1,721,058 research outputs found
Some studies on human alpha-beta+ and gamma-delta+ T lymphocytes in health and disease
No full textT Iymphocytes use the T cell receptor (TCR) to specifically recognize antigens. According to the type of TCR heterodimer, T cells can be phenotypically divided into alpha-beta+ or gamma-delta+ subsets. In many human inflammatory/autoimmune diseases significant expansions of ab+ and gd+ T cells have been described. Interestingly, in most of these diseases several microorganisms (including mycobacteria) are suspected as causative agents. In this thesis quantitative and qualitative studies of human T Iymphocytes, with particular interest in TCR V usage, were performed. Initially, the frequency and distribution of TCR ab+ and gd+ T Iymphocytes in healthy humans were studied. The existence of a site-specific TCR VB distribution pattern, different from that of peripheral blood, was demonstrated in the healthy human gut. Significantly higher gd+ T cell levels in peripheral blood were detected in the Asian and Turkish groups as compared to Swedish and Japanese groups. These results suggest a possible influence of environmental antigenic exposure in the form of infections on the distribution and frequency of ab+ and/or gd+ T cells among healthy adults. Behcet's disease (BD) is a chronic multisystemic inflammatory disorder with unknown etiology. Most of the immunological studies suggest a central role for T cells in the pathogenesis of BD. In our study, significant oligoclonal expansions of peripheral blood T cells were recorded in BD patients. All ab+CD4+ T cell expansions correlated with disease activity. The observed restricted V and J gene usages in the T cell expansions are consistent with a response to a conventional antigen and suggest a possible involvement of antigen-specific T Iymphocytes in the pathogenesis of BD. To investigate the interactions between T-cells and an infectious agent, we then explored, by use of an in vifro infection model, the proliferative response of human peripheral blood T cells from healthy adults upon stimulation with mycobacteria. Cell proliferation was evaluated by a novel flow cytometric technique which allows direct identification of phenotype of the proliferating cells within complex cell populations. In response to various mycobacterial antigen preparations, proliferation of distinct (T) cell subsets (gd+, ab+CD8+, ab+CD4+, NK cells) was recorded. In order to explore if the T cell proliferation was associated with particular TCR V usage we subsequently analysed TCR Va/VB expression upon in vitro stimulation with M tuberculosis. Expansion of CD4+Va2.3+ T cells with preference to short CDR3-lengths was recorded in HLA-DR17(3)+ healthy individuals. Interestingly, Va2.3+ T cell expansions in broncho-alveolar lavage fluid from HLA-DR17(3)+ sarcoidosis patients have been reported. Such similarity in expanded T cell populations might suggest a mycobacterial involvement in the pathogenesis of sarcoidosis. The present findings are discussed in the context of infectious organisms playing a significant role in the regulation and restriction of human TCR repertoire in health and autoimmune diseases
Flow cytometry based proliferation assay: In vivo and in vitro identification of proliferating cell populations
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Interaction between innate immune cell receptors and Mycobacterium tuberculosis.
No full textIntroduction: Tuberculosis is still a leading cause of bacterial infection worldwide, with an estimate of over two billion people latently infected with Mycobacterium tuberculosis (MTB). A delicate interplay between MTB and the host’s innate and acquired immune system can influence the outcome of the infection, which ranges from pathogen elimination to the establishment of a latent infection or a progressive disease. Although the host cell-mediated adaptive immune response is of vital importance in the control of MTB infection, growing evidence indicates innate immunity as an important arm of antimycobacterial host defence mechanism that senses various pathogen-associated molecular patterns (PAMP) of microbes by a variety of pattern recognition receptors (PRRs). Among PRRs, Toll-like receptors (TLRs), Nucleotide Oligomerization Domain (NOD)-like receptors and C-type lectins have been implicated in recognition of mycobacteria and in the initiation of the immune activation. Materials and Methods: Human innate immune cells (i.e. monocyte derived dendritic cells (DC) and macrophages, NK cells) were stimulated in vitro with whole mycobacteria, with a MTB H37Rv mutant strain in which the gene rv1794 at the ESX-5 locus was inactivated (Mtbrv1794ko), or with mycobacterial cell-wall components (CWC), and the cytokine production and the expression of activation markers were analyzed. In addition, binding of MTB CWC to soluble PRRs (e.g. TLR2, Natural Cytotoxicity Receptors [NCRs]) were assessed by ELISA. Results: MTB preferentially induced production of IL-23 but not IL-12 from infected DC, similarly to the stimulation of such cells with NOD and TLR2 ligands. DC priming with IFN-g strongly increased IL-12 production, a pivotal cytokine in immunity against pathogens. The macrophages infected with Mtbrv1794ko produced significantly higher amounts of the pro-inflammatory cytokine IL-1b as compared to wild type MTB suggesting that Rv1794 might be involved in the modulation of IL-1b production from human macrophages. Finally, mycobacteria directly induced the proliferation, IFN-g production, and cytotoxic activity of NK cells. Further experiments demonstrated that CWC were able to bind to NCR NKp44 (arabinogalactan, mycolic acids) and TLR2 (peptidoglycan), respectively, and the interaction of TLR2 with peptidoglycan promoted activation of resting NK cells and IFN-g production. Discussion and Conclusion: The differential ability of pathogens to induce innate immune cells to produce cytokines regulates the immune response to infection. A successful outcome of the immune response to MTB largely depends on the initial phases of the infection when cells of innate immunity recognize the PAMPs of MTB by their PRRs and mount a correctly orchestrated cytokine production
Natural Killer Cells: A Coherent Model for Their Functional Role in Mycobacterium tuberculosis Infection.
No full textTuberculosis is still a leading cause of bacterial infection worldwide, with an estimate of over two billion people latently infected with Mycobacterium tuberculosis (MTB). A delicate interplay between MTB and the host's innate and acquired immune system can influence the outcome of the infection, which ranges from pathogen elimination to the establishment of a latent infection or a progressive disease. Although the host cell-mediated adaptive immune response is of vital importance in the control of MTB infection, growing evidence indicates that innate immune cells may greatly influence the outcome of the interaction between the bacterium and the host. Among the cell populations likely to play a role in the host immune response to MTB, natural killer (NK) cells have recently attracted considerable interest. This review is dedicated to dissecting the role of NK cells in immunity to tuberculosis, reporting the most relevant findings and providing a working model of the possible contribution of NK cells in early and late events associated with MTB infection
Antimicrobial peptides and their interaction with biofilms of medically relevant bacteria
Full text linkBiofilm-associated infections represent one of the major threats of the modern medicine. Biofilmforming bacteria are encased in a complex mixture of extracellular polymeric substances (EPS) and acquire properties that render them highly tolerant to conventional antibiotics and host immune response. Therefore, there is a pressing demand of new drugs active against microbial biofilms. In this regard, antimicrobial peptides (AMPs) represent an option taken increasingly in consideration. After dissecting the peculiar biofilm features that may greatly affect the development of new antibiofilm drugs, the present article provides a general overview of the rationale behind the use of AMPs against biofilms of medically relevant bacteria and on the possible mechanisms of AMP antibiofilm activity. An analysis of the interactions of AMPs with biofilm components, especially those constituting the EPS, and the obstacles and/or opportunities that may arise from such interactions in the development of new AMP-based antibiofilm strategies is also presented and discussed
Human beta-defensin-3: a promising antimicrobial peptide
No full textThe field of naturally occurring antimicrobial peptides is a research area rapidly expanding due to the high potential of such molecules as new antimicrobial drugs. In this regard, the human beta-defensin-3 is particularly attractive because of its strong antibacterial activity, relative salt-insensitiveness and low toxicity for host cells
The antibacterial and antibiofilm activity of Granudacyn in vitro in a 3D collagen wound infection model
No full textIt is widely agreed that infection and the formation of biofilms play a major role in increasing inflammation and delaying wound healing. The aim of this study was to evaluate, in vitro, the antimicrobial activity of the wound irrigation solution, Granudacyn (Mölnlycke Health Care AB, Sweden) against planktonic bacteria and mature biofilms of clinically relevant bacterial species
Therapeutic Potential of Antimicrobial Peptides in Polymicrobial Biofilm-Associated Infections
No full textIt is widely recognized that many chronic infections of the human body have a polymicrobial etiology. These include diabetic foot ulcer infections, lung infections in cystic fibrosis patients, periodontitis, otitis, urinary tract infections and even a proportion of systemic infections. The treatment of mixed infections poses serious challenges in the clinic. First, polymicrobial communities of microorganisms often organize themselves as biofilms that are notoriously recalcitrant to antimicrobial therapy and clearance by the host immune system. Secondly, a plethora of interactions among community members may affect the expression of virulence factors and the susceptibility to antimicrobials of individual species in the community. Therefore, new strategies able to target multiple pathogens in mixed populations need to be urgently developed and evaluated. In this regard, antimicrobial or host defense peptides (AMPs) deserve particular attention as they are endowed with many favorable features that may serve to this end. The aim of the present review is to offer a comprehensive and updated overview of studies addressing the therapeutic potential of AMPs in mixed infections, highlighting the opportunities offered by this class of antimicrobials in the fight against polymicrobial infections, but also the limits that may arise in their use for this type of application
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