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The bone marrow is a specialized niche responsible for the maintenance of hematopoietic stem and progenitor cells during homeostasis and inflammation. Recent studies, however, have extended this essential role to the extramedullary and extravascular lung microenvironment. Here, we provide further evidence for a reservoir of hematopoietic stem and progenitor cells within the lung from Embryonic Day 18.5 until adulthood. These lung progenitors display distinct microenvironment-specific developmental kinetics compared with their bone marrow counterparts, exemplified by a rapid shift from a common myeloid to a megakaryocyte-erythrocyte progenitor-dominated niche with increasing age. In adult mice, influenza A viral infection results in a transient reduction in multipotent progenitors within the lungs, with a parallel increase in downstream granulocyte-monocyte progenitors and dendritic cell populations associated with acute viral infections. Our findings suggest that lung hematopoietic progenitors play a role in reestablishing immunological homeostasis in the respiratory mucosa, which may have significant clinical implications for maintaining pulmonary health after inflammatory perturbation.

Airway inflammation is a defense mechanism against inhaled agents characterized by infiltration of circulating immune cells. Given the inconsistent cellular identification across pre-clinical rat model, we have developed a flow cytometry panel of six colors to characterize macrophages subsets, lymphocytes and granulocytes in bronchoalveolar lavage fluid (BAL). Rats were challenged with intratracheal instillation of lipopolysaccharide (LPS). BAL were harvested 24 h after one LPS exposure in rats. This flow cytometry panel involve the description of macrophage subsets, T and B lymphocytes and neutrophils, which are central to airway immune responses, as based on scientific literature. By using a relatively small number of parameters to identify multiple cell types, additional parameters can be used for project/disease-specific activation markers., (© 2023 The Authors. Cytometry Part A published by Wiley Periodicals LLC on behalf of International Society for Advancement of Cytometry.)

Allergic asthma is a chronic inflammatory disease characterized by Th2, conventional dendritic cell, and B-cell activation. In addition to excessive inflammation, asthma pathogenesis includes dysregulation of anti-inflammatory pathways, such as the CD200/CD200R pathway. Thus, we investigated whether a CD200R agonist, CD200Fc, could disrupt the inflammatory cascade in chronic allergic asthma pathogenesis using a mice model of experimental asthma. Mice were exposed to house dust mites for 5 wk, and CD200Fc treatment was initiated after chronic inflammation was established (starting on week 4). We demonstrate that chronic house dust mite exposure altered CD200 and CD200R expression on lung immune cell populations, including upregulation of CD200 on alveolar macrophages and reduced expression of CD200 on conventional dendritic cells. CD200Fc treatment does not change bronchoalveolar cellular infiltration, but it attenuates B-cell activation and skews the circulating immunoglobulin profile toward IgG2a. This is accompanied by reduced activation of conventional dendritic cells, including lower expression of CD40, especially on conventional dendritic cell subset 2 CD200R+. Furthermore, we confirm that CD200Fc can directly modulate conventional dendritic cell activation in vitro using bone marrow-derived dendritic cells. Thus, the CD200/CD200R pathway is dysregulated during chronic asthma pathogenesis, and the CD200R agonist modulates B-cell and dendritic cell activation but, in our chronic model, is not sufficient to alter inflammation measured in bronchoalveolar lavage., (© The Author(s) 2023. Published by Oxford University Press on behalf of Society for Leukocyte Biology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Introduction: At lung mucosal surfaces, immune cells must initiate inflammatory response against pathogen without inducing tissue damage. Loss of this equilibrium can lead to acute respiratory distress syndrome (ARDS), a severe lung inflammatory disease characterized by excessive inflammation and dysregulation of anti-inflammatory pathways., Methods: To investigate the role of anti-inflammatory pathway CD200/CD200R in lung inflammatory response, we administered LPS intratracheally in CD200 KO and wild type (WT) rats. Inflammation was evaluated using bronchoalveolar lavage (BAL) cellularity. Lung injury was measured by total protein level in BAL fluid, and levels of proinflammatory cytokines (TNF, IL-6) and chemokines (CXCL2, CCL2) were determined in BAL supernatants. In a second series of experiments, recombinant CD200Fc was administered to KO rats to restore the anti-inflammatory response., Results: At baseline, CD200 KO rats did not show sign of inflammation, however KO rats had lower number of alveolar macrophages. In addition, LPS administration induced greater pulmonary edema in CD200 KO rats. This was accompanied with a higher recruitment of neutrophils as well as levels of TNF, IL-6, CXCL2, and CCL2 in BAL compared to WT rats. CD200Fc administration in KO rats reduced neutrophil accumulation and TNF and CXCL2 levels in BAL. Interestingly, the increased inflammatory response of CD200 KO rats could be attributed to greater activation potential of alveolar macrophages with higher levels of ERK and P-ERK MAPK., Conclusion: This study shows that lung inflammatory response is exacerbated in absence of CD200 in an experimental model of ARDS in rats. In addition, CD200/CD200R pathway shows selective regulation of acute lung inflammation and cannot completely abrogate the complex LPS-induced inflammatory response. However, addition of CD200 agonist in a multi-target therapy strategy could have beneficial impacts., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Patoine, Bouchard, Lemay, Bissonnette and Lauzon-Joset.)

Background: Hypersensitivity pneumonitis (HP) is an interstitial lung disease characterized by antigen-triggered neutrophilic exacerbations. Although CD4 + T cells are sufficient for HP pathogenesis, this never translated into efficient T cell-specific therapies. Increasing evidence shows that B cells also play decisive roles in HP. Here, we aimed to further define the respective contributions of B and T cells in subacute experimental HP., Methods: Mice were subjected to a protocol of subacute exposure to the archaeon Methanosphaera stadmanae to induce experimental HP. Using models of adoptive transfers of B cells and T cells in Rag1-deficient mice and of B cell-specific S1P 1 deletion, we assessed the importance of B cells in the development of HP by evaluating inflammation in bronchoalveolar lavage fluid. We also aimed to determine if injected antibodies targeting B and/or T cells could alleviate HP exacerbations using a therapeutic course of intervention., Results: Even though B cells are not sufficient to induce HP, they strongly potentiate CD4 + T cell-induced HP‑associated neutrophilic inflammation in the airways. However, the reduction of 85% of lung B cells in mice with a CD19-driven S1P 1 deletion does not dampen HP inflammation, suggesting that lung B cells are not necessary in large numbers to sustain local inflammation. Finally, we found that injecting antibodies targeting B cells after experimental HP was induced does not dampen neutrophilic exacerbation. Yet, injection of antibodies directed against B cells and T cells yielded a potent 76% inhibition of neutrophilic accumulation in the lungs. This inhibition occurred despite partial, sometimes mild, depletion of B cells and T cells subsets., Conclusions: Although B cells are required for maximal inflammation in subacute experimental HP, partial reduction of B cells fails to reduce HP-associated inflammation by itself. However, co-modulation of T cells and B cells yields enhanced inhibition of HP exacerbation caused by an antigenic rechallenge., (© 2022. The Author(s).)

High risk for virus-induced asthma exacerbations in children is associated with an IRF7lo immunophenotype, but the underlying mechanisms are unclear. Here, we applied a Systems Biology approach to an animal model comprising rat strains manifesting high (BN) versus low susceptibility (PVG) to experimental asthma, induced by virus/allergen coexposure, to elucidate the mechanism(s)-of-action of the high-risk asthma immunophenotype. We also investigated potential risk mitigation via pretreatment with the immune training agent OM-85. Virus/allergen coexposure in low-risk PVG rats resulted in rapid and transient airways inflammation alongside IRF7 gene network formation. In contrast, responses in high-risk BN rats were characterized by severe airways eosinophilia and exaggerated proinflammatory responses that failed to resolve, and complete absence of IRF7 gene networks. OM-85 had more profound effects in high-risk BN rats, inducing immune-related gene expression changes in lung at baseline and reducing exaggerated airway inflammatory responses to virus/allergen coexposure. In low-risk PVG rats, OM-85 boosted IRF7 gene networks in the lung but did not alter baseline gene expression or cellular influx. Distinct IRF7-associated asthma risk immunophenotypes have dichotomous responses to virus/allergen coexposure and respond differentially to OM-85 pretreatment. Extrapolating to humans, our findings suggest that the beneficial effects OM-85 pretreatment may preferentially target those in high-risk subgroups., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 de Jong, Lauzon-Joset, Leffler, Serralha, Larcombe, Christophersen, Holt, Strickland and Bosco.)

Objectives: Incomplete maturation of immune regulatory functions at birth is antecedent to the heightened risk for severe respiratory infections during infancy. Our forerunner animal model studies demonstrated that maternal treatment with the microbial-derived immune training agent OM-85 during pregnancy promotes accelerated postnatal maturation of mechanisms that regulate inflammatory processes in the offspring airways. Here, we aimed to provide proof of concept for a novel solution to reduce the burden and potential long-term sequelae of severe early-life respiratory viral infection through maternal oral treatment during pregnancy with OM-85, already in widespread human clinical use., Methods: In this study, we performed flow cytometry and targeted gene expression (RT-qPCR) analysis on lungs from neonatal offspring whose mothers received oral OM-85 treatment during pregnancy. We next determined whether neonatal offspring from OM-85 treated mothers demonstrate enhanced protection against lethal lower respiratory infection with mouse-adapted rhinovirus (vMC 0 ), and associated lung immune changes., Results: Offspring from mothers treated with OM-85 during pregnancy display accelerated postnatal seeding of lung myeloid populations demonstrating upregulation of function-associated markers. Offspring from OM-85 mothers additionally exhibit enhanced expression of TLR4/7 and the IL-1β/NLRP3 inflammasome complex within the lung. These treatment effects were associated with enhanced capacity to clear an otherwise lethal respiratory viral infection during the neonatal period, with concomitant regulation of viral-induced IFN response intensity., Conclusion: These results demonstrate that maternal OM-85 treatment protects offspring against lethal neonatal respiratory viral infection by accelerating development of innate immune mechanisms crucial for maintenance of local immune homeostasis in the face of pathogen challenge., Competing Interests: All authors declare that no competing interests exist., (© 2021 The Authors. Clinical & Translational Immunology published by John Wiley & Sons Australia, Ltd on behalf of Australian and New Zealand Society for Immunology, Inc.)

We recently reported that offspring of mice treated during pregnancy with the microbial-derived immunomodulator OM-85 manifest striking resistance to allergic airways inflammation, and localized the potential treatment target to fetal conventional dendritic cell (cDC) progenitors. Here, we profile maternal OM-85 treatment-associated transcriptomic signatures in fetal bone marrow, and identify a series of immunometabolic pathways which provide essential metabolites for accelerated myelopoiesis. Additionally, the cDC progenitor compartment displayed treatment-associated activation of the XBP1-ERN1 signalling axis which has been shown to be crucial for tissue survival of cDC, particularly within the lungs. Our forerunner studies indicate uniquely rapid turnover of airway mucosal cDCs at baseline, with further large-scale upregulation of population dynamics during aeroallergen and/or pathogen challenge. We suggest that enhanced capacity for XBP1-ERN1-dependent cDC survival within the airway mucosal tissue microenvironment may be a crucial element of OM-85-mediated transplacental innate immune training which results in postnatal resistance to airway inflammatory disease., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2020 Mincham, Jones, Bodinier, Scott, Lauzon-Joset, Stumbles, Bosco, Holt and Strickland.)

The main function of the lung is to perform gas exchange while maintaining lung homeostasis despite environmental pathogenic and non-pathogenic elements contained in inhaled air. Resident cells must keep lung homeostasis and eliminate pathogens by inducing protective immune response and silently remove innocuous particles. Which lung cell type is crucial for this function is still subject to debate, with reports favoring either alveolar macrophages (AMs) or lung epithelial cells (ECs) including airway and alveolar ECs. AMs are the main immune cells in the lung in steady-state and their function is mainly to dampen inflammatory responses. In addition, they phagocytose inhaled particles and apoptotic cells and can initiate and resolve inflammatory responses to pathogens. Although AMs release a plethora of mediators that modulate immune responses, ECs also play an essential role as they are more than just a physical barrier. They produce anti-microbial peptides and can secrete a variety of mediators that can modulate immune responses and AM functions. Furthermore, ECs can maintain AMs in a quiescent state by expressing anti-inflammatory membrane proteins such as CD200. Thus, AMs and ECs are both very important to maintain lung homeostasis and have to coordinate their action to protect the organism against infection. Thus, AMs and lung ECs communicate with each other using different mechanisms including mediators, membrane glycoproteins and their receptors, gap junction channels, and extracellular vesicles. This review will revisit characteristics and functions of AMs and lung ECs as well as different communication mechanisms these cells utilize to maintain lung immune balance and response to pathogens. A better understanding of the cross-talk between AMs and lung ECs may help develop new therapeutic strategies for lung pathogenesis., (Copyright © 2020 Bissonnette, Lauzon-Joset, Debley and Ziegler.)

In a proportion of patients with hypersensitivity pneumonitis, the biological and environmental factors that sustain inflammation are ill defined, resulting in no effective treatment option. Bioaerosols found in occupational settings are complex and often include Toll-like receptor ligands, such as endotoxins. How Toll-like receptor ligands contribute to the persistence of hypersensitivity pneumonitis, however, remains poorly understood. In a previous study, we found that an S1P 1 (sphingosine-1-phosphate receptor 1) agonist prevented the reactivation of antigen-driven B-cell responses in the lung. Here, we assessed the impact of endotoxins on B-cell activation in preexisting hypersensitivity pneumonitis and the role of S1P 1 in this phenomenon. The impact of endotoxins on pre-established hypersensitivity pneumonitis was studied in vivo . S1P 1 levels were tracked on B cells in the course of the disease using S1P 1 -eGFP knockin mice, and the role of S1P 1 on B-cell functions was assessed using pharmacological tools. S1P 1 was found on B cells in experimental hypersensitivity pneumonitis. Endotoxin exposure enhanced neutrophil accumulation in the BAL of mice with experimental hypersensitivity pneumonitis. This was associated with enhanced CD69 cell-surface expression on lymphocytes in the BAL. In isolated B cells, endotoxins increased cell-surface levels of costimulatory molecules and CD69, which was prevented by an S1P 1 agonist. S1P 1 modulators also reduced TNF production by B cells and their capacity to trigger T-cell cooperation ex vivo . An S1P 1 ligand directly inhibited endotoxin-induced B-cell activation.

Nasopharyngeal colonization with nontypeable Haemophilus influenzae (NTHi) is a prerequisite for developing NTHi-associated infections, including otitis media. Therapies that block NTHi colonization may prevent disease development. We previously demonstrated that Haemophilus haemolyticus , a closely related human commensal, can inhibit NTHi colonization and infection of human respiratory epithelium in vitro We have now assessed whether Muribacter muris (a rodent commensal from the same family) can prevent NTHi colonization and disease in vivo using a murine NTHi otitis media model. Otitis media was modeled in BALB/c mice using coinfection with 1 × 10 4.5 PFU of influenza A virus MEM H3N2, followed by intranasal challenge with 5 × 10 7 CFU of NTHi R2866 Spec r Mice were pretreated or not with an intranasal inoculation of 5 × 10 7 CFU M. muris 24 h before coinfection. NTHi and M. muris viable counts and inflammatory mediators (gamma interferon [IFN-γ], interleukin-1β [IL-1β], IL-6, keratinocyte chemoattractant [KC], and IL-10) were measured in nasal washes and middle ear tissue homogenate. M. muris pretreatment decreased the median colonization density of NTHi from 6 × 10 5 CFU/ml to 9 × 10 3 CFU/ml ( P  = 0.0004). Only 1/12 M. muris -pretreated mice developed otitis media on day 5 compared to 8/15 mice with no pretreatment (8% versus 53%, P  = 0.0192). Inflammation, clinical score, and weight loss were also lower in M. muris -pretreated mice. We have demonstrated that a single dose of a closely related commensal can delay onset of NTHi otitis media in vivo Human challenge studies investigating prevention of NTHi colonization are warranted to reduce the global burden of otitis media and other NTHi diseases., (Copyright © 2020 Granland et al.)

Background: The prevalence and severity of asthma, particularly the most common (atopic) form of the disease, increase amongst females but not males after puberty, and asthma activity also changes throughout the menstrual cycle and during pregnancy. The contribution of female sex hormones to asthma pathogenesis is incompletely understood., Objective: To obtain insight into the role of oestrogen (E2) in experimental atopic asthma, and guide future research on sex-related variations in atopic asthma susceptibility/intensity in humans., Methods: We utilized an experimental model comprising rat strains expressing dichotomous Th2-high vs Th2-low immunophenotypes exemplified by eosinophilia, mirroring differences between human atopics/non-atopics. We compared the efficiency of Th2-associated immunoinflammatory mechanisms, which differed markedly between the two strains, and between sexes in the Th2-high strain, and determined the effects of E2 administration on these differences., Results: Unique to the Th2-high strain, eosinophil: neutrophil ratios in the airways at baseline and following sensitization/aeroallergen challenge were logfold higher in females relative to males, and this was reflected by higher baseline blood eosinophil numbers in females. Pretreatment of Th2-high males with E2 abrogated this sex difference by selectively boosting Th2-associated genes in the airways and eosinophilia, but was without corresponding effect in the Th2-low strain. In contrast, parallel E2 effects on myeloid and lymphoid cell populations were relatively modest., Conclusions and Clinical Relevance: E2 acts to amplify the eosinophilic component of pre-existing Th2-high immunophenotype, possibly acting at the level of the common eosinophil/neutrophil precursor in bone marrow to preferentially drive eosinophil differentiation. Constitutive granulocyte profiles in which the balance between eosinophils and neutrophils is skewed towards eosinophils have been identified in independent cohort studies as markers of asthma risk, and these findings suggest that more detailed studies on the role of E2 in this context, and in relation to asthma pathogenesis in post-pubertal females in particular, appear warranted., (© 2019 John Wiley & Sons Ltd.)

Constant exposure to foreign particles in the airways requires tight immune regulation in order to maintain sufficient anti-microbial defences, while preventing immunopathological responses that could impair gas exchange. Dysregulation of immunoregulatory pathways has been associated with asthma and allergy. This review will focus on the CD200 regulatory pathway and its role in the asthmatic cascade. CD200 and its receptors are highly expressed in the lung, on epithelial cells and leukocytes, and emerging evidence links dysregulation of the CD200 pathway with asthma. Moreover, pharmacological modulation of CD200 receptors was shown to improve clinical and inflammatory outcomes of preclinical asthma models. Therefore, the involvement of CD200 in asthma is increasingly recognized and preclinical studies support the contention that it could constitute an additional target to alleviate asthma exacerbation and/or reduce disease severity., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Background: Influenza virus infection during pregnancy is associated with enhanced disease severity. However, the underlying mechanisms are still not fully understood. We hypothesized that normal alveolar macrophage (AM) functions, which are central to maintaining lung immune homeostasis, are altered during pregnancy and that this dysregulation contributes to the increased inflammatory response to influenza virus infection., Methods: Time-mated BALB/c mice were infected with a low dose of H1N1 influenza A virus at gestation day 9.5. Inflammatory cells in bronchoalveolar lavage (BAL) fluid were assessed by flow cytometry., Results: Our findings confirm previous reports of increased severity of influenza virus infection in pregnant mice. The heightened inflammatory response detected in BAL fluid from infected pregnant mice was characterized by neutrophil-rich inflammation with concomitantly reduced numbers of AM, which were slower to return to baseline counts, compared with nonpregnant infected mice. The increased infection severity and inflammatory responses to influenza during pregnancy were associated with a pregnancy-induced shift in AM phenotype at homeostatic baseline, from the M1 (ie, classical activation) state toward the M2 (ie, alternative activation) state, as evidence by increased expression of CD301 and reduced levels of CCR7., Conclusion: These results show that pregnancy is associated with an alternatively activated phenotype of AM before infection, which may contribute to heightened disease severity., (© The Author(s) 2018. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

Murine models of allergic airway disease are frequently used as a tool to elucidate the cellular and molecular mechanisms of tissue-specific asthmatic disease pathogenesis. Paramount to the success of these models is the induction of experimental antigen sensitization, as indicated by the presence of antigen-specific serum immunoglobulin E. The quantification of antigen-specific serum IgE is routinely performed via enzyme-linked immunosorbent assay. However, the reproducibility of these in vitro assays can vary dramatically in our experience. Furthermore, quantifying IgE via in vitro methodologies does not enable the functional relevance of circulating IgE levels to be considered. As a biologically appropriate alternative method, we describe herein a highly reproducible in vivo passive cutaneous anaphylaxis assay using Sprague Dawley rats for the quantification of ovalbumin-specific IgE in serum samples from ovalbumin-sensitized murine models. Briefly, this in vivo assay involves subcutaneous injections of serum samples on the back of a Sprague Dawley rat, followed 24 h later by intravenous injection of ovalbumin and a blue detection dye. The subsequent result of antigen-IgE mediated inflammation and leakage of blue dye into the initial injection site indicates the presence of ovalbumin-specific IgE within the corresponding serum sample., Competing Interests: Competing interestsThe authors declare no financial or non-financial competing interests related to this work., (Copyright © 2019 The Authors; exclusive licensee Bio-protocol LLC.)

The early life period represents a time of immunological plasticity whereby the functionally immature immune system is highly susceptible to environmental stimulation. Perennial aeroallergen and respiratory viral infection induced sporadic episodes of lung inflammation during this temporal window represent major risk factors for initiation of allergic asthmatic disease. Murine models are widely used as an investigative tool to examine the pathophysiology of allergic asthma; however, models in current usage typically do not encapsulate the early life period which represents the time of maximal risk for disease inception in humans. To address this issue, this protocol adapted an experimental animal model of disease for sensitization to ovalbumin during the immediate post-weaning period beginning at 21 days of age. By initially sensitizing mice during this early life post-weaning period, researchers can more closely align experimental allergic airway disease models with the human age group most at risk for asthma development., Competing Interests: Competing interestsThe authors declare no financial or non-financial competing interests related to this work., (Copyright © 2019 The Authors; exclusive licensee Bio-protocol LLC.)

Chronic allergic inflammatory diseases are a major cause of morbidity, with allergic asthma alone affecting over 300 million people worldwide. Epidemiological studies demonstrate that environmental stimuli are associated with either the promotion or prevention of disease. Major reductions in asthma prevalence are documented in European and US farming communities. Protection is associated with exposure of mothers during pregnancy to microbial breakdown products present in farm dusts and unprocessed foods and enhancement of innate immune competence in the children. We sought to develop a scientific rationale for progressing these findings toward clinical application for primary disease prevention. Treatment of pregnant mice with a defined, clinically approved immune modulator was shown to markedly reduce susceptibility of their offspring to development of the hallmark clinical features of allergic airway inflammatory disease. Mechanistically, offspring displayed enhanced dendritic cell-dependent airway mucosal immune surveillance function, which resulted in more efficient generation of mucosal-homing regulatory T cells in response to local inflammatory challenge. We provide evidence that the principal target for maternal treatment effects was the fetal dendritic cell progenitor compartment, equipping the offspring for accelerated functional maturation of the airway mucosal dendritic cell network following birth. These data provide proof of concept supporting the rationale for developing transplacental immune reprogramming approaches for primary disease prevention.

Allergic (Th2 high immunophenotype) asthmatics have a heightened susceptibility to common respiratory viral infections such as human rhinovirus. Evidence suggests that the innate interferon response is deficient in asthmatic/atopic individuals, while other studies show no differences in antiviral response pathways. Unsensitized and OVA-sensitized/challenged Th2 high (BN rats) and Th2 low immunophenotype (PVG rats) animals were inoculated intranasally with attenuated mengovirus (vMC 0 ). Sensitized animals were exposed/unexposed during the acute viral response phase. Cellular and transcriptomic profiling was performed on bronchoalveolar lavage cells. In unsensitized PVG rats, vMC 0 elicits a prototypical antiviral response (neutrophilic airways inflammation, upregulation of Th1/type I interferon-related pathways). In contrast, response to infection in the Th2 high BN rats was associated with a radically altered intrinsic host response to respiratory viral infection, characterized by macrophage influx/Th2-associated pathways. In sensitized animals, response to virus infection alone was not altered compared to unsensitized animals. However, allergen exposure of sensitized animals during viral infection unleashes a notably exaggerated airways inflammatory response profile orders of magnitude higher in BN versus PVG rats despite similar viral loads. The co-exposure responses in the Th2 high BN incorporated type I interferon/Th1, alternative macrophage activation/Th2 and Th17 signatures. Similar factors may underlie the hyper-susceptibility to infection-associated airways inflammation characteristic of the human Th2 high immunophenotype.

Infection-associated inflammatory stress during pregnancy is the most common cause of fetal growth restriction and/or miscarriage. Treatment strategies for protection of at-risk mothers are limited to a narrow range of vaccines, which do not cover the bulk of the common pathogens most frequently encountered. Using mouse models, we demonstrate that oral treatment during pregnancy with a microbial-derived immunomodulator (OM85), currently used clinically for attenuation of infection-associated airway inflammatory symptoms in infants-adults, markedly reduces risk for fetal loss/growth restriction resulting from maternal challenge with bacterial lipopolysaccharide or influenza. Focusing on LPS exposure, we demonstrate that the key molecular indices of maternal inflammatory stress, notably high levels of RANTES, MIP-1α, CCL2, KC, and G-CSF (granulocyte colony-stimulating factor) in gestational tissues/serum, are abrogated by OM85 pretreatment. Systems-level analyses conducted in parallel using RNASeq revealed that OM85 pretreatment selectively tunes LPS-induced activation in maternal gestational tissues for attenuated expression of TNF, IL1, and IFNG-driven proinflammatory networks, without constraining Type1-IFN-associated networks central to first-line antimicrobial defense. This study suggests that broad-spectrum protection-of-pregnancy against infection-associated inflammatory stress, without compromising capacity for efficient pathogen eradication, represents an achievable therapeutic goal.

In allergic asthma, homeostatic pathways are dysregulated, which leads to an immune response toward normally innocuous antigens. The CD200-CD200 receptor pathway is a central regulator of inflammation, and CD200 expression was recently found to be down-regulated in circulating leukocytes of patients with asthma. Given the antiinflammatory properties of CD200, we investigated whether local delivery of recombinant CD200 (rCD200) could reinstate lung homeostasis in an experimental model of asthma. Brown Norway rats were sensitized with ovalbumin (OVA) and alum. rCD200 was intratracheally administered 24 hours before OVA challenge, and airway responsiveness to methacholine was measured 24 hours after the allergen challenge. Inflammation was also assessed by measuring cell recruitment and cytokine levels in bronchoalveolar lavages, as well as lung and draining lymph node accumulation of dendritic cells (DCs) and T cells. In sensitized rats, rCD200 abolished airway hyperresponsiveness, whereas the sham treatment had no effect. In addition, rCD200 strongly reduced OVA-induced lung accumulation of myeloid DCs, CD4(+) T cells, and T helper type 2 cells. This was associated with a strong reduction of OVA-induced IL-13 level and with an increase of IL-10 in supernatants of bronchoalveolar lavages. Lung eosinophilia and draining lymph node accumulation of myeloid DCs and T cells were not affected by rCD200. Overall, these data reveal that rCD200 can inhibit airway hyperresponsiveness in a model of asthma by a multistep mechanism associated with local alterations of the T cell response and the cytokine milieu.

Allergic asthma is a chronic inflammatory disorder characterized by eosinophilia and T helper type 2 (Th2) cell activation. However, little information is available on the mechanisms leading to this pathology. We previously showed that alveolar macrophages (AM) from rats with experimental asthma lose their ability to prevent asthma symptoms. To understand the implication of AM in lung immunity, we investigated the influence of AM sensitization status on lung dendritic cell (DC) activation induced by allergen challenge in vivo. Rat sensitized to ovalbumin developed airway inflammation (eosinophils and Th2 cells) and demonstrated myeloid DC (mDC) activation following allergen exposure. The replacement of AM of sensitized animals by AM from naive animals did not affect allergen-triggered eosinophilia but completely abolished lung mDC allergen capture and migration to the lymph nodes, as well as Th2 cell polarization. Moreover, immunosuppressive functions of naive AM occurred in conjunction with low engulfment of allergens but without variation of major histocompatibility complex II and CD23 expression. Interestingly, sensitized AM that were withdrawn from the inflammatory environment regained their immunosuppressive functions when transferred to sensitized rats. Thus, these are the first in vivo evidences showing that dysregulation of AM functions is sufficient to induce DC-triggered allergic response.

Background: Pulmonary arterial hypertension (PAH) is a vasculopathy characterized by enhanced pulmonary artery smooth muscle cell (PASMC) proliferation and suppressed apoptosis. This results in both increase in pulmonary arterial pressure and pulmonary vascular resistance. Recent studies have shown the implication of the signal transducer and activator of transcription 3 (STAT3)/bone morphogenetic protein receptor 2 (BMPR2)/peroxisome proliferator-activated receptor gamma (PPARγ) in PAH. STAT3 activation induces BMPR2 downregulation, decreasing PPARγ, which both contribute to the proproliferative and antiapoptotic phenotype seen in PAH. In chondrocytes, activation of this axis has been attributed to the advanced glycation end-products receptor (RAGE). As RAGE is one of the most upregulated proteins in PAH patients' lungs and a strong STAT3 activator, we hypothesized that by activating STAT3, RAGE induces BMPR2 and PPARγ downregulation, promoting PAH-PASMC proliferation and resistance to apoptosis., Methods and Results: In vitro, using PASMCs isolated from PAH and healthy patients, we demonstrated that RAGE is overexpressed in PAH-PASMC (6-fold increase), thus inducing STAT3 activation (from 10% to 40% positive cells) and decrease in BMPR2 and PPARγ levels (>50% decrease). Pharmacological activation of RAGE in control cells by S100A4 recapitulates the PAH phenotype (increasing RAGE by 6-fold, thus activating STAT3 and decreasing BMPR2 and PPARγ). In both conditions, this phenotype is totally reversed on RAGE inhibition. In vivo, RAGE inhibition in monocrotaline- and Sugen-induced PAH demonstrates therapeutic effects characterized by PA pressure and right ventricular hypertrophy decrease (control rats have an mPAP around 15 mm Hg, PAH rats have an mPAP >40 mm Hg, and with RAGE inhibition, mPAP decreases to 20 and 28 mm Hg, respectively, in MCT and Sugen models). This was associated with significant improvement in lung perfusion and vascular remodeling due to decrease in proliferation (>50% decrease) and BMPR2/PPARγ axis restoration (increased by ≥60%)., Conclusion: We have demonstrated the implications of RAGE in PAH etiology. Thus, RAGE constitutes a new attractive therapeutic target for PAH.

The authors have recently demonstrated that alveolar macrophages (AMs) are important in protecting against early phase reactions and airway hyperresponsiveness following allergen challenge. To further understand the mechanisms involved, the authors investigated the capacity of AMs to modulate airway inflammation and cytokine levels in bronchoalveolar lavage (BAL). AMs from allergy-susceptible Brown Norway (BN) rats or allergy-resistant Sprague-Dawley (SD) rats were transferred into AM-depleted BN rats 24 hours prior to allergen challenge. Methacholine-induced airway hyperresponsiveness was examined 24 hours following ovalbumin challenge. Total cells, cell types, and cytokine levels (tumor necrosis factor [TNF], interleukin [IL]-4, IL-10, IL-12 and IL-13) in BAL were measured 24 hours after allergen challenge. The transfer of AMs from SD rats into AM-depleted BN rats 24 hours before allergen challenge eliminated methacholine-induced airway hyperresponsiveness, but did not modify the number and the type of inflammatory cells in BAL. Levels of IL-13 and TNF were significantly higher in BAL of BN rats compared with SD rats. Interestingly, IL-13 and TNF levels were significantly increased and inhibited, respectively, in BN rats that received AMs from SD rats compared with BN rats. Our data suggest that AM modulation of cytokine milieu is involved in the reduction of airway hyperresponsiveness.

Busulfan (BU) is a key compound in conditioning myeloablative regimens for children undergoing hematopoietic stem cell transplantation (HSCT). There are wide interindividual differences in BU pharmacokinetics, which increase the risk of veno-occlusive disease, graft rejection and disease relapse. As BU is mainly metabolized by glutathione S-transferase (GST), it is hypothesized that functional polymorphisms in GST genes may explain in part the variability in BU pharmacokinetics. We analyzed polymorphisms in GSTA1 (C-69T, A-513G, G-631T, C-1142G), GSTM1 (deletion) and GSTP1 (A1578G, C2293T) genes in 28 children undergoing HSCT. All patients had individualized dosing based on pharmacokinetics after the first dose of intravenous BU. GSTM1-null individuals had higher drug exposure (P(Cmax)=0.008; P(AUC)=0.003; P(Css)=0.02) and lower clearance (P(CL)=0.001). Multivariate regression models showed that, other than the drug dose and age, the GSTM1 genotype was the best predictor of first-dose pharmacokinetic variability. GSTM1-null patients also received lower cumulative BU doses (P=0.02). No association was found between BU exposure and major GSTA1 or GSTP1 gene variants. In children, GSTM1 polymorphism seems to modify BU pharmacokinetics after intravenous drug administration.