GM-CSF regulates alveolar macrophage differentiation and innate immunity in the lung through PU.1

A toxicology study of Csf2ra complementation and pulmonary macrophage transplantation therapy of hereditary PAP in mice

Pulmonary macrophage transplantation (PMT) is a gene and cell transplantation approach in development as therapy for hereditary pulmonary alveolar proteinosis (hPAP), a surfactant accumulation disorder caused by mutations in CSF2RA/B (and murine homologs). We conducted a toxicology study of PMT of Csf2ra gene-corrected macrophages (mGM-Rα+Mϕs) or saline-control intervention in Csf2raKO or wild-type (WT) mice including single ascending dose and repeat ascending dose studies evaluating safety, tolerability, pharmacokinetics, and pharmacodynamics. Lentiviral-mediated Csf2ra cDNA transfer restored GM-CSF signaling in mGM-Rα+Mϕs. Following PMT, mGM-Rα+Mϕs engrafted, remained within the lungs, and did not undergo uncontrolled proliferation or result in bronchospasm, pulmonary function abnormalities, pulmonary or systemic inflammation, anti-transgene product antibodies, or pulmonary fibrosis. Aggressive male fighting caused a similarly low rate of serious adverse events in saline- and PMT-treated mice. Transient, minor pulmonary neutrophilia and exacerbation of pre-existing hPAP-related lymphocytosis were observed 14 days after PMT of the safety margin dose but not the target dose (5,000,000 or 500,000 mGM-Rα+Mϕs, respectively) and only in Csf2raKO mice but not in WT mice. PMT reduced lung disease severity in Csf2raKO mice. Results indicate PMT of mGM-Rα+Mϕs was safe, well tolerated, and therapeutically efficacious in Csf2raKO mice, and established a no adverse effect level and 10-fold safety margin.

BHLHE40 Regulates Myeloid Cell Polarization through IL-10-Dependent and -Independent Mechanisms

Better understanding of the host responses to Mycobacterium tuberculosis infections is required to prevent tuberculosis and develop new therapeutic interventions. The host transcription factor BHLHE40 is essential for controlling M. tuberculosis infection, in part by repressing Il10 expression, where excess IL-10 contributes to the early susceptibility of Bhlhe40-/- mice to M. tuberculosis infection. Deletion of Bhlhe40 in lung macrophages and dendritic cells is sufficient to increase the susceptibility of mice to M. tuberculosis infection, but how BHLHE40 impacts macrophage and dendritic cell responses to M. tuberculosis is unknown. In this study, we report that BHLHE40 is required in myeloid cells exposed to GM-CSF, an abundant cytokine in the lung, to promote the expression of genes associated with a proinflammatory state and better control of M. tuberculosis infection. Loss of Bhlhe40 expression in murine bone marrow-derived myeloid cells cultured in the presence of GM-CSF results in lower levels of proinflammatory associated signaling molecules IL-1β, IL-6, IL-12, TNF-α, inducible NO synthase, IL-2, KC, and RANTES, as well as higher levels of the anti-inflammatory-associated molecules MCP-1 and IL-10 following exposure to heat-killed M. tuberculosis. Deletion of Il10 in Bhlhe40-/- myeloid cells restored some, but not all, proinflammatory signals, demonstrating that BHLHE40 promotes proinflammatory responses via both IL-10-dependent and -independent mechanisms. In addition, we show that macrophages and neutrophils within the lungs of M. tuberculosis-infected Bhlhe40-/- mice exhibit defects in inducible NO synthase production compared with infected wild-type mice, supporting that BHLHE40 promotes proinflammatory responses in innate immune cells, which may contribute to the essential role for BHLHE40 during M. tuberculosis infection in vivo.

Macrophage Polarization and Functions in Pathogenesis of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD), the major leading cause of mortality worldwide, is a progressive and irreversible respiratory condition characterized by peripheral airway and lung parenchymal inflammation, accompanied by fibrosis, emphysema, and airflow limitation, and has multiple etiologies, including genetic variance, air pollution, and repetitive exposure to harmful substances. However, the precise mechanisms underlying the pathogenesis of COPD have not been identified. Recent multiomics-based evidence suggests that the plasticity of alveolar macrophages contributes to the onset and progression of COPD through the coordinated modulation of numerous transcription factors. Therefore, this review focuses on understanding the mechanisms and functions of macrophage polarization that regulate lung homeostasis in COPD. These findings may provide a better insight into the distinct role of macrophages in COPD pathogenesis and perspective for developing novel therapeutic strategies targeting macrophage polarization.

The ouroboros of autoimmunity

Human autoimmunity against elements conferring protective immunity can be symbolized by the 'ouroboros', a snake eating its own tail. Underlying infection is autoimmunity against three immunological targets: neutrophils, complement and cytokines. Autoantibodies against neutrophils can cause peripheral neutropenia underlying mild pyogenic bacterial infections. The pathogenic contribution of autoantibodies against molecules of the complement system is often unclear, but autoantibodies specific for C3 convertase can enhance its activity, lowering complement levels and underlying severe bacterial infections. Autoantibodies neutralizing granulocyte-macrophage colony-stimulating factor impair alveolar macrophages, thereby underlying pulmonary proteinosis and airborne infections, type I interferon viral diseases, type II interferon intra-macrophagic infections, interleukin-6 pyogenic bacterial diseases and interleukin-17A/F mucocutaneous candidiasis. Each of these five cytokine autoantibodies underlies a specific range of infectious diseases, phenocopying infections that occur in patients with the corresponding inborn errors. In this Review, we analyze this ouroboros of immunity against immunity and posit that it should be considered as a factor in patients with unexplained infection.

Epigallocatechin gallate regulates the myeloid-specific transcription factor PU.1 in macrophages

Our previous research demonstrated that PU.1 regulates expression of the genes involved in inflammation in macrophages. Selective knockdown of PU.1 in macrophages ameliorated LPS-induced acute lung injury (ALI) in bone marrow chimera mice. Inhibitors that block the transcriptional activity of PU.1 in macrophages have the potential to mitigate the pathophysiology of LPS-induced ALI. However, complete inactivation of PU.1 gene disrupts normal myelopoiesis. Although the green tea polyphenol Epigallocatechin gallate (EGCG) has been shown to regulate inflammatory genes in various cell types, it is not known if EGCG alters the transcriptional activity of PU.1 protein. Using Schrodinger Glide docking, we have identified that EGCG binds with PU.1 protein, altering its DNA-binding and self-dimerization activity. In silico analysis shows that EGCG forms Hydrogen bonds with Glutamic Acid 209, Leucine 250 in DNA binding and Lysine 196, Tryptophan 193, and Leucine 182 in the self-dimerization domain of the PU.1 protein. Experimental validation using mouse bone marrow-derived macrophages (BMDM) confirmed that EGCG inhibits both DNA binding by PU.1 and self-dimerization. Importantly, EGCG had no impact on expression of the total PU.1 protein levels but significantly reduced expression of various inflammatory genes and generation of ROS. In summary, we report that EGCG acts as an inhibitor of the PU.1 transcription factor in macrophages.

Pulmonary Alveolar Proteinosis and new therapeutic concepts

Pulmonary alveolar proteinosis (PAP) is an umbrella term used to refer to a pulmonary syndrome which is characterized by excessive accumulation of surfactant in the lungs of affected individuals. In general, PAP is a rare lung disease affecting children and adults, although its prevalence and incidence is variable among different countries. Even though PAP is a rare disease, it is a prime example on how modern medicine can lead to new therapeutic concepts, changing ways and techniques of (genetic) diagnosis which ultimately led into personalized treatments, all dedicated to improve the function of the impaired lung and thus life expectancy and quality of life in PAP patients. In fact, new technologies, such as new sequencing technologies, gene therapy approaches, new kind and sources of stem cells and completely new insights into the ontogeny of immune cells such as macrophages have increased our understanding in the onset and progression of PAP, which have paved the way for novel therapeutic concepts for PAP and beyond. As of today, classical monocyte-derived macrophages are known as important immune mediator and immune sentinels within the innate immunity. Furthermore, macrophages (known as tissue resident macrophages (TRMs)) can also be found in various tissues, introducing e. g. alveolar macrophages in the broncho-alveolar space as crucial cellular determinants in the onset of PAP and other lung disorders. Given recent insights into the onset of alveolar macrophages and knowledge about factors which impede their function, has led to the development of new therapies, which are applied in the context of PAP, with promising implications also for other diseases in which macrophages play an important role. Thus, we here summarize the latest insights into the various forms of PAP and introduce new pre-clinical work which is currently conducted in the framework of PAP, introducing new therapies for children and adults who still suffer from this severe, potentially life-threatening disease.

Role of macrophage colony stimulating factor and interferon regulatory factor 7 in modulating the immune profile of mouse testicular macrophages

Testicular macrophages (TM) are critical for the function of the testis by regulating homeostasis and inflammatory responses. However, the mechanisms by which TM fulfil these roles remain elusive. In this study, we explored the impact of two key testicular microenvironmental factors, namely 25-hydroxycholesterol (25HC), an oxysterol related to sex hormones and macrophage colony-stimulating factor (M-CSF), a factor crucial for macrophage survival and differentiation, on the regulation of the TM phenotype. Specifically, we examined their role in controlling the expression of the transcription factor interferon regulatory factor 7 (Irf7), a factor critical for maintaining the alternative macrophage phenotype. To achieve this, we used an in vitro bone marrow-derived macrophage (BMDM) model as a surrogate for TM to investigate the roles of 25HC and M-CSF in regulating the expression of Irf7 during the polarization of murine TM. M-CSF was identified as the main regulator of Irf7 expression, while 25HC production is a consequence of Irf7 activation in BMDM. In turn, 25HC plays a role in a negative feedback loop on the expression levels of Irf7 in BMDM. Using flow cytometry in Irf7-/- mouse testis the CD64loMHChi TM subpopulation was found to be decreased. Together with lower IL-10 protein levels in Irf7-/- TM this indicates a shift towards an M1-like macrophage profile. In summary, our data indicates that M-CSF could act as an inducer of high Irf7 expression levels in the mouse testis. However, the exact role of the high 25HC concentration in the testis in maintaining the local immune milieu still needs further study.

Monocyte-derived alveolar macrophages are key drivers of smoke-induced lung inflammation and tissue remodeling

Smoking is a leading risk factor of chronic obstructive pulmonary disease (COPD), that is characterized by chronic lung inflammation, tissue remodeling and emphysema. Although inflammation is critical to COPD pathogenesis, the cellular and molecular basis underlying smoking-induced lung inflammation and pathology remains unclear. Using murine smoke models and single-cell RNA-sequencing, we show that smoking establishes a self-amplifying inflammatory loop characterized by an influx of molecularly heterogeneous neutrophil subsets and excessive recruitment of monocyte-derived alveolar macrophages (MoAM). In contrast to tissue-resident AM, MoAM are absent in homeostasis and characterized by a pro-inflammatory gene signature. Moreover, MoAM represent 46% of AM in emphysematous mice and express markers causally linked to emphysema. We also demonstrate the presence of pro-inflammatory and tissue remodeling associated MoAM orthologs in humans that are significantly increased in emphysematous COPD patients. Inhibition of the IRAK4 kinase depletes a rare inflammatory neutrophil subset, diminishes MoAM recruitment, and alleviates inflammation in the lung of cigarette smoke-exposed mice. This study extends our understanding of the molecular signaling circuits and cellular dynamics in smoking-induced lung inflammation and pathology, highlights the functional consequence of monocyte and neutrophil recruitment, identifies MoAM as key drivers of the inflammatory process, and supports their contribution to pathological tissue remodeling.

Human inherited CCR2 deficiency underlies progressive polycystic lung disease

We describe a human lung disease caused by autosomal recessive, complete deficiency of the monocyte chemokine receptor C-C motif chemokine receptor 2 (CCR2). Nine children from five independent kindreds have pulmonary alveolar proteinosis (PAP), progressive polycystic lung disease, and recurrent infections, including bacillus Calmette Guérin (BCG) disease. The CCR2 variants are homozygous in six patients and compound heterozygous in three, and all are loss-of-expression and loss-of-function. They abolish CCR2-agonist chemokine C-C motif ligand 2 (CCL-2)-stimulated Ca2+ signaling in and migration of monocytic cells. All patients have high blood CCL-2 levels, providing a diagnostic test for screening children with unexplained lung or mycobacterial disease. Blood myeloid and lymphoid subsets and interferon (IFN)-γ- and granulocyte-macrophage colony-stimulating factor (GM-CSF)-mediated immunity are unaffected. CCR2-deficient monocytes and alveolar macrophage-like cells have normal gene expression profiles and functions. By contrast, alveolar macrophage counts are about half. Human complete CCR2 deficiency is a genetic etiology of PAP, polycystic lung disease, and recurrent infections caused by impaired CCL2-dependent monocyte migration to the lungs and infected tissues.

Pyroptotic cell death: an emerging therapeutic opportunity for radiotherapy

Pyroptotic cell death, an inflammatory form of programmed cell death (PCD), is emerging as a potential therapeutic opportunity for radiotherapy (RT). RT is commonly used for cancer treatment, but its effectiveness can be limited by tumor resistance and adverse effects on healthy tissues. Pyroptosis, characterized by cell swelling, membrane rupture, and release of pro-inflammatory cytokines, has been shown to enhance the immune response against cancer cells. By inducing pyroptotic cell death in tumor cells, RT has the potential to enhance treatment outcomes by stimulating anti-tumor immune responses and improving the overall efficacy of RT. Furthermore, the release of danger signals from pyroptotic cells can promote the recruitment and activation of immune cells, leading to a systemic immune response that may target distant metastases. Although further research is needed to fully understand the mechanisms and optimize the use of pyroptotic cell death in RT, it holds promise as a novel therapeutic strategy for improving cancer treatment outcomes. This review aims to synthesize recent research on the regulatory mechanisms underlying radiation-induced pyroptosis and to elucidate the potential significance of this process in RT. The insights gained from this analysis may inform strategies to enhance the efficacy of RT for tumors.

Time-Course Progression of Whole Transcriptome Expression Changes of Trigeminal Ganglia Compared to Dorsal Root Ganglia in Rats Exposed to Nerve Injury

Mechanisms underlying neuropathic pain (NP) are complex with multiple genes, their interactions, environmental and epigenetic factors being implicated. Transcriptional changes in the trigeminal (TG) and dorsal root (DRG) ganglia have been implicated in the development and maintenance of NP. Despite efforts to unravel molecular mechanisms of NP, many remain unknown. Also, most of the studies focused on the spinal system. Although the spinal and trigeminal systems share some of the molecular mechanisms, differences exist. We used RNA-sequencing technology to identify differentially expressed genes (DEGs) in the TG and DRG at baseline and 3 time points following the infraorbital or sciatic nerve injuries, respectively. Pathway analysis and comparison analysis were performed to identify differentially expressed pathways. Additionally, upstream regulator effects were investigated in the two systems. DEG (differentially expressed genes) analyses identified 3,225 genes to be differentially expressed between TG and DRG in naïve animals, 1,828 genes 4 days post injury, 5,644 at day 8 and 9,777 DEGs at 21 days postinjury. A comparison of top enriched canonical pathways revealed that a number of signaling pathway was significantly inhibited in the TG and activated in the DRG at 21 days postinjury. Finally, CORT upstream regulator was predicted to be inhibited in the TG while expression levels of the CSF1 upstream regulator were significantly elevated in the DRG at 21 days postinjury. This study provides a basis for further in-depth studies investigating transcriptional changes, pathways, and upstream regulation in TG and DRG in rats exposed to peripheral nerve injuries. PERSPECTIVE: Although trigeminal and dorsal root ganglia are homologs of each other, they respond differently to nerve injury and therefore treatment. Activation/inhibition of number of biological pathways appear to be ganglion/system specific suggesting that different approaches might be required to successfully treat neuropathies induced by injuries in spinal and trigeminal systems.

Infections in autoimmune pulmonary alveolar proteinosis: a large retrospective cohort

BACKGROUND

Autoimmune pulmonary alveolar proteinosis (aPAP) is a rare disease, predisposing to an increased risk of infection. A complete picture of these infections is lacking.

RESEARCH QUESTION

Describe the characteristics and clinical outcomes of patients diagnosed with aPAP, and to identify risk factors associated with opportunistic infections.

METHODS

We conducted a retrospective cohort including all patients diagnosed with aPAP between 2008 and 2018 in France and Belgium. Data were collected using a standardised questionnaire including demographics, comorbidities, imaging features, outcomes and microbiological data.

RESULTS

We included 104 patients, 2/3 were men and median age at diagnosis was 45 years. With a median follow-up of 3.4 years (IQR 1.7-6.6 years), 60 patients (58%), developed at least one infection, including 23 (22%) with opportunistic infections. Nocardia spp was the main pathogen identified (n=10). Thirty-five (34%) patients were hospitalised due to infection. In univariate analysis, male gender was associated with opportunistic infections (p=0.04, OR=3.88; 95% CI (1.02 to 22.06)). Anti-granulocyte macrophage colony-stimulating factor antibody titre at diagnosis was significantly higher among patients who developed nocardiosis (1058 (316-1591) vs 580 (200-1190), p=0.01). Nine patients had died (9%), but only one death was related to infection.

INTERPRETATION

Patients with aPAP often presented with opportunistic infections, especially nocardiosis, which highlights the importance of systematic search for slow-growing bacteria in bronchoalveolar lavage or whole lung lavage.

Pulmonary alveolar proteinosis in Taiwan

BACKGROUND/PURPOSE

Pulmonary alveolar proteinosis (PAP) is rare disease manifested as alveolar macrophage dysfunction and abnormal accumulation of surfactant protein in the alveoli. In this nationwide, population-based study, we investigated the epidemiology of PAP in Taiwan, and discovered the comorbidities and prognostic factors of PAP.

METHODS

From the National Health Insurance Research Database (NHIRD), we obtained comprehensive information about all patients of PAP in Taiwan between 1995 and 2013. The incidence, baseline characteristics comorbidities, and prognostic factors of PAP were investigated.

RESULTS

The annual incidence rate of PAP was around 0.79 (range: 0.49-1.17) patients per million people after 2000, and the prevalence rate was 7.96 patients per million people by the end of 2013. In total, 276 patients of PAP were identified, including 177 (64%) and 99 (36%) patients with primary and secondary PAP, respectively. The median age of diagnosis was 53.8 years. The median survival was 9.6 years after the initial PAP diagnosis, and the 5-year survival rate was 65.96%. Twenty (7%) patients received whole lung lavage (WLL) within three months after the diagnosis had significantly better survival compared to the others. Multivariable Cox regression analyses showed that elder age, secondary PAP, and malignancy were associated with poorer survival, while WLL within 3 months of diagnosis might greatly improve the survival.

CONCLUSION

We demonstrated the epidemiology of PAP in Taiwan, showing several poor prognostic factors and the potential effectiveness of WLL. Further prospective studies based on registry are warranted to improve the diagnosis and treatment of PAP.

Combined regulation of pro-inflammatory cytokines production by STAT3 and STAT5 in a model of B. pertussis infection of alveolar macrophages

Bordetella pertussis is a highly contagious respiratory pathogen responsible for whooping-cough or pertussis. Despite high vaccination coverage worldwide, this gram-negative bacterium continues to spread among the population. B. pertussis is transmitted by aerosol droplets from an infected individual to a new host and will colonize its upper respiratory tract. Alveolar macrophages (AMs) are effector cells of the innate immune system that phagocytose B. pertussis and secrete both pro-inflammatory and antimicrobial mediators in the lungs. However, understanding their role in B. pertussis pathogenesis at the molecular level is hampered by the limited number of primary AMs that can be collected in vivo. In order to decipher the regulation of innate response induced by B. pertussis infection, we used for the first time self-renewing, non-transformed cells, called Max Planck Institute (MPI) cells, which are phenotypically and functionally very close to pulmonary AMs. Using optimized infection conditions, we characterized the entry and the clearance of B. pertussis within MPI macrophages. We showed that under these conditions, MPI cells exhibit a pro-inflammatory phenotype with the production of TNF, IL-1β, IL-6 and MIP-2α, similarly to primary AMs purified from broncho-alveolar fluids of mice. In addition, we explored the yet uncharacterized role of the signal transduction activator of transcription (STAT) proteins family in the innate immune response to B. pertussis infection and showed for the first time the parallel regulation of pro-inflammatory cytokines by STAT3 and STAT5 in MPI macrophages infected by B. pertussis. Altogether, this work highlights the interest of using MPI cells for experiments optimization and preliminary data acquisition to understand B. pertussis interaction with AMs, and thus significantly reduce the number of animals to be sacrificed.

A multi-organ, lung-derived inflammatory response following in vitro airway exposure to cigarette smoke and next-generation nicotine delivery products

Despite increasing use of in vitro models that closely resemble in vivo human biology, their application in understanding downstream effects of airway toxicity, such as inflammation, are at an early stage. In this study, we used various assays to examine the inflammatory response induced in MucilAir™ tissues and A549 cells exposed to three products known to induce toxicity. Reduced barrier integrity was observed in tissues following exposure to each product, with reduced viability and increased cytotoxicity also shown. Similar changes in viability were also observed in A549 cells. Furthermore, whole cigarette smoke (CS) induced downstream phenotypic THP-1 changes and endothelial cell adhesion, an early marker of atherosclerosis. In contrast, exposure to next-generation delivery product (NGP) aerosol did not induce this response. Cytokine, histological and RNA analysis highlighted increased biomarkers linked to inflammatory pathways and immune cell differentiation following exposure to whole cigarette smoke, including GM-CSF, IL-1β, cleaved caspase-3 and cytochrome P450 enzymes. As a result of similar observations in human airway inflammation, we propose that our exposure platform could act as a representative model for studying such events in vitro. Furthermore, this model could be used to test the inflammatory or anti-inflammatory impact posed by inhaled compounds delivered to the lung.

Altered macrophage phenotypes in a case of autoimmune pulmonary alveolar proteinosis

Mass cytometry of BALF cells from a pulmonary alveolar proteinosis patient, positive for anti-GM-CSF antibodies, suggests potential impairment in human alveolar macrophage differentiation https://bit.ly/45JHUrz.

MiR-223-3p attenuates radiation-induced inflammatory response and inhibits the activation of NLRP3 inflammasome in macrophages

Macrophage pyroptosis plays an important role in the development of radiation-induced cell and tissue damage, leading to acute lung injury. However, the underlying mechanisms of NOD-like receptor thermal protein domain-associated protein 3 (NLRP3)-mediated macrophage pyroptosis and the regulatory factors involved in radiation-induced pyroptosis are unclear. In this study, the expression of the NLRP3 inflammasome and pyroptosis-associated factors in murine macrophage cell lines was investigated after ionizing radiation. High-throughput RNA sequencing was performed to identify and characterize miRNAs and mRNA transcripts associated with NLRP3-mediated cell death. Our results demonstrated that cleaved-caspase-1 (p10) and N-terminal domain of gasdermin-D (GSDMD-N) were upregulated, and the number of NLRP3 inflammasomes and pyroptotic cells increased in murine macrophage cell lines after irradiation (8 Gy). Comparativeprofiling of 300miRNAs revealed that 41 miRNAsexhibited significantly different expression after 8 Gy of irradiation. Granulocyte-specific microRNA-223-3p (miR-223-3p) is a negative regulator of NLRP3. In vitro experiments revealed that the expression of miR-223-3p was significantly altered by irradiation. Moreover, miR-223-3p decreased the expression of NLRP3 and proinflammatory factors, resulting in reduced pyroptosis in irradiated murine macrophages. Subsequently, in vivo experiments revealed the efficacy of miR-223-3p supplementation in ameliorating alveolar macrophage (AM) pyroptosis, attenuating the infiltration of inflammatory monocytes, and significantly alleviating the severity of acute radiation-induced lung injury (ARILI). Our findings suggest that the miR-223-3p/NLRP3/caspase-1 axis is involved in radiation-induced AM pyroptosis and ARILI.

Emerging aspects of cytokine storm in COVID-19: The role of proinflammatory cytokines and therapeutic prospects

COVID-19 has claimed millions of lives during the last 3 years since initial cases were reported in Wuhan, China, in 2019. Patients with COVID-19 suffer from severe pneumonia, high fever, acute respiratory distress syndrome (ARDS), and multiple-organ dysfunction, which may also result in fatality in extreme cases. Cytokine storm (CS) is hyperactivation of the immune system, wherein the dysregulated production of proinflammatory cytokines could result in excessive immune cell infiltrations in the pulmonary tissues, resulting in tissue damage. The immune cell infiltration could also occur in other tissues and organs and result in multiple organs' dysfunction. The key cytokines implicated in the onset of disease severity include TNF-α, IFN-γ, IL-6, IL-1β, GM-CSF, and G-CSF. Controlling the CS is critical in treating COVID-19 disease. Therefore, different strategies are employed to mitigate the effects of CS. These include using monoclonal antibodies directed against soluble cytokines or the cytokine receptors, combination therapies, mesenchymal stem cell therapy, therapeutic plasma exchange, and some non-conventional treatment methods to improve patient immunity. The current review describes the role/s of critical cytokines in COVID-19-mediated CS and the respective treatment modalities.

Bridging the Gap between Innate and Adaptive Immunity in the Lung: Summary of the Aspen Lung Conference 2022

Although significant strides have been made in the understanding of pulmonary immunology, much work remains to be done to comprehensively explain coordinated immune responses in the lung. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic only served to highlight the inadequacy of current models of host-pathogen interactions and reinforced the need for current and future generations of immunologists to unravel complex biological questions. As part of that effort, the 64th Annual Thomas L. Petty Aspen Lung Conference was themed "Bridging the Gap between Innate and Adaptive Immunity in the Lung" and featured exciting work from renowned immunologists. This report summarizes the proceedings of the 2022 Aspen Lung Conference, which was convened to discuss the roles played by innate and adaptive immunity in disease pathogenesis, evaluate the interface between the innate and adaptive immune responses, assess the role of adaptive immunity in the development of autoimmunity and autoimmune lung disease, discuss lessons learned from immunologic cancer treatments and approaches, and define new paradigms to harness the immune system to prevent and treat lung diseases.

A new tractable method for generating human alveolar macrophage-like cells in vitro to study lung inflammatory processes and diseases

Alveolar macrophages (AMs) are unique lung resident cells that contact airborne pathogens and environmental particulates. The contribution of human AMs (HAMs) to pulmonary diseases remains poorly understood due to the difficulty in accessing them from human donors and their rapid phenotypic change during in vitro culture. Thus, there remains an unmet need for cost-effective methods for generating and/or differentiating primary cells into a HAM phenotype, particularly important for translational and clinical studies. We developed cell culture conditions that mimic the lung alveolar environment in humans using lung lipids, that is, Infasurf (calfactant, natural bovine surfactant) and lung-associated cytokines (granulocyte macrophage colony-stimulating factor, transforming growth factor-β, and interleukin 10) that facilitate the conversion of blood-obtained monocytes to an AM-like (AML) phenotype and function in tissue culture. Similar to HAM, AML cells are particularly susceptible to both Mycobacterium tuberculosis and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. This study reveals the importance of alveolar space components in the development and maintenance of HAM phenotype and function and provides a readily accessible model to study HAM in infectious and inflammatory disease processes, as well as therapies and vaccines. IMPORTANCE Millions die annually from respiratory disorders. Lower respiratory track gas-exchanging alveoli maintain a precarious balance between fighting invaders and minimizing tissue damage. Key players herein are resident AMs. However, there are no easily accessible in vitro models of HAMs, presenting a huge scientific challenge. Here, we present a novel model for generating AML cells based on differentiating blood monocytes in a defined lung component cocktail. This model is non-invasive, significantly less costly than performing a bronchoalveolar lavage, yields more AML cells than HAMs per donor, and retains their phenotype in culture. We have applied this model to early studies of M. tuberculosis and SARS-CoV-2. This model will significantly advance respiratory biology research.

Lethal eosinophilic crystalline pneumonia in mice expressing a stabilized Csf2 mRNA

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine that stimulates the proliferation and differentiation of granulocyte and macrophage precursors. The mouse gene-encoding GM-CSF, Csf2, is regulated at both transcriptional and post-transcriptional levels. An adenine-uridine-rich element (ARE) within the 3'-untranslated region of Csf2 mRNA was shown in cell transfection studies to confer instability on this transcript. To explore the physiological importance of this element in an intact animal, we generated mice with a knock-in deletion of the 75-nucleotide ARE. Mice heterozygous for this ARE deletion developed severe respiratory distress and death within about 12 weeks of age. There was dense infiltration of lung alveolar spaces by crystal-containing macrophages. Increased stability of Csf2 mRNA was confirmed in bone marrow-derived macrophages, and elevated GM-CSF levels were observed in serum and lung. These mice did not exhibit notable abnormalities in blood or bone marrow, and transplantation of bone marrow from mutant mice into lethally irradiated WT mice did not confer the pulmonary phenotype. Mice with a conditional deletion of the ARE restricted to lung type II alveolar cells exhibited an essentially identical lethal lung phenotype at the same ages as the mice with the whole-body deletion. In contrast, mice with the same conditional ARE deletion in myeloid cells, including macrophages, exhibited lesser degrees of macrophage infiltration into alveolar spaces much later in life, at approximately 9 months of age. Post-transcriptional Csf2 mRNA stability regulation in pulmonary alveolar epithelial cells appears to be essential for normal physiological GM-CSF secretion and pulmonary macrophage homeostasis.

Interferon regulatory factor-8-dependent innate immune alarm senses GATA2 deficiency to alter hematopoietic differentiation and function

PURPOSE OF REVIEW

Recent discoveries have provided evidence for mechanistic links between the master regulator of hematopoiesis GATA2 and the key component of interferon and innate immunity signaling pathways, interferon-regulatory factor-8 (IRF8). These links have important implications for the control of myeloid differentiation in physiological and pathological states.

RECENT FINDINGS

GATA2 deficiency resulting from loss of the Gata2 -77 enhancer in progenitors triggers an alarm that instigates the transcriptional induction of innate immune signaling and distorts a myeloid differentiation program. This pathological alteration renders progenitors hyperresponsive to interferon γ, toll-like receptor and interleukin-6 signaling and impaired in granulocyte-macrophage colony-stimulating factor signaling. IRF8 upregulation in -77-/- progenitors promotes monocyte and dendritic cell differentiation while suppressing granulocytic differentiation. As PU.1 promotes transcription of Irf8 and other myeloid and B-lineage genes, GATA2-mediated repression of these genes opposes the PU.1-dependent activating mechanism.

SUMMARY

As GATA2 deficiency syndrome is an immunodeficiency disorder often involving myelodysplastic syndromes and acute myeloid leukemia, elucidating how GATA2 commissions and decommissions genome activity and developmental regulatory programs will unveil mechanisms that go awry when GATA2 levels and/or activities are disrupted.

Alveolar macrophages in pulmonary alveolar proteinosis: origin, function, and therapeutic strategies

Pulmonary alveolar proteinosis (PAP) is a rare pulmonary disorder that is characterized by the abnormal accumulation of surfactant within the alveoli. Alveolar macrophages (AMs) have been identified as playing a pivotal role in the pathogenesis of PAP. In most of PAP cases, the disease is triggered by impaired cholesterol clearance in AMs that depend on granulocyte-macrophage colony-stimulating factor (GM-CSF), resulting in defective alveolar surfactant clearance and disruption of pulmonary homeostasis. Currently, novel pathogenesis-based therapies are being developed that target the GM-CSF signaling, cholesterol homeostasis, and immune modulation of AMs. In this review, we summarize the origin and functional role of AMs in PAP, as well as the latest therapeutic strategies aimed at addressing this disease. Our goal is to provide new perspectives and insights into the pathogenesis of PAP, and thereby identify promising new treatments for this disease.

The role of monocyte-derived macrophages in the lung: it's all about context

Macrophages are present in every tissue of the body where they play crucial roles in maintaining tissue homeostasis and providing front line defence against pathogens. Arguably, this is most important at mucosal barrier tissues, such as the lung and gut, which are major ports of entry for pathogens. However, a common feature of inflammation, infection or injury is the loss of tissue resident macrophages and accumulation of monocytes from the circulation, which differentiate, to different extents, into macrophages. The exact fate and function of these elicited, monocyte-derived macrophages in infection, injury and inflammation remains contentious. While some studies have documented the indispensable nature of monocytes and their macrophage derivatives in combatting infection and restoration of lung homeostasis following insult, observations from clinical studies and preclinical models of lung infection/injury shows that monocytes and their progeny can become dysregulated in severe pathology, often perpetuating rather than resolving the insult. In this Mini Review, we aim to bring together these somewhat contradictory reports by discussing how the plasticity of monocytes allow them to assume distinct functions in different contexts in the lung, from health to infection, and effective tissue repair to fibrotic disease.

scTenifoldXct: A semi-supervised method for predicting cell-cell interactions and mapping cellular communication graphs

We present scTenifoldXct, a semi-supervised computational tool for detecting ligand-receptor (LR)-mediated cell-cell interactions and mapping cellular communication graphs. Our method is based on manifold alignment, using LR pairs as inter-data correspondences to embed ligand and receptor genes expressed in interacting cells into a unified latent space. Neural networks are employed to minimize the distance between corresponding genes while preserving the structure of gene regression networks. We apply scTenifoldXct to real datasets for testing and demonstrate that our method detects interactions with high consistency compared with other methods. More importantly, scTenifoldXct uncovers weak but biologically relevant interactions overlooked by other methods. We also demonstrate how scTenifoldXct can be used to compare different samples, such as healthy vs. diseased and wild type vs. knockout, to identify differential interactions, thereby revealing functional implications associated with changes in cellular communication status.

Fibronectin leucine-rich transmembrane protein 2 drives monocyte differentiation into macrophages via the UNC5B-Akt/mTOR axis

Upon migrating into the tissues, hematopoietic stem cell (HSC)-derived monocytes differentiate into macrophages, playing a crucial role in determining innate immune responses towards external pathogens and internal stimuli. However, the regulatory mechanisms underlying monocyte-to-macrophage differentiation remain largely unexplored. Here we divulge a previously uncharacterized but essential role for an axon guidance molecule, fibronectin leucine-rich transmembrane protein 2 (FLRT2), in monocyte-to-macrophage maturation. FLRT2 is almost undetectable in human monocytic cell lines, human peripheral blood mononuclear cells (PBMCs), and mouse primary monocytes but significantly increases in fully differentiated macrophages. Myeloid-specific deletion of FLRT2 (Flrt2ΔMyel) contributes to decreased peritoneal monocyte-to-macrophage generation in mice in vivo, accompanied by impaired macrophage functions. Gain- and loss-of-function studies support the promoting effect of FLRT2 on THP-1 cell and human PBMC differentiation into macrophages. Mechanistically, FLRT2 directly interacts with Unc-5 netrin receptor B (UNC5B) via its extracellular domain (ECD) and activates Akt/mTOR signaling. In vivo administration of mTOR agonist MYH1485 reverses the impaired phenotypes observed in Flrt2ΔMyel mice. Together, these results identify FLRT2 as a novel pivotal endogenous regulator of monocyte differentiation into macrophages. Targeting the FLRT2/UNC5B-Akt/mTOR axis may provide potential therapeutic strategies directly relevant to human diseases associated with aberrant monocyte/macrophage differentiation.

A new tractable method for generating Human Alveolar Macrophage Like cells in vitro to study lung inflammatory processes and diseases

Alveolar macrophages (AMs) are unique lung resident cells that contact airborne pathogens and environmental particulates. The contribution of human AMs (HAM) to pulmonary diseases remains poorly understood due to difficulty in accessing them from human donors and their rapid phenotypic change during in vitro culture. Thus, there remains an unmet need for cost-effective methods for generating and/or differentiating primary cells into a HAM phenotype, particularly important for translational and clinical studies. We developed cell culture conditions that mimic the lung alveolar environment in humans using lung lipids, i.e. , Infasurf (calfactant, natural bovine surfactant) and lung-associated cytokines (GM-CSF, TGF-β, and IL-10) that facilitate the conversion of blood-obtained monocytes to an AM-Like (AML) phenotype and function in tissue culture. Similar to HAM, AML cells are particularly susceptible to both Mycobacterium tuberculosis and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. This study reveals the importance of alveolar space components in the development and maintenance of HAM phenotype and function, and provides a readily accessible model to study HAM in infectious and inflammatory disease processes, as well as therapies and vaccines.

IMPORTANCE

Millions die annually from respiratory disorders. Lower respiratory track gas-exchanging alveoli maintain a precarious balance between fighting invaders and minimizing tissue damage. Key players herein are resident AMs. However, there are no easily accessible in vitro models of HAMs, presenting a huge scientific challenge. Here we present a novel model for generating AML cells based on differentiating blood monocytes in a defined lung component cocktail. This model is non-invasive, significantly less costly than performing a bronchoalveolar lavage, yields more AML cells than HAMs per donor and retains their phenotype in culture. We have applied this model to early studies of M. tuberculosis and SARS-CoV-2. This model will significantly advance respiratory biology research.

Shaping of the alveolar landscape by respiratory infections and long-term consequences for lung immunity

Respiratory infections and especially viral infections, along with other extrinsic environmental factors, have been shown to profoundly affect macrophage populations in the lung. In particular, alveolar macrophages (AMs) are important sentinels during respiratory infections and their disappearance opens a niche for recruited monocytes (MOs) to differentiate into resident macrophages. Although this topic is still the focus of intense debate, the phenotype and function of AMs that recolonize the niche after an inflammatory insult, such as an infection, appear to be dictated in part by their origin, but also by local and/or systemic changes that may be imprinted at the epigenetic level. Phenotypic alterations following respiratory infections have the potential to shape lung immunity for the long-term, leading to beneficial responses such as protection against allergic airway inflammation or against other infections, but also to detrimental responses when associated with the development of immunopathologies. This review reports the persistence of virus-induced functional alterations in lung macrophages, and discusses the importance of this imprinting in explaining inter-individual and lifetime immune variation.

Role of GM-CSF in lung balance and disease

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a hematopoietic growth factor originally identified as a stimulus that induces the differentiation of bone marrow progenitor cells into granulocytes and macrophages. GM-CSF is now considered to be a multi-origin and pleiotropic cytokine. GM-CSF receptor signals activate JAK2 and induce nuclear signals through the JAK-STAT, MAPK, PI3K, and other pathways. In addition to promoting the metabolism of pulmonary surfactant and the maturation and differentiation of alveolar macrophages, GM-CSF plays a key role in interstitial lung disease, allergic lung disease, alcoholic lung disease, and pulmonary bacterial, fungal, and viral infections. This article reviews the latest knowledge on the relationship between GM-CSF and lung balance and lung disease, and indicates that there is much more to GM-CSF than its name suggests.

Utility of atherosclerosis-associated serum antibodies against colony-stimulating factor 2 in predicting the onset of acute ischemic stroke and prognosis of colorectal cancer

Introduction

Autoantibodies against inflammatory cytokines may be used for the prevention of atherosclerosis. Preclinical studies consider colony-stimulating factor 2 (CSF2) as an essential cytokine with a causal relationship to atherosclerosis and cancer. We examined the serum anti-CSF2 antibody levels in patients with atherosclerosis or solid cancer.

Methods

We measured the serum anti-CSF2 antibody levels via amplified luminescent proximity homogeneous assay-linked immunosorbent assay based on the recognition of recombinant glutathione S-transferase-fused CSF2 protein or a CSF2-derived peptide as the antigen.

Results

The serum anti-CSF2 antibody (s-CSF2-Ab) levels were significantly higher in patients with acute ischemic stroke (AIS), acute myocardial infarction (AMI), diabetes mellitus (DM), and chronic kidney disease (CKD) compared with healthy donors (HDs). In addition, the s-CSF2-Ab levels were associated with intima-media thickness and hypertension. The analyzes of samples obtained from a Japan Public Health Center-based prospective study suggested the utility of s-CSF2-Ab as a risk factor for AIS. Furthermore, the s-CSF2-Ab levels were higher in patients with esophageal, colorectal, gastric, and lung cancer than in HDs but not in those with mammary cancer. In addition, the s-CSF2-Ab levels were associated with unfavorable postoperative prognosis in colorectal cancer (CRC). In CRC, the s-CSF2-Ab levels were more closely associated with poor prognosis in patients with p53-Ab-negative CRC despite the lack of significant association of the anti-p53 antibody (p53-Ab) levels with the overall survival.

Conclusion

S-CSF2-Ab was useful for the diagnosis of atherosclerosis-related AIS, AMI, DM, and CKD and could discriminate poor prognosis, especially in p53-Ab-negative CRC.

Translating the biology of β common receptor-engaging cytokines into clinical medicine

The family of cytokines that comprises IL-3, IL-5, and GM-CSF was discovered over 30 years ago, and their biological activities and resulting impact in clinical medicine has continued to expand ever since. Originally identified as bone marrow growth factors capable of acting on hemopoietic progenitor cells to induce their proliferation and differentiation into mature blood cells, these cytokines are also recognized as key mediators of inflammation and the pathobiology of diverse immunologic diseases. This increased understanding of the functional repertoire of IL-3, IL-5, and GM-CSF has led to an explosion of interest in modulating their functions for clinical management. Key to the successful clinical translation of this knowledge is the recognition that these cytokines act by engaging distinct dimeric receptors and that they share a common signaling subunit called β-common or βc. The structural determination of how IL-3, IL-5, and GM-CSF interact with their receptors and linking this to their differential biological functions on effector cells has unveiled new paradigms of cell signaling. This knowledge has paved the way for novel mAbs and other molecules as selective or pan inhibitors for use in different clinical settings.

Regulatory T cell and macrophage crosstalk in acute lung injury: future perspectives

Acute lung injury (ALI) describes the injury to endothelial cells in the lungs and associated vessels due to various factors. Furthermore, ALI accompanied by inflammation and thrombosis has been reported as a common complication of SARS-COV-2 infection. It is widely accepted that inflammation and the cytokine storm are main causes of ALI. Two classical anti-inflammatory cell types, regulatory T cells (Tregs) and M2 macrophages, are theoretically capable of resisting uncontrolled inflammation. Recent studies have indicated possible crosstalk between Tregs and macrophages involving their mutual activation. In this review, we discuss the current findings related to ALI pathogenesis and the role of Tregs and macrophages. In particular, we review the molecular mechanisms underlying the crosstalk between Tregs and macrophages in ALI pathogenesis. Understanding the role of Tregs and macrophages will provide the potential targets for treating ALI.

Understanding the development of Th2 cell-driven allergic airway disease in early life

Allergic diseases, including atopic dermatitis, allergic rhinitis, asthma, and food allergy, are caused by abnormal responses to relatively harmless foreign proteins called allergens found in pollen, fungal spores, house dust mites (HDM), animal dander, or certain foods. In particular, the activation of allergen-specific helper T cells towards a type 2 (Th2) phenotype during the first encounters with the allergen, also known as the sensitization phase, is the leading cause of the subsequent development of allergic disease. Infants and children are especially prone to developing Th2 cell responses after initial contact with allergens. But in addition, the rates of allergic sensitization and the development of allergic diseases among children are increasing in the industrialized world and have been associated with living in urban settings. Particularly for respiratory allergies, greater susceptibility to developing allergic Th2 cell responses has been shown in children living in urban environments containing low levels of microbial contaminants, principally bacterial endotoxins [lipopolysaccharide (LPS)], in the causative aeroallergens. This review highlights the current understanding of the factors that balance Th2 cell immunity to environmental allergens, with a particular focus on the determinants that program conventional dendritic cells (cDCs) toward or away from a Th2 stimulatory function. In this context, it discusses transcription factor-guided functional specialization of type-2 cDCs (cDC2s) and how the integration of signals derived from the environment drives this process. In addition, it analyzes observational and mechanistic studies supporting an essential role for innate sensing of microbial-derived products contained in aeroallergens in modulating allergic Th2 cell immune responses. Finally, this review examines whether hyporesponsiveness to microbial stimulation, particularly to LPS, is a risk factor for the induction of Th2 cell responses and allergic sensitization during infancy and early childhood and the potential factors that may affect early-age response to LPS and other environmental microbial components.

Surfactant protein A alters endosomal trafficking of influenza A virus in macrophages

Influenza A virus infection (IAV) often leads to acute lung injury that impairs breathing and can lead to death, with disproportionate mortality in children and the elderly. Surfactant Protein A (SP-A) is a calcium-dependent opsonin that binds a variety of pathogens to help control pulmonary infections by alveolar macrophages. Alveolar macrophages play critical roles in host resistance and susceptibility to IAV infection. The effect of SP-A on IAV infection and antiviral response of macrophages, however, is not understood. Here, we report that SP-A attenuates IAV infection in a dose-dependent manner at the level of endosomal trafficking, resulting in infection delay in a model macrophage cell line. The ability of SP-A to suppress infection was independent of its glycosylation status. Binding of SP-A to hemagglutinin did not rely on the glycosylation status or sugar binding properties of either protein. Incubation of either macrophages or IAV with SP-A slowed endocytic uptake rate of IAV. SP-A interfered with binding to cell membrane and endosomal exit of the viral genome as indicated by experiments using isolated cell membranes, an antibody recognizing a pH-sensitive conformational epitope on hemagglutinin, and microscopy. Lack of SP-A in mice enhanced IFNβ expression, viral clearance and reduced mortality from IAV infection. These findings support the idea that IAV is an opportunistic pathogen that co-opts SP-A to evade host defense by alveolar macrophages. Our study highlights novel aspects of host-pathogen interactions that may lead to better understanding of the local mechanisms that shape activation of antiviral and inflammatory responses to viral infection in the lung.

The impact on colostrum oxidative stress, cytokines, and immune cells composition after SARS-CoV-2 infection during pregnancy

Background

Limited data are available regarding the differences between immunological, biochemical, and cellular contents of human colostrum following maternal infection during pregnancy with coronavirus 2 disease (COVID-19).

Objective

To investigate whether maternal COVID-19 infection may affect immunological, biochemical, and cellular contents of human colostrum.

Methods

Using a case-control study design, we collected colostrum from 14 lactating women with a previous diagnosis of COVID-19 during pregnancy and 12 without a clear diagnosis during September 2020 to May 2021. Colostrum samples were analysed for some enzymes and non-enzymatic oxidative stress markers (SOD, CAT, GPx, MDA, GSH, GSSG, H2O2, MPO) and for IL-1β, IL-6, tumour necrosis factor (TNF)-α, protein induced by interferon gamma (IP)-10, IL-8, IFN-λ1, IL12p70, IFN-α2, IFN-λ2/3, granulocyte macrophage colony stimulating factor (GM-CSF), IFN-β, IL-10 and IFN-γ, along with IgA and IgG for the SARS-CoV-2 S protein. We perform immunophenotyping to assess the frequency of different cell types in the colostrum.

Results

Colostrum from the COVID-19 symptomatic group in pregnancy contained reduced levels of H2O2, IFN-α2, and GM-CSF. This group had higher levels of GSH, and both NK cell subtypes CD3-CD56brightCD16-CD27+IFN-γ+ and CD3-CD56dimCD16+CD27- were also increased.

Conclusion

The present results reinforce the protective role of colostrum even in the case of mild SARS-Cov-2 infection, in addition to demonstrating how adaptive the composition of colostrum is after infections. It also supports the recommendation to encourage lactating women to continue breastfeeding after COVID-19 illness.

Alcohol impairs recognition and uptake of Mycobacterium tuberculosis by suppressing toll-like receptor 2 expression

BACKGROUND

Alcohol impairs pulmonary innate immune function and is associated with an increased risk of tuberculosis (TB). Toll-like receptor 2 (TLR2) is a pattern recognition receptor on alveolar macrophages that recognizes Mycobacterium tuberculosis (Mtb). The expression of TLR2 depends, in part, on granulocyte-macrophage colony-stimulating factor (GM-CSF) signaling. Given our prior work demonstrating the suppression of GM-CSF signaling following chronic alcohol ingestion, we hypothesized that alcohol impairs TLR2 expression via the suppression of GM-CSF and thereby reduces the ability of the macrophage to recognize and phagocytose Mtb.

METHODS

Primary alveolar macrophages were isolated from control-fed and alcohol-fed rats. Prior to cell isolation, some alcohol-fed rats were treated with intranasal GM-CSF and then endotracheally inoculated with an attenuated strain of Mtb. Primary macrophages were then isolated and immunofluorescence was used to determine phagocytic efficiency and TLR2 expression in the presence and absence of GM-CSF treatment and phagocytic efficiency in the presence and absence of TLR2 neutralization.

RESULTS

TLR2 expression and phagocytosis of Mtb were significantly lower in the alveolar macrophages of alcohol-fed rats than control-fed rats. In parallel, blocking TLR2 signaling recapitulated this decreased phagocytosis of Mtb. In contrast, intranasal GM-CSF treatment restored TLR2 expression and Mtb phagocytosis in the alveolar macrophages of alcohol-fed rats to levels comparable to those of control-fed rats.

CONCLUSIONS

Chronic alcohol ingestion reduces TLR2 protein expression and phagocytosis of Mtb, likely due to impaired GM-CSF signaling. GM-CSF restores membrane-bound TLR2 expression and phagocytic function.

Alveolar macrophage metabolic programming via a C-type lectin receptor protects against lipo-toxicity and cell death

Alveolar macrophages (AM) hold lung homeostasis intact. In addition to the defense against inhaled pathogens and deleterious inflammation, AM also maintain pulmonary surfactant homeostasis, a vital lung function that prevents pulmonary alveolar proteinosis. Signals transmitted between AM and pneumocytes of the pulmonary niche coordinate these specialized functions. However, the mechanisms that guide the metabolic homeostasis of AM remain largely elusive. We show that the NK cell-associated receptor, NKR-P1B, is expressed by AM and is essential for metabolic programming. Nkrp1b^-/- mice are vulnerable to pneumococcal infection due to an age-dependent collapse in the number of AM and the formation of lipid-laden AM. The AM of Nkrp1b^-/- mice show increased uptake but defective metabolism of surfactant lipids. We identify a physical relay between AM and alveolar type-II pneumocytes that is dependent on pneumocyte Clr-g expression. These findings implicate the NKR-P1B:Clr-g signaling axis in AM-pneumocyte communication as being important for maintaining metabolism in AM.

Mice with lung airway ciliopathy develop persistent Mycobacterium abscessus lung infection and have a proinflammatory lung phenotype associated with decreased T regulatory cells

Introduction

Human pulmonary infection with non-tuberculous mycobacteria (NTM) such as Mycobacterium abscessus (Mabs) occurs in seemingly immunocompetent patients with underlying structural lung disease such as bronchiectasis in which normal ciliary function is perturbed. In addition to alterations in mucociliary clearance, the local immunologic milieu may be altered in patients with structural lung disease, but the nature of these changes and how they relate to NTM persistence remain unclear.

Methods

We used a mouse strain containing a conditional floxed allele of the gene IFT88, which encodes for the protein Polaris. Deletion of this gene in adult mice reportedly leads to loss of cilia on lung airway epithelium and to the development of bronchiectasis. In a series of experiments, IFT88 control mice and IFT88 KO mice received different preparations of Mabs lung inocula with lung CFU assessed out to approximately 8 weeks post-infection. In addition, cytokine levels in bronchoalveolar lavage (BAL) fluid, lung T cell subset analysis, and lung histopathology and morphometry were performed at various time points.

Results

Mabs embedded in agarose beads persisted in the lungs of IFT88 KO mice out to approximately 8 weeks (54 days), while Mabs agarose beads in the lungs of IFT88 control mice was cleared from the lungs of all mice at this time point. T cells subset analysis showed a decrease in the percentage of CD4⁺FoxP3⁺ T cells in the total lymphocyte population in the lungs of IFT88 KO mice relative to IFT88 control mice. Proinflammatory cytokines were elevated in the BAL fluid from infected IFT88 KO mice compared to infected IFT88 control mice, and histopathology showed an increased inflammatory response and greater numbers of granulomas in the lungs of infected IFT88 KO mice compared to the lungs of infected IFT88 control mice. Scanning lung morphometry did not show a significant difference comparing lung airway area and lung airway perimeter between IFT88 KO mice and IFT88 control mice.

Discussion

Persistent lung infection in our model was established using Mabs embedded in agarose beads. The utility of using IFT88 mice is that a significant difference in Mabs lung CFU is observed comparing IFT88 KO mice to IFT88 control mice thus allowing for studies assessing the mechanism(s) of Mabs lung persistence. Our finding of minimal differences in lung airway area and lung airway diameter comparing IFT88 KO mice to IFT88 control mice suggests that the development of a proinflammatory lung phenotype in IFT88 KO mice contributes to Mabs lung persistence independent of bronchiectasis. The contribution of cilia to immune regulation is increasingly recognized, and our results suggest that ciliopathy associated with structural lung disease may play a role in NTM pulmonary infection via alteration of the local immunologic lung milieu.

Recombinant Human Granulocyte-Macrophage Colony-Stimulating Factor (rhu GM-CSF) as Adjuvant Therapy for Invasive Fungal Diseases

BACKGROUND

Sargramostim (yeast-derived, glycosylated recombinant human granulocyte-macrophage colony-stimulating factor [rhu GM-CSF]) augments innate and adaptive immune responses and accelerates hematopoietic recovery of chemotherapy-induced neutropenia. However, considerably less is known about its efficacy as adjunctive immunotherapy against invasive fungal diseases (IFDs).

METHODS

The clinical courses of 15 patients with pediatric malignancies and IFDs treated adjunctively with sargramostim at a single institution were analyzed in a retrospective cohort review. Further, a systematic review of published reports of rhu GM-CSF for IFDs was also conducted.

RESULTS

Among 65 cases, 15 were newly described pediatric patients and 50 were previously published cases of IFDs treated with rhu GM-CSF. Among the newly reported pediatric patients, IFDs were caused by Candida spp., Trichosporon sp., and molds (Aspergillus spp., Rhizopus sp., Lichtheimia sp., and Scedosporium sp). Twelve (80%) were neutropenic at baseline, and 12 (80%) were refractory to antifungal therapy. Among 12 evaluable patients, the overall response rate was 92% (8 [67%] complete responses, 3 [25%] partial responses, and 1 [8%] stable). Treatment is ongoing in the remaining 3 patients. Among 50 published cases (15 Candida spp., 13 Mucorales, 11 Aspergillus spp., 11 other organisms), 20 (40%) had baseline neutropenia and 36 (72%) were refractory to standard therapy before rhu GM-CSF administration. Consistent with responses in the newly reported patients, the overall response rate in the literature review was 82% (40 [80%] complete responses, 1 [2%] partial response, and 9 [18%] no response).

CONCLUSIONS

Sargramostim may be a potential adjunctive immunomodulator for selected patients with hematological malignancies and refractory IFDs.

Reprogramming alveolar macrophage responses to TGF-β reveals CCR2+ monocyte activity that promotes bronchiolitis obliterans syndrome

Bronchiolitis obliterans syndrome (BOS) is a major impediment to lung transplant survival and is generally resistant to medical therapy. Extracorporeal photophoresis (ECP) is an immunomodulatory therapy that shows promise in stabilizing BOS patients, but its mechanisms of action are unclear. In a mouse lung transplant model, we show that ECP blunts alloimmune responses and inhibits BOS through lowering airway TGF-β bioavailability without altering its expression. Surprisingly, ECP-treated leukocytes were primarily engulfed by alveolar macrophages (AMs), which were reprogrammed to become less responsive to TGF-β and reduce TGF-β bioavailability through secretion of the TGF-β antagonist decorin. In untreated recipients, high airway TGF-β activity stimulated AMs to express CCL2, leading to CCR2+ monocyte-driven BOS development. Moreover, we found TGF-β receptor 2-dependent differentiation of CCR2+ monocytes was required for the generation of monocyte-derived AMs, which in turn promoted BOS by expanding tissue-resident memory CD8+ T cells that inflicted airway injury through Blimp-1-mediated granzyme B expression. Thus, through studying the effects of ECP, we have identified an AM functional plasticity that controls a TGF-β-dependent network that couples CCR2+ monocyte recruitment and differentiation to alloimmunity and BOS.

ATP citrate lyase links increases in glycolysis to diminished release of vesicular suppressor of cytokine signaling 3 by alveolar macrophages

Extracellular vesicles (EVs) are important vectors for intercellular communication. Lung-resident alveolar macrophages (AMs) tonically secrete EVs containing suppressor of cytokine signaling 3 (SOCS3), a cytosolic protein that promotes homeostasis in the distal lung via its actions in recipient neighboring epithelial cells. AMs are metabolically distinct and exhibit low levels of glycolysis at steady state. To our knowledge, whether cellular metabolism influences the packaging and release of an EV cargo molecule has never been explored in any cellular context. Here, we report that increases in glycolysis following in vitro exposure of AMs to the growth and activating factor granulocyte-macrophage colony-stimulating factor inhibit the release of vesicular SOCS3 by primary AMs. Glycolytically diminished SOCS3 secretion requires export of citrate from the mitochondria to the cytosol and its subsequent conversion to acetyl-CoA by ATP citrate lyase. Our data for the first time implicate perturbations in intracellular metabolites in the regulation of vesicular cargo packaging and secretion.

Lyl1-deficiency promotes inflammatory responses and increases mycobacterial burden in response to Mycobacterium tuberculosis infection in mice

Lymphoblastic leukemia 1 (Lyl1) is a well-studied transcription factor known to exhibit oncogenic potential in various forms of leukemia with pivotal roles in hematopoietic stem cell biology. While its role in early hematopoiesis is well established, its function in mature innate cells is less explored. Here, we identified Lyl1 as a drastically perturbed gene in the Mycobacterium tuberculosis (Mtb) infected mouse macrophage transcriptome. We report that Lyl1 downregulation upon immune stimulation is a host-driven process regulated by NFκB and MAP kinase pathways. Interestingly, Lyl1-deficient macrophages have decreased bacterial killing potential with reduced nitric oxide (NO) levels while expressing increased levels of pro-inflammatory interleukin-1 and CXCL1. Lyl1-deficient mice show reduced survival to Mtb HN878 infection with increased bacterial burden and exacerbated inflammatory responses in chronic stages. We observed that increased susceptibility to infection was accompanied by increased neutrophil recruitment and IL-1, CXCL1, and CXCL5 levels in the lung homogenates. Collectively, these results suggest that Lyl1 controls Mtb growth, reduces neutrophilic inflammation and reveals an underappreciated role for Lyl1 in innate immune responses.

GM-CSF elicits antibodies to tumor-associated proteins when used as a prostate cancer vaccine adjuvant

Antibody responses to off-target cancer-associated proteins have been detected following immunotherapies for cancer, suggesting these may be the result of antigen spread. We have previously reported that serum antibodies to prostate cancer-associated proteins were detectable using a high-throughput peptide array. We hypothesized that the breadth of antibody responses elicited by a vaccine could serve as a measure of the magnitude of its induced antigen spread. Consequently, sera from patients with prostate cancer, treated prior to or after vaccination in one of four separate clinical trials, were evaluated for antibody responses to an array of 177,604 peptides derived from over 1600 prostate cancer-associated gene products. Antibody responses to the same group of 5680 peptides previously reported were identified following vaccinations in which patients were administered GM-CSF as an adjuvant, but not with vaccine in the absence of GM-CSF. Hence, antibody responses to off-target proteins following vaccination may not necessarily serve as evidence of antigen spread and must be interpreted with particular caution following vaccine strategies that use GM-CSF, as GM-CSF appears to have direct effects on the production of antibodies. The evaluation of T cell responses to non-target antigens is likely a preferred approach for detection of immune-mediated antigen spread.

Comprehensive overview of COVID-19-related respiratory failure: focus on cellular interactions

The pandemic outbreak of coronavirus disease 2019 (COVID-19) has created health challenges in all parts of the world. Understanding the entry mechanism of this virus into host cells is essential for effective treatment of COVID-19 disease. This virus can bind to various cell surface molecules or receptors, such as angiotensin-converting enzyme 2 (ACE2), to gain cell entry. Respiratory failure and pulmonary edema are the most important causes of mortality from COVID-19 infections. Cytokines, especially proinflammatory cytokines, are the main mediators of these complications. For normal respiratory function, a healthy air-blood barrier and sufficient blood flow to the lungs are required. In this review, we first discuss airway epithelial cells, airway stem cells, and the expression of COVID-19 receptors in the airway epithelium. Then, we discuss the suggested molecular mechanisms of endothelial dysfunction and blood vessel damage in COVID-19. Coagulopathy can be caused by platelet activation leading to clots, which restrict blood flow to the lungs and lead to respiratory failure. Finally, we present an overview of the effects of immune and non-immune cells and cytokines in COVID-19-related respiratory failure.

[Anti-cytokine autoantibodies: Review of the literature]

Anti-cytokine antibodies (ACA) are an emerging cause of acquired immunodeficiency, especially in previously healthy adults. The most frequently reported are anti-IFN-γ responsible for disseminated non-tuberculous mycobacteria infections, and anti-GM-CSF mainly in mycobacteria, cryptococcosis and nocardiosis infections. The presence of anti-IFN-α in severe COVID-19 infections has recently been described. The search for and detection of these ACAs in an unusual infection situation makes it possible to set up specific therapies in addition to the anti-infective treatment. ACAs are also frequent in various autoimmune pathologies where, in addition to being indicators of the breakdown of immune tolerance, they can modulate the activity of the disease according to their cytokine target. In this review of the literature, we will focus on the epidemiology and the clinical impact of these ACAs in healthy subjects and in infectious or dysimmune diseases.

Anti-cytokine autoantibodies and inborn errors of immunity

The past quarter of a century has witnessed an inordinate increase in our understanding of primary immunodeficiencies / inborn errors of immunity. These include a significant increase in the number of identified conditions, broadening the phenotypes of existing entities, delineation of classical inborn errors of immunity from those with a narrow phenotype, and a gradual shift from supportive to definitive care in patients afflicted with these diseases. It has also seen the discovery of conditions broadly defined as phenocopies of primary immunodeficiencies, where somatic mutations or autoantibodies mimic a recognised primary immunodeficiency's presentation in the absence of the underlying genetic basis for that disease. This article will provide a review of the anti-cytokine autoantibody-mediated phenocopies of inborn errors of immunity and discuss the therapeutic and laboratory aspects of this group of diseases.

GM-CSF: A Double-Edged Sword in Cancer Immunotherapy

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine that drives the generation of myeloid cell subsets including neutrophils, monocytes, macrophages, and dendritic cells in response to stress, infections, and cancers. By modulating the functions of innate immune cells that serve as a bridge to activate adaptive immune responses, GM-CSF globally impacts host immune surveillance under pathologic conditions. As with other soluble mediators of immunity, too much or too little GM-CSF has been found to promote cancer aggressiveness. While too little GM-CSF prevents the appropriate production of innate immune cells and subsequent activation of adaptive anti-cancer immune responses, too much of GM-CSF can exhaust immune cells and promote cancer growth. The consequences of GM-CSF signaling in cancer progression are a function of the levels of GM-CSF, the cancer type, and the tumor microenvironment. In this review, we first discuss the secretion of GM-CSF, signaling downstream of the GM-CSF receptor, and GM-CSF’s role in modulating myeloid cell homeostasis. We then outline GM-CSF’s anti-tumorigenic and pro-tumorigenic effects both on the malignant cells and on the non-malignant immune and other cells in the tumor microenvironment. We provide examples of current clinical and preclinical strategies that harness GM-CSF’s anti-cancer potential while minimizing its deleterious effects. We describe the challenges in achieving the Goldilocks effect during administration of GM-CSF-based therapies to patients with cancer. Finally, we provide insights into how technologies that map the immune microenvironment spatially and temporally may be leveraged to intelligently harness GM-CSF for treatment of malignancies.

Complete remission of pulmonary alveolar proteinosis after anti-tuberculous chemotherapy: a case report

Pulmonary alveolar proteinosis (PAP) is a rare respiratory system disorder. Patients with PAP are at risk for a wide variety of secondary infections. This current case report describes a patient with PAP complicated by tuberculosis. A 48-year-old male patient with multiple follow-up chest computed tomography scans that showed predominant diffuse ground glass opacity in both lung fields, presented a few years later with new calcified lesions and pleural effusion. At this point, the associated auxiliary examination indicated the possibility of PAP combined with tuberculosis infection. The patient achieved complete remission after anti-tuberculosis treatment. PAP is an easily overlooked clinical syndrome due to its low prevalence and lack of specific clinical manifestations, especially when combined with other pulmonary lesions. Therefore, clinicians should consider this rare disease in patients presenting with pulmonary disease and plan for its co-morbidity with other secondary outcomes, such as opportunistic infections, which are a common and life-threatening complication in patients with PAP. This case indicates the possibility that anti-tuberculosis therapy can improve alveolar proteinosis in patients with PAP and secondary Mycobacterium tuberculosis infection.

Radioresistant cells initiate lymphocyte-dependent lung inflammation and IFNγ-dependent mortality in STING gain-of-function mice

Pediatric patients with constitutively active mutations in the cytosolic double-stranded-DNA-sensing adaptor STING develop an autoinflammatory syndrome known as STING-associated vasculopathy with onset in infancy (SAVI). SAVI patients have elevated interferon-stimulated gene expression and suffer from interstitial lung disease (ILD) with lymphocyte predominate bronchus-associated lymphoid tissue (BALT). Mice harboring SAVI mutations (STING V154M [VM]) that recapitulate human disease also develop lymphocyte-rich BALT. Ablation of either T or B lymphocytes prolongs the survival of SAVI mice, but lung immune aggregates persist, indicating that T cells and B cells can independently be recruited as BALT. VM T cells produced IFNγ, and IFNγR deficiency prolonged the survival of SAVI mice; however, T-cell-dependent recruitment of infiltrating myeloid cells to the lung was IFNγ independent. Lethally irradiated VM recipients fully reconstituted with wild type bone-marrow-derived cells still developed ILD, pointing to a critical role for VM-expressing radioresistant parenchymal and/or stromal cells in the recruitment and activation of pathogenic lymphocytes. We identified lung endothelial cells as radioresistant cells that express STING. Transcriptional analysis of VM endothelial cells revealed up-regulation of chemokines, proinflammatory cytokines, and genes associated with antigen presentation. Together, our data show that VM-expressing radioresistant cells play a key role in the initiation of lung disease in VM mice and provide insights for the treatment of SAVI patients, with implications for ILD associated with other connective tissue disorders.

Beyond antibiotics: recent developments in the diagnosis and management of nontuberculous mycobacterial infection

Nontuberculous mycobacteria (NTM) pulmonary disease represents a significant clinical challenge with suboptimal therapy and increasing prevalence globally. Although clinical practice guidelines seek to standardise the approach to diagnosis and treatment of NTM disease, a lack of robust evidence limits their utility and significant variability exists in clinical practice. Here we walk through some novel approaches in diagnosis and therapy that are under development to tackle a disease where traditional strategies are failing.

Prevalence of NTM disease is rising globally, yet current diagnostic and therapeutic strategies are lacking. This review describes some burgeoning diagnostic and therapeutic approaches, but it is clear that real progress will need more focused attention.https://bit.ly/3O0K2SP