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The naive T-cell pool in peripheral lymphoid tissues is fairly stable in terms of number, diversity and functional capabilities in spite of the absence of prominent stimuli. This stability is attributed to continuous tuning of the composition of the T-cell pool by various homeostatic signals. Despite extensive research into the link between signal transducer and activator of transcription 3 ( Stat3) and T-cell survival, little is known about how Stat3 regulates homeostasis by maintaining the required naive T-cell population in peripheral lymphoid organs. We assessed whether the elimination of Stat3 in T cells limits T-cell survival. We demonstrated that the proportion and number of single-positive thymocytes as well as T cells in the spleen and lymph nodes were significantly decreased in the Stat3-deficient group as a result of the enhanced susceptibility of Stat3-deleted T lymphocytes to apoptosis. Importantly, expression of the anti-apoptotic Bcl-2 and Bcl-xL was markedly decreased in Stat3-deleted single-positive thymocytes and T lymphocytes, suggesting that Stat3 helps to maintain the T-cell pool in the resting condition by promoting the expression of Bcl-2 family genes. These findings suggest the importance of Stat3 in the integration of homeostatic cues for the maintenance and functional tuning of the T-cell pool. [ABSTRACT FROM AUTHOR]

We have previously demonstrated co‐receptor level‐associated functional heterogeneity in apparently homogeneous naive peripheral CD4 T cells, dependent on MHC‐mediated tonic signals. Maturation pathways can differ between naive CD4 and naive CD8 cells, so we tested whether the latter showed similar co‐receptor level‐associated functional heterogeneity. We report that, when either polyclonal and T‐cell receptor (TCR)‐transgenic monoclonal peripheral naive CD8 T cells from young mice were separated into CD8hi and CD8lo subsets, CD8lo cells responded poorly, but CD8hi and CD8lo subsets of CD8 single‐positive (SP) thymocytes responded similarly. CD8lo naive CD8 T cells were smaller and showed lower levels of some cell‐surface molecules, but higher levels of the negative regulator CD5. In addition to the expected peripheral decline in CD8 levels on transferred naive CD8 T cells in wild‐type (WT) but not in MHC class I‐deficient recipient mice, short‐duration naive T‐cell–dendritic cell (DC) co‐cultures in vitro also caused co‐receptor down‐modulation in CD8 T cells but not in CD4 T cells. Constitutive pZAP70/pSyk and pERK levels ex vivo were lower in CD8lo naive CD8 T cells and dual‐specific phosphatase inhibition partially rescued their hypo‐responsiveness. Bulk mRNA sequencing showed major differences in the transcriptional landscapes of CD8hi and CD8lo naive CD8 T cells. CD8hi naive CD8 T cells showed enrichment of genes involved in positive regulation of cell cycle and survival. Our data show that naive CD8 T cells show major differences in their signaling, transcriptional and functional landscapes associated with subtly altered CD8 levels, consistent with the possibility of peripheral cellular aging. The data demonstrate that lowered cell‐surface CD8 levels are associated with peripheral post‐thymic 'aging' of naïve CD8 T cells due to 'tonic' MHC‐dependent signalling. This peripheral aging of naïve CD8 T cells is associated with hypo‐responsiveness and transcriptomic alterations. Thus, the data reveal functional and transcriptomic heterogeneity in the seemingly homogenous peripheral naive CD8 T cell population, identified by subtle modulation of CD8 levels, driven by MHC class I‐mediated tonic signals, as a consequence of post‐thymic peripheral cellular aging. [ABSTRACT FROM AUTHOR]

The responses of allergen-specific CD4+ T cells of allergic and healthy individuals are still incompletely understood. Our objective was to investigate the functional and phenotypic properties of CD4+ T cells of horse-allergic and healthy subjects specific to the immunodominant epitope region of the major horse allergen Equ c 1. Specific T-cell lines (TCLs) and clones were generated from peripheral blood mononuclear cells with Equ c 1143-160, the peptide containing the immunodominant epitope region of Equ c 1. The frequency, proliferative response, cytokine production and HLA restriction of the cells were examined. The frequency of Equ c 1-specific CD4+ T cells was low (approximately 1 per 106 CD4+ T cells) in both allergic and non-allergic subjects. The cells of allergic subjects had a stronger proliferative capacity than those of non-allergic subjects, and they predominantly emerged from the memory T-cell pool and expressed the T helper type 2 cytokine profile, whereas the cells of non-allergic subjects emerged from the naive T-cell pool and produced low levels of interferon-γ and interleukin-10. T-cell response to Equ c 1143-160 was restricted by several common HLA class II molecules from both DQ and DR loci. As the phenotypic and functional properties of Equ c 1-specific CD4+ T cells differ between allergic and non-allergic subjects, allergen-specific T cells appear to be tightly implicated in the development of diseased or healthy outcome. Restriction of the specific CD4+ T-cell response by multiple HLA alleles suggests that Equ c 1143-160 is a promising candidate for peptide-based immunotherapy. [ABSTRACT FROM AUTHOR]

Naive T cells have long been thought to recirculate exclusively between secondary lymphoid organs via the lymph and blood. Evidence is now emerging that this view may be too simplistic and that naive T cells routinely traffic through non-lymphoid organs in a manner similar to that of memory T cells, albeit in lower numbers. This represents a fundamental shift in the current paradigm of T-cell migration through different types of tissue. This review summarizes these recent findings, along with the similarities and differences in migratory properties of naive and memory T cells, and discusses how and why naive T cells might access non-lymphoid tissues. [ABSTRACT FROM AUTHOR]

Membrane transport of cationic amino acids is essential for cells which are actively metabolizing Larginine or L-lysine. In human cells most of this transport occurs through y+, a transport system which is only now being characterized at the molecular level. We have previously shown that phytohaemagglutinin (PHA) stimulation of peripheral blood E rosette positive (T) lymphocytes specifically activated lysine transport through system y+, whereas Staphlyococcus aureus Cowan A (SAC) stimulation of the E rosette negative fraction did not. We have now analysed this effect in PHA-activated CD4, CDS, CD45RO and CD45RA T-cell subsets. Both PHA-activated CD4+ and CD8+ T cells have increased lysine transport through y+, and in seven out of eight experiments, more activity was seen in the CD8+ fraction. In contrast, marked differences in y+ activity were seen between the PHA-activated CD45RO and CD45RA subsets. Thus in six experiments y+ activity was markedly increased in the CD45RA (naive T cell) population but not in the CD45RO (memory) cells. In one further experiment the activated CD45RO, CD4- population (enriched for CD45RA+, CD8+) was studied and y+ activity was shown to be maximal in this cell subset. Transport of arginine is essential for nitric oxide synthesis. Our findings therefore suggest that activated CD45RA, CD8+ T cells are capable of nitric oxide production. [ABSTRACT FROM AUTHOR]

We examined the capacity of human Langerhans' cells (LC) to sensitize autologous T cells to the trinitrophenyl hapten (TNP) in vitro, Two-day cultured Langerhans' cells, but not freshly prepared Langerhans' cells, can induce in vitro primary proliferative reactions to the TNP hapten. Using a CE45RA+ naive T-cell subset, similar results were found, therefore making the possibility of a previous in vivo T-cell contact with the hapten unlikely. The primary in vitro response was strongly inhibited by monoclonal antibodies to major histocompatibility complex (MHC) class I and II, CD4 antigens and ICAM-1 and LFA-3 adhesion molecules. Furthermore, we found that fresh LC can prime T cells to TNP, as revealed by a significant secondary T-cell proliferation after restimulation of the recovered T lymphocytes by fresh hapten-modified autologous LC. Nevertheless, the ability of these fresh LC to stimulate in vitro secondary hapten-specific T-cell proliferation was very limited in comparison with that of 2-day incubated Langerhans' cells. After secondary stimulation with TNPcultured LC, sensitized T cells could be non-specifically expanded without losing hapten specificity. The TNP-specific T-cell lines were mostly of the CD4+ phenotype. The present findings extend previous studies in the mouse, showing that cultured LC are potent antigen-presenting cells (APC) in primary hapten-dependent proliferation assays. Furthermore, this in vitro priming assay, using cultured human Langerhans' cells as APC, might be useful to analyse the early steps of T-cell sensitization and subsequently to develop in vitro predictive tests allowing detection of sensitizing compounds. [ABSTRACT FROM AUTHOR]

To assess the role of CD5 and CD28 in the pathogenesis of the decreased cellular immune function in patients with rheumatoid arthritis (RA) we analysed the expression and function of these T-cell surface molecules. The expression of CD5 as well as of CD28 in synovial and peripheral blood T cells was similar to that of control T cells. Monoclonal antibodies (mAb) directed at CD28 and CD5 were able to provide an accessory signal to anti-CD3 activated T cells both from the synovial fluid and from the peripheral blood. However, the proliferation induced by anti-CD3 mAb in conjunction with anti-CD5 or anti-CD28 mAb was always higher in peripheral blood (PB) T cells compared to the paired synovial fluid T cells, After simultaneous ligation of CD5 and CD28, proliferation was induced in the PB T cells. However, when compared to control PB T cells, this proliferation was significantly lower in the RA patients. Purified normal memory (CD45RO+) T cells proliferated less strongly than naive (CD45RA+) T cells, but no difference was observed between rheumatoid and normal memory T-cell proliferative responses. However, enriched PB CD45RA+ T cells from rheumatoid patients proliferated less vigorously to CD5 and CD28 ligation when compared to normal enriched CD45RA+ T cells. Synovial fluid (SF) T cells, which are mainly of the memory cell type, did not proliferate after simultaneous ligation of CD5 and CD28. This refractory state of synovial T cells could not be explained by a difference in the surface expression of CD5 or CD28. Our data suggest that the cellular immune dysfunction in the PB from rheumatoid patients may be due to a decreased responsiveness of the naive T-cell subset to accessory signals provided by CD5 and CD28. In addition, SF T cells appear hyporesponsive to stimulating signals provided through CD5 and CD28. [ABSTRACT FROM AUTHOR]

The costimulation molecule CD226 is widely involved in T cell differentiation, activation and immune functional regulation in peripheral immune tissues. CD226‐deficient mice have impaired immune response capacity. The function of CD226 in regulating T cell development in the thymus, a central immune organ, is not yet fully understood. We investigated the development of thymocytes using CD226 knockout mice and single‐cell sequencing techniques. CD226 began to be expressed in the second half of thymocyte development, with a gradual increase from the double‐positive (DP) to single‐positive (SP) phase and higher levels of CD226 on CD8+ T cells than on CD4+ T cells from the SP phase to mature T cells. In the thymus of CD226KO mice, the proportion of DPT at the quiescent phase (DPT‐Q) increased, of which the Gzma+ cluster that tends to be CD8+ T cells and CD5+ cluster that is undergoing positive selection decreased dramatically. Afterward, the proportion of mature CD8+ T cells reduced dramatically. Depletion of CD226 impaired TCR activation signalling and diminished AKT/ERK/NF‐κB/p38 phosphorylation levels. The diminished TCR responsiveness of DPT cells impeded their positive selection process and influenced the maturation of CD8+ T cells. In mechanism, CD226 knockout enhanced DPT cell apoptosis via impairing AKT phosphorylation. These results suggest that CD226 plays a significant role in T cell thymic development via modulation of TCR signalling, affecting CD8+ T cell maturation. [ABSTRACT FROM AUTHOR]

Evidence suggests that the anti‐inflammatory nucleoside adenosine can shape immune responses by shifting the regulatory (Treg)/helper (Th17) T‐cell balance in favour of Treg. Since this observation is based on in vivo and in vitro studies mostly confined to murine models, we comprehensively analysed effects of adenosine on human T‐cells. Proliferation, phenotype and cytokine production of stimulated T‐cells were assessed by flow cytometry, multiplex assay and ELISA, gene expression profiling was determined by microarray. We found that the pan‐adenosine agonist 5′‐N‐ethylcarboxamidoadenosine (NECA) skews human CD3+ T‐cell responses towards non‐inflammatory Th17 cells. Addition of NECA during T‐cell activation increased the development of IL‐17+ cells with a CD4+ RORγt+ phenotype and enhanced CD161 and CD196 surface expression. Remarkably, these Th17 cells displayed non‐inflammatory cytokine and gene expression profiles including reduced Th1/Th17 transdifferentiation, a stem cell‐like molecular signature and induced surface expression of the adenosine‐producing ectoenzymes CD39 and CD73. Thus, T‐cells cultured under Th17‐inducing conditions together with NECA were capable of suppressing responder T‐cells. Finally, genome‐wide gene expression profiling revealed metabolic quiescence previously associated with non‐pathogenic Th17 cells in response to adenosine signalling. Our data suggest that adenosine induces non‐inflammatory Th17 cells in human T‐cell differentiation, potentially through regulation of metabolic pathways. [ABSTRACT FROM AUTHOR]

Age‐associated changes in T‐cell function play a central role in immunosenescence. The role of aging in the decreased T‐cell repertoire, primarily because of thymic involution, has been extensively studied. However, increasing evidence indicates that aging also modulates the mechanical properties of cells and the internal ordering of diverse cell components. Cellular functions are generally dictated by the biophysical phenotype of cells, which itself is also tightly regulated at the molecular level. Based on previous evidence suggesting that the relative nuclear size contributes to variations of T‐cell stiffness, here we examined whether age‐associated changes in T‐cell migration are dictated by biophysical parameters, in part through nuclear cytoskeleton organization and cell deformability. In this study, we first performed longitudinal analyses of a repertoire of 111 functional, biophysical and biomolecular features of the nucleus and cytoskeleton of mice CD4+ and CD8+ T cells, in both naive and memory state. Focusing on the pairwise correlations, we found that age‐related changes in nuclear architecture and internal ordering were correlated with T‐cell stiffening and declined interstitial migration. A similarity analysis confirmed that cell‐to‐cell variation was a direct result of the aging process and we applied regression models to identify biomarkers that can accurately estimate individuals' age. Finally, we propose a biophysical model for a comprehensive understanding of the results: aging involves an evolution of the relative nuclear size, in part through DNA‐hypomethylation and nuclear lamin B1, which implies an increased cell stiffness, thus inducing a decline in cell migration. [ABSTRACT FROM AUTHOR]

Autoreactive T cells with the phenotype and function of different memory subsets are present in patients who developed type 1 diabetes (TID). According to the progressive differentiation model, memory subsets generate from naïve precursors in a linear and unidirectional path depending on the strength and quality of stimulatory signals. By observing human naïve T cells in contact with GAD65 loaded autologous dendritic cells, we observed that approximately 10% of cells divided with the plane of cell division parallel to the one of the immune synapse, causing phenotypic asymmetries in the proximal and distal daughter T cells. After the first T cell division, proximal and distal daughter T cells showed different phenotype, metabolic signature and commitment to differentiate towards long‐lived memory T cells or T cells with effector function. Subjects with or without T1D showed a similar frequency of asymmetric T cell division (ATCD) for autoantigens and recall antigens specific T cells, however the frequency of ATCD is significantly increased in autoreactive T cells in patients with T1D when IL‐7 was added to the culture. An increased upregulation of GLUT1 in response to IL‐7 in patients with T1D was related to the rate of ATCD. Our results showed that ATCD is associated with an early divergence in the differentiation fate of naïve T cells specific for GAD65 during first antigen encounter. [ABSTRACT FROM AUTHOR]

Neutrophils are the most abundant leucocytes in human blood, promptly recruited to the site of tissue injury, where they orchestrate inflammation and tissue repair. The multifaceted functions of neutrophils have been more appreciated during the recent decade, and these cells are now recognized as sophisticated and essential players in infection, cancer and chronic inflammatory diseases. Consequently, our understanding of the role of neutrophils in inflammatory bowel disease (IBD), their immune responses and their ability to shape adaptive immunity in the gut have been recognized. Here, current knowledge on neutrophil responses in IBD and their capacity to influence T cells are summarized with an emphasis on the role of these cells in human disease. [ABSTRACT FROM AUTHOR]

Summary: Within each individual, the adaptive immune system generates a repertoire of cells expressing receptors capable of recognizing diverse potential pathogens. The theoretical diversity of the T‐cell receptor (TCR) repertoire exceeds the actual size of the T‐cell population in an individual by several orders of magnitude – making the observation of identical TCRs in different individuals extremely improbable if all receptors were equally likely. Despite this disparity between the theoretical and the realized diversity of the repertoire, these 'public' receptor sequences have been identified in autoimmune, cancer and pathogen interaction contexts. Biased generation processes explain the presence of public TCRs in the naive repertoire, but do not adequately explain the different abundances of these public TCRs. We investigate and characterize the distribution of genomic TCR‐β sequences of naive CD8+ T cells from three genetically identical mice, comparing non‐productive (non‐functional sequences) and productive sequences. We find public TCR‐β sequences at higher abundances compared with unshared sequences in the productive, but not in the non‐productive, repertoire. We show that neutral processes such as recombination biases, codon degeneracy and generation probability do not fully account for these differences, and conclude that thymic or peripheral selection plays an important role in increasing the abundances of public TCR‐β sequences. [ABSTRACT FROM AUTHOR]

Coronavirus disease 2019 (COVID‐19) is caused by SARS‐CoV‐2, a novel coronavirus strain. Some studies suggest that COVID‐19 could be an immune‐related disease, and failure of effective immune responses in initial stages of viral infection could contribute to systemic inflammation and tissue damage, leading to worse disease outcomes. T cells can act as a double‐edge sword with both pro‐ and anti‐roles in the progression of COVID‐19. Thus, better understanding of their roles in immune responses to SARS‐CoV‐2 infection is crucial. T cells primarily react to the spike protein on the coronavirus to initiate antiviral immunity; however, T‐cell responses can be suboptimal, impaired or excessive in severe COVID‐19 patients. This review focuses on the multifaceted roles of T cells in COVID‐19 pathogenesis and rationalizes their significance in eliciting appropriate antiviral immune responses in COVID‐19 patients and unexposed individuals. In addition, we summarize the potential therapeutic approaches related to T cells to treat COVID‐19 patients. These include adoptive T‐cell therapies, vaccines activating T‐cell responses, recombinant cytokines, Th1 activators and Th17 blockers, and potential utilization of immune checkpoint inhibitors alone or in combination with anti‐inflammatory drugs to improve antiviral T‐cell responses against SARS‐CoV‐2. [ABSTRACT FROM AUTHOR]

Summary: The immune system is essential for maintaining a delicate balance between eliminating pathogens and maintaining tolerance to self‐tissues to avoid autoimmunity. An enormous and complex community of gut microbiota provides essential health benefits to the host, particularly by regulating immune homeostasis. Many of the metabolites derived from commensals can impact host health by directly regulating the immune system. Many autoimmune diseases arise from an imbalance between pathogenic effector T cells and regulatory T (Treg) cells. Recent interest has emerged in understanding how cross‐talk between gut microbiota and the host immune system promotes autoimmune development by controlling the differentiation and plasticity of T helper and Treg cells. At the molecular level, our recent study, along with others, demonstrates that asymptomatic colonization by commensal bacteria in the gut is capable of triggering autoimmune disease by molecular mimicking self‐antigen and skewing the expression of dual T‐cell receptors on T cells. Dysbiosis, an imbalance of the gut microbiota, is involved in autoimmune development in both mice and humans. Although it is well known that dysbiosis can impact diseases occurring within the gut, growing literature suggests that dysbiosis also causes the development of gut‐distal/non‐gut autoimmunity. In this review, we discuss recent advances in understanding the potential molecular mechanisms whereby gut microbiota induces autoimmunity, and the evidence that the gut microbiota triggers gut‐distal autoimmune diseases. 'Dysbiosis (gut microbiota imbalance) ‐related diseases have become a new epidemic. In this review, we discuss recent advances in understanding the potential molecular mechanisms whereby gut microbiota impacts autoimmunity, with a focus on both human and mouse gut‐distal autoimmune diseases. Specifically, this review emphasizes how microbiota‐mediated metabolite production and T‐cell receptor recognition impact T cells and other immune players, leading to autoimmunity.' [ABSTRACT FROM AUTHOR]

Summary: Human cytomegalovirus (CMV) is a ubiquitous, persistent beta herpesvirus. CMV infection contributes to the accumulation of functional antigen‐specific CD8+ T‐cell pools with an effector‐memory phenotype and enrichment of these immune cells in peripheral organs. We review here this 'memory T‐cell inflation' phenomenon and associated factors including age and sex. 'Collateral damage' due to CMV‐directed immune reactivity may occur in later stages of life – arising from CMV‐specific immune responses that were beneficial in earlier life. CMV may be considered an age‐dependent immunomodulator and a double‐edged sword in editing anti‐tumour immune responses. Emerging evidence suggests that CMV is highly prevalent in patients with a variety of cancers, particularly glioblastoma. A better understanding of CMV‐associated immune responses and its implications for immune senescence, especially in patients with cancer, may aid in the design of more clinically relevant and tailored, personalized treatment regimens. 'Memory T‐cell inflation' could be applied in vaccine development strategies to enrich for immune reactivity where long‐term immunological memory is needed, e.g. in long‐term immune memory formation directed against transformed cells. The immunomodulatory effect of inflationary cytomegalovirus (CMV)‐specific memory T cells stretches across immunological niches, including long‐term memory T cells. The CMV‐driven cellular immune repertoire may cause shifts in immune recognition profiles, or lead to reduced survival of 'inflationary T cells', and potentially shapes the quality and quantity of the anti‐tumour cellular immune response in patients with cancer. [ABSTRACT FROM AUTHOR]

Summary: Exosomes derived from heat‐stressed tumour cells (HS‐TEXs), which contain abundant heat shock protein (HSP) 70, strongly induce antitumour immune responses. HSP70‐induced interleukin (IL)‐6 promotes IL‐17 expression and causes rejection of established prostate tumours. However, it remains unclear whether HS‐TEXs exhibit antitumour effects by converting regulatory T cells (Tregs) into T helper type 17 (Th17) cells. In this study, we found that compared with TEXs, HS‐TEXs were more potent in stimulating secretion of IL‐6 from dendritic cells. In vitro, IL‐6 blocked tumour cell‐derived transforming growth factor beta 1‐induced Treg differentiation and promoted Th17 cell differentiation. HS‐TEXs exerted strong antitumour effects, converting Tregs into Th17 cells with high efficiency, a process that was entirely dependent upon IL‐6. Neutralization of IL‐17 completely abolished the antitumour effect of TEXs, but only partially inhibited that of HS‐TEXs. In addition, we found higher levels of IL‐6 and IL‐17 in serum from tumour patients treated with hyperthermia, and an increase in Th17 cells and a decrease in Tregs was detected in peripheral blood mononuclear cells isolated from these patients after hyperthermia. Therefore, our results demonstrate that HS‐TEXs possess a powerful capacity to convert immunosuppressive Tregs into Th17 cells via IL‐6, which contributes to their potent antitumour effect. [ABSTRACT FROM AUTHOR]

Summary: Epidemiological studies have consistently shown associations between elevated concentrations of urban particulate matter (UPM) air pollution and exacerbations of asthma and chronic obstructive pulmonary disease, which are both associated with viral respiratory infections. The effects of UPM on dendritic cell (DC) ‐stimulated CD4 T lymphocytes have been investigated previously, but little work has focused on CD8 T‐lymphocyte responses despite their importance in anti‐viral immunity. To address this, we examined the effects of UPM on DC‐stimulated naive CD8 T‐cell responses. Expression of the maturation/activation markers CD83, CCR7, CD40 and MHC class I on human myeloid DCs (mDCs) was characterized by flow cytometry after stimulation with UPMin vitro in the presence/absence of granulocyte–macrophage colony‐stimulating factor (GM‐CSF). The capacity of these mDCs to stimulate naive CD8 T‐lymphocyte responses in allogeneic co‐culture was then assessed by measuring T‐cell cytokine secretion using cytometric bead array, and proliferation and frequency of interferon‐γ (IFN‐γ)‐producing T lymphocytes by flow cytometry. Treatment of mDCs with UPM increased expression of CD83 and CCR7, but not MHC class I. In allogeneic co‐cultures, UPM treatment of mDCs enhanced CD8 T‐cell proliferation and the frequency of IFN‐γ+ cells. The secretion of tumour necrosis factor‐α, interleukin‐13, Granzyme A and Granzyme B were also increased. GM‐CSF alone, and in concert with UPM, enhanced many of these T‐cell functions. The PM‐induced increase in Granzyme A was confirmed in a human experimental diesel exposure study. These data demonstrate that UPM treatment of mDCs enhances priming of naive CD8 T lymphocytes and increases production of pro‐inflammatory cytokines. Such UPM‐induced stimulation of CD8 cells may potentiate T‐lymphocyte cytotoxic responses upon concurrent airway infection, increasing bystander damage to the airways. [ABSTRACT FROM AUTHOR]

Thalidomide (TM) has been reported to have anti-cancer and antiinflammatory properties, and dexamethasone (DX) is known to reduce inflammation and inhibit production of inflammatory cytokines. Many studies have reported that combinatorial therapy with TM and DX is clinically used to treat multiple myeloma and lupus nephritis, but the mechanism responsible for its effects has not been elucidated. In this study, we determined that TM and DX co-treatment had an enhanced immunemodulatory effect on T cells through regulating the expression of co-stimulatory molecules. Splenic naive T cells from C57BL/6 mice were sort-purified and cultured for CD4+ T cell proliferation and regulatory T (Treg) cell conversion in the presence of TM and/or DX. Following incubation with the drugs, cells were collected and OX40, 4-1BB, and glucocorticoid- induced tumour necrosis factor receptor-related protein (GITR) expression was quantified by flow cytometry. TM (1 or 10 µM) decreased CD4+ T cell proliferation in a dose-dependent manner, whereas TM/DX (0.1 or 1 nM) co-treatment further decreased proliferation. Treg cell populations were preserved following drug treatment. Furthermore, expression of co-stimulatory molecules decreased upon TM/DX co-treatment in effector T (Teff) cells and was preserved in Treg cells. Splenic CD4+ T cells isolated from TM- and DX-treated mice exhibited the same patterns of Teff and Treg cell populations as observed in vitro. Considering the selective effect of TM on different T cell subsets, we suggest that TM may play an immunomodulatory role and that TM/DX combinatorial treatment could further enhance these immunomodulatory effects by regulating GITR, OX40, and 4-1BB expression in CD4+ T cells. [ABSTRACT FROM AUTHOR]

B-cell memory was long characterized as isotype-switched, somatically mutated and germinal centre (GC)-derived. However, it is now clear that the memory pool is a complex mixture that includes unswitched and unmutated cells. Further, expression of CD73, CD80 and CD273 has allowed the categorization of B-cell memory into multiple subsets, with combinatorial expression of the markers increasing with GC progression, isotype-switching and acquisition of somatic mutations. We have extended these findings to determine whether these markers can be used to identify IgM memory phenotypically as arising from T-dependent versus T-independent responses. We report that CD73 expression identifies a subset of antigen-experienced IgM+ cells that share attributes of functional B-cell memory. This subset is reduced in the spleens of T-cell-deficient and CD40-deficient mice and in mixed marrow chimeras made with mutant and wild-type marrow, the proportion of CD73+ IgM memory is restored in the T-cell-deficient donor compartment but not in the CD40-deficient donor compartment, indicating that CD40 ligation is involved in its generation. We also report that CD40 signalling supports optimal expression of CD73 on splenic T cells and age-associated B cells (ABCs), but not on other immune cells such as neutrophils, marginal zone B cells, peritoneal cavity B-1 B cells and regulatory T and B cells. Our data indicate that in addition to promoting GC-associated memory generation during B-cell differentiation, CD40-signalling can influence the composition of the unswitched memory B-cell pool. They also raise the possibility that a fraction of ABCs may represent T-cell-dependent IgM memory. [ABSTRACT FROM AUTHOR]

The success of immune system-based cancer therapies depends on a broad immune response engaging a range of effector cells and mechanisms. Immune mobilizing monoclonal T cell receptors ( TCRs) against cancer (Imm TAC™ molecules: fusion proteins consisting of a soluble, affinity enhanced TCR and an anti- CD3 scFv antibody) were previously shown to redirect CD8+ and CD4+ T cells against tumours. Here we present evidence that IMCgp100 (Imm TAC recognizing a peptide derived from the melanoma-specific protein, gp100, presented by HLA-A*0201) efficiently redirects and activates effector and memory cells from both CD8+ and CD4+ repertoires. Using isolated subpopulations of T cells, we find that both terminally differentiated and effector memory CD8+ T cells redirected by IMCgp100 are potent killers of melanoma cells. Furthermore, CD4+ effector memory T cells elicit potent cytotoxic activity leading to melanoma cell killing upon redirection by IMCgp100. The majority of T cell subsets belonging to both the CD8+ and CD4+ repertoires secrete key pro-inflammatory cytokines (tumour necrosis factor- α, interferon- γ, interleukin-6) and chemokines (macrophage inflammatory protein-1 α- β, interferon- γ-inducible protein-10, monocyte chemoattractant protein-1). At an individual cell level, IMCgp100-redirected T cells display a polyfunctional phenotype, which is a hallmark of a potent anti-cancer response. This study demonstrates that IMCgp100 induces broad immune responses that extend beyond the induction of CD8+ T cell-mediated cytotoxicity. These findings are of particular importance because IMCgp100 is currently undergoing clinical trials as a single agent or in combination with check point inhibitors for patients with malignant melanoma. [ABSTRACT FROM AUTHOR]

Cell adhesion is generally considered to depend on positive regulation through ligation of integrins and cytokine receptors. However, here we show that T-cell adhesion, and notably also T-cell receptor ( TCR) -induced activation, are subject to constant suppression through shedding of low-density lipoprotein receptor-related protein 1 ( LRP1). The broad-spectrum metalloprotease inhibitor GM6001 abrogated shedding, so inducing prominent cell surface expression of LRP1 while enhancing TCR-induced activation and adhesion to β1 and β2 integrin ligands, hence arresting the cells. Integrin ligands also inhibited shedding but the effect was less potent than that of GM6001. Unlike GM6001, integrin ligands also induced cell surface expression of full-length thrombospondin-1 ( TSP170) and TSP130, which associated with LRP1, and TSP110, which did not associate with LRP1. Cell surface expression of LRP1 and TSP130 were induced exclusively in adhering cells, expression of TSP110 preferentially in non-adhering cells and expression of TSP170 correlated with T-cell motility. The pro-adhesive chemokine CXCL12 also inhibited LRP1 shedding and induced surface expression of TSP170 and TSP130 while inhibiting TSP110. Exogenous TSP-1 and ligation of CD28 inhibited shedding although less effectively than GM6001, and the inhibition through CD28 was independent of TSP-1. Small interfering RNA silencing experiments confirmed involvement of LRP1 and TSP-1 in integrin-dependent adhesion and TCR-induced activation. Hence, the poor LRP1 expression in T cells depends on shedding. Integrin ligands and CXCL12 antagonize shedding through a TSP-1-dependent pathway and ligation of CD28 antagonizes shedding independent of TSP-1. The disappearance of LRP1 from the cell surface may provide basic immunosuppression at the T-cell level. [ABSTRACT FROM AUTHOR]

CD43 is one of the most abundant co-stimulatory molecules on a T-cell surface; it transduces activation signals through its cytoplasmic domain, contributing to modulation of the outcome of T-cell responses. The aim of this study was to uncover new signalling pathways regulated by this sialomucin. Analysis of changes in protein abundance allowed us to identify pyruvate kinase isozyme M2 ( PKM2), an enzyme of the glycolytic pathway, as an element potentially participating in the signalling cascade resulting from the engagement of CD43 and the T-cell receptor ( TCR). We found that the glycolytic activity of this enzyme was not significantly increased in response to TCR+ CD43 co-stimulation, but that PKM2 was tyrosine phosphorylated, suggesting that it was performing moonlight functions. We report that phosphorylation of both Y105 of PKM2 and of Y705 of signal transducer and activator of transcription 3 was induced in response to TCR+ CD43 co-stimulation, resulting in activation of the mitogen-activated protein kinase kinase 5/extracellular signal-regulated kinase 5 ( MEK5/ ERK5) pathway. ERK5 and the cAMP response element binding protein ( CREB) were activated, and c-Myc and nuclear factor- κB (p65) nuclear localization, as well as Bad phosphorylation, were augmented. Consistent with this, expression of human CD43 in a murine T-cell hybridoma favoured cell survival. Altogether, our data highlight novel signalling pathways for the CD43 molecule in T lymphocytes, and underscore a role for CD43 in promoting cell survival through non-glycolytic functions of metabolic enzymes. [ABSTRACT FROM AUTHOR]

T-cell immunoglobulin and mucin ( TIM) family molecules are cell membrane proteins, preferentially expressed on various immune cells and implicated in recognition and clearance of apoptotic cells. Little is known of their function outside human and mouse, and nothing outside mammals. We identified only two TIM genes ( ch TIM) in the chicken genome, putative orthologues of mammalian TIM1 and TIM4, and cloned the respective cDNAs. Like mammalian TIM1, ch TIM1 expression was restricted to lymphoid tissues and immune cells. The gene ch TIM4 encodes at least five splice variants with distinct expression profiles that also varied between strains of chicken. Expression of ch TIM4 was detected in myeloid antigen-presenting cells, and in γδ T cells, whereas mammalian TIM4 is not expressed in T cells. Like the mammalian proteins, ch TIM1 and ch TIM4 fusion proteins bind to phosphatidylserine, and are thereby implicated in recognition of apoptotic cells. The ch TIM4-immunoglobulin fusion protein also had co-stimulatory activity on chicken T cells, suggesting a function in antigen presentation. [ABSTRACT FROM AUTHOR]

Calcineurin inhibitors ( CNI) and mammalian target of rapamycin inhibitors ( mTORi) are the main immunosuppressants used for long-term maintenance therapy in transplant recipients to avoid acute rejection episodes. Both groups of immunosuppressants have wide effects and are focused against the T cells, although different impacts on specific T-cell subsets, such as regulatory T cells, have been demonstrated. A greater knowledge of the impact of immunosuppression on the cellular components involved in allograft rejection could facilitate decisions for individualized immunosuppression when an acute rejection event is suspected. Memory T cells have recently gained focus because they might induce a more potent response compared with naive cells. The impact of immunosuppressants on different memory T-cell subsets remains unclear. In the present study, we have studied the specific impact of CNI (tacrolimus) and mTORi (rapamycin and everolimus) over memory and naive CD4+ T cells. To do so, we have analysed the proliferation, phenotypic changes and cytokine synthesis in vitro in the presence of these immunosuppressants. The present work shows a more potent effect of CNI on proliferation and cytokine production in naive and memory T cells. However, the mTORi permit the differentiation of naive T cells to the memory phenotype and allow the production of interleukin-2. Taken together, our data show evidence to support the combined use of CNI and mTORi in transplant immunosuppression. [ABSTRACT FROM AUTHOR]

The voltage-gated potassium channel Kv1.3 is a novel target for immunomodulation of autoreactive effector memory T cells, which play a major role in the pathogenesis of autoimmune diseases. In this study, the Ts6 and Ts15 toxins isolated from Tityus serrulatus (Ts) were investigated for their immunosuppressant roles on CD4+ cell subsets: naive, effector ( TEF), central memory ( TCM) and effector memory ( TEM). The electrophysiological assays confirmed that both toxins were able to block Kv1.3 channels. Interestingly, an extended Kv channel screening shows that Ts15 blocks Kv2.1 channels. Ts6 and Ts15 significantly inhibit the proliferation of TEM cells and interferon- γ production; however, Ts15 also inhibits other CD4+ cell subsets (naive, TEF and TCM). Based on the Ts15 inhibitory effect of proliferation of all CD4+ cell subsets, and based on its blocking effect on Kv2.1, we investigated the Kv2.1 expression in T cells. The assays showed that CD4+ and CD8+ cells express the Kv2.1 channels mainly extracellularly with TCM cells expressing the highest number of Kv2.1 channels. We also provide in vivo experimental evidence to the protective effect of Ts6 and Ts15 on delayed-type hypersensitivity reaction. Altogether, this study presents the immunosuppressive behaviour of Ts6 and Ts15 toxins, indicating that these toxins could be promising candidates for autoimmune disease therapy. Moreover, this is the first report illustrating the involvement of a novel K+ channel subtype, Kv2.1, and its distribution in T-cell subsets. [ABSTRACT FROM AUTHOR]

Recent data suggest that thymic output, which provides the naive T cells necessary for the normal functioning of T-cell-dependent immunosurveillance cellular immunity including anti-cancer protection, can be disturbed in the course of type 2 diabetes. Metformin, an anti-diabetic drug commonly confirmed as an agent with many potential anti-cancer activities, might be helpful in this immune correction. The profile of thymic output was evaluated in the current study on the basis of the signal-joint T-cell receptor excision circle (sj TREC) concentration in peripheral blood polymorphonuclear cells and thymic emigrant content in peripheral blood evaluated from CD127 and/or CD132 antigen expression. It was revealed that recent thymic emigrants and more differentiated CD127+ CD132+ cell populations were decreased among naive T cells and CD8+ T cells, whereas RTE count was increased in CD4+ T cells, and the CD127+ CD132+ cell population was less numerous than in non-diabetic participants. Terminally differentiated thymic emigrants, i.e. CD127− CD132+ cells, were increased in naive T cells and in CD8+ T cells. Metformin affects mainly the early phases of thymic export, increasing CD127+ CD132− and CD127+ CD132+ cell populations in naive T cells and the CD127+ CD132− population in CD4+ T lymphocytes. It could be concluded that type 2 diabetes deteriorates thymic immunostasis. The decreased thymic output could be compensated by metformin, especially with regard to CD4+ naive T cells. It is the first time that therapy with metformin has been documented by us as particularly useful in the control and normalization of thymus function, regarding correction of early populations of thymic emigrants. [ABSTRACT FROM AUTHOR]

The p38 mitogen-activated protein kinase cascade is required for the induction of a T helper type 17 (Th17) -mediated autoimmune response, which underlies the development and progression of several autoimmune diseases, such as experimental autoimmune encephalomyelitis, the animal model of multiple sclerosis (MS). However, the contribution of p38 phosphorylation to human Th cell differentiation has not been clarified. Here we demonstrate that the p38 signalling pathway is implicated in the generation of Th17 lymphocytes from human CD4+ CD27+ CD45RA+ naive T cells, both in healthy donors and in patients affected by the relapsing-remitting form of MS. Our data also indicate that p38 activation is essential for interleukin-17 release from central memory lymphocytes and committed Th17 cell clones. Furthermore, CD4+ T cells isolated from individuals with relapsing-remitting MS display an altered responsiveness of the p38 cascade, resulting in increased p38 phosphorylation upon stimulation. These findings suggest that the p38 signalling pathway, by modulating the Th17 differentiation and response, is involved in the pathogenesis of MS, and open new perspectives for the use of p38 inhibitors in the treatment of Th17-mediated autoimmune diseases. [ABSTRACT FROM AUTHOR]

Natural killer T cells ( NKT cells) are comprised of several subsets. However, the possible differences in their developmental mechanisms have not been fully investigated. To evaluate the dependence of some NKT subpopulations on nuclear factor- κB-inducing kinase ( NIK) for their generation, we analysed the differentiation of NKT cells, dividing them into subsets in various tissues of alymphoplasia ( aly/ aly), a mutant mouse strain that lacks functional NIK. The results indicated that the efficient differentiation of both invariant NKT ( iNKT) and non- iNKT cells relied on NIK expression in non-haematopoietic cells; however, the dependence of non- iNKT cells was lower than that of iNKT cells. Especially, the differentiation of CD8+ non- iNKT cells was markedly resistant to the aly mutation. The proportion of two other NKT cell subsets, NK1.1+ γδ T cells and NK1.1− iNKT cells, was also significantly reduced in aly/ aly mice, and this defect in their development was reversed in wild-type host mice given aly/ aly bone marrow cells. In exerting effector functions, NIK in NKT- αβ cells appeared dispensable, as NIK-deficient NKT- αβ cells could secrete interleukin-4 or interferon- γ and exhibit cytolytic activity at a level comparable to that of aly/+ NKT- αβ cells. Collectively, these results imply that the NIK in thymic stroma may be critically involved in the differentiation of most NKT cell subsets (although the level of NIK dependence may vary among the subsets), and also that NIK in NKT- αβ cells may be dispensable for their effector function. [ABSTRACT FROM AUTHOR]

The orphan nuclear receptor, retinoic acid receptor-related orphan nuclear receptor γt ( ROR γt), is required for the development and pathogenic function of interleukin-17A-secreting CD4+ T helper type 17 (Th17) cells. Whereas small molecule ROR γt antagonists impair Th17 cell development and attenuate autoimmune inflammation in vivo, the broader effects of these inhibitors on ROR γt-dependent gene expression in vivo has yet to be characterized. We show that the ROR γt inverse agonist TMP778 acts potently and selectively to block mouse Th17 cell differentiation in vitro and to impair Th17 cell development in vivo upon immunization with the myelin antigen MOG35-55 plus complete Freund's adjuvant. Importantly, we show that TMP778 acts in vivo to repress the expression of more than 150 genes, most of which fall outside the canonical Th17 transcriptional signature and are linked to a variety of inflammatory pathologies in humans. Interestingly, more than 30 genes are related with SMAD3, a transcription factor involved in the Th17 cell differentiation. These results reveal novel disease-associated genes regulated by ROR γt during inflammation in vivo, and provide an early read on potential disease indications and safety concerns associated with pharmacological targeting of ROR γt. [ABSTRACT FROM AUTHOR]

Factors influencing T-cell responses are important for vaccine development but are incompletely understood. Here, vaccinia virus (VACV) protein N1 is shown to impair the development of both effector and memory CD8+ T cells and this correlates with its inhibition of nuclear factor- κB (NF- κB) activation. Infection with VACVs that either have the N1L gene deleted (vΔN1) or contain a I6E mutation (v N1.I6E) that abrogates its inhibition of NF- κB resulted in increased central and memory CD8+ T-cell populations, increased CD8+ T-cell cytotoxicity and lower virus titres after challenge. Furthermore, CD8+ memory T-cell function was increased following infection with v N1.I6E, with more interferon- γ production and greater protection against VACV infection following passive transfer to naive mice, compared with CD8+ T cells from mice infected with wild-type virus (v N1.WT). This demonstrates the importance of NF- κB activation within infected cells for long-term CD8+ T-cell memory and vaccine efficacy. Further, it provides a rationale for deleting N1 from VACV vectors to enhance CD8+ T-cell immunogenicity, while simultaneously reducing virulence to improve vaccine safety. [ABSTRACT FROM AUTHOR]

Antigen-specific multifunctional T cells that secrete interferon- γ, interleukin-2 and tumour necrosis factor- α simultaneously after activation are important for the control of many infections. It is unclear if these CD8+ T cells are at an early or late stage of differentiation and whether telomere erosion restricts their replicative capacity. We developed a multi-parameter flow cytometric method for investigating the relationship between differentiation (CD45RA and CD27 surface phenotype), function (cytokine production) and replicative capacity (telomere length) in individual cytomegalovirus (CMV) antigen-specific CD8+ T cells. This involves surface and intracellular cell staining coupled to fluorescence in situ hybridization to detect telomeres (flow-FISH). The end-stage/senescent CD8+ CD45RA+ CD27− T-cell subset increases significantly during ageing and this is exaggerated in CMV immune-responsive subjects. However, these end-stage cells do not have the shortest telomeres, implicating additional non-telomere-related mechanisms in inducing their senescence. The telomere lengths in total and CMV (NLV)-specific CD8+ T cells in all four subsets defined by CD45RA and CD27 expression were significantly shorter in old compared with young individuals in both a Caucasian and an Asian cohort. Following stimulation by anti-CD3 or NLV peptide, similar proportions of triple-cytokine-producing cells are found in CD8+ T cells at all stages of differentiation in both age groups. Furthermore, these multi-functional cells had intermediate telomere lengths compared with cells producing only one or two cytokines after activation. Therefore, global and CMV (NLV)-specific CD8+ T cells that secrete interferon- γ, interleukin-2 and tumour necrosis factor- α are at an intermediate stage of differentiation and are not restricted by excessive telomere erosion. [ABSTRACT FROM AUTHOR]

Antigen recognition reduces T-cell motility, and induces prolonged contact with antigen-presenting cells and activation through mechanisms that remain unclear. Here we show that the T-cell receptor ( TCR) and CD28 regulate T-cell motility, contact with antigen-presenting cells and activation through endogenous thrombospondin-1 ( TSP-1) and its receptors low-density lipoprotein receptor-related protein 1 ( LRP1), calreticulin and CD47. Antigen stimulation induced a prominent up-regulation of TSP-1 expression, and transiently increased and subsequently decreased LRP1 expression whereas calreticulin was unaffected. This antigen-induced TSP-1/ LRP1 response down-regulated a motogenic mechanism directed by LRP1-mediated processing of TSP-1 in cis within the same plasma membrane while promoting contact with antigen-presenting cells and activation through cis interaction of the C-terminal domain of TSP-1 with CD47 in response to N-terminal TSP-1 triggering by calreticulin. The antigen-induced TSP-1/ LRP1 response maintained a reduced but significant motility level in activated cells. Blocking CD28 co-stimulation abrogated LRP1 and TSP-1 expression and motility. TCR/ CD3 ligation alone enhanced TSP-1 expression whereas CD28 ligation alone enhanced LRP1 expression. Silencing of TSP-1 inhibited T-cell conjugation to antigen-presenting cells and T helper type 1 ( Th1) and Th2 cytokine responses. The Th1 response enhanced motility and increased TSP-1 expression through interleukin-2, whereas the Th2 response weakened motility and reduced LRP1 expression through interleukin-4. Ligation of the TCR and CD28 therefore elicits a TSP-1/ LRP1 response that stimulates prolonged contact with antigen-presenting cells and, although down-regulating motility, maintains a significant motility level to allow serial contacts and activation. Th1 and Th2 cytokine responses differentially regulate T-cell expression of TSP-1 and LRP1 and motility. [ABSTRACT FROM AUTHOR]

The great variety of pathogens present in the environment has obliged the immune system to evolve different mechanisms for tailored and maximally protective responses. Initially, two major types of CD4+ T helper (Th) effector cells were identified, and named as type 1 (Th1) and type 2 (Th2) cells because of the different cytokines they produce. More recently, a third type of CD4+ Th effectors has been identified and named as Th17 cells. Th17 cells, however, have been found to exhibit high plasticity because they rapidly shift into the Th1 phenotype in the inflammatory sites. Therefore, in these sites there is usually a dichotomous mixture of classic and non-classic (Th17-derived) Th1 cells. In humans, non-classic Th1 cells express CD161, as well as the retinoic acid orphan receptor C, interleukin-17 receptor E (IL-17RE), IL-1RI, CCR6, and IL-4-induced gene 1 and Tob-1, which are all virtually absent from classic Th1 cells. The possibility to distinguish between these two cell subsets may allow the opportunity to better establish their respective pathogenic role in different chronic inflammatory disorders. In this review, we discuss the different origin, the distinctive phenotypic features and the major biological activities of classic and non-classic Th1 cells. [ABSTRACT FROM AUTHOR]

We have reported that in vivo administration of the hybrid cytokine r IL-7/HGF β or r IL-7/HGF α, which contains interleukin-7 (IL-7) and the β- or α-chain of hepatocyte growth factor (HGF), significantly enhances thymopoiesis in mice after bone marrow transplantation. We have shown that the HGF receptor, c-Met, is involved in the effect of the hybrid cytokines. To address the role of c-Met signalling in thymocyte development and recovery, we generated conditional knockout (cKO) mice in which c-Met was specifically deleted in T cells by crossing c-Met ft/ft mice with CD4-Cre transgenic mice. We show here that although the number of total thymocytes and thymocyte subsets in young c-Met c KO mice is comparable to age-matched control (Ctrl) mice, the c KO mice were more susceptible to sub-lethal irradiation and dexamethasone treatment. This was demonstrated by low recovery in thymic cellularity in c-Met c KO mice after insult. Furthermore, the number of total thymocytes and thymocyte subsets was markedly reduced in 6- to 12-month-old c KO mice compared with age-matched Ctrl mice, and the thymic architecture of 12-month-old c KO mice was similar to that of 20-month-old wild-type mice. In addition, c-Met deficiency reduced cell survival and the expression of Bcl-x L in double-positive thymocytes, and decreased cell proliferation and the expression of cyclin E and cyclin-dependent kinase 5 in single-positive thymocytes. Our data indicate that c-Met signalling plays an important role in thymic regeneration after thymic insult. In addition, T-cell-specific inactivation of c-Met accelerates age-related thymic involution. [ABSTRACT FROM AUTHOR]

Micro RNAs (mi RNAs) are instrumental to many aspects of immunity, including various levels of T-cell immunity. Over the last decade, crucial immune functions were shown to be regulated by specific mi RNAs. These 'immuno-miRs' regulate generic cell biological processes in T cells, such as proliferation and apoptosis, as well as a number of T-cell-specific features that are fundamental to the development, differentiation and function of T cells. In this review, we give an overview of the current literature with respect to the role of mi RNAs at various stages of T-cell development, maturation, differentiation, activation and ageing. Little is known about the involvement of mi RNAs in thymic T-cell development, although miR-181a and miR-150 have been implicated herein. In contrast, several broadly expressed mi RNAs including miR-21, miR-155 and miR-17~92, have now been shown to regulate T-cell activation. Other mi RNAs, including miR-146a, show a more T-cell-subset-specific expression pattern and are involved in the regulation of processes unique to that specific T-cell subset. Importantly, differences in the mi RNA target gene repertoires of different T-cell subsets allow similar mi RNAs to control different T-cell-subset-specific functions. Interestingly, several of the here described immuno-miRs have also been implicated in T-cell ageing and there are clear indications for causal involvement of mi RNAs in immunosenescence. It is concluded that immuno-miRs have a dynamic regulatory role in many aspects of T-cell differentiation, activation, function and ageing. An important notion when studying mi RNAs in relation to T-cell biology is that specific immuno-miRs may have quite unrelated functions in closely related T-cell subsets. [ABSTRACT FROM AUTHOR]

Differences in lifestyle and break with natural environment appear to be associated with changes in the immune system resulting in various adverse health effects. Although genetics can have a major impact on the immune system and disease susceptibility, the contribution of environmental factors is thought to be substantial. Here, we investigated the immunological profile of healthy volunteers living in a rural and an urban area of a developing African country (Senegal), and in a European country (the Netherlands). Using flow cytometry, we investigated T helper type 1 (Th1), Th2, Th17, Th22 and regulatory T cells, as well as CD4+ T-cell and B-cell activation markers, and subsets of memory T and B cells in the peripheral blood. Rural Senegalese had significantly higher frequencies of Th1, Th2 and Th22 cells, memory CD4+ T and B cells, as well as activated CD4+ T and B cells compared with urban Senegalese and urban Dutch people. Within the Senegalese population, rural paritcipants displayed significantly higher frequencies of Th2 and Th22 cells, as well as higher pro-inflammatory and T-cell activation and memory profiles compared with the urban population. The greater magnitude of immune activation and the enlarged memory pool, together with Th2 polarization, seen in rural participants from Africa, followed by urban Africans and Europeans suggest that environmental changes may define immunological footprints, which could have consequences for disease patterns in general and vaccine responses in particular. [ABSTRACT FROM AUTHOR]

Sphingosine-1-phosphate (S1P) is a lipid second messenger that signals via five G protein-coupled receptors (S1P1-5). S1P receptor (S1 PR) signalling is associated with a wide variety of physiological processes including lymphocyte biology, their recirculation and determination of T-cell phenotypes. The effect of FTY720 (Fingolimod, Gilenya™) to regulate lymphocyte egress and to ameliorate paralysis in experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis led to the use of FTY720 as a first-line oral agent for treatment of relapsing-remitting multiple sclerosis. However, a significant body of research suggests that S1P signalling may participate in diverse immune regulatory functions other than lymphocyte trafficking. This review article discusses the current knowledge of S1P signalling in the fate and function of T regulatory, T helper type 17 and memory T cells in health and disease. [ABSTRACT FROM AUTHOR]

The adaptive immune system requires a diverse T-cell repertoire to be able to respond to a wide variety of pathogens. Worryingly, the repertoire diversity declines dramatically in old age. As thymic output generates novel T cells, the conventional view holds that a decrease in this output with age is responsible for the loss in the repertoire. However, many additional factors affect the repertoire such as homeostatic turnover and antigen-dependent expansion in response to infection. Mathematical models taking a population biology perspective are important tools for understanding how the interplay between these factors affects the immune repertoire. These models suggest that thymic decline is not a major factor but rather that some combination of virus-induced proliferation and T-cell-intrinsic genetic or epigenetic changes gives rise to the oligoclonal expansions that cause the decline in T-cell diversity. We also discuss consequences for strategies to rejuvenate the immune repertoire in old age. [ABSTRACT FROM AUTHOR]

After the development of highly active anti-retroviral therapy, it became clear that the majority of emergent HIV-1 is macrophage-tropic and infects CD4+, CCR5-expressing cells (R5-tropic). There are three distinct cell populations, R5-tropic, HIV-1-susceptible CD4+ cells: (i) natural killer T ( NKT) cells, (ii) dendritic cells and macrophages, and (iii) tissue-associated T cells residing primarily at mucosal surfaces. We have confirmed that CD4+ NKT cells derived from peripheral blood mononuclear cells ( PBMCs) predominantly express CCR5 rather than CXCR4, whereas the reverse is true for CD4+ T cells derived from circulating PBMCs, and that R5-tropic HIV-1 expands efficiently in the CD4+ NKT cells. Moreover, when PBMCs depleted of CD8 α+ cells were stimulated in the presence of α-galactosylceramide ( α-GalCer) and R5-tropic HIV-1 [ NL( AD8)], the production of HIV-1 virions was not suppressed, whereas, similar to the untreated PBMCs, depletion of CD8 β+ cells from PBMCs significantly inhibited virion production. These findings suggest that CD8 αα+ but not CD8 αβ+ cells may have the ability to inhibit R5-tropic HIV-1 replication in CD4+ NKT cells. Here, we show that co-culturing R5-tropic HIV-1-infected CD4+ NKT cells with CD8 αα+ γδ T cells, in particular V γ1V δ1 cells, but not with CD8 αα+ NKT cells or CD8 αα+ dendritic cells, inhibits HIV-1 replication mainly by secreting chemokines, such as macrophage inflammatory proteins 1 α and 1 β and RANTES. Collectively, these results indicate the importance of CD8 αα+ γδ T cells in the control of R5-tropic HIV-1 replication and persistence in CD4+ NKT cells. [ABSTRACT FROM AUTHOR]

The gut microbiota provides an important stimulus for the induction of regulatory T (Treg) cells in mice, whether this applies to newborn children is unknown. In Swedish children, Staphylococcus aureus has become a common early colonizer of the gut. Here, we sought to study the effects of bacterial stimulation on neonatal CD4+ T cells for the induction of CD25+ CD127low Treg cells in vitro. The proportion of circulating CD25+ CD127low Treg cells and their expression of FOXP3, Helios and CTLA-4 was examined in newborns and adults. To evaluate if commensal gut bacteria could induce Treg cells, CellTrace violet-stained non-Treg cells from cord or peripheral blood from adults were co-cultured with autologous CD25+ CD127low Treg cells and remaining mononuclear cells and stimulated with S. aureus. Newborns had a significantly lower proportion of CD25+ CD127low Treg cells than adults, but these cells were Helios+ and CTLA-4+ to a higher extent than in adults. FOXP3+ CD25+ CD127low T cells were induced mainly in neonatal Cell-Trace-stained non-Treg cells after stimulation with S. aureus. In cell cultures from adults, S. aureus induced CD25+ CD127low T cells only if sorted naive CD45RA+ non-Treg cells were used, but these cells expressed less FOXP3 than those induced from newborns. Sorted neonatal CD25+ CD127low T cells from S. aureus-stimulated cultures were still suppressive. Finally, blocking PD-L1 during stimulation reduced the induction of FOXP3+ CD25+ CD127low T cells. These results suggest that newborns have a higher proportion of circulating thymically derived Helios+ Treg cells than adults and that S. aureus possess an ability to convert neonatal conventional CD4+ T cells into FOXP3+ CD25+ CD127low Treg cells via the PD-1/PD-L1 axis. [ABSTRACT FROM AUTHOR]

The co-ordination of T-cell motility, adhesion and activation remains poorly understood. It is also unclear how these functions are co-ordinated with external stimuli. Here we unveil a series of molecular interactions in cis at the surface of T lymphocytes with potent effects on motility and adhesion in these cells, and communicating with proliferative responses. These interactions were controlled by the signature cytokines of T helper subsets interleukin-2 ( IL-2) and IL-4. Low-density lipoprotein receptor-related protein 1 ( LRP1) was found to play a key role for T-cell motility by promoting development of polarized cell shape and cell movement. Endogenous thrombospondin-1 ( TSP-1) enhanced cell surface expression of LRP1 through CD47. Cell surface expressed LRP1 induced motility and processing of TSP-1 while inhibiting adhesion to intercellular adhesion molecule 1 and fibronectin. Interleukin-2, but not IL-4, stimulated synthesis of TSP-1 and motility through TSP-1 and LRP1. Stimulation of the T-cell receptor ( TCR)/ CD3 complex inhibited TSP-1 expression. Inhibitor studies indicated that LRP1 regulated TSP-1 expression and promoted motility through JAK signalling. This LRP1-mediated motogenic signalling was connected to CD47/ Gi protein signalling and IL-2-induced signalling through TSP-1. The motogenic TSP-1/ LRP1 mechanism antagonized TCR/ CD3-induced T-cell proliferation. These results indicate that LRP1 in collaboration with TSP-1 directs a counter-adhesive and counter-proliferative motogenic cascade. T cells seem programmed to prioritize movement before adhesion through this cascade. In conclusion, vital decision-making in T lymphocytes regulating motility, adhesive interactions and proliferation, are integrated through a molecular mechanism connecting different cell surface receptors and their signalling pathways. [ABSTRACT FROM AUTHOR]

In addition to archetypal cognitive defects, Down syndrome ( DS) is characterized by altered lymphocyte development and function, including premature thymic involution and increased incidence of infections. However, the potential mechanisms for these changes have not been fully elucidated. The current study used the Ts65 Dn mouse model of DS to assess deficiencies in T-cell development and possible molecular alterations. Ts65 Dn mice exhibited premature thymic involution and a threefold to fourfold decrease in the number and proportion of immature, double-negative thymocyte progenitors. In addition, there were twofold fewer double-positive and CD4 single-positive thymocytes in Ts65 Dn thymuses. Reflecting this deficient thymic function, there were fewer naive T cells in the spleen and polyclonal stimulation of peripheral T cells exhibited a marked reduction in proliferation, suggesting a senescent phenotype. In contrast, B-cell progenitors were unchanged in the bone marrow of Ts65 Dn mice, but in the spleen, there were decreased transitional and follicular B cells and these cells proliferated less upon antigen receptor stimulus but not in response to lipopolysaccharide. As a potential mechanism for diminished thymic function, immature thymocyte populations expressed diminished levels of the cytokine receptor interleukin-7 Rα, which was associated with decreased proliferation and increased apoptosis. Increased oxidative stress and inhibition of the Notch pathway were identified as possible mediators of decreased interleukin-7 Rα expression in Ts65 Dn mice. The data suggest that immature thymocyte defects underlie immune dysfunction in DS and that increased oxidative stress and reduced cytokine signalling may alter lymphocyte development in Ts65 Dn mice. [ABSTRACT FROM AUTHOR]

Human metapneumovirus (h MPV) is the second most common cause of acute lower respiratory tract infections in children, causing a significant public health burden worldwide. Given that h MPV can repeatedly infect the host without major antigenic changes, it has been suggested that h MPV may have evolved molecular mechanisms to impair host adaptive immunity and, more specifically, T-cell memory. Recent studies have shown that h MPV can interfere with superantigen-induced T-cell activation by infecting conventional dendritic cells ( DCs). Here, we show that h MPV infects mouse DCs in a restricted manner and induces moderate maturation. Nonetheless, h MPV-infected DCs are rendered inefficient at activating naive antigen-specific CD4+ T cells ( OT-II), which not only display reduced proliferation, but also show a marked reduction in surface activation markers and interleukin-2 secretion. Decreased T-cell activation was not mediated by interference with DC-T-cell immunological synapse formation as recently described for the human respiratory syncytial virus (hRSV), but rather by soluble factors secreted by h MPV-infected DCs. These data suggest that although h MPV infection is restricted within DCs, it is sufficient to interfere with their capacity to activate naive T cells. Altogether, by interfering with DC function and productive priming of antigen-inexperienced T cells, h MPV could impair the generation of long-term immunity. [ABSTRACT FROM AUTHOR]

The IMi Ds® immunomodulatory compounds lenalidomide and pomalidomide are agents with anti-inflammatory, immunomodulatory and anti-cancer activity. An excellent success rate has been shown for multiple myeloma in phase I/ II clinical trials leading to Food and Drug Administration approval of lenalidomide. One mechanism by which these drugs could enhance anti-tumour immunity may be through enhanced dendritic cell ( DC) function. Thalidomide, a compound structurally related to lenalidomide and pomalidomide, is known to enhance DC function, and we have investigated whether its analogues, pomalidomide and lenalidomide, also have functional effects on DCs. We used mouse bone marrow-derived DCs treated with 5 or 10 μ m pomalidomide, or lenalidomide from day 1 of culture. Treatment with IMi D® immunomodulatory compounds increased expression of Class I ( H2- Kb), CD86, and pomalidomide also increased Class II (I- Ab) expression in bone marrow-derived DCs, as measured by flow cytometry. Fluorescent bead uptake was increased by up to 45% when DCs were treated with 5 or 10 μ m pomalidomide or lenalidomide compared with non-treated DCs. Antigen presentation assays using DCs primed with ovalbumin, and syngeneic T cells from transgenic OTI and OTII mice (containing MHC restricted, ovalbumin-specific, T cells) showed that both pomalidomide and lenalidomide effectively increased CD8+ T-cell cross-priming (by up to 47%) and that pomalidomide alone was effective in increasing CD4+ T-cell priming (by 30%). Our observations suggest that pomalidomide and lenalidomide enhance tumour antigen uptake by DCs with an increased efficacy of antigen presentation, indicating a possible use of these drugs in DC vaccine therapies. [ABSTRACT FROM AUTHOR]

Plasmacytoid dendritic cells ( pDC) in mesenteric lymph nodes (MLN) may be important regulators of both inflammatory and non-inflammatory mucosal immune responses but human studies are rare. Here we compare pDC from human MLN and peripheral blood (PB) by phenotype and function. MLN from patients with or without inflammatory bowel disease (IBD) undergoing colon surgery and PB from patients with IBD and from controls were used to isolate mononuclear cells. The pDC were analysed by flow cytometry for the expression of CD40, CD80, CD83, CD86, CCR6, CCR7, CX3CR1, CD103 and HLA-DR. Purified pDC from MLN and PB were stimulated with staphylococcus enterotoxin B (SEB), CpG-A, interleukin-3 (IL-3), SEB + IL-3, CpG-A + IL-3 or left unstimulated, and cultured alone or with purified allogeneic CD4+ CD45RA+ HLA-DR- T cells. Subsequently, concentrations of IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-17, interferon-α (IFN-α), IFN-γ and tumour necrosis factor-α (TNF-α) in culture supernatants were determined by multiplex bead array. The PB pDC from IBD patients exhibited an activated and matured phenotype whereas MLN pDC and control PB pDC were less activated. CpG-A and CpG-A + IL-3-stimulated MLN pDC secreted less IL-6 and TNF-α compared with PB pDC from controls. Compared with co-cultures of naive CD4 T cells with PB pDC, co-cultures with MLN pDC contained more IL-2, IL-10 and IFN-γ when stimulated with SEB and SEB + IL-3, and less IFN-α when stimulated with CpG-A. MLN pDC differ phenotypically from PB pDC and their pattern of cytokine secretion and may contribute to specific outcomes of mucosal immune reactions. [ABSTRACT FROM AUTHOR]

In a companion article to this study,1 the successful programming of a JAWSII dendritic cell ( DC) line's antigen uptake and processing was demonstrated based on pre-treatment of DCs with a specific 'cocktail' of select chemokines. Chemokine pre-treatment modulated cytokine production before and after DC maturation [by lipopolysaccharide (LPS)]. After DC maturation, it induced an antigen uptake and processing capacity at levels 36% and 82% higher than in immature DCs, respectively. Such programming proffers a potential new approach to enhance vaccine efficiency. Unfortunately, simply enhancing antigen uptake does not guarantee the desired activation and proliferation of lymphocytes, e.g. CD4+ T cells. In this study, phenotype changes and antigen presentation capacity of chemokine pre-treated murine bone marrow-derived DCs were examined in long-term co-culture with antigen-specific CD4+ T cells to quantify how chemokine pre-treatment may impact the adaptive immune response. When a model antigen, ovalbumin ( OVA), was added after intentional LPS maturation of chemokine-treated DCs, OVA-biased CD4+ T-cell proliferation was initiated from ~ 100% more undivided naive T cells as compared to DCs treated only with LPS. Secretion of the cytokines interferon-γ, interleukin-1β, interleukin-2 and interleukin-10 in the CD4+ T cell : DC co-culture (with or without chemokine pre-treatment) were essentially the same. Chemokine programming of DCs with a 7 : 3 ratio of CCL3 : CCL19 followed by LPS treatment maintained partial immature phenotypes of DCs, as indicated by surface marker ( CD80 and CD86) expression over time. Results here and in our companion paper suggest that chemokine programming of DCs may provide a novel immunotherapy strategy to obviate the natural endocytosis limit of DC antigen uptake, thus potentially increasing DC-based vaccine efficiency. [ABSTRACT FROM AUTHOR]

Compared with adults, the circulating Vγ2Vδ2 T-cell population in cord blood is present at low levels and does not show the strong bias for Vγ2-Jγ1.2 rearrangements. These features may be a result of limited exposure to stimulatory phosphoantigens, lack of T-cell-derived interleukin-2 ( IL-2) or both. In cord blood mononuclear cell cultures, a single round of stimulation, using aminobisphosphonates to elevate phosphoantigen levels, resulted in expansion of adult-like Vγ2 chains and accumulation of memory cells with cytotoxic potential. Selection was similar using IL-2 or myeloid-derived IL-15. The Vγ2Vδ2 T cells present in neonates are capable of generating potent immune responses even when relying on IL-15. [ABSTRACT FROM AUTHOR]

Ligands for E-selectin and P-selectin ( E-lig and P-lig) are induced on CD4+ T cells upon differentiation into effector T cells. Glycosyltransferases, especially α 1,3-fucosyltransferase VII ( Fuc T-VII) and core 2 β1,6- N-acetyl-glycosaminyltransferase I ( C2 Glc NAc T-I), are critical for their synthesis. We here analysed the signals that control the expression of E-lig, P-lig and m RNA coding for Fuc T-VII and C2 Glc NAc T-I. In line with previous reports, we found that P-lig expression correlates with the regulation of C2 Glc NAc T-I, whereas E-lig expression can occur at low levels of C2 Glc NAc T-I m RNA but requires high Fuc T-VII m RNA expression. Interestingly, the two enzymes are regulated by different signals. Activation-induced C2 Glc NAc T-I up-regulation under permissive (T helper type 1) conditions was strongly reduced by cyclosporin A ( Cs A), suggesting the involvement of T-cell receptor-dependent, calcineurin/ NFAT-dependent signals in combination with interleukin-12 ( IL-12) -mediated signals in the regulation of C2 Glc NAc T-I. In contrast, expression of Fuc T-VII m RNA was not significantly inhibited by Cs A. Interleukin-4 inhibited the expression of Fuc T-VII but IL-2 and IL-7 were found to support induction of Fuc T-VII and E-lig. E-selectin, P-selectin and their ligands initially appeared to have rather overlapping functions. These findings however, unravel striking differences in the regulation of E-lig and P-lig expression, dictated by the dominance of Fuc T-VII and C2 Glc NAc T-I, respectively, and their dependency on signals from either promiscuous or homeostatic cytokines ( Fuc T-VII) or a strong T-cell receptor signal in combination with inflammatory cytokines in case of C2 Glc NAc T-I. [ABSTRACT FROM AUTHOR]

Human polymorphonuclear leucocytes ( PMN) are thought to be immunosuppressive. The suppressive mechanism(s) used by PMN are, however, not well defined and in this study they were analysed using T-cell responses to CD3+ CD28 monoclonal antibodies (m Ab) as a readout. We demonstrate that in vitro activated PMN ( PMNact) can, without any T-cell interaction, induce apparent T-cell suppression by inhibiting the stimulatory capacity of the CD3 m Ab. However, a cell-directed suppression of T-cell proliferation was observed when PMNact were added to pre-activated T cells that are already committed to polyclonal proliferation. This suppression was partially reversed by catalase addition ( P < 0·01) and largely reversed by addition of exogenous interleukin-2 ( P < 0·001) but was not significantly reduced by nitric oxide synthase inhibition, myeloperoxidase inhibition or addition of excess arginine. Following removal of PMNact, suppressed T cells could respond normally to further stimulation. In addition to suppressing proliferation, co-culture with PMNact also induced a significant decrease in T-cell viability that was reversed by catalase addition ( P < 0·05). The addition of the arginase inhibitor N-hydroxy-nor- l-arginine induced both a further significant, catalase-sensitive, loss in T-cell viability and increased nitrite release ( P < 0·001). These data demonstrate that PMN, when activated, can both induce T-cell death and reversibly inhibit proliferation of activated T cells. The mechanisms underlying these distinct processes and the effects of arginase inhibitors on PMN induced cytotoxicity merit further investigation. [ABSTRACT FROM AUTHOR]