Showing papers in "Immunology and Cell Biology in 2016"

Exercise and type 2 diabetes: focus on metabolism and inflammation

Abstract: Type 2 diabetes mellitus (T2DM) is associated with metabolic dysregulation and chronic inflammation, and regular exercise may provide a strong stimulus for improving both. In this review, we first discuss the link between inflammation and metabolism. Next, we give an update on the clinical metabolic effects of exercise in T2DM patients with special focus on which parameters to consider for optimizing metabolic improvements. We then discuss the mechanisms whereby exercise exerts its anti-inflammatory and related metabolic effects. Evidence exists that interleukin (IL)-1β is involved in pancreatic β-cell damage, whereas tumor necrosis factor (TNF)-α appears to be a key molecule in peripheral insulin resistance. Mechanistic studies in humans suggest that moderate acute elevations in IL-6, as provoked by exercise, exert direct anti-inflammatory effects by an inhibition of TNF-α and by stimulating IL-1ra (IL-1 receptor antagonist), thereby limiting IL-1β signaling. In addition, IL-6 has direct impact on glucose and lipid metabolism. Moreover, indirect anti-inflammatory effects of exercise may be mediated via improvements in, for example, body composition. While waiting for the outcome of long-term randomized clinical training studies with hard end points, it should be emphasized that physical activity represents a natural strong anti-inflammatory and metabolism-improving strategy with minor side effects.

Inflammation during skeletal muscle regeneration and tissue remodeling: application to exercise-induced muscle damage management.

Abstract: Increase in the practice of sport by more and more numerous people in the Western countries is associated with an increase in muscle injuries, and in demand for improving muscle function and acceleration of muscle recovery after damage. Most of the treatments used target inflammation. Indeed, several lines of experimental evidence in animal models that are supported by human studies identify inflammatory cells, and particularly macrophages, as essential players in skeletal muscle regeneration. Macrophages act not only through their immune functions, but also control myogenesis and extracellular matrix remodeling by directly acting on myogenic precursors and fibro-adipogenic precursors. In light of these recent biological advances, the question of early treatment aiming at blunting inflammation after exercise-induced muscle injury is discussed.

Respiratory inflammation and infections in high-performance athletes.

Abstract: Upper respiratory illness is the most common reason for non-injury-related presentation to a sports medicine clinic, accounting for 35-65% of illness presentations. Recurrent or persistent respiratory illness can have a negative impact on health and performance of athletes undertaking high levels of strenuous exercise. The cause of upper respiratory symptoms (URS) in athletes can be uncertain but the majority of cases are related to common respiratory viruses, viral reactivation, allergic responses to aeroallergens and exercise-related trauma to the integrity of respiratory epithelial membranes. Bacterial respiratory infections are uncommon in athletes. Undiagnosed or inappropriately treated asthma and/or allergy are common findings in clinical assessments of elite athletes experiencing recurrent URS. High-performance athletes with recurrent episodes of URS should undergo a thorough clinical assessment to exclude underlying treatable conditions of respiratory inflammation. Identifying athletes at risk of recurrent URS is important in order to prescribe preventative clinical, training and lifestyle strategies. Monitoring secretion rates and falling concentrations of salivary IgA can identify athletes at risk of URS. Therapeutic interventions are limited by the uncertainty of the underlying cause of inflammation. Topical anti-inflammatory sprays can be beneficial for some athletes. Dietary supplementation with bovine colostrum, probiotics and selected antioxidants can reduce the incidence or severity of URS in some athletes. Preliminary studies on athletes prone to URS indicate a genetic predisposition to a pro-inflammatory response and a dysregulated anti-inflammatory cytokine response to intense exercise as a possible mechanism of respiratory inflammation. This review focuses on respiratory infections and inflammation in elite/professional athletes.

Linking the T cell receptor to the single cell transcriptome in antigen-specific human T cells.

Abstract: Heterogeneity of T cells is a hallmark of a successful adaptive immune response, harnessing the vast diversity of antigen-specific T cells into a coordinated evolution of effector and memory outcomes. The T cell receptor (TCR) repertoire is highly diverse to account for the highly heterogeneous antigenic world. During the response to a virus multiple individual clones of antigen specific CD8+ (Ag-specific) T cells can be identified against a single epitope and multiple epitopes are recognised. Advances in single-cell technologies have provided the potential to study Ag-specific T cell heterogeneity at both surface phenotype and transcriptome levels, thereby allowing investigation of the diversity within the same apparent sub-population. We propose a new method (VDJPuzzle) to reconstruct the native TCRαβ from single cell RNA-seq data of Ag-specific T cells and then to link these with the gene expression profile of individual cells. We applied this method using rare Ag-specific T cells isolated from peripheral blood of a subject who cleared hepatitis C virus infection. We successfully reconstructed productive TCRαβ in 56 of a total of 63 cells (89%), with double α and double β in 18, and 7% respectively, and double TCRαβ in 2 cells. The method was validated via standard single cell PCR sequencing of the TCR. We demonstrate that single-cell transcriptome analysis can successfully distinguish Ag-specific T cell populations sorted directly from resting memory cells in peripheral blood and sorted after ex vivo stimulation. This approach allows a detailed analysis of the TCR diversity and its relationship with the transcriptional profile of different clones.

The MS4A family: counting past 1, 2 and 3.

Abstract: The MS4A (membrane-spanning 4-domain family, subfamily A) family of proteins contains some well-known members including MS4A1 (CD20), MS4A2 (FcɛRIβ) and MS4A3 (HTm4) These three MS4A family members are expressed on the cell surface of specific leukocyte subsets and have been well characterized as having key roles in regulating cell activation, growth and development However, beyond MS4A1-3 there are a large number of related molecules (18 to date in humans) where our understanding of their biological roles is at a relatively nascent stage This review examines the larger MS4A family focusing on their structure, expression, regulation and characterized and/or emerging biological roles Our own work on one family member MS4A8B, and its possible role in epithelial cell regulation, is also highlighted

Exercise and gut immune function: evidence of alterations in colon immune cell homeostasis and microbiome characteristics with exercise training.

Abstract: There is robust evidence that habitual physical activity is anti-inflammatory and protective against developing chronic inflammatory disease. Much less is known about the effects of habitual moderate exercise in the gut, the compartment that has the greatest immunological responsibility and interactions with the intestinal microbiota. The link between the two has become evident, as recent studies have linked intestinal dysbiosis, or the disproportionate balance of beneficial to pathogenic microbes, with increased inflammatory disease susceptibility. Limited animal and human research findings imply that exercise may have a beneficial role in preventing and ameliorating such diseases by having an effect on gut immune function and, recently, microbiome characteristics. Emerging data from our laboratory show that different forms of exercise training differentially impact the severity of intestinal inflammation during an inflammatory insult (for example, ulcerative colitis) and may be jointly related to gut immune cell homeostasis and microbiota-immune interactions. The evidence we review and present will provide data in support of rigorous investigations concerning the effects of habitual exercise on gut health and disease.

Exercise, immune function and respiratory infection: An update on the influence of training and environmental stress.

Abstract: This review outlines recent advancements in the understanding of athlete immune health. Controversies discussed include whether high levels of athletic training and environmental stress (for example, heat acclimation, cryotherapy and hypoxic training) compromise immunity and increase upper respiratory tract infection (URTI). Recent findings challenge early exercise immunology doctrine by showing that international athletes performing high-volume training suffer fewer, not greater, URTI episodes than lower-level performers and URTI incidence decreases, not increases, around the time of competition compared with heavy training. Herein we raise the possibility of host genetic influences on URTI and modifiable behavioural and training-related factors underpinning these recent observations. Continued controversy concerns the proportion of URTI symptoms reported by athletes that are due to infectious pathogens, airway inflammation or as yet unknown causes and indeed whether the proportion differs in athletes and non-athletes. Irrespective of the cause of URTI symptoms (infectious or non-infectious), experts broadly agree that self-reported URTI hinders high-volume athletic training but, somewhat surprisingly, less is known about the influence on athletic performance. In athletes under heavy training, both innate and acquired immunity are often observed to decrease, typically 15-25%, but whether relatively modest changes in immunity increase URTI susceptibility remains a major gap in knowledge. With the exception of cell-mediated immunity that tends to be decreased, exercising in environmental extremes does not provide an additional threat to immunity and host defence. Recent evidence suggests that immune health may actually be enhanced by regular intermittent exposures to environmental stress (for example, intermittent hypoxia training).

IgG subclass co-expression brings harmony to the quartet model of murine IgG function

Abstract: A model of murine IgG function is presented in which the co-expression of the IgG subclasses is a central feature, class switching occurs before the commencement of somatic hypermutation, and there is little switching between subclasses. It is named the quartet model to emphasize the harmony that comes from the simultaneous presence of the four subclasses. In this model, IgG3 and IgG2b antibodies are particularly important early in the response, when T-cell help may be limiting. IgG3 initiates inflammation through complement fixation, whereas IgG2b provides early FcγR-mediated effector functions. As T-cell help strengthens, IgG2a antibodies increase the power of the response, whereas IgG1 production helps limit the inflammatory drive and limits immunopathology. The model highlights the fact that murine IgG subclasses function quite differently to human IgG subclasses. This allows them to serve the special immunological needs of a species that is vulnerable because of its small size.

Human macrophages induce CD4(+)Foxp3(+) regulatory T cells via binding and re-release of TGF-β.

Abstract: While pro-inflammatory immune responses are a requirement to combat microbes, uncontrolled self-directed inflammatory immune responses are the hallmark of autoimmune diseases. Restoration of immunological tolerance involves both suppression of ongoing tissue-destructive immune responses and re-education of the host immune system. Both functionally immunosuppressive macrophages (M2) and regulatory T cells (Tregs) are implicated in these processes. Their mutual interaction is synergistic in this context and adoptive transfer of each cell type has been functioning as immunotherapy in experimental models, being particularly effective when using M2 macrophages generated with an optimized interleukin-4 (IL-4)/interleukin-10 (IL-10)/transforming growth factor-β (TGF-β) combination. As a prerequisite for eventual translation of M2 therapy into clinical settings we herein studied the induction, stability and mechanism of generation of human induced Tregs (iTregs) by M2 macrophages generated with IL-4/IL-10/TGF-β. The supernatants of monocyte-derived human M2 macrophages robustly induced FOXP3 and other Treg signature molecules such as CTLA-4 and IKZF4 in human naive CD4 T cells. M2-induced iTregs displayed enhanced FOXP3 stability and low expression of pro-inflammatory cytokines interferon-γ and IL-17, as well as functional immunosuppressive activity compared with control T cells. The FOXP3-inducing activity was dependent on TGF-β, which was both expressed and captured with re-release by M2 macrophages into the soluble supernatant fraction, in which the TGF-β was not confined to extracellular vesicles such as exosomes. We propose that adoptive transfer of human M2 macrophages may be exploited in the future to induce Tregs in situ by delivering TGF-β, which could be developed as a therapeutic strategy to target autoimmune and other inflammatory diseases.

Single-cell technologies are revolutionizing the approach to rare cells

Abstract: In the last lustrum single-cell techniques such as single-cell quantitative PCR, RNA and DNA sequencing, and the state-of-the-art cytometry by time of flight (CyTOF) mass cytometer have allowed a detailed analysis of the sub-composition of different organs from the bone marrow hematopoietic compartment to the brain. These fine-grained analyses have highlighted the great heterogeneity within each cell compartment revealing previously unknown subpopulations of cells. In this review, we analyze how this fast technological evolution has improved our understanding of the biological processes with a particular focus on rare cells of the immune system.

Discovery of functionally selective C5aR2 ligands: novel modulators of C5a signalling

Abstract: The complement cascade is comprised of a highly sophisticated network of innate immune proteins that are activated in response to invading pathogens or tissue injury. The complement activation peptide, C5a, binds two seven transmembrane receptors, namely the C5a receptor 1 (C5aR1) and C5a receptor 2 (C5aR2, or C5L2). C5aR2 is a non-G-protein-signalling receptor whose biological role remains controversial. Some of this controversy arises owing to the lack of selective ligands for C5aR2. In this study, a library of 61 peptides based on the C-terminus of C5a was assayed for the ability to selectively modulate C5aR2 function. Two ligands (P32 and P59) were identified as functionally selective C5aR2 ligands, exhibiting selective recruitment of β-arrestin 2 via C5aR2, partial inhibition of C5a-induced ERK1/2 activation and lipopolysaccharide-stimulated interleukin-6 release from human monocyte-derived macrophages. Importantly, neither ligand could induce ERK1/2 activation or inhibit C5a-induced ERK1/2 activation via C5aR1 directly. Finally, P32 inhibited C5a-mediated neutrophil mobilisation in wild-type, but not C5aR2(-/-) mice. These functionally selective ligands for C5aR2 are novel tools that can selectively modulate C5a activity in vitro and in vivo, and thus will be valuable tools to interrogate C5aR2 function.

Immunological aspects of sport nutrition

Abstract: Prolonged bouts of exercise and heavy training regimens are associated with depression of immune system functions that can increase the risk of picking up opportunistic infections such as the common cold and influenza. Some common sport nutrition practices including high-carbohydrate diets and carbohydrate ingestion during exercise, training with low-glycogen stores, intentional dieting for weight loss, ingestion of high-dose antioxidant supplements and protein ingestion post exercise may influence immune system status in athletes. In order to maintain robust immunity, athletes need to consume a well-balanced diet that is sufficient to meet their requirements for energy, carbohydrate, protein and micronutrients. Dietary deficiencies of protein and specific micronutrients are well known to be potential causes of immune dysfunction and an adequate intake of some essential minerals including iron and zinc and the vitamins A, D, E, B6 and B12 are important to maintain a healthy immune function. Vitamin D may be a particular concern as recent studies have emphasised its importance in limiting infection episode incidence and duration in both the general population and in athletes and many individuals exhibit inadequate vitamin D status during the winter months. There is only limited evidence that individual amino acids, β-glucans, herbal extracts and zinc are capable of boosting immunity or reducing infection risk in athletes. The ingestion of carbohydrate during exercise and daily consumption of probiotics, vitamin D3, bovine colostrum and plant polyphenol containing supplements or foodstuffs currently offer the best chance of success, particularly for those individuals who are prone to illness.

Perturbation of gut bacteria induces a coordinated cellular immune response in the purple sea urchin larva.

Abstract: The purple sea urchin (Strongylocentrotus purpuratus) genome sequence contains a complex repertoire of genes encoding innate immune recognition proteins and homologs of important vertebrate immune regulatory factors. To characterize how this immune system is deployed within an experimentally tractable, intact animal, we investigate the immune capability of the larval stage. Sea urchin embryos and larvae are morphologically simple and transparent, providing an organism-wide model to view immune response at cellular resolution. Here we present evidence for immune function in five mesenchymal cell types based on morphology, behavior and gene expression. Two cell types are phagocytic; the others interact at sites of microbial detection or injury. We characterize immune-associated gene markers for three cell types, including a perforin-like molecule, a scavenger receptor, a complement-like thioester-containing protein and the echinoderm-specific immune response factor 185/333. We elicit larval immune responses by (1) bacterial injection into the blastocoel and (2) seawater exposure to the marine bacterium Vibrio diazotrophicus to perturb immune state in the gut. Exposure at the epithelium induces a strong response in which pigment cells (one type of immune cell) migrate from the ectoderm to interact with the gut epithelium. Bacteria that accumulate in the gut later invade the blastocoel, where they are cleared by phagocytic and granular immune cells. The complexity of this coordinated, dynamic inflammatory program within the simple larval morphology provides a system in which to characterize processes that direct both aspects of the echinoderm-specific immune response as well as those that are shared with other deuterostomes, including vertebrates.

The molecular mechanisms of TLR-signaling cooperation in cytokine regulation

Abstract: Innate immune cells recognize pathogens through pattern recognition receptors (PRRs), and activation of PRRs induces downstream signaling pathways to mount appropriate immune responses. Pathogens usually carry multiple ligands, which can simultaneously activate multiple PRRs. The cooperation of multiple PRRs and consequential crosstalk between their downstream pathways could enhance cytokine expression, which is required for effective immune responses. On the other hand, immune over-activation could also harm the host if immune homeostasis is not restored. Therefore, it is important to understand the mechanisms of PRR cooperation during an infection. As the best characterized PRRs, Toll-like receptors (TLRs) have an important role in pathogen recognition, and crosstalk among TLRs is common. In this review, we provide an update on the recent findings on the mechanisms of TLR cooperation. We summarize the known mechanisms and provide a future perspective on TLR crosstalk study, with a caution against the use of multiple TLR ligands as adjuvants in therapeutic strategies.

Interferon-β therapy specifically reduces pathogenic memory B cells in multiple sclerosis patients by inducing a FAS-mediated apoptosis.

Abstract: Growing evidences put B lymphocytes on a central stage in multiple sclerosis (MS) immunopathology. While investigating the effects of interferon-β (IFN-β) therapy, one of the most used first-line disease-modifying drugs for the treatment of relapsing-remitting MS, in circulating B-cell sub-populations, we found a specific and marked decrease of CD27+ memory B cells. Interestingly, memory B cells are considered a population with a great disease-driving relevance in MS and resulted to be also target of B-cell depleting therapies. In addition, Epstein-Barr virus (EBV), associated with MS etiopathogenesis, harbors in this cell type and an IFN-β-induced reduction of the memory B-cell compartment, in turn, resulted in a decreased expression of the EBV gene latent membrane protein 2A in treated patients. We found that in vivo IFN-β therapy specifically and highly induced apoptosis in memory B cells, in accordance with a strong increase of the apoptotic markers Annexin-V and active caspase-3, via a mechanism requiring the FAS-receptor/TACI (transmembrane activator and CAML interactor) signaling. Thus, efficacy of IFN-β therapy in MS may rely not only on its recognized anti-inflammatory activities but also on the specific depletion of memory B cells, considered to be a pathogenic cell subset, reducing their inflammatory impact in target organs.

A multi-subunit Chlamydia vaccine inducing neutralizing antibodies and strong IFN-γ + CMI responses protects against a genital infection in minipigs

Abstract: Chlamydia is the most widespread sexually transmitted bacterial disease and a prophylactic vaccine is highly needed. Ideally, this vaccine is required to induce a combined response of Th1 cell-mediated immune (CMI) response in concert with neutralizing antibodies. Using a novel Gottingen minipig animal model, we evaluated the immunogenicity and efficacy of a multi-subunit vaccine formulated in the strong Th1-inducing adjuvant CAF01. We evaluated a mixture of two fusion proteins (Hirep1 and CTH93) designed to promote either neutralizing antibodies or cell-mediated immunity, respectively. Hirep1 is a novel immunogen based on the variant domain (VD) 4 region from major outer membrane protein (MOMP) serovar (Sv) D, SvE and SvF, and CTH93 is a fusion molecule of three antigens (CT043, CT414 and MOMP). Pigs were immunized twice intramuscularly with either Hirep1+CTH93/CAF01, UV-inactivated Chlamydia trachomatis SvD bacteria (UV-SvD/CAF01) or CAF01. The Hirep1+CTH93/CAF01 vaccine induced a strong CMI response against the vaccine antigens and high titers of antibodies, particularly against the VD4 region of MOMP. Sera from Hirep1+CTH93/CAF01 immunized pigs neutralized C. trachomatis SvD and SvF infectivity in vitro. Both Hirep1+CTH93/CAF01 and UV-SvD/CAF01 vaccination protected pigs against a vaginal C. trachomatis SvD infection. In conclusion, the Hirep1+CTH93/CAF01 vaccine proved highly immunogenic and equally protective as UV-SvD/CAF01 showing promise for the development of a subunit vaccine against Chlamydia.

The contribution of Chlamydia-specific CD8⁺ T cells to upper genital tract pathology.

Abstract: Genital chlamydial infections lead to severe upper reproductive tract pathology in a subset of untreated women We demonstrated previously that tumor necrosis factor (TNF)-α-producing CD8(+) T cells contribute significantly to chlamydial upper genital tract pathology in female mice In addition, we observed that minimal chlamydial oviduct pathology develops in OT-1 transgenic (OT-1) mice, wherein the CD8(+) T-cell repertoire is restricted to recognition of the ovalbumin peptide Ova(257-264), suggesting that non-Chlamydia-specific CD8(+) T cells may not be responsible for chlamydial pathogenesis In the current study, we evaluated whether antigen-specific CD8(+) T cells mediate chlamydial pathology Groups of wild-type (WT) C57BL/6J, OT-1 mice, and OT-1 mice replete with WT CD8(+) T cells (1 × 10(6) cells per mouse intravenously) were infected intravaginally with C muridarum (5 × 10(4) IFU/mouse) Serum total anti-Chlamydia antibody and total splenic anti-Chlamydia interferon (IFN)-γ and TNF-α responses were comparable among the three groups of animals However, Chlamydia-specific IFN-γ and TNF-α production from purified splenic CD8(+) T cells of OT-1 mice was minimal, whereas responses in OT-1 mice replete with WT CD8(+) T cells were comparable to those in WT animals Vaginal chlamydial clearance was comparable between the three groups of mice Importantly, the incidence and severity of oviduct and uterine horn pathology was significantly reduced in OT-1 mice but reverted to WT levels in OT-1 mice replete with WT CD8(+) T cells Collectively, these results demonstrate that Chlamydia-specific CD8(+) T cells contribute significantly to upper genital tract pathology

Immunometabolism and autoimmunity

Abstract: A continuous increase in the prevalence of autoimmune diseases is to be expected in the aging societies worldwide. Autoimmune disorders not only cause severe disability and chronic pain, but also lead to considerable socio-economic costs. Given that the current treatment options are not curative, have substantial side effects and a high percentage of non-responders, innovative options to the existing therapeutic armament against autoimmune diseases are urgently required. Accumulating evidence suggests that changes in the metabolism of immune cells are associated with, and contribute to the pathogenesis of autoimmunity. Additionally, some autoimmune diseases share alterations in metabolic pathways, key metabolites or metabolic byproducts such as reactive oxygen species. Other examples for metabolic changes in autoimmune settings include modifications in amino acid and cholesterol levels or glucose catabolism. Thus, the emerging field of immunometabolism may hold the potential to discover new therapeutic targets. Here, we discuss recent findings describing metabolic changes in autoimmune arthritis, multiple sclerosis as well as type 1 diabetes, focusing on pathophysiological aspects.

The majority of murine γδ T cells at the maternal-fetal interface in pregnancy produce IL-17.

Abstract: Compared with lymphoid tissues, the immune cell compartment at mucosal sites is enriched with T cells bearing the γδ T-cell receptor (TCR). The female reproductive tract, along with the placenta and uterine decidua during pregnancy, are populated by γδ T cells predominantly expressing the invariant Vγ6(+)Vδ1(+) receptor. Surprisingly little is understood about the function of these cells. We found that the majority of γδ T cells in the non-pregnant uterus, pregnant uterus, decidua and placenta of mice express the transcription factor RORγt and produce interleukin-17 (IL-17). In contrast, IFNγ-producing γδ T cells were markedly reduced in gestational tissues compared with uterine-draining lymph nodes and spleen. Both uterine-resident invariant Vγ6(+) and Vγ4(+) γδ T cells which are more typically found in lymphoid tissues and circulating blood, were found to express IL-17. Vγ4(+) γδ T cells were particularly enriched in the placenta, suggesting a pregnancy-specific recruitment or expansion of these cells. A small increase in IL-17-producing γδ T cells was observed in allogeneic compared with syngeneic pregnancy, suggesting a contribution to regulating the maternal response to paternally-derived alloantigens. However, their high proportions also in non-pregnant uteri and gestational tissues of syngeneic pregnancy imply a role in the prevention of intrauterine infection or quality control of fetal development. These data suggest the need for a more rigorous evaluation of the role of IL-17 in sustaining normal pregnancy, particularly as emerging data points to a pathogenic role for IL-17 in pre-eclampsia, pre-term birth, miscarriage and maternal immune activation-induced behavioral abnormalities in offspring.

The memory of a killer T cell: models of CD8(+) T cell differentiation

Abstract: CD8(+) T cells have an important role in protection against infections and reinfections of intra-cellular pathogens like viruses. Naive CD8(+) T cells circulating in blood or lymphoid tissues can get activated upon stimulation by cognate antigen. The activated T cells undergo rapid proliferation and can expand more than 10(4)-folds comprising largely of effector T cells. Upon antigen clearance, the CD8(+) T-cell population contracts due to apoptosis, leaving behind a small population of memory T cells. The timing and mechanisms underlying the differentiation of naive cells into effector cells and memory cells is not yet clear. In this article, we review the recent quantitative studies that support different hypotheses of CD8(+) T-cell differentiation.

Early-life exercise may promote lasting brain and metabolic health through gut bacterial metabolites

Abstract: The 100 trillion microorganisms residing within our intestines contribute roughly 5 million additional genes to our genetic gestalt, thus posing the potential to influence many aspects of our physiology. Microbial colonization of the gut shortly after birth is vital for the proper development of immune, neural and metabolic systems, while sustaining a balanced, diverse gut flora populated with beneficial bacteria is necessary for maintaining optimal function of these systems. Although symbiotic host-microbial interactions are important throughout the lifespan, these interactions can have greater and longer lasting impacts during certain critical developmental periods. A better understanding of these sensitive periods is necessary to improve the impact and effectiveness of health-promoting interventions that target the microbial ecosystem. We have recently reported that exercise initiated in early life increases gut bacterial species involved in promoting psychological and metabolic health. In this review, we emphasize the ability of exercise during this developmentally receptive time to promote optimal brain and metabolic function across the lifespan through microbial signals.

Interleukin-6 controls uterine Th9 cells and CD8(+) T regulatory cells to accelerate parturition in mice.

Abstract: Interleukin-6 controls uterine Th9 cells and CD8 + T regulatory cells to accelerate parturition in mice

Tumour-specific CD4 T cells eradicate melanoma via indirect recognition of tumour-derived antigen.

Abstract: The importance of CD4 T cells in tumour immunity has been increasingly recognised, with recent reports describing robust CD4 T cell-dependent tumour control in mice whose immune-regulatory mechanisms have been disturbed by irradiation, chemotherapy, immunomodulatory therapy and/or constitutive immunodeficiency. Tumour control in such models has been attributed in large part to direct Major Histocompatibility Complex (MHC) class II-dependent CD4 T cell killing of tumour cells. To test whether CD4 T cells can eradicate tumours without directly killing tumour cells, we developed an animal model in which tumour-derived antigen could be presented to T-cell receptor (TCR)-transgenic CD4 T cells by host but not tumour MHC class II molecules. In I-E(+) mice bearing I-E(null) tumours, naive I-E-restricted CD4 T cells proliferated locally in tumour-draining lymph nodes after recognising tumour-derived antigen on migratory dendritic cells. In lymphopaenic but not immunosufficient hosts, CD4 T cells differentiated into polarised T helper type 1 (Th1) cells expressing interferon gamma (IFNγ), tumor necrosis factor alpha (TNFα) and interleukin (IL)-2 but little IL-17, and cleared established tumours. Tumour clearance was enhanced by higher TCR affinity for tumour antigen-MHC class II and was critically dependent on IFNγ, as demonstrated by early tumour escape in animals treated with an IFNγ blocking antibody. Thus, CD4 T cells and IFNγ can control tumour growth without direct T-cell killing of tumour cells, and without requiring additional adaptive immune cells such as CD8 T cells and B cells. Our results support a role for effective CD4 T cell-dependent tumour immunity against MHC class II-negative tumours.

Melanoma‐derived factors alter the maturation and activation of differentiated tissue‐resident dendritic cells

Abstract: Dendritic cells (DCs) are key regulators of host immunity that are capable of inducing either immune tolerance or activation. In addition to their well-characterized role in shaping immune responses to foreign pathogens, DCs are also known to be critical for the induction and maintenance of anti-tumor immune responses. Therefore, it is important to understand how tumors influence the function of DCs and the quality of immune responses they elicit. Although the majority of studies in this field to date have utilized either immortalized DC lines or DC populations that have been generated under artificial conditions from hematopoietic precursors in vitro, we wished to investigate how tumors impact the function of already differentiated, tissue-resident DCs. Therefore, we used both an ex vivo and in vivo model system to assess the influence of melanoma-derived factors on DC maturation and activation. In ex vivo studies with freshly isolated splenic DCs, we demonstrate that the extent to which DC maturation and activation are altered by these factors correlates with melanoma tumorigenicity, and we identify partial roles for tumor-derived transforming growth factor (TGF)β1 and vascular endothelial growth factor (VEGF)-A in the altered functionality of DCs. In vivo studies using a lung metastasis model of melanoma also demonstrate tumorigenicity-dependent alterations to the function of lung-resident DCs, and skewed production of proinflammatory cytokines and chemokines by these tumor-altered cells is associated with recruitment of an immune infiltrate that may ultimately favor tumor immune escape and outgrowth.

Towards identification of immune and genetic correlates of severe influenza disease in Indigenous Australians

Abstract: Indigenous populations, including Indigenous Australians, are highly susceptible to severe influenza disease and the underlying mechanisms are unknown. We studied immune and genetic factors that could predicate severe influenza disease in Indigenous Australians enrolled in the LIFT study: looking into influenza T-cell immunity. To examine CD8(+) T-cell immunity, we characterised human leukocyte antigen (HLA) profiles. HLA typing confirmed previous studies showing predominant usage of HLA-A*02:01, 11:01, 24:02, 34:01 and HLA-B*13:01, 15:21, 40:01/02, 56:01/02 in Indigenous Australians. We identified two new HLA alleles (HLA-A*02:new and HLA-B*56:new). Modelling suggests that variations within HLA-A*02:new (but not HLA-B56:new) could affect peptide binding. There is a relative lack of known influenza epitopes for the majority of these HLAs, with the exception of a universal HLA-A*02:01-M158 epitope and proposed epitopes presented by HLA-A*11:01/HLA-A*24:02. To dissect universal CD8(+) T-cell responses, we analysed the magnitude, function and T-cell receptor (TCR) clonality of HLA-A*02:01-M158(+)CD8(+) T cells. We found comparable IFN-γ, TNF and CD107a and TCRαβ characteristics in Indigenous and non-Indigenous Australians, suggesting that the ~15% of Indigenous people that express HLA-A*02:01 have universal influenza-specific CD8(+) T-cell immunity. Furthermore, the frequency of an influenza host risk factor, IFITM3-C/C, was comparable between Indigenous Australians and Europeans, suggesting that expression of this allele does not explain increased disease severity at a population level. Our study indicates a need to identify novel influenza-specific CD8(+) T-cell epitopes restricted by HLA-A and HLA-B alleles prevalent in Indigenous populations for the rational design of universal T-cell vaccines.

Emerging role of immunoproteasomes in pathophysiology

Abstract: The immunoproteasome is a proteasome variant that is found only in jawed vertebrates. It is responsible for degrading intracellular proteins to generate a major source of peptides with substantial major histocompatibility complex I binding affinity. The immunoproteasome also has roles in T-cell survival, differentiation and proliferation in various pathological conditions. In humans, any alteration in the expression, assembly or function of the immunoproteasome can lead to cancer, autoimmune disorders or inflammatory diseases. Although the roles of the immunoproteasome in cancer and neurodegenerative disorders have been extensively studied, its significance in other disease conditions has only recently become known. Therefore, there is renewed interest in the development of drugs, vaccines and biomarkers that target the immunoproteasome. The current review highlights the involvement of this complex in disease pathology in addition to the advances made in immunoproteasome research.

A CD2 high‐expressing stress‐resistant human plasmacytoid dendritic‐cell subset

Abstract: Human plasmacytoid dendritic cells (pDCs) were considered to be a phenotypically and functionally homogeneous cell population; however, recent analyses indicate potential heterogeneity. This is of major interest, given their importance in the induction of anti-viral responses and their role in creating immunologically permissive environments for human malignancies. For this reason, we investigated the possible presence of human pDC subsets in blood and bone marrow, using unbiased cell phenotype clustering and functional studies. This defined two major functionally distinct human pDC subsets, distinguished by differential expression of CD2. The CD2(hi) and CD2(lo) pDCs represent discontinuous subsets, each with hallmark pDC functionality, including interferon-alpha production. The rarer CD2(hi) pDC subset demonstrated a significant survival advantage over CD2(lo) pDC during stress and upon exposure to glucocorticoids (GCs), which was associated with higher expression of the anti-apoptotic molecule BCL2. The differential sensitivity of these two human pDC subsets to GCs is demonstrated in vivo by a relative increase in CD2(hi) pDC in multiple myeloma patients treated with GCs. Hence, the selective apoptosis of CD2(lo) pDC during stress represents a novel mechanism for the control of innate responses.

Galectin-8 promotes regulatory T-cell differentiation by modulating IL-2 and TGFβ signaling

Abstract: Galectins (Gals) have emerged as potent immunoregulatory molecules that control chronic inflammation through distinct mechanisms. Gal-8, a tandem-repeat type Gal with unique preference for α2,3-sialylated glycans, is ubiquitously expressed, but little is known about its role in T-cell differentiation. Here we report that Gal-8 promotes the polyclonal differentiation of primary mouse regulatory T (Treg) cells in vitro. We further show that Gal-8 also facilitates antigen-specific differentiation of Treg cells, and that Treg cells polarized in the presence of Gal-8 express cytotoxic T-lymphocyte antigen-4 and interleukin (IL)-10 at a higher frequency than control Treg cells, and efficiently inhibit proliferation of activated T-cells in vitro. Investigation of the mechanism by which Gal-8 promotes Treg conversion revealed that Gal-8 activates transforming growth factor-β signaling and promotes sustained IL-2R signaling. Taken together, these data suggest that Gal-8 promotes the differentiation of highly suppressive Treg cells, which has implications for the treatment of inflammatory and autoimmune diseases.

Mevalonate kinase deficiency leads to decreased prenylation of Rab GTPases

Abstract: Mevalonate kinase deficiency (MKD) is caused by mutations in a key enzyme of the mevalonate-cholesterol biosynthesis pathway, leading to recurrent autoinflammatory disease characterised by enhanced release of interleukin-1β (IL-1β). It is currently believed that the inflammatory phenotype of MKD is triggered by temperature-sensitive loss of mevalonate kinase activity and reduced biosynthesis of isoprenoid lipids required for the prenylation of small GTPase proteins. However, previous studies have not clearly shown any change in protein prenylation in patient cells under normal conditions. With lymphoblast cell lines from two compound heterozygous MKD patients, we used a highly sensitive in vitro prenylation assay, together with quantitative mass spectrometry, to reveal a subtle accumulation of unprenylated Rab GTPases in cells cultured for 3 days or more at 40 °C compared with 37 °C. This included a 200% increase in unprenylated Rab7A, Rab14 and Rab1A. Inhibition of sterol regulatory element-binding protein (SREBP) activation by fatostatin led to more pronounced accumulation of unprenylated Rab proteins in MKD cells but not parent cells, suggesting that cultured MKD cells may partially overcome the loss of isoprenoid lipids by SREBP-mediated upregulation of enzymes required for isoprenoid biosynthesis. Furthermore, while inhibition of Rho/Rac/Rap prenylation promoted the release of IL-1β, specific inhibition of Rab prenylation by NE10790 had no effect in human peripheral blood mononuclear cells or human THP-1 monocytic cells. These studies demonstrate for the first time that mutations in mevalonate kinase can lead to a mild, temperature-induced defect in the prenylation of small GTPases, but that loss of prenylated Rab GTPases is not the cause of enhanced IL-1β release in MKD.

Retinoic acid suppresses IL-17 production and pathogenic activity of γδ T cells in CNS autoimmunity.

Abstract: Retinoic acid (RA) in the steady state enhances induction of Foxp3(+) regulatory T (Treg) cells and inhibits differentiation of Th1 and Th17 cells, thereby maintaining tolerance, but can in inflammatory conditions promote effector Th1 and Th17 cells that mediate inflammation. IL-17-producing γδ T cells have recently been shown to have a major pathogenic role in autoimmune diseases. Here, we examined the immunomodulatory effects of RA on γδ T cells. We found that RA had a dramatic suppressive effect on IL-17A and IL-17F production by γδ T cells stimulated with IL-1β and IL-23. RA suppressed RORγt, IL-1R and IL-23R expression in γδ T cells. Treatment of mice with RA suppressed IL-17 production by γδ T cells in vivo. Furthermore, treatment of T cells with RA attenuated their ability to induce disease in experimental autoimmune encephalomyelitis (EAE), a murine model for multiple sclerosis. This was associated with a reduction in the number of central nervous system-infiltrating γδ T cells, but also CD4(+) T cells that produced IL-17A, IL-17F or GM-CSF. Interestingly, treatment of γδ T cells with RA or removal of γδ T cells from a bulk population of T cells significantly reduced their capacity to induce EAE, demonstrating a critical role for γδ T cells in promoting pathogenic Th17 cells. Our findings demonstrate that the anti-inflammatory properties of RA are mediated in part by suppressing STAT3-mediated activation of cytokine production and cytokine receptor expression in γδ T cells, which suppresses their ability to activate Th17 cells.