of anti-inflammatory cytokines gene expression could be considered therapeutic options to improve lung allograft survival. Therefore, it is essential to describe the cytokines alteration during inflammatory events to gain a better insight into their role in developing the abovementioned complications. Herein, cytokine fluctuations in lung tissue, bronchoalveolar fluid, peripheral blood, and exhaled breath condensate in different phases of lung transplantation have been reviewed; besides, cytokine gene polymorphisms with clinical significance have been summarized.

Transcripts associated with chronic lung allograft dysfunction in transbronchial biopsies of lung transplants

Transplanted lungs suffer worse outcomes than other organ transplants with many developing chronic lung allograft dysfunction (CLAD), diagnosed by physiologic changes. Histology of transbronchial biopsies (TBB) yields little insight, and the molecular basis of CLAD is not defined. We hypothesized that gene expression in TBBs would reveal the nature of CLAD and distinguish CLAD from changes due simply to time posttransplant. Whole-genome mRNA profiling was performed with microarrays in 498 prospectively collected TBBs from the INTERLUNG study, 90 diagnosed as CLAD. Time was associated with increased expression of inflammation genes, for example, CD1E and immunoglobulins. After correcting for time, CLAD manifested not as inflammation but as parenchymal response-to-wounding, with increased expression of genes such as HIF1A, SERPINE2, and IGF1 that are increased in many injury and disease states and cancers, associated with development, angiogenesis, and epithelial response-to-wounding in pathway analysis. Fibrillar collagen genes were increased in CLAD, indicating matrix changes, and normal transcripts were decreased-dedifferentiation. Gene-based classifiers predicted CLAD with AUC 0.70 (no time-correction) and 0.87 (time-corrected). CLAD related gene sets and classifiers were strongly prognostic for graft failure and correlated with CLAD stage. Thus, in TBBs, molecular changes indicate that CLAD primarily reflects severe parenchymal injury-induced changes and dedifferentiation.

Markers of rejection of a lung allograft: state of the art

Chronic lung allograft dysfunction (CLAD) affects approximately 50% of all lung transplant recipients by 5 post-operative years and is the leading cause of death in lung transplant recipients. Early CLAD diagnosis or ideally prediction of CLAD is essential to enable early intervention before significant lung injury occurs. New technologies have emerged to facilitate biomarker discovery, including epigenetic modification and single-cell RNA sequencing. This review examines new and existing technologies for biomarker discovery and the current state of research on biomarkers for identifying lung transplant rejection.

Effector immune cells in Chronic Lung Allograft Dysfunction: a Systematic Review

Chronic lung allograft dysfunction (CLAD) remains the major barrier to long‐term survival after lung transplantation and improved insight into its underlying immunological mechanisms is critical to better understand the disease and to identify treatment targets. We systematically searched the electronic databases of PubMed and EMBASE for original research publications, published between January 2000 and April 2021, to comprehensively assess current evidence on effector immune cells in lung tissue and bronchoalveolar lavage fluid from lung transplant recipients with CLAD. Literature search revealed 1351 articles, 76 of which met the criteria for inclusion in our analysis. Our results illustrate significant complexity in both innate and adaptive immune cell responses in CLAD, along with presence of numerous immune cell products, including cytokines, chemokines and proteases associated with tissue remodelling. A clear link between neutrophils and eosinophils and CLAD incidence has been seen, in which eosinophils more specifically predisposed to restrictive allograft syndrome. The presence of cytotoxic and T‐helper cells in CLAD pathogenesis is well‐documented, although it is challenging to draw conclusions about their role in tissue processes from predominantly bronchoalveolar lavage data. In restrictive allograft syndrome, a more prominent humoral immune involvement with increased B cells, immunoglobulins and complement deposition is seen. Our evaluation of published studies over the last 20 years summarizes the complex multifactorial immunopathology of CLAD onset and progression. It highlights the phenotype of several key effector immune cells involved in CLAD pathogenesis, as well as the paucity of single cell resolution spatial studies in lung tissue from patients with CLAD.

Bioinspired carbon monoxide delivery using artificial blood attenuates the progression of obliterative bronchiolitis via suppression of macrophage activation by IL-17A

Carbon monoxide (CO) is expected to attenuate the progression of obliterative bronchiolitis (OB), which is a serious complication after lung transplantation. However, issues in terms of feasible exogenous CO supply, such as continuousness and safety, remain unsolved. Here, we applied nano red blood cells, namely hemoglobin vesicles (Hb-V), as a CO cargo based on the biomimetic concept and investigated the therapeutic potential of CO-loaded Hb-V on OB in orthotopic tracheal transplant model mice. The CO-loaded Hb-V was comprised of negatively charged liposomes encapsulating carbonylhemoglobin with a size of ca. 220 nm. The results of histological evaluation showed that allograft luminal occlusion and fibrosis were significantly ameliorated by treatment with CO-loaded Hb-V compared to treatment with saline, cyclosporine, and Hb-V. The therapeutic effects of CO-loaded Hb-V on OB were due to the suppression of M1 macrophage activation in tracheal allografts, resulting from decreased IL-17A production. Furthermore, the expression of TNF-α and TGF-β in tracheal allografts was decreased by CO-loaded Hb-V treatment but not saline and Hb-V treatment, indicating that CO liberated from CO-loaded Hb-V inhibits epithelial-mesenchymal transition. These findings suggest that CO-loaded Hb-V exerts strong therapeutic efficacy against OB via the regulation of macrophage activation by IL-17A and TGF-β-driven epithelial-mesenchymal transition.

Recipient bone marrow-derived IL-17 receptor A-positive cells drive allograft fibrosis in a mouse intrapulmonary tracheal transplantation model

IL-17A is implicated in the pathogenesis of chronic lung allograft dysfunction, which limits survival after lung transplantation. While many cells express the IL-17 receptor A (IL-17RA) which is the main receptor for IL-17A, the cellular targets of IL-17A in development of post-transplant fibrosis are unknown. The purpose of this study was to determine whether IL-17RA expression by donor or recipient structural or bone marrow (BM) cells is required for the development of allograft fibrosis in a mouse intrapulmonary tracheal transplantation (IPTT) model. BM chimeras were generated using C57BL/6 and IL-17RA-knockout mice. After engraftment, allogeneic IPTTs were performed using the chimeric and BALB/c mice as donors or recipients. This allowed us to assess the effect of IL-17RA deficiency in recipient BM, recipient structural, donor BM, or donor structural compartments separately. Tracheal grafts, the surrounding lung, and mediastinal lymph nodes were assessed 28 days after IPTT. Only recipient BM IL-17RA deficiency resulted in attenuation of tracheal graft obliteration. In the setting of recipient BM IL-17RA deficiency, T cells and neutrophils were decreased in mediastinal lymph nodes. Additionally, recipient BM IL-17RA deficiency was associated with increased B220⁺PNAd⁺ lymphoid aggregates, consistent with tertiary lymphoid organs, in proximity to the tracheal allograft. In this IPTT model, recipient BM-derived cells appear to be the primary targets of IL-17RA signaling during fibrotic obliteration of the tracheal allograft.

Chronic Lung Allograft Dysfunction: Evolving Concepts and Therapies

The primary factor that limits long-term survival after lung transplantation is chronic lung allograft dysfunction (CLAD). CLAD also impairs quality of life and increases the costs of medical care. Our understanding of CLAD continues to evolve. Consensus definitions of CLAD and the major CLAD phenotypes were recently updated and clarified, but it remains to be seen whether the current definitions will lead to advances in management or impact care. Understanding the potential differences in pathogenesis for each CLAD phenotype may lead to novel therapeutic strategies, including precision medicine. Recognition of CLAD risk factors may lead to earlier interventions to mitigate risk, or to avoid risk factors all together, to prevent the development of CLAD. Unfortunately, currently available therapies for CLAD are usually not effective. However, novel therapeutics aimed at both prevention and treatment are currently under investigation. We provide an overview of the updates to CLAD-related terminology, clinical phenotypes and their diagnosis, natural history, pathogenesis, and potential strategies to treat and prevent CLAD.

Immunomodulatory Effects of Azithromycin Revisited: Potential Applications to COVID-19

The rapid advancement of the COVID-19 pandemic has prompted an accelerated pursuit to identify effective therapeutics. Stages of the disease course have been defined by viral burden, lung pathology, and progression through phases of the immune response. Immunological factors including inflammatory cell infiltration and cytokine storm have been associated with severe disease and death. Many immunomodulatory therapies for COVID-19 are currently being investigated, and preliminary results support the premise of targeting the immune response. However, because suppressing immune mechanisms could also impact the clearance of the virus in the early stages of infection, therapeutic success is likely to depend on timing with respect to the disease course. Azithromycin is an immunomodulatory drug that has been shown to have antiviral effects and potential benefit in patients with COVID-19. Multiple immunomodulatory effects have been defined for azithromycin which could provide efficacy during the late stages of the disease, including inhibition of pro-inflammatory cytokine production, inhibition of neutrophil influx, induction of regulatory functions of macrophages, and alterations in autophagy. Here we review the published evidence of these mechanisms along with the current clinical use of azithromycin as an immunomodulatory therapeutic. We then discuss the potential impact of azithromycin on the immune response to COVID-19, as well as caution against immunosuppressive and off-target effects including cardiotoxicity in these patients. While azithromycin has the potential to contribute efficacy, its impact on the COVID-19 immune response requires additional characterization so as to better define its role in individualized therapy.

Diesel Exhaust Particulates Enhances Susceptibility of LPS-Induced Acute Lung Injury through Upregulation of the IL-17 Cytokine-Derived TGF-β1/Collagen I Expression and Activation of NLRP3 Inflammasome Signaling in Mice

Diesel exhaust particulates (DEP) adversely affect the respiratory system and exacerbate lung diseases, resulting in high mortality rates. However, its pathogenesis is complicated, and the mechanisms involved are incompletely understood. We investigated the effects of DEP pre-exposure on lipopolysaccharide (LPS)-induced acute lung injury (ALI) and identified the roles of interleukin (IL)-17 in mice. Mice were divided into vehicle control, DEP, LPS, and DEP pre-exposed and LPS-instilled groups. Pre-exposure to DEP enhanced the number of total cells, neutrophils, and lymphocytes in the BAL fluid of LPS-instilled mice. Pre-exposure to DEP synergistically exacerbated pulmonary acute lung inflammation and granulomatous inflammation/pulmonary fibrosis, concomitant with the enhanced expression of inflammatory cytokines in the BAL fluid and of collagen I and TGF-β1 in the lungs of LPS-instilled mice. The number of TGF-β1-positive cells in the DEP pre-exposed and LPS-instilled group was higher than that in the LPS group. The expression of NLR family pyrin domain containing 3 (NLRP3) inflammasome components was markedly increased in the DEP pre-exposed and LPS-instilled group. IL-17 levels in the BAL fluid and IL-17-positive cells in the lungs were significantly increased by pre-exposure to DEP in the LPS-induced group compared to that in the DEP or LPS group. These results suggest that DEP predominantly contributes to fibrotic lung disease in LPS-related acute lung injury by upregulating IL-17 cytokine-mediated collagen I and TGF-β1 and, at least in part, by activating LPS-induced NLRP3 inflammasome signaling. The study should be useful in devising better strategies for prevention and management of ALI.

Microbiome dysbiosis in lung cancer: from composition to therapy

The correlations between microbiota dysbiosis and cancer have gained extensive attention and been widely explored. As a leading cancer diagnosis worldwide, lung cancer poses a great threat to human health. The healthy human lungs are consistently exposed to external environment and harbor a specific pattern of microbiota, sharing many key pathological and physiological characteristics with the intestinal tract. Although previous findings uncovered the critical roles of microbiota in tumorigenesis and response to anticancer therapy, most of them were focused on the intestinal microbiota rather than lung microbiota. Notably, the considerable functions of microbiota in maintaining lung homeostasis should not be neglected as the microbiome dysbiosis may promote tumor development and progression through production of cytokines and toxins and multiple other pathways. Despite the fact that increasing studies have revealed the effect of microbiome on the induction of lung cancer and different disease status, the underlying mechanisms and potential therapeutic strategies remained unclear. Herein, we summarized the recent progresses about microbiome in lung cancer and further discussed the role of microbial communities in promoting lung cancer progression and the current status of therapeutic approaches targeting microbiome to alleviate and even cure lung cancer.

Advances in Human Lung Transplantation

Lung transplantation improves survival and quality of life in patients with advanced pulmonary disease. Over the past several decades, the volume of lung transplants has grown substantially, with increasing transplantation of older and acutely ill individuals facilitated by improved utilization and preservation of available donor organs. Other advances include improvements in the diagnosis and mechanistic understanding of frequent post-transplant complications, such as primary graft dysfunction, acute rejection, and chronic lung allograft dysfunction (CLAD). CLAD occurs as a result of the host immune response to the allograft and is the principal factor limiting long-term survival after lung transplantation. Two distinct clinical phenotypes of CLAD have emerged, bronchiolitis obliterans syndrome and restrictive allograft syndrome, and this distinction has enabled further understanding of underlying immune mechanisms. Building on these advances, ongoing studies are exploring novel approaches to diagnose, prevent, and treat CLAD. Such studies are necessary to improve long-term outcomes for lung transplant recipients.

Bronchoalveolar lavage T cell cytokine profiles and their association with lung function in children with Mycoplasma pneumoniae -associated bronchiolitis obliterans

BACKGROUND

Mycoplasma pneumoniae (M. pneumoniae) infection may progress to bronchiolitis obliterans (BO), with an underlying chronic inflammatory process. The aim of this study was to investigate the cytokine profiles in pulmonary T-lymphocytes and their associations with lung function in patients with BO following M. pneumoniae infection.

METHODS

Bronchoalveolar lavage (BAL) samples were obtained from 10 controls and 18 children with M. pneumoniae-associated BO. We analyzed the BAL T cells for interferon (IFN)-γ, interleukin (IL)-4, IL-9, IL-17, CD25, and Foxp3 by intercellular flow cytometry. The associations with T-cell subpopulations and lung function parameters were determined.

RESULTS

In BAL fluid, significantly increased proportions of T-helper 1 (Th1), Th17, and Tc1 cells were found in M. pneumoniae-associated BO patients when compared with controls. The percentages of Th17 cells showed correlations with forced expiratory volume in 1 second % predicted value (r = -0585; P < .05) and forced expiratory flow at 25% to 75% (FEF_25%-75% ) % predicted value (r = -.618; P < .01). Higher proportions of Tc1 (r = -.488; P < .05) and Tc17 (r = -.542; P < .05) were significantly correlated with a reduced FEF_25%-75% % predicted value in M. pneumoniae-associated BO patients.

CONCLUSIONS

Our comprehensive cytokines analysis of BAL T cells revealed correlations of IL-17-producing and IFN-γ-producing T cells with lung function, suggesting that increased T-cell subpopulations may play a role in M. pneumoniae-associated BO progression.

IL-17A Contributes to Lung Fibrosis in a Model of Chronic Pulmonary Graft-versus-host Disease

BACKGROUND

Chronic pulmonary graft-versus-host disease (cpGVHD) after hematopoietic cell transplant (HCT) manifests as progressive airway and parenchymal lung fibrosis. On the basis of our prior data, mice that undergo allogeneic HCT with Tbet-knockout donors (AlloTbet) have increased lung Th17 cells and IL-17A and develop fibrosis resembling human cpGVHD. The role of IL-17A in posttransplant pulmonary fibrosis remains incompletely understood. We hypothesized that IL-17A is necessary for development of murine cpGVHD in this model.

METHODS

AlloTbet mice received weekly intraperitoneal anti-IL-17A or IgG (200 μg/mouse) starting 2 weeks post-HCT and were sacrificed after week 5. Histologic airway and parenchymal fibrosis were semiquantitatively graded in a blinded fashion. Lung cells and proteins were measured by flow cytometry, ELISA, and multicytokine assays.

RESULTS

Anti-IL-17A modestly decreased airway and parenchymal lung fibrosis, along with a striking reduction in pulmonary neutrophilia, IL-6, MIP-1α, MIP-1β, CXCL1, and CXCL5 in AlloTbet mice. Additionally, anti-IL-17A decreased CCL2, inflammatory monocytes and macrophages, and Th17 cells.

CONCLUSIONS

In the setting of murine AlloHCT with Tbet donors, IL-17A blockade decreases fibrotic features of cpGVHD. This may be mediated by the observed reduction in neutrophils or specific lung monocyte and macrophage populations or alternatively via a direct effect on fibroblasts. Collectively, our results further suggest that anti-IL-17A strategies could prove useful in preventing alloimmune-driven fibrotic lung diseases.

The role of inflammatory cytokines in the development of idiopathic subglottic stenosis

Idiopathic subglottic stenosis (iSGS) is a debilitating extrathoracic obstruction involving the lower laryngeal and upper tracheal airway. It arises without a known antecedent injury or associated disease process. iSGS is a fibrotic disease marked histologically by excessive accumulation of fibrous connective tissue components of the extracellular matrix (ECM, i.e., collagen and fibronectin) in inflamed tissue, which leads to airway obstruction and clinical dyspnea. Diverse diseases in divergent organ systems are associated with fibrosis, suggesting common pathogenic pathways. One of the most common is sustained host inflammation. Recent investigations focusing on the inflammatory response associated with iSGS have sought to characterize the immunophenotype and cytokine profile of the airway scar in iSGS. While the role of the immune response as inciting event in iSGS remains unresolved, the centrality of an active immune response to the observed subglottic tissue remodeling is becoming more defined.

Postinfectious Bronchiolitis Obliterans in Children: Diagnostic Workup and Therapeutic Options: A Workshop Report

Bronchiolitis obliterans (BO) is a rare, chronic form of obstructive lung disease, often initiated with injury of the bronchiolar epithelium followed by an inflammatory response and progressive fibrosis of small airways resulting in nonuniform luminal obliteration or narrowing. The term BO comprises a group of diseases with different underlying etiologies, courses, and characteristics. Among the better recognized inciting stimuli leading to BO are airway pathogens such as adenovirus and mycoplasma, which, in a small percentage of infected children, will result in progressive fixed airflow obstruction, an entity referred to as postinfectious bronchiolitis obliterans (PIBO). The present knowledge on BO in general is reasonably well developed, in part because of the relatively high incidence in patients who have undergone lung transplantation or bone marrow transplant recipients who have had graft-versus-host disease in the posttransplant period. The cellular and molecular pathways involved in PIBO, while assumed to be similar, have not been adequately elucidated. Since 2016, an international consortium of experts with an interest in PIBO assembles on a regular basis in Geisenheim, Germany, to discuss key areas in PIBO which include diagnostic workup, treatment strategies, and research fields.

Early Identification of Chronic Lung Allograft Dysfunction: The Need of Biomarkers

A growing number of patients with end-stage lung disease have benefited from lung transplantation (LT). Improvements in organ procurement, surgical techniques and intensive care management have greatly increased short-term graft survival. However, long-term outcomes remain limited, mainly due to the onset of chronic lung allograft dysfunction (CLAD), whose diagnosis is based on permanent loss of lung function after the development of irreversible lung lesions. CLAD is associated with high mortality and morbidity, and its exact physiopathology is still only partially understood. Many researchers and clinicians have searched for CLAD biomarkers to improve diagnosis, to refine the phenotypes associated with differential prognosis and to identify early biological processes that lead to CLAD to enable an early intervention that could modify the inevitable degradation of respiratory function. Donor-specific antibodies are currently the only biomarkers used in routine clinical practice, and their significance for accurately predicting CLAD is still debated. We describe here significant studies that have highlighted potential candidates for reliable and non-invasive biomarkers of CLAD in the fields of imaging and functional monitoring, humoral immunity, cell-mediated immunity, allograft injury, airway remodeling and gene expression. Such biomarkers would improve CLAD prediction and allow differential LT management regarding CLAD risk.

Specific Donor HLA-DR Types Correlate With Altered Susceptibility to Development of Chronic Lung Allograft Dysfunction

BACKGROUND

The greatest challenge to long-term graft survival is the development of chronic lung allograft dysfunction. Th17 responses to collagen type V (colV) predispose lung transplant patients to the severe obstructive form of chronic lung allograft dysfunction, known as bronchiolitis obliterans syndrome (BOS). In a previous study cohort (n = 54), pretransplant colV responses were increased in recipients expressing HLA-DR15, consistent with the high binding avidity of colV (α1) peptides for HLA-DR15, whereas BOS incidence, which was known to be strongly associated with posttransplant autoimmunity to colV, was higher in patients who themselves lacked HLA-DR15, but whose lung donor expressed it.

METHODS

To determine if this DR-restricted effect on BOS incidence could be validated in a larger cohort, we performed a retrospective analysis of outcomes for 351 lung transplant recipients transplanted between 1988 and 2008 at the University of Wisconsin. All subjects were followed until graft loss, death, loss to follow-up, or through 2014, with an average follow-up of 7 years. Comparisons were made between recipients who did or did not develop BOS. Grading of BOS followed the recommendations of the international society for heart and lung transplantation.

RESULTS

Donor HLA-DR15 was indeed associated with increased susceptibility to severe BOS in this population. We also discovered that HLA-DR7 expression by the donor or HLA-DR17 expression by the recipient decreased susceptibility.

CONCLUSIONS

We show in this retrospective study that specific donor HLA class II types are important in lung transplantation, because they are associated with either protection from or susceptibility to development of severe BOS.

Pathologic Fibroblasts in Idiopathic Subglottic Stenosis Amplify Local Inflammatory Signals

OBJECTIVE

To characterize the phenotype and function of fibroblasts derived from airway scar in idiopathic subglottic stenosis (iSGS) and to explore scar fibroblast response to interleukin 17A (IL-17A).

STUDY DESIGN

Basic science.

SETTING

Laboratory.

SUBJECTS AND METHODS

Primary fibroblast cell lines from iSGS subjects, idiopathic pulmonary fibrosis subjects, and normal control airways were utilized for analysis. Protein, molecular, and flow cytometric techniques were applied in vitro to assess the phenotype and functional response of disease fibroblasts to IL-17A.

RESULTS

Mechanistically, IL-17A drives iSGS scar fibroblast proliferation ( P < .01), synergizes with transforming growth factor ß1 to promote extracellular matrix production (collagen and fibronectin; P = .04), and directly stimulates scar fibroblasts to produce chemokines (chemokine ligand 2) and cytokines (IL-6 and granulocyte-macrophage colony-stimulating factor) critical to the recruitment and differentiation of myeloid cells ( P < .01). Glucocorticoids abrogated IL-17A-dependent iSGS scar fibroblast production of granulocyte-macrophage colony-stimulating factor ( P = .02).

CONCLUSION

IL-17A directly drives iSGS scar fibroblast proliferation, synergizes with transforming growth factor ß1 to promote extracellular matrix production, and amplifies local inflammatory signaling. Glucocorticoids appear to partially abrogate fibroblast-dependent inflammatory signaling. These results offer mechanistic support for future translational study of clinical reagents for manipulation of the IL-17A pathway in iSGS patients.

Sequential broncho-alveolar lavages reflect distinct pulmonary compartments: clinical and research implications in lung transplantation

Background

Bronchoalveolar lavage (BAL) has proven to be very useful to monitor the lung allograft after transplantation. In addition to allowing detection of infections, multiple BAL analytes have been proposed as potential biomarkers of lung allograft rejection or dysfunction. However, BAL collection is not well standardized and differences in BAL collection represent an important source of variation. We hypothesized that there are systematic differences between sequential BALs that are relevant to BAL analysis.

Methods

As part of 126 consecutive bronchoscopies in lung transplant recipients, two sequential BALs (BAL1 and BAL2) were performed in one location during each bronchoscopy by instilling and suctioning 50 ml of normal saline twice into separate containers. Cell concentration, viability and differentials, Surfactant Protein-D (SP-D), Club Cell Secretory Protein (CCSP), and levels of CXCL10, IL-10, CCL2, CCL5, VEGF-C, RAGE, CXCL9, CXCL1, IL-17A, IL-21, PDGF, and GCSF were compared between BAL1 and BAL2.

Results

Total cell concentration did not differ between BAL1 and BAL2; however, compared to BAL2, BAL1 had more dead cells, epithelial cells, neutrophils, and higher concentrations of airway epithelium-derived CCSP and inflammatory markers. BAL2 had a higher concentration of SP-D compared to BAL1.

Conclusion

In this study performed in lung transplant recipients, we show that sequential BALs represent different lung compartments and have distinct compositions. BAL1 represents the airway compartment with more epithelial cells, neutrophils, and epithelium-derived CCSP. Conversely, BAL2 samples preferentially the distal bronchoalveolar space with greater cell viability and higher SP-D. Our findings illustrate how the method of BAL collection can influence analyte concentrations and further emphasize the need for a standardized approach in translational research involving BAL samples.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0786-z) contains supplementary material, which is available to authorized users.

Azithromycin Fails to Prevent Accelerated Airway Obliteration in T-bet-/- Mouse Lung Allograft Recipients

BACKGROUND

Cellular and molecular mechanisms of acute and chronic lung allograft rejection have yet to be clearly defined, and obliterative bronchiolitis (OB) remains the primary limitation to survival in lung transplant recipients (LTRs). We have previously shown that T-bet-deficient recipients of full major histocompatibility complex (MHC)-mismatched, orthotopic left lung transplants develop accelerated obliterative airway disease (OAD) in the setting of acute cellular rejection characterized by robust alloimmune CD8⁺ interleukin (IL)-17 and interferon (IFN)-γ responses that are attenuated with neutralization of IL-17. Azithromycin has been shown to be beneficial in some LTRs with bronchiolitis obliterans syndrome/OB. Here, we evaluated the effects of azithromycin on rejection pathology and T-cell effector responses in T-bet^-/- recipients of lung transplants.

METHODS

Orthotopic left lung transplantation was performed in BALB/c → B6 wild type or BALB/c → B6 T-bet^-/- strain combinations as previously described. Mice treated with azithromycin received 10 mg/kg or 50 mg/kg subcutaneously daily. Lung allograft histopathology was analyzed at day 10 or day 21 post-transplantation, and neutrophil staining for quantification was performed using anti-myeloperoxidase. Allograft mononuclear cells were isolated at day 10 for T-cell effector cytokine response assessment using flow cytometry.

RESULTS

We show that while azithromycin significantly decreases lung allograft neutrophilia and CXCL1 levels and attenuates allospecific CD8⁺ IL-17 responses early post-transplantation, OAD persists in T-bet-deficient mice.

CONCLUSIONS

Our results indicate that lung allograft neutrophilia is not essential for the development of OAD in this model and suggest allospecific T-cell responses that remain despite marked attenuation of CD8⁺ IL-17 are sufficient for obliterative airway inflammation and fibrosis.

The Lung Microbiome, Immunity, and the Pathogenesis of Chronic Lung Disease

The development of culture-independent techniques for microbiological analysis has uncovered the previously unappreciated complexity of the bacterial microbiome at various anatomic sites. The microbiome of the lung has relatively less bacterial biomass when compared with the lower gastrointestinal tract yet displays considerable diversity. The composition of the lung microbiome is determined by elimination, immigration, and relative growth within its communities. Chronic lung disease alters these factors. Many forms of chronic lung disease demonstrate exacerbations that drive disease progression and are poorly understood. Mounting evidence supports ways in which microbiota dysbiosis can influence host defense and immunity, and in turn may contribute to disease exacerbations. Thus, the key to understanding the pathogenesis of chronic lung disease may reside in deciphering the complex interactions between the host, pathogen, and resident microbiota during stable disease and exacerbations. In this brief review we discuss new insights into these labyrinthine relationships.

IL-17A Blockade Attenuates Obliterative Bronchiolitis and IFN-γ Cellular Immune Response in Lung Allografts

Obliterative bronchiolitis (OB), characterized by fibrous obliteration of the small airways, is a major impediment to long-term survival in lung allograft recipients. We found previously that IL-17A is produced primarily by CD4⁺ T cells and γδ T cells after lung transplant in a mouse model of orthotopic lung transplant. The absence of either subset of T cells was compensated for by expansion of the other subset, which suggested that systemic blockade of IL-17A was necessary. To determine the specific role of IL-17A in the development of OB, we treated lung allograft recipients with an IL-17A antagonistic antibody. After IL-17A blockade, the incidence of OB was significantly reduced in lung allografts. IL-17A blockade also significantly attenuated the severity of acute rejection and overall lung fibrosis. The decreased OB incidence was associated with reduced lymphocyte recruitment, particularly CD8⁺ T cells and other IFN-γ-producing lymphocytes, to the lung allograft. Interestingly, IL-17A blockade led to an increase in the frequency of IL-17A-producing T-helper cell type 17 cells and γδ T cells in lung allografts, suggesting that IL-17A is a negative regulator of these T cells. Our data suggest that blocking IL-17A after lung transplant reduces the overall IFN-γ-mediated lymphocyte response and decreases the development of OB.

Analysis of long term CD4+CD25highCD127- T-reg cells kinetics in peripheral blood of lung transplant recipients

Background

The role of CD4⁺CD25^highCD127⁻ T-reg cells in solid-organ Transplant (Tx) acceptance has been extensively studied. In previous studies on kidney and liver recipients, peripheral T-reg cell counts were associated to graft survival, while in lung Tx, there is limited evidence for similar findings. This study aims to analyze long term peripheral kinetics of T-reg-cells in a cohort of lung recipients and tests its association to several clinical variables.

Methods

From jan 2009 to dec 2014, 137 lung Tx recipients were submitted to an immunological follow up (median: 105.9 months (6.7–310.5)). Immunological follow up consisted of a complete blood peripheral immuno-phenotype, inclusive of CD4⁺CD25^highCD127⁻ T and FOXP3+ cells. We tested the association between T-reg and relevant variables by linear OR regression models for repeated measures, adjusting for time from Tx. Also, by ordered logistic models for panel data, the association between Chronic Lung Allograft Dysfuncton (CLAD) onset/progression and T-reg counts in the previous 3 months was tested.

Results

Among all variables analyzed at multivariate analysis: Bronchiolitis Obliterans Syndrome (OR −6.51, p < 0.001), Restrictive Allograft Syndrome (OR −5.19, p = 0.04) and Extracorporeal photopheresis (OR −5.65, p < 0.001) were significantly associated to T-reg cell. T-reg cell counts progressively decreased according to the severity of CLAD. Furthermore, patients with higher mean T-reg counts in a trimester had a significantly lower risk (OR 0.97, p = 0.012) of presenting CLAD or progressing in the graft dysfunction in the following trimester.

Conclusions

Our present data confirm animal observations on the possible role of T-reg in the evolution of CLAD.

Transcriptomic Analysis on Responses of Murine Lungs to Pasteurella multocida Infection

Pasteurella multocida infection in cattle causes serious epidemic diseases and leads to great economic losses in livestock industry; however, little is known about the interaction between host and P. multocida in the lungs. To explore a fully insight into the host responses in the lungs during P. multocida infection, a mouse model of Pasteurella pneumonia was established by intraperitoneal infection, and then transcriptomic analysis of infected lungs was performed. P. multocida localized and grew in murine lungs, and induced inflammation in the lungs, as well as mice death. With transcriptomic analysis, approximately 10⁷ clean reads were acquired. 4236 differently expressed genes (DEGs) were detected during P. multocida infection, of which 1924 DEGs were up-regulated. By gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichments, 5,303 GO enrichments and 116 KEGG pathways were significantly enriched in the context of P. multocida infection. Interestingly, genes related to immune responses, such as pattern recognition receptors (PRRs), chemokines and inflammatory cytokines, were significantly up-regulated, suggesting the key roles of these genes in P. multocida infection. Transcriptomic data showed that IFN-γ/IL-17-related genes were increased, which were validated by qRT-PCR, ELISA, and immunoblotting. Our study characterized the transcriptomic profile of the lungs in mice upon Pasteurella infection, and our findings could provide valuable information with respect to better understanding the responses in mice during P. multocida infection.

Cell-surface C-type lectin-like receptor CLEC-1 dampens dendritic cell activation and downstream Th17 responses

Dendritic cells (DCs) represent essential antigen-presenting cells that are critical for linking innate and adaptive immunity, and influencing T-cell responses. Among pattern recognition receptors, DCs express C-type lectin receptors triggered by both exogenous and endogenous ligands, therefore dictating pathogen response, and also shaping T-cell immunity. We previously described in rat, the expression of the orphan C-type lectin-like receptor-1 (CLEC-1) by DCs and demonstrated in vitro its inhibitory role in downstream T helper 17 (Th17) activation. In this study, we examined the expression and functionality of CLEC-1 in human DCs, and show a cell-surface expression on the CD16^- subpopulation of blood DCs and on monocyte-derived DCs (moDCs). CLEC-1 expression on moDCs is downregulated by inflammatory stimuli and enhanced by transforming growth factor β. Moreover, we demonstrate that CLEC-1 is a functional receptor on human moDCs and that although not modulating the spleen tyrosine kinase-dependent canonical nuclear factor-κB pathway, represses subsequent Th17 responses. Interestingly, a decreased expression of CLEC1A in human lung transplants is predictive of the development of chronic rejection and is associated with a higher level of interleukin 17A (IL17A). Importantly, using CLEC-1-deficient rats, we showed that disruption of CLEC-1 signaling led to an enhanced Il12p40 subunit expression in DCs, and to an exacerbation of downstream in vitro and in vivo CD4⁺ Th1 and Th17 responses. Collectively, our results establish a role for CLEC-1 as an inhibitory receptor in DCs able to dampen activation and downstream effector Th responses. As a cell-surface receptor, CLEC-1 may represent a useful therapeutic target for modulating T-cell immune responses in a clinical setting.

Interleukin-1α induced release of interleukin-8 by human bronchial epithelial cells in vitro: assessing mechanisms and possible treatment options

Survival after lung transplantation is hampered by chronic lung allograft dysfunction (CLAD). Persistently elevated BAL-neutrophilia is observed in some patients despite treatment with azithromycin, which may be induced by IL-1α. Our aim is to establish an in vitro model, assess mechanistic pathways and test different therapeutic strategies of IL-1α-induced release of IL-8 by human bronchial epithelial cells. Bronchial epithelial cells (16HBE) were stimulated with IL-1α with or without azithromycin or dexamethasone. IL-8 protein was analyzed in cell supernatant. Different MAP kinases (p38, JNK, ERK^1/2 , Iκβ) and targets known to be involved in tumor formation (PI3K, Akt) were investigated. Finally, different treatment options were tested for their potential inhibitory effect. IL-1α induced IL-8 in bronchial epithelial cells, which was dose-dependently inhibited by dexamethasone but not by azithromycin. IL-1α induced p38 and Akt phosphorylation, but activation of these MAPK was not inhibited by dexamethasone. JNK, ERK^1/2 , Iκβ and PI3K were not activated. None of the tested drugs reduced the IL-1α induced IL-8 production. We established an in vitro model wherein steroids inhibit the IL-1α-induced IL-8 production, while azithromycin was ineffective. Despite using this simple in vitro model, we could not identify a new treatment option for azithromycin-resistant airway neutrophilia.

Impact of Immune-Modulatory Drugs on Regulatory T Cell

Immunosuppression strategies that selectively inhibit effector T cells while preserving and even enhancing CD4FOXP3 regulatory T cells (Treg) permit immune self-regulation and may allow minimization of immunosuppression and associated toxicities. Many immunosuppressive drugs were developed before the identity and function of Treg were appreciated. A good understanding of the interactions between Treg and immunosuppressive agents will be valuable to the effective design of more tolerable immunosuppression regimens. This review will discuss preclinical and clinical evidence regarding the influence of current and emerging immunosuppressive drugs on Treg homeostasis, stability, and function as a guideline for the selection and development of Treg-friendly immunosuppressive regimens.

The role of recipient derived interleukin-17A in a murine orthotopic lung transplant model of restrictive chronic lung allograft dysfunction

The single most important cause of late mortality after lung transplantation is chronic lung allograft dysfunction (CLAD). However, the pathological development of CLAD was not as simple as previously presumed and subclassification phenotypes, bronchiolitis obliterans syndrome (BOS) and restrictive CLAD (rCLAD), have been introduced. We want to re-investigate how CLAD manifests in the murine orthotopic lung transplant model and investigate the role of interleukin 17A (IL-17A) within this model. Orthotopic LTx was performed in CB57BL/6, IL-17 WT and IL-17 KO mice. In a first experiment, CB57BL/6 mice receiving an isograft (CB57BL/6) or allograft (BALB/C) were compared. In a second experiment IL-17 WT and IL-17 KO mice (both CB57BL/6 background) received an allograft (BALB/C). Mice received daily immunosuppression with steroids and cyclosporine and were sacrificed 10weeks after transplantation for histopathological analysis by an experienced lung pathologist. After murine orthotopic lung transplantation, the allograft histopathologically presented features of human rCLAD (i.e. overt inflammation, pleural/parenchymal fibrosis and obliterative bronchiolitis). In the IL-17A KO group, less inflammation in the bronchovascular axis (p=0.03) was observed and a non-significant trend towards less bronchovascular fibrosis, pleural/septal inflammation and fibrosis, and parenchymal inflammation and fibrosis when compared to WT mice. The major mismatch orthotopic lung transplant model resembles features of human rCLAD. IL-17A mediated immunity is involved in the inflammatory component, but had little influence on the degree of fibrosis. Further mechanistic and therapeutic studies in this mouse model are needed to fully understand the mechanisms in rCLAD.

Idiopathic subglottic stenosis is associated with activation of the inflammatory IL-17A/IL-23 axis

OBJECTIVES/HYPOTHESIS

Idiopathic subglottic stenosis (iSGS) is a rare and devastating extrathoracic obstruction involving the lower laryngeal and upper tracheal airway. It arises without known antecedent injury or associated disease process. Persistent mucosal inflammation and a localized fibrotic response are hallmarks of the disease. Despite the initial clinical description of iSGS more than 40 year ago, there have been no substantive investigations into the pathogenesis of this enigmatic and progressive airway obstruction. In these studies, we present the initial characterization of the molecular pathogenesis underlying the fibrosing phenotype of iSGS.

METHODS

Utilizing 20 human iSGS and healthy control specimens, we applied histologic, immunohistochemical, molecular, and immunologic techniques.

RESULTS

We demonstrate significant activation of the canonical IL-23/IL-17A pathway in the tracheal mucosa of iSGS patients, as well as identify γδ T cells as the primary cellular source of IL-17A.

CONCLUSION

Our results suggest that aberrant mucosal immune activation is a component in of the pathogenesis of iSGS. Most critically, our work offers new targets for future therapeutic intervention.

LEVEL OF EVIDENCE

NA Laryngoscope, 126:E356-E361, 2016.

Role of interleukin-17A in early graft rejection after orthotopic lung transplantation in mice

BACKGROUND

The cellular and molecular mechanisms underlying lung allograft rejection remain poorly understood. We investigated the potential role of interleukin (IL)-17A in lung transplant rejection in a mouse model, because previous studies in clinical and rodent models have implicated IL-17A in both acute and chronic rejection.

METHODS

To generate an orthotopic lung transplantation model, lungs from C57BL/6 or BALB/c mice were transplanted into C57BL/6 mice (isograft and allograft models, respectively). The effects of anti-IL-17A treatment in allograft recipients were investigated. The histological features and rejection status of isografts and allografts were assessed at 3, 7, and 28 days after transplantation, and differences in graft infiltrating cells and mRNA expression of relevant cytokines were quantified at 3 and 7 days after transplantation.

RESULTS

As expected, isografts showed no obvious signs of rejection, whereas allografts exhibited minimal-to-mild rejection (grade A1-A2) by day 3 and moderate-to-severe rejection (grade A3-A4) by day 7, without evidence of obliterative bronchiolitis (OB). However, by 28 days, evidence of OB was observed in 67% (2/3) of allografts and severe rejection (grade A4) was observed in all. IL-17 mRNA expression in allografts was increased with rejection, and interferon (IFN)-γ and IL-6 mRNA expression levels followed a similar pattern. In contrast, IL-22 expression in allografts was only slightly increased. Antibody (Ab) neutralization of IL-17A diminished the signs of acute rejection at 7 days after transplantation in allografts, and this early protection was accompanied by a decrease in cellular stress according to histological evaluation, suggesting the involvement of IL-17A in the development of early post-transplantation lesions.

CONCLUSIONS

Our data indicate that IL-17A is important in the pathophysiology of allograft rejection, and neutralization of IL-17A is a potential therapeutic strategy to preventing lung transplant rejection.

Bone marrow transplantation alters lung antigen-presenting cells to promote TH17 response and the development of pneumonitis and fibrosis following gammaherpesvirus infection

Hematopoietic stem cell transplantation (HSCT) efficacy is limited by numerous pulmonary complications. We developed a model of syngeneic bone marrow transplantion (BMT) followed by infection with murine gamma herpesvirus-68 that results in pneumonitis and fibrosis and mimics human "noninfectious" HSCT complications. BMT mice experience increased early lytic replication, but establish viral latency by 21 days post infection. CD4 T cells in BMT mice are skewed toward interleukin (IL)-17A rather than interferon (IFN)-γ production. Transplantation of bone marrow from Il-17a(-/-) donors or treatment with anti-IL-17A neutralization antibodies at late stages attenuates pneumonitis and fibrosis in infected BMT mice, suggesting that hematopoietic-derived IL-17A is essential for development of pathology. IL-17A directly influences activation and extracellular matrix production by lung mesenchymal cells. Lung CD11c+ cells of BMT mice secrete more transforming growth factor beta-β1, and pro-TH17 mRNAs for IL-23 and IL-6, and less TH1-promoting cytokine mRNA for IFN-γ but slightly more IL-12 mRNA in response to viral infection. Adoptive transfer of non-BMT lung CD11c-enriched cells restores robust TH1 response and suppresses aberrant TH17 response in BMT mice to improve lung pathology. Our data suggest that "noninfectious" HSCT lung complications may reflect preceding viral infections and demonstrate that IL-17A neutralization may offer therapeutic advantage even after disease onset.

Environmental Exposures-The Missing Link in Immune Responses After Transplantation

In transplantation, immunosuppression has been directed at controlling acute responses, but treatment of chronic rejection has been ineffective. It is possible that factors that have previously been unaccounted for, such as exposure to inhaled pollution, ultraviolet light, or loss of the normal equilibrium between the gut immune system and the outside environment may be responsible for shifting immune responses to an effector/inflammatory phenotype, which leads to loss of self-tolerance and graft acceptance, and a shift towards autoimmunity and chronic rejection. Cells of the immune system are in a constant balance of effector response, regulation, and quiescence. Endogenous and exogenous signals can shift this balance through the aryl hydrocarbon receptor, which serves as a thermostat to modulate the response one way or the other, both at mucosal surfaces of interface organs to the outside environment, and in the internal milieu. Better understanding of this balance will identify a target for maintenance of self-tolerance and continued graft acceptance in patients who have achieved a "steady state" after transplantation.

Early-onset obesity dysregulates pulmonary adipocytokine/insulin signaling and induces asthma-like disease in mice

Childhood obesity is a risk factor for asthma, but the molecular mechanisms linking both remain elusive. Since obesity leads to chronic low-grade inflammation and affects metabolic signaling we hypothesized that postnatal hyperalimentation (pHA) induced by maternal high-fat-diet during lactation leads to early-onset obesity and dysregulates pulmonary adipocytokine/insulin signaling, resulting in metabolic programming of asthma-like disease in adult mice. Offspring with pHA showed at postnatal day 21 (P21): (1) early-onset obesity, greater fat-mass, increased expression of IL-1β, IL-23, and Tnf-α, greater serum leptin and reduced glucose tolerance than Control (Ctrl); (2) less STAT3/AMPKα-activation, greater SOCS3 expression and reduced AKT/GSK3β-activation in the lung, indicative of leptin resistance and insulin signaling, respectively; (3) increased lung mRNA of IL-6, IL-13, IL-17A and Tnf-α. At P70 body weight, fat-mass, and cytokine mRNA expression were similar in the pHA and Ctrl, but serum leptin and IL-6 were greater, and insulin signaling and glucose tolerance impaired. Peribronchial elastic fiber content, bronchial smooth muscle layer, and deposition of connective tissue were not different after pHA. Despite unaltered bronchial structure mice after pHA exhibited significantly increased airway reactivity. Our study does not only demonstrate that early-onset obesity transiently activates pulmonary adipocytokine/insulin signaling and induces airway hyperreactivity in mice, but also provides new insights into metabolic programming of childhood obesity-related asthma.

Chronic lung allograft dysfunction: evolving practice

PURPOSE OF REVIEW

Chronic lung allograft dysfunction (CLAD) was recently introduced as an overarching term covering different phenotypes of chronic allograft dysfunction, including obstructive CLAD (bronchiolitis obliterans syndrome), restrictive CLAD (restrictive allograft syndrome) and graft dysfunction due to causes not related to chronic rejection. In the present review, we will highlight the latest insights and current controversies regarding the new CLAD terminology, underlying pathophysiologic mechanisms, diagnostic approach and possible treatment options.

RECENT FINDINGS

Different pathophysiological mechanisms are clearly involved in clinically distinct phenotypes of chronic rejection, as is reflected by differences in histology, allograft function and imaging. Therefore, not all CLAD patients may equally benefit from specific therapies.

SUMMARY

The recent introduction of CLAD importantly changed the clinical practice in lung transplant recipients. Given the relative low accuracy of the current diagnostic tools, future research should focus on specific biomarkers, more sensitive pulmonary function parameters and imaging techniques for timely CLAD diagnosis and phenotyping. Personalized or targeted therapeutic options for adequate prevention and treatment of CLAD are required.

Platelet factor 4 protects kidney allograft in a rat kidney transplantation model

Platelets are the cellular mediator of thrombosis, but it is becoming increasingly evident that platelets actively participate in inflammation and immune responses. A recent paper indicated that platelet factor 4 (PF4) alleviated cardiac allograft rejection in mice. But the role of PF4 on kidney transplantation has never been investigated. In our current experiment, PF4 administration alleviates immune responses to kidney transplantation. PF4 significantly alleviates vascular and glomerular changes, as well as interstitial inflammation, fibrosis, and tubular atrophy at day 56 after transplantation. PF4 decreases interleukin (IL)-17 production in vivo and also limits Th17 differentiation in vitro. Furthermore, the alleviated chronic vasculopathy and tubulointerstitial inflammation induced by PF4 were abolished with additional IL-17 administration. Meanwhile, decreased serum creatinine and urea induced by PF4 were also reversed by recombinant mouse IL-17 (rmIL-17). In conclusion, PF4 plays a protective role in chronic kidney allograft and this was associated with inhibition of IL-17 production.

CD26 costimulatory blockade improves lung allograft rejection and is associated with enhanced interleukin-10 expression

BACKGROUND

The ectoenzyme CD26/dipeptidyl peptidase 4 (DPP4) has costimulatory activity that contributes to T cell activation and proliferation. Here, we aimed to target this costimulatory activity for the attenuation of the alloreactive Th17-cell response during acute rejection after mouse lung transplantation.

METHODS

To test the CD26-costimulatory blockade in vitro, mixed lymphocyte reaction was performed between major histocompatibility complex class I and II fully mismatched cells (CD4(+) splenocytes, C57BL/6, responders, and antigen-presenting cells, BALB/c, stimulators) by adding the CD26 inhibitor vildagliptin (0-15 μg). Lung transplantation between BALB/c (donor) and C57BL/6 (recipient) mice was performed, including controls, CD26-inhibited (CD26-I, daily administration of vildagliptin [GLSynthesis, Worcester, MA], 10 mg/kg subcutaneous), and CD26 knockout (CD26KO) mice was performed. Analysis on Day 1 and 5 after transplant included immunohistochemistry, fluorescence-activated cell sorting, and enzyme-linked immunosorbent assay (ELISA) for immune cell detection and their key cytokines.

RESULTS

In vitro, there was a significant reduction of the Th17 cytokines interleukin (IL)-17 and IL-21. In vivo, CD26-I-treated and CD26KO mice showed significantly preserved macroscopic and histologic characteristics on Day 5 (p < 0.01), a higher partial pressure of arterial oxygen/fraction of inspired oxygen ratio (p ≤ 0.05), fewer infiltrating CD3(+) T cells (p < 0.01), but more interstitial macrophages on Day 1 (p < 0.01) compared with control. Fewer IL-17(+) cells were found in CD26-I allografts on Day 1 (p = 0.05). Higher levels of IL-10 in CD26-I and CD26KO allografts on day 5 were seen (p < 0.05). IL-10/CD206 double-staining (alternative macrophages) revealed more positive cells in CD26-I and CD26KO on Day 1 and 5 (p < 0.01).

CONCLUSIONS

CD26 costimulatory blockade promotes lung allograft acceptance via reduced T cell infiltration, less expression of IL-17, and increased expression of IL-10, likely to be derived from alternatively activated macrophages.

Molecular Profiling in Lung Biopsies of Human Pulmonary Allografts to Predict Chronic Lung Allograft Dysfunction

Chronic lung allograft dysfunction (CLAD) is the main reason for poor long-term outcome of lung transplantation, with bronchiolitis obliterans (BO) representing the predominant pathological feature. BO is defined as a progressive fibrous obliteration of the small airways, thought to be triggered by a combination of nonimmune bronchial injury and alloimmune and autoimmune mechanisms. Because biopsy samples are too insensitive to reliably detect BO and a decline in lung function test results, which is clinically used to define CLAD, does not detect early stages, there is need for alternative biomarkers for early diagnosis. Herein, we analyzed the cellular composition and differential expression of 45 tissue remodeling-associated genes in transbronchial lung biopsy specimens from two cohorts with 18 patients each: patients who did not develop CLAD within 3 years after transplantation (48 biopsy specimens) and patients rapidly developing CLAD within the first 3 postoperative years (57 biopsy specimens). Integrating the mRNA expression levels of the five most significantly dysregulated genes from the transforming growth factor-β axis (BMP4, IL6, MMP1, SMAD1, and THBS1) into a score, patient groups could be confidently separated and the outcome predicted (P < 0.001). We conclude that overexpression of fibrosis-associated genes may be valuable as a tissue-based molecular biomarker to more accurately diagnose or predict the development of CLAD.