| 1. |
- Baharom, Faezzah, et al.
(författare)
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Dendritic Cells and Monocytes with Distinct Inflammatory Responses Reside in Lung Mucosa of Healthy Humans
- 2016
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 196:11, s. 4498-4509
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Tidskriftsartikel (refereegranskat)abstract
- Every breath we take contains potentially harmful pathogens or allergens. Dendritic cells (DCs), monocytes, and macrophages are essential in maintaining a delicate balance of initiating immunity without causing collateral damage to the lungs because of an exaggerated inflammatory response. To document the diversity of lung mononuclear phagocytes at steady-state, we performed bronchoscopies on 20 healthy subjects, sampling the proximal and distal airways (bronchial wash and bronchoalveolar lavage, respectively), as well as mucosal tissue (endobronchial biopsies). In addition to a substantial population of alveolar macrophages, we identified subpopulations of monocytes, myeloid DCs (MDCs), and plasmacytoid DCs in the lung mucosa. Intermediate monocytes and MDCs were highly frequent in the airways compared with peripheral blood. Strikingly, the density of mononuclear phagocytes increased upon descending the airways. Monocytes from blood and airways produced 10-fold more proinflammatory cytokines than MDCs upon ex vivo stimulation. However, airway monocytes were less inflammatory than blood monocytes, suggesting a more tolerant nature. The findings of this study establish how to identify human lung mononuclear phagocytes and how they function in normal conditions, so that dysregulations in patients with respiratory diseases can be detected to elucidate their contribution to immunity or pathogenesis.
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| 2. |
- Baharom, Faezzah
(författare)
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Human dendritic cells in blood and airways during respiratory viral infection
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The air we inhale contains oxygen necessary for life, but also potentially harmful microorganisms, toxins and allergens. This presents an important immunological dilemma: how can our lungs quickly and selectively eliminate harmful agents without inflicting damage on the delicate tissues of the lungs? We have thus evolved a network of cells involved in immune surveillance, made up of dendritic cells (DCs), monocytes and macrophages. Together, these mononuclear phagocytes sample the lungs and airways for presence of foreign pathogens such as viruses or bacteria. Recognition of pathogenic patterns – for instance the genetic material of viruses or the lipid membrane of bacteria – triggers a cascade of events in these immune cells. They produce inflammatory mediators to signal that a source of danger has been detected, and to contain the infection while awaiting the arrival of other immune cells. DCs migrate to lymphoid organs where they present antigens to naïve T cells, thus shaping the generation of protective and adaptive immunity. Much of what we know of how our immune system functions come from studies in murine models. In this thesis, we focus our attention on human DCs. Using super resolution microscopy, we assessed the early trafficking events that take place upon internalisation of influenza A virus (IAV) by human DCs. We report that IAV trafficked via early and late endosomes in DCs, similar to epithelial cells, but with more delayed kinetics. Next, we investigated whether maturation of monocyte-derived versus bona fide DCs affects their susceptibility to IAV infection. Indeed, the two subsets of DCs are inherently different in their ability to respond to pathogenic signals by producing antiviral mediators, which protect them from IAV infection. The accessibility of human blood has improved our understanding of human DCs. However, immune cells residing at mucosal barriers are our first line of defence against respiratory viruses. Increasing data suggest that there is tissue-specific regulation of immune cells due to factors present in the local microenvironment. Hence, we performed bronchoscopies on healthy subjects and hantavirus-infected patients to characterise DCs residing in the airways and bronchial mucosal tissue. We identified several subsets of respiratory DCs at steady state, alongside alveolar macrophages and monocyte-derived cells. During acute hantavirus disease, DCs and monocytes were depleted from circulation, whereas the lungs were infiltrated with monocytes and DCs. Collectively, our findings reveal the heterogeneity of human DCs in their response to respiratory viruses, depending on their origin and anatomical location. A deeper understanding of the complex interplay between respiratory viruses and human DCs reveals how DCs contribute to immunity or pathogenesis. This knowledge may help us develop better preventive and therapeutic strategies by targeting or modulating DCs to achieve favourable immune responses.
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| 3. |
- Baharom, Faezzah, et al.
(författare)
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Human lung dendritic cells : spatial distribution and phenotypic identification in endobronchial biopsies using immunohistochemistry and flow cytometry
- 2017
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Ingår i: Journal of Visualized Experiments. - Cambridge : MyJoVE Corp.. - 1940-087X. ; :119
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Tidskriftsartikel (refereegranskat)abstract
- The lungs are constantly exposed to the external environment, which in addition to harmless particles, also contains pathogens, allergens, and toxins. In order to maintain tolerance or to induce an immune response, the immune system must appropriately handle inhaled antigens. Lung dendritic cells (DCs) are essential in maintaining a delicate balance to initiate immunity when required without causing collateral damage to the lungs due to an exaggerated inflammatory response. While there is a detailed understanding of the phenotype and function of immune cells such as DCs in human blood, the knowledge of these cells in less accessible tissues, such as the lungs, is much more limited, since studies of human lung tissue samples, especially from healthy individuals, are scarce. This work presents a strategy to generate detailed spatial and phenotypic characterization of lung tissue resident DCs in healthy humans that undergo a bronchoscopy for the sampling of endobronchial biopsies. Several small biopsies can be collected from each individual and can be subsequently embedded for ultrafine sectioning or enzymatically digested for advanced flow cytometric analysis. The outlined protocols have been optimized to yield maximum information from small tissue samples that, under steady-state conditions, contain only a low frequency of DCs. While the present work focuses on DCs, the methods described can directly be expanded to include other (immune) cells of interest found in mucosal lung tissue. Furthermore, the protocols are also directly applicable to samples obtained from patients suffering from pulmonary diseases where bronchoscopy is part of establishing the diagnosis, such as chronic obstructive pulmonary disease (COPD), sarcoidosis, or lung cancer.
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| 4. |
- Baharom, Faezzah, et al.
(författare)
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Human Lung Mononuclear Phagocytes in Health and Disease
- 2017
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Ingår i: Frontiers in Immunology. - : FRONTIERS MEDIA SA. - 1664-3224. ; 8
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Forskningsöversikt (refereegranskat)abstract
- The lungs are vulnerable to attack by respiratory insults such as toxins, allergens, and pathogens, given their continuous exposure to the air we breathe. Our immune system has evolved to provide protection against an array of potential threats without causing collateral damage to the lung tissue. In order to swiftly detect invading pathogens, monocytes, macrophages, and dendritic cells (DCs)-together termed mononuclear phagocytes (MNPs)-line the respiratory tract with the key task of surveying the lung microenvironment in order to discriminate between harmless and harmful antigens and initiate immune responses when necessary. Each cell type excels at specific tasks: monocytes produce large amounts of cytokines, macrophages are highly phagocytic, whereas DCs excel at activating naive T cells. Extensive studies in murine models have established a division of labor between the different populations of MNPs at steady state and during infection or inflammation. However, a translation of important findings in mice is only beginning to be explored in humans, given the challenge of working with rare cells in inaccessible human tissues. Important progress has been made in recent years on the phenotype and function of human lung MNPs. In addition to a substantial population of alveolar macrophages, three subsets of DCs have been identified in the human airways at steady state. More recently, monocyte-derived cells have also been described in healthy human lungs. Depending on the source of samples, such as lung tissue resections or bronchoalveolar lavage, the specific subsets of MNPs recovered may differ. This review provides an update on existing studies investigating human respiratory MNP populations during health and disease. Often, inflammatory MNPs are found to accumulate in the lungs of patients with pulmonary conditions. In respiratory infections or inflammatory diseases, this may contribute to disease severity, but in cancer patients this may improve clinical outcomes. By expanding on this knowledge, specific lung MNPs may be targeted or modulated in order to attain favorable responses that can improve preventive or treatment strategies against respiratory infections, lung cancer, or lung inflammatory diseases.
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| 5. |
- Lepzien, Rico, et al.
(författare)
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Monocytes in sarcoidosis are potent tumour necrosis factor producers and predict disease outcome
- 2021
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Ingår i: European Respiratory Journal. - : European Respiratory Society (ERS). - 0903-1936 .- 1399-3003. ; 58:1
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Tidskriftsartikel (refereegranskat)abstract
- Background Pulmonary sarcoidosis is an inflammatory disease characterised by granuloma formation and heterogeneous clinical outcome. Tumour necrosis factor (TNF) is a pro-inflammatory cytokine contributing to granuloma formation and high levels of TNF have been shown to associate with progressive disease. Mononuclear phagocytes (MNPs) are potent producers of TNF and highly responsive to inflammation. In sarcoidosis, alveolar macrophages have been well studied. However, MNPs also include monocytes/monocyte-derived cells and dendritic cells, which are poorly studied in sarcoidosis, despite their central role in inflammation.Objective To determine the role of pulmonary monocyte-derived cells and dendritic cells during sarcoidosis.Methods We performed in-depth phenotypic, functional and transcriptomic analysis of MNP subsets from blood and bronchoalveolar lavage (BAL) fluid from 108 sarcoidosis patients and 30 healthy controls. We followed the clinical development of patients and assessed how the repertoire and function of MNP subsets at diagnosis correlated with 2-year disease outcome.Results Monocytes/monocyte-derived cells were increased in blood and BAL of sarcoidosis patients compared to healthy controls. Interestingly, high frequencies of blood intermediate monocytes at time of diagnosis associated with chronic disease development. RNA sequencing analysis showed highly inflammatory MNPs in BAL of sarcoidosis patients. Furthermore, frequencies of BAL monocytes/ monocyte-derived cells producing TNF without exogenous stimulation at time of diagnosis increased in patients that were followed longitudinally. In contrast to alveolar macrophages, the frequency of TNFproducing BAL monocytes/monocyte-derived cells at time of diagnosis was highest in sarcoidosis patients that developed progressive disease.Conclusion Our data show that pulmonary monocytes/monocyte-derived cells are highly inflammatory and can be used as a predictor of disease outcome in sarcoidosis patients.
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| 6. |
- Scholz, Saskia, et al.
(författare)
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Human hantavirus infection elicits pronounced redistribution of mononuclear phagocytes in peripheral blood and airways
- 2017
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Ingår i: PLoS Pathogens. - : Public library science. - 1553-7366 .- 1553-7374. ; 13:6
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Tidskriftsartikel (refereegranskat)abstract
- Hantaviruses infect humans via inhalation of virus-contaminated rodent excreta. Infection can cause severe disease with up to 40% mortality depending on the viral strain. The virus primarily targets the vascular endothelium without direct cytopathic effects. Instead, exaggerated immune responses may inadvertently contribute to disease development. Mononuclear phagocytes (MNPs), including monocytes and dendritic cells (DCs), orchestrate the adaptive immune responses. Since hantaviruses are transmitted via inhalation, studying immunological events in the airways is of importance to understand the processes leading to immunopathogenesis. Here, we studied 17 patients infected with Puumala virus that causes a mild form of hemorrhagic fever with renal syndrome (HFRS). Bronchial biopsies as well as longitudinal blood draws were obtained from the patients. During the acute stage of disease, a significant influx of MNPs expressing HLA-DR, CD11c or CD123 was detected in the patients' bronchial tissue. In parallel, absolute numbers of MNPs were dramatically reduced in peripheral blood, coinciding with viremia. Expression of CCR7 on the remaining MNPs in blood suggested migration to peripheral and/or lymphoid tissues. Numbers of MNPs in blood subsequently normalized during the convalescent phase of the disease when viral RNA was no longer detectable in plasma. Finally, we exposed blood MNPs in vitro to Puumala virus, and demonstrated an induction of CCR7 expression on MNPs. In conclusion, the present study shows a marked redistribution of blood MNPs to the airways during acute hantavirus disease, a process that may underlie the local immune activation and contribute to immunopathogenesis in hantavirus-infected patients.
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| 7. |
- Vangeti, Sindhu, et al.
(författare)
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Human Blood and Tonsil Plasmacytoid Dendritic Cells Display Similar Gene Expression Profiles but Exhibit Differential Type I IFN Responses to Influenza A Virus Infection
- 2019
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Ingår i: Journal of Immunology. - : AMER ASSOC IMMUNOLOGISTS. - 0022-1767 .- 1550-6606. ; 202:7, s. 2069-2081
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Tidskriftsartikel (refereegranskat)abstract
- Influenza A virus (IAV) infection constitutes an annual health burden across the globe. Plasmacytoid dendritic cells (PDCs) are central in antiviral defense because of their superior capacity to produce type I IFNs in response to viruses. Dendritic cells (DCs) differ depending on their anatomical location. However, only limited host-pathogen data are available from the initial site of infection in humans. In this study, we investigated how human tonsil PDCs, likely exposed to virus because of their location, responded to IAV infection compared with peripheral blood PDCs. In tonsils, unlike in blood, PDCs are the most frequent DC subset. Both tonsil and blood PDCs expressed several genes necessary for pathogen recognition and immune response, generally in a similar pattern. MxA, a protein that renders cells resistant to IAV infection, was detected in both tonsil and blood PDCs. However, despite steady-state MxA expression and contrary to previous reports, at high IAV concentrations (typically cytopathic to other immune cells), both tonsil and blood PDCs supported IAV infection. IAV exposure resulted in PDC maturation by upregulation of CD86 expression and IFN-alpha secretion. Interestingly, blood PDCs secreted 10-fold more IFN-alpha in response to IAV compared with tonsil PDCs. Tonsil PDCs also had a dampened cytokine response to purified TLR ligands compared with blood PDCs. Our findings suggest that tonsil PDCs may be less responsive to IAV than blood PDCs, highlighting the importance of studying immune cells at their proposed site of function.
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