1,720,960 research outputs found
The responses of conventional T cells and mucosal-associated invariant T cells to nontypeable Haemophilus Influenzae infection
No full textNontypeable Haemophilus influenzae (NTHi) is a component of the normal lung microbiome, but is also highly associated with respiratory tract infections and exacerbations of major chronic respiratory diseases such as chronic obstructive pulmonary disease (COPD). It is not known how commensal bacteria can become pathogenic and cause inflammation in the lung, but is likely due to a breakdown in local immunity. T cell immunity may be key to controlling NTHi infection, although the responses of T cells to NTHi are not well understood. Mucosal-associated invariant T (MAIT) cells are a newly-discovered subset of innate-like T cells, which may play a role in controlling NTHi, as they recognise non-peptide antigens derived from the highly conserved vitamin B2 pathway. The role of MAIT cells in lung immunity to NTHi is also unclear.The aim of this thesis was to study the cytokine and cytotoxic responses of MAIT cells to NTHi infection, comparing these responses to those of conventional T cells. The antigen presentation and co-stimulatory mechanisms that regulate MAIT cell activation have also been explored.Conventional T cell and MAIT cell responses to NTHi were investigated using a human ex vivo lung tissue explant model and an autologous monocyte-derived macrophage (MDM)-T cell co-culture model. Cytokine and cytotoxic responses were measured by a combination of flow cytometry, ELISA and ELISpot. Blocking antibodies were used to determine the role of antigen presentation and cytokine signalling in conventional T cell and MAIT cell activation. Lung MAIT cells significantly upregulated the cytokines; IFNγ, IL-17a and TNFα, and the cytotoxic markers; granzyme B and CD107a, following NTHi infection. A greater proportion of MAIT cells were active compared to conventional T cells. In the blood-derived MDM-T cell co-culture, IFNγ expression by MAIT cells was dependent on MR1 antigen presentation and IL-12 signalling in a time-dependent manner. Cytotoxic responses were regulated by MR1 but also by a novel mechanism where IL-12 and IL-7 signalling synergised to induce granzyme B expression by upregulation of the IL-12 receptor. In contrast, conventional T cell responses predominantly relied on antigen presentation for activation. MAIT cell responses were also impaired by treatment with corticosteroids, which are commonly used to manage inflammation in chronic lung diseases, but are associated with a higher risk of developing pneumonia in COPD patients.Overall, the data in this thesis provide evidence for a role for MAIT cells in controlling NTHi infection in the lung and also highlight key differences in the regulation of innate and adaptive T cells. A further understanding of the mechanism underpinning T cell responses to NTHi infection may yield new therapeutic opportunities and improve the outcome for patients with respiratory diseases
The response of macrophages to Moraxella catarrhalis infection
No full textInfection by certain bacterial species can predispose an individual to developing asthma and trigger asthmatic exacerbations. Moraxella catarrhalis is one such organism, yet there is little data on the innate immune responses to this pathogen. Alveolar macrophages are the predominant immune cell isolated from the airway and show phenotypic differences in health and asthma. Macrophages are crucial in the immune response by pathogen recognition receptor (PRR)mediated detection of organisms, release of pro-inflammatory mediators and presentation of antigens to other cells of the immune system to link the innate and adaptive immune response. The aim of this work was to investigate the response of macrophages to M.catarrhalis. Monocyte-derived macrophages (MDM) were exposed to M.catarrhalis for 2h, incubated with antiobiotics for 22h before analysis at 24h. The expression of PRRs were analysed by real time PCR. A significant increase of retinoic acid-inducible gene(RIG)I expression(p<0.0001) was found; however, IFN-β was not detected. Conversely, expression of toll-like receptor (TLR)4 decreased(p=0.0003). Despite this, the release of IL-1β and IL-8 was detected in a dose-dependent manner by ELISA(p<0.0001). The surface expression of antigen presentation molecules were analysed by flow cytometry and showed an upregulation of major histocompatibility complex (MHC)-II(p=0.002) and MR1(p=0.0015), but only a slight upregulation of MHC-I(p=0.0728). This work suggests that MDM respond to M.catarrhalis and act to induce further immune cell effector actions. Understanding the MDM response to M.catarrhalis will allow for future comparisons to determine differences between the phenotypically distinctive macrophages in health and asthma
IL-12 and IL-7 synergise to control MAIT cell cytotoxic responses to bacterial infection
No full textBackgroundBacterial respiratory tract infections and exacerbations of chronic lung diseases are commonly caused by nontypeable Haemophilus influenzae (NTHi). Cell-mediated cytotoxicity may be key to controlling infection, but the responses of NTHi-specific T cell populations are not well understood. Mucosal-associated invariant T (MAIT) cells are a recently-discovered, innate-like subset of T cells with cytotoxic function, whose role in lung immunity is unclear. ObjectiveThe aim of this study was to determine the mechanisms behind conventional T and MAIT cell cytotoxic responses to NTHi. MethodsHuman ex vivo lung explants were infected with a clinical strain of NTHi. Monocyte-derived macrophages were also infected with NTHi in vitro and co-cultured with autologous T cells. Cytotoxic responses of T cell subsets were measured by flow cytometry. ResultsWe found significant upregulation of the cytotoxic markers, CD107a and granzyme B, in lung CD4+, CD8+ and MAIT cell populations. We show that MAIT cell cytotoxic responses were upregulated by a combination of both time-dependent antigen presentation and through a novel mechanism by which IL-12 and IL-7 synergistically control granzyme B through upregulation of the IL-12 receptor. ConclusionsOverall our data provide evidence for a cytotoxic role of MAIT cells in the lung and highlight important differences in the control of adaptive and innate-like T cell responses. Understanding these mechanisms may lead to new therapeutic opportunities to modulate the anti-bacterial response and improve clinical outcome. <br/
Steroid-induced deficiency of mucosal-associated invariant T cells in the chronic Obstructive Pulmonary Disease lung: Implications for Nontypeable <i>Haemophilus influenzae</i> Infection
Full text linkRationale: Mucosal associated invariant T (MAIT) cells are a recently-described, abundant, pro-inflammatory T cell subset with unknown roles in pulmonary immunity. Non-typeable Haemophilus influenzae (NTHi) is the leading bacterial pathogen during COPD exacerbations and a plausible target for MAIT cells.Objectives: To investigate whether MAIT cells respond to NTHi and the effects of inhaled corticosteroids on their frequency and function in COPD. Methods: 11 participants with COPD receiving inhaled corticosteroids (ICS), 8 with steroid-naïve COPD and 21 healthy controls underwent phlebotomy, sputum induction, bronchoalveolar-lavage and endobronchial biopsy. Pulmonary and monocyte-derived macrophages were cultured in vitro with NTHi. Measurements: Frequencies of Va7.2+CD161+ MAIT cells, surface expression of MHC-related protein 1 (MR1) and intracellular IFN-y expression were measured by flow cytometry.Main Results: MAIT cell frequencies were reduced in peripheral blood in ICS-treated COPD (median 0.38% (IQR, 0.25-0.96) compared with health (1.8% (IQR, 1.4-2.5), P=0.001)) or steroid-naïve COPD (1.8% (1.2-2.3), P=0.04). MAIT cells were reduced in bronchial biopsies in steroid-treated COPD (0.73% (0.46-1.3)) compared with health (4.0% (1.6-5.0), P=0.02). Co-culture of live NTHi increased macrophage surface expression of MR1 and induced IFN-? from CD4 cells and CD8 cells, but most potently from MAIT cells (median IFN-y positive frequencies 2.9%, 8.6% and 27.6% respectively). In vitro fluticasone and budesonide reduced MR1 surface expression 2-fold and decreased NTHi-induced IFN-y secretion 8-fold.Conclusions: MAIT cells are deficient in blood and bronchial tissue in steroid-treated, but not steroid-naïve COPD. NTHi constitutes a target for pulmonary MAIT cell immune responses, which are significantly impaired by corticosteroids.<br/
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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