The biological mechanisms linking obesity to insulin resistance have not been fully elucidated. We have shown that insulin resistance or glucose intolerance in diet-induced obese mice is related to a ...shift in the ratio of pro- and anti-inflammatory T cells in adipose tissue. We sought to test the hypothesis that the balance of T-cell phenotypes would be similarly related to insulin resistance in human obesity.
Healthy overweight or obese human subjects underwent adipose-tissue biopsies and quantification of insulin-mediated glucose disposal by the modified insulin suppression test. T-cell subsets were quantified by flow cytometry in visceral (VAT) and subcutaneous adipose tissue (SAT). Results showed that CD4 and CD8 T cells infiltrate both depots, with proinflammatory T-helper (Th)-1, Th17, and CD8 T cells, significantly more frequent in VAT as compared with SAT. T-cell profiles in SAT and VAT correlated significantly with one another and with peripheral blood. Th1 frequency in SAT and VAT correlated directly, whereas Th2 frequency in VAT correlated inversely, with plasma high-sensitivity C-reactive protein concentrations. Th2 in both depots and peripheral blood was inversely associated with systemic insulin resistance. Furthermore, Th1 in SAT correlated with plasma interleukin-6. Relative expression of associated cytokines, measured by real-time polymerase chain reaction, reflected flow cytometry results. Most notably, adipose tissue expression of anti-inflammatory interleukin-10 was inversely associated with insulin resistance.
CD4 and CD8 T cells populate human adipose tissue and the relative frequency of Th1 and Th2 are highly associated with systemic inflammation and insulin resistance. These findings point to the adaptive immune system as a potential mediator between obesity and insulin resistance or inflammation. Identification of antigenic stimuli in adipose tissue may yield novel targets for treatment of obesity-associated metabolic disease.
•Mass cytometry's niche within cutting edge single cell analysis methods.•Unbiased analysis of lymphoid and myeloid immune cell diversity.•Simultaneous screening and deep-profiling of antigen ...specific T cells.•Tackling the diversity of tumor immune infiltrates using mass cytometry.
Advancement in methodologies for single cell analysis has historically been a major driver of progress in immunology. Currently, high dimensional flow cytometry, mass cytometry and various forms of single cell sequencing-based analysis methods are being widely adopted to expose the staggering heterogeneity of immune cells in many contexts. Here, we focus on mass cytometry, a form of flow cytometry that allows for simultaneous interrogation of more than 40 different marker molecules, including cytokines and transcription factors, without the need for spectral compensation. We argue that mass cytometry occupies an important niche within the landscape of single-cell analysis platforms that enables the efficient and in-depth study of diverse immune cell subsets with an ability to zoom-in on myeloid and lymphoid compartments in various tissues in health and disease. We further discuss the unique features of mass cytometry that are favorable for combining multiplex peptide-MHC multimer technology and phenotypic characterization of antigen specific T cells. By referring to recent studies revealing the complexities of tumor immune infiltrates, we highlight the particular importance of this technology for studying cancer in the context of cancer immunotherapy. Finally, we provide thoughts on current technical limitations and how we imagine these being overcome.
Obesity has reached epidemic proportions, but little is known about its influence on the intestinal immune system. Here we show that the gut immune system is altered during high-fat diet (HFD) ...feeding and is a functional regulator of obesity-related insulin resistance (IR) that can be exploited therapeutically. Obesity induces a chronic phenotypic pro-inflammatory shift in bowel lamina propria immune cell populations. Reduction of the gut immune system, using beta7 integrin-deficient mice (Beta7null), decreases HFD-induced IR. Treatment of wild-type HFD C57BL/6 mice with the local gut anti-inflammatory, 5-aminosalicylic acid (5-ASA), reverses bowel inflammation and improves metabolic parameters. These beneficial effects are dependent on adaptive and gut immunity and are associated with reduced gut permeability and endotoxemia, decreased visceral adipose tissue inflammation, and improved antigen-specific tolerance to luminal antigens. Thus, the mucosal immune system affects multiple pathways associated with systemic IR and represents a novel therapeutic target in this disease.
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•High-fat diet induces low-grade bowel inflammatory changes in resident immune cells•Altered gut immunity in obesity contributes to obesity-related insulin resistance•Gut immunity alters gut barrier, fat inflammation, and oral tolerance in obesity•Targeting gut inflammation is a novel treatment approach for metabolic disease
Luck and Tsai et al. report that altered gut immunity during obesity contributes to systemic insulin resistance through changes in intestinal barrier function, endotoxemia, fat inflammation, and oral tolerance to gut luminal antigen. Targeting gut inflammation with 5-ASA improves these parameters and represents a novel treatment approach for metabolic disease.
Obesity-associated insulin resistance, a common precursor of type 2 diabetes, is characterized by chronic inflammation of tissues, including visceral adipose tissue (VAT). Here we show that B-1a ...cells, a subpopulation of B lymphocytes, are novel and important regulators of this process. B-1a cells are reduced in frequency in obese high-fat diet (HFD)-fed mice, and EGFP interleukin-10 (IL-10) reporter mice show marked reductions in anti-inflammatory IL-10 production by B cells in vivo during obesity. In VAT, B-1a cells are the dominant producers of B cell-derived IL-10, contributing nearly half of the expressed IL-10 in vivo. Adoptive transfer of B-1a cells into HFD-fed B cell-deficient mice rapidly improves insulin resistance and glucose tolerance through IL-10 and polyclonal IgM-dependent mechanisms, whereas transfer of B-2 cells worsens metabolic disease. Genetic knockdown of B cell-activating factor (BAFF) in HFD-fed mice or treatment with a B-2 cell-depleting, B-1a cell-sparing anti-BAFF antibody attenuates insulin resistance. These findings establish B-1a cells as a new class of immune regulators that maintain metabolic homeostasis and suggest manipulation of these cells as a potential therapy for insulin resistance.
T cells play important multifaceted roles during dengue infection, and understanding their responses is important for defining correlates of protective immunity and identifying effective vaccine ...antigens. Using mass cytometry and a highly multiplexed peptide-HLA (human leukocyte antigen) tetramer staining strategy, we probed T cells from dengue patients—a total of 430 dengue and control candidate epitopes—together with key markers of activation, trafficking, and differentiation. During acute disease, dengue-specific CD8+ T cells expressed a distinct profile of activation and trafficking receptors that distinguished them from non-dengue-specific T cells. During convalescence, dengue-specific T cells differentiated into two major cell fates, CD57+ CD127−-resembling terminally differentiated senescent memory cells and CD127+ CD57−-resembling proliferation-capable memory cells. Validation in an independent cohort showed that these subsets remained at elevated frequencies up to one year after infection. These analyses aid our understanding of the generation of T cell memory in dengue infection or vaccination.
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•Dengue infection causes broad activation and proliferation of many immune subsets•EBV- and influenza-specific T cells show no bystander activation during dengue infection•Dengue-specific T cells showed HLA-associated differences in activation markers•Dengue-specific T cells differentiated into two major cell fates
Understanding T cell responses to dengue infection is important for developing effective vaccines. Chng et al. used high-dimensional CyTOF profiling and peptide-HLA tetramer screening to track dengue-specific T cell activation and differentiation into memory cells in naturally infected patients. They found that dengue infection causes broad immune cell activation and that dengue-specific T cells differentiate into two major cell fates.
Obesity-related inflammation of metabolic tissues, including visceral adipose tissue (VAT) and liver, are key factors in the development of insulin resistance (IR), though many of the contributing ...mechanisms remain unclear. We show that nucleic-acid-targeting pathways downstream of extracellular trap (ET) formation, unmethylated CpG DNA, or ribonucleic acids drive inflammation in IR. High-fat diet (HFD)-fed mice show increased release of ETs in VAT, decreased systemic clearance of ETs, and increased autoantibodies against conserved nuclear antigens. In HFD-fed mice, this excess of nucleic acids and related protein antigens worsens metabolic parameters through a number of mechanisms, including activation of VAT macrophages and expansion of plasmacytoid dendritic cells (pDCs) in the liver. Consistently, HFD-fed mice lacking critical responders of nucleic acid pathways, Toll-like receptors (TLR)7 and TLR9, show reduced metabolic inflammation and improved glucose homeostasis. Treatment of HFD-fed mice with inhibitors of ET formation or a TLR7/9 antagonist improves metabolic disease. These findings reveal a pathogenic role for nucleic acid targeting as a driver of metabolic inflammation in IR.
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•Obesity promotes increased release and decreased clearance of nucleic acid antigens•Aberrant handling of nucleic acid and related antigens results in autoantibodies•Excess nucleic acids worsen metabolism through VAT macrophages and liver pDCs•Inhibiting TLR7/9 improves obesity-related inflammation and glucose homeostasis
Revelo et al. show that diet-induced obesity promotes excess release and diminished clearance of nucleic acid and related antigens, with appearance of autoantibodies. Aberrant handling of nucleic acids activates VAT macrophages and liver pDCs via TLR7/9 to promote inflammation. Nucleic acid-sensing pathways may represent therapeutic targets for obesity-related metabolic disease.
Type 2 diabetes mellitus (T2D) is a metabolic disease that is strongly tied to obesity and often preceded by insulin resistance (IR). It has been established that chronic inflammation of hypertrophic ...adipose tissue depots in obese individuals leads to obesity-associated IR and is mediated by cells of the innate immune system, particularly macrophages. More recently, cells of the adaptive immune system, B and T lymphocytes, have also emerged as important regulators of glucose homeostasis, raising the intriguing possibility that antigen-driven immune responses play a role in disease. In this review, we critically evaluate the roles that various B and T cell subsets play in IR, and then we examine the data suggesting that antigen-driven mechanisms, such as antigen presentation and costimulation, may drive the activity of these lymphocytes.
Memory T cells induced by previous pathogens can shape susceptibility to, and the clinical severity of, subsequent infections
. Little is known about the presence in humans of pre-existing memory T ...cells that have the potential to recognize severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Here we studied T cell responses against the structural (nucleocapsid (N) protein) and non-structural (NSP7 and NSP13 of ORF1) regions of SARS-CoV-2 in individuals convalescing from coronavirus disease 2019 (COVID-19) (n = 36). In all of these individuals, we found CD4 and CD8 T cells that recognized multiple regions of the N protein. Next, we showed that patients (n = 23) who recovered from SARS (the disease associated with SARS-CoV infection) possess long-lasting memory T cells that are reactive to the N protein of SARS-CoV 17 years after the outbreak of SARS in 2003; these T cells displayed robust cross-reactivity to the N protein of SARS-CoV-2. We also detected SARS-CoV-2-specific T cells in individuals with no history of SARS, COVID-19 or contact with individuals who had SARS and/or COVID-19 (n = 37). SARS-CoV-2-specific T cells in uninfected donors exhibited a different pattern of immunodominance, and frequently targeted NSP7 and NSP13 as well as the N protein. Epitope characterization of NSP7-specific T cells showed the recognition of protein fragments that are conserved among animal betacoronaviruses but have low homology to 'common cold' human-associated coronaviruses. Thus, infection with betacoronaviruses induces multi-specific and long-lasting T cell immunity against the structural N protein. Understanding how pre-existing N- and ORF1-specific T cells that are present in the general population affect the susceptibility to and pathogenesis of SARS-CoV-2 infection is important for the management of the current COVID-19 pandemic.
Prior immunological exposure to dengue virus can be both protective and disease-enhancing during subsequent infections with different dengue virus serotypes. We provide here a systematic, ...longitudinal analysis of B cell, T cell, and antibody responses in the same patients. Antibody responses as well as T and B cell activation differentiate primary from secondary responses. Hospitalization is associated with lower frequencies of activated, terminally differentiated T cells and higher percentages of effector memory CD4 T cells. Patients with more severe disease tend to have higher percentages of plasmablasts. This does not translate into long-term antibody titers, since neutralizing titers after 6 months correlate with percentages of specific memory B cells, but not with acute plasmablast activation. Overall, our unbiased analysis reveals associations between cellular profiles and disease severity, opening opportunities to study immunopathology in dengue disease and the potential predictive value of these parameters.
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T cell, B cell phenotypes, and antibodies are associated with dengue disease severityCXCR3+ CD8 T cell responses are associated with memory B cell formationTreg responses are associated with plasmablast responsesMemory B cell numbers correlate with long-lasting neutralizing antibody titers
Rouers et al. examine the phenotype of dengue immune responses in a longitudinal patient cohort and find associations between cellular profiles and disease severity. Immune cells that are associated with long-lasting neutralizing antibodies up to 1 year after disease onset are described.
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