Successful and Maladaptive T Cell Aging

The metabolic signature of T cells in rheumatoid arthritis

PURPOSE OF REVIEW

Rheumatoid arthritis (RA) is a prototypic autoimmune disease manifesting as chronic inflammation of the synovium and leading to acceleration of cardiovascular disease and shortening of life expectancy. The basic defect causing autoimmunity has remained elusive, but recent insights have challenged the notion that autoantigen is the core driver.

RECENT FINDINGS

Emerging data have added metabolic cues involved in the proper maintenance and activation of immune cells as pathogenic regulators. Specifically, studies have unveiled metabolic pathways that enforce T cell fate decisions promoting tissue inflammation; including T cell tissue invasiveness, T cell cytokine release, T cell-dependent macrophage activation and inflammatory T cell death. At the center of the metabolic abnormalities lies the mitochondria, which is consistently underperforming in RA T cells. The mitochondrial defect results at least partially from insufficient DNA repair and leads to lipid droplet accumulation, formation of invasive membrane ruffles, inflammasome activation and pyroptotic T cell death.

SUMMARY

T cells in patients with RA, even naïve T cells never having been involved in inflammatory lesions, have a unique metabolic signature and the changes in intracellular metabolites drive pathogenic T cell behavior. Recognizing the role of metabolic signals in cell fate decisions opens the possibility for immunomodulation long before the end stage synovial inflammation encountered in clinical practice.

The Transcription Factor TCF1 in T Cell Differentiation and Aging

The transcription factor T cell factor 1 (TCF1), a pioneer transcription factor as well as a downstream effector of WNT/β-catenin signaling, is indispensable for T cell development in the thymus. Recent studies have highlighted the additional critical role of TCF1 in peripheral T cell responses to acute and chronic infections as well as cancer. Here, we review the regulatory functions of TCF1 in the differentiation of T follicular helper cells, memory T cells and recently described stem-like exhausted T cells, where TCF1 promotes less differentiated stem-like cell states by controlling common gene-regulatory networks. These studies also provide insights into the mechanisms of defective T cell responses in older individuals. We discuss alterations in TCF1 expression and related regulatory networks with age and their consequences for T cell responses to infections and vaccination. The increasing understanding of the pathways regulating TCF1 expression and function in aged T cells holds the promise of enabling the design of therapeutic interventions aiming at improving T cell responses in older individuals.

T cell responses in patients with COVID-19

The role of T cells in the resolution or exacerbation of COVID-19, as well as their potential to provide long-term protection from reinfection with SARS-CoV-2, remains debated. Nevertheless, recent studies have highlighted various aspects of T cell responses to SARS-CoV-2 infection that are starting to enable some general concepts to emerge.

Pathogenesis of Giant Cell Arteritis and Takayasu Arteritis-Similarities and Differences

PURPOSE OF REVIEW

Giant cell arteritis (GCA) and Takayasu arteritis (TAK) are auto-inflammatory and autoimmune diseases with a highly selective tissue tropism for medium and large arteries. In both diseases, CD4⁺ T cells and macrophages form granulomatous lesions within the arterial wall, a tissue site normally protected by immune privilege. Vascular lesions can be accompanied by an extravascular component, typically an intense hepatic acute phase response that produces well-known laboratory abnormalities, e.g., elevated ESR and CRP. It is unclear whether GCA and TAK lie on a spectrum of disease or whether they represent fundamentally different disease processes.

RECENT FINDINGS

GCA and TAK share many clinical features, but there are substantial differences in genetics, epidemiology, disease mechanisms, response to treatment, and treatment complications that give rise to different disease trajectories. A significant difference lies in the composition of the wall-infiltrating immune cell compartment, which in TAK includes a significant population of CD8⁺ T cells as well as natural killer cells, specifying disparate disease effector pathways mediating tissue damage and vessel wall remodeling. Despite the similarities in tissue tropism and histomorphology, GCA and TAK are two distinct vasculitides that rely on separate disease mechanisms and require disease-specific approaches in diagnosis and management.

Mechanisms of T-Cell Exhaustion in Pancreatic Cancer

T-cell exhaustion is a phenomenon that represents the dysfunctional state of T cells in chronic infections and cancer and is closely associated with poor prognosis in many cancers. The endogenous T-cell immunity and genetically edited cell therapies (CAR-T) failed to prevent tumor immune evasion. The effector T-cell activity is perturbed by an imbalance between inhibitory and stimulatory signals causing a reprogramming in metabolism and the high levels of multiple inhibitory receptors like programmed cell death protein-1 (PD-1), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), and Lymphocyte-activation gene 3 (Lag-3). Despite the efforts to neutralize inhibitory receptors by a single agent or combinatorial immune checkpoint inhibitors to boost effector function, PDAC remains unresponsive to these therapies, suggesting that multiple molecular mechanisms play a role in stimulating the exhaustion state of tumor-infiltrating T cells. Recent studies utilizing transcriptomics, mass cytometry, and epigenomics revealed a critical role of Thymocyte selection-associated high mobility group box protein (TOX) genes and TOX-associated pathways, driving T-cell exhaustion in chronic infection and cancer. Here, we will review recently defined molecular, genetic, and cellular factors that drive T-cell exhaustion in PDAC. We will also discuss the effects of available immune checkpoint inhibitors and the latest clinical trials targeting various molecular factors mediating T-cell exhaustion in PDAC.

Severe COVID-19 and aging: are monocytes the key?

The ongoing pandemic severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) causes a disproportionate number of severe cases and deaths in older adults. Severe SARS-CoV-2-associated disease (coronavirus disease 2019 (COVID-19)) was declared a pandemic by the World Health Organization in March 2020 and is characterized by cytokine storm, acute respiratory distress syndrome, and in some cases by systemic inflammation-related pathology. Currently, our knowledge of the determinants of severe COVID-19 is primarily observational. Here, I review emerging evidence to argue that monocytes, a circulating innate immune cell, are principal players in cytokine storm and associated pathologies in COVID-19. I also describe changes in monocyte function and phenotype that are characteristic of both aging and severe COVID-19, which suggests a potential mechanism underlying increased morbidity and mortality due to SARS-CoV-2 infection in older adults. The innate immune system is therefore a potentially important target for therapeutic treatment of COVID-19, but experimental studies are needed, and SARS-CoV-2 presents unique challenges for pre-clinical and mechanistic studies in vivo. The immediate establishment of colonies of SARS-CoV-2-susceptible animal models for aging studies, as well as strong collaborative efforts in the geroscience community, will be required in order to develop the therapies needed to combat severe COVID-19 in older adult populations.

Premature aging of circulating T cells predicts all-cause mortality in hemodialysis patients

Background

Patients with end-stage renal disease (ESRD) exhibit a premature aging phenotype of immune system, which is recently concerned as a significant factor for increased risk of various morbidities. Nevertheless, there are few dates explicating the relevancy of T cell senescence to mortality. In this study, we prospectively studied the predictive value of T cell senescence for mortality in hemodialysis patients.

Methods

Patients who had been on hemodialysis treatment for at least 6 months were enrolled. T cell senescence determined by differentiation status was evaluated by flow cytometry. Survival outcomes were estimated using the Kaplan-Meier method. Univariate and multivariate analyses were performed to evaluate the prognostic impact of T cell premature aging and other clinical factors on all-cause mortality.

Results

A total of 466 patients (277 man and 169 women) were enrolled in this study. Decreased number of naïve T cell, as the most prominent feature of T cell senescence, did not change in parallel with age in these patients. Decreased absolute count of T cell, naïve T cell, CD4⁺ naïve T cell were independently associated with all-cause mortality. Decreased percentage of T cell and increased percentage of CD8⁺central-memory T cell were also independently associated with all-cause mortality. After including all the T cell parameters in one regression model, only decreased count of naïve T cell was significantly associated with increased mortality in these patients.

Conclusions

Aging-associated T cell changes are aggravated in ESRD patients. For the first time, our study demonstrates that naïve T cell depletion is a strong predictor of all-cause mortality in HD patients.

Immunological aging and clinical consequences

Immunosenescence is defined as the changes in the immune system associated with age. It is a progressive and irreversible process involving a decrease in the number of naïve T and B cells, NK cells cytotoxic and activity, and disruption of pro and anti-inflammatory balance by altering the production of IL-2, -4, -6, -10, -10, TNF-α, interferon γ and others. With age there is an increase in autoimmunity and generalized inflammation with simultaneous immunodeficiency, which results in greater susceptibility to infectious diseases, a decrease in reactivity to prophylactic vaccinations, the incidence of autoimmune diseases, and increased risk of infectious injury complications, exacerbation of symptoms of chronic diseases and an insufficient response to the presence of cells cancer. For years, based on the analysis of the frequency of viral and bacterial infections, immunological indicators and inflammation, attempts have been made to develop the immune risk profile (IRP) and effective methods of preventing disorders of the immune system and prolonging the functional capacity of the elderly.

The Link between Chronic Stress and Accelerated Aging

People exposed to chronic stress age rapidly. The telomeres in their cells of all types shorten faster. Inflammation is another important feature of stress that, along with aging, accounts for the phenomenon of inflammaging. In addition to aging itself, inflammaging can contribute to the development of several pathologies, including atherosclerosis, diabetes, hypertension, and others. Oxidative stress is one of the main mechanisms related to stress. Oxidative stress is caused by the over-production of reactive oxygen species (ROS) that can damage various tissues. The main source of ROS is mitochondria. Being suppressed by mitochondrial mutations, mitophagy can aggravate the situation. In this case, the aging-specific pro-inflammatory changes are amplified. It happens because of the inability of cells to maintain the normal state of mitochondria. Macrophages are the crucial element of the innate immunity associated with the chronic inflammation and, subsequently, with the inflammaging. In this review, we focus on the therapy approaches potentially reducing the deleterious effects of oxidative stress. These include stimulation of mitophagy, activation of mitochondrial uncoupling, induction of the expression of the telomerase catalytic component gene, and use of antioxidants. Any method reducing oxidative stress should improve post-traumatic stress disorder.

A single-cell transcriptomic atlas characterizes ageing tissues in the mouse

Ageing is characterized by a progressive loss of physiological integrity, leading to impaired function and increased vulnerability to death1. Despite rapid advances over recent years, many of the molecular and cellular processes that underlie the progressive loss of healthy physiology are poorly understood2. To gain a better insight into these processes, here we generate a single-cell transcriptomic atlas across the lifespan of Mus musculus that includes data from 23 tissues and organs. We found cell-specific changes occurring across multiple cell types and organs, as well as age-related changes in the cellular composition of different organs. Using single-cell transcriptomic data, we assessed cell-type-specific manifestations of different hallmarks of ageing-such as senescence3, genomic instability4 and changes in the immune system2. This transcriptomic atlas-which we denote Tabula Muris Senis, or 'Mouse Ageing Cell Atlas'-provides molecular information about how the most important hallmarks of ageing are reflected in a broad range of tissues and cell types.

The Pathobiology of Skin Aging: New Insights into an Old Dilemma

Long considered both physiologic and inevitable, skin aging is a degenerative phenomenon whereby both intrinsic and environmental factors conspire to produce an authentic disease. The consequences of this disorder are many and varied, ranging from atrophy and fragility to defective repair to deficient immunity and vulnerability to certain infections. The pathobiologic basis for skin aging remains poorly understood. At a cellular level, stem cell dysfunction and attrition appear to be key events, and both genetic and epigenetic factors are involved in a complex interplay that over time results in deterioration of our main protective interface with the external environment. Past and current understanding of the cellular and molecular intricacies of skin aging provide a foundation for future approaches designed to thwart the aging phenotype. Herein, the authors provide a review of current insights into skin aging, including the mechanisms of skin aging, the role of stem cells in skin aging and the implications of skin aging for the microbiome and for the development of cancer. Conquest of the oft overlooked disease of skin aging should have broad implications that transcend the integument and inform novel approaches to retarding aging and age-related dysfunction in those internal organs that youthful skin was designed to envelop and safeguard.

Partial recovery of disturbed V-J pairing profiles of T-cell receptor in people living with HIV receiving long-term antiretroviral therapy

Chronic human immunodeficiency virus (HIV) infection not only causes a gradual loss of CD4⁺ T cells but also leads to a disturbance of the T cell receptor (TCR) repertoire. In people living with HIV (PLWH), monitoring TCR repertoire is challenged by the inconsistency of complementarity determining region 3 (CDR3) and limited cell numbers in clinical samples. Thus, a quantitative method is necessary for monitoring the TCR repertoire in PLWH. We characterized the TCR V-J pairing profile of naïve and memory CD4⁺ T cells in healthy donors, HIV-infected antiretroviral therapy (ART)-naïve patients and long-term (over 5 years) ART-experienced patients by performing TCR sequencing. We developed a V-J index with 18 parameters which were subdivided into five categories (expression coverage, cumulative percentage of the top tenth percentile, diversity, intra-individual similarity and inter-individual similarity). In ART-naïve patients, 14 of the 18 parameters were significantly altered. Long-term ART recovered ten parameters. The four unrecovered parameters were related to inter-individual similarity. Therefore, these findings indicate that long-term ART could only partially recover TCR V-J pairs and introduce newly impacted V-J pairs. Moreover, these results provide new insights into the V-J pairing of the TCR and into the disturbance of TCR repertoire in HIV infection.

The Tat Protein of HIV-1 Prevents the Loss of HSV-Specific Memory Adaptive Responses and Favors the Control of Viral Reactivation

The development of therapeutic strategies to control the reactivation of the Herpes Simplex Virus (HSV) is an unaddressed priority. In this study, we evaluated whether Tat, a HIV-1 protein displaying adjuvant functions, could improve previously established HSV-specific memory responses and prevent viral reactivation. To this aim, mice were infected with non-lethal doses of HSV-1 and, 44 days later, injected or not with Tat. Mice were then monitored to check their health status and measure memory HSV-specific cellular and humoral responses. The appearance of symptoms associated with HSV-reactivation was observed at significantly higher frequencies in the control group than in the Tat-treated mice. In addition, the control animals experienced a time-dependent decrease in HSV-specific Immunoglobulin G (IgG), while the Tat-treated mice maintained antibody titers over time. IgG levels were directly correlated with the number of HSV-specific CD8⁺ T cells, suggesting an effect of Tat on both arms of the adaptive immunity. Consistent with the maintenance of HSV-specific immune memory, Tat-treated mice showed a better control of HSV-1 re-infection. Although further studies are necessary to assess whether similar effects are observed in other models, these results indicate that Tat exerts a therapeutic effect against latent HSV-1 infection and re-infection by favoring the maintenance of adaptive immunity.

The lethal sex gap: COVID-19

While Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is disrupting lives across the globe for everyone, it has a more devastating impact on the health of older adults, especially that of older men. This pandemic has highlighted the crucial importance of considering an individual’s age and biological sex in the clinic in addition to other confounding diseases (Kuchel, G.A, J Am Geriatr Soc, 67, 203, 2019, Tannenbaum, C., Nature, 575 451-458, 2009) As an interdisciplinary team of scientists in immunology, hematology, genomics, bioinformatics, and geriatrics, we have been studying how age and sex shape the human immune system. Herein we reflect on how our recent findings on the alterations of the immune system in aging might contribute to our current understanding of COVID-19 infection rate and disease risk.

Immunosenescent characteristics of T cells in young patients following haploidentical haematopoietic stem cell transplantation from parental donors

Objectives

Paediatric and adolescent patients in need of allogeneic haematopoietic stem cell transplantation (HSCT) generally receive stem cells from older, unrelated or parental donors when a sibling donor is not available. Despite encouraging clinical outcomes, it has been suggested that immune reconstitution accompanied by increased replicative stress and a large difference between donor and recipient age may worsen immunosenescence in paediatric recipients.

Methods

In this study, paired samples were collected at the same time from donors and recipients of haploidentical haematopoietic stem cell transplantation (HaploSCT). We then conducted flow cytometry‐based phenotypic and functional analyses and telomere length (TL) measurements of 21 paired T‐cell sets from parental donors and children who received T‐cell‐replete HaploSCT with post‐transplant cyclophosphamide (PTCy).

Results

Senescent T cells, CD28⁻ or CD57⁺ cells, were significantly expanded in patients. Further, not only CD4⁺CD28⁻ T cells, but also CD4⁺CD28⁺ T cells showed reduced cytokine production capacity and impaired polyfunctionality compared with parental donors, whereas their TCR‐mediated proliferation capacity was comparable. Of note, the TL in patient T cells was preserved, or even slightly longer, in senescent T cells compared with donor cells. Regression analysis showed that senescent features of CD4⁺ and CD8⁺ T cells in patients were influenced by donor age and the frequency of CD28⁻ cells, respectively.

Conclusion

Our data suggest that in paediatric HaploSCT, premature immunosenescent changes occur in T cells from parental donors, and therefore, long‐term immune monitoring should be conducted.

Physical Activity and Diet Shape the Immune System during Aging

With increasing age, the immune system undergoes a remodeling process, termed immunosenescence, which is accompanied by considerable shifts in leukocyte subpopulations and a decline in various immune cell functions. Clinically, immunosenescence is characterized by increased susceptibility to infections, a more frequent reactivation of latent viruses, decreased vaccine efficacy, and an increased prevalence of autoimmunity and cancer. Physiologically, the immune system has some adaptive strategies to cope with aging, while in some settings, maladaptive responses aggravate the speed of aging and morbidity. While a lack of physical activity, decreased muscle mass, and poor nutritional status facilitate immunosenescence and inflammaging, lifestyle factors such as exercise and dietary habits affect immune aging positively. This review will discuss the relevance and mechanisms of immunoprotection through physical activity and specific exercise interventions. In the second part, we will focus on the effect of dietary interventions through the supplementation of the essential amino acid tryptophan, n-3 polyunsaturated fatty acids, and probiotics (with a special focus on the kynurenine pathway).

The long road to the first FDA-approved gene therapy: chimeric antigen receptor T cells targeting CD19

Thirty years after initial publications of the concept of a chimeric antigen receptor (CAR), the U.S. Food and Drug Administration (FDA) approved the first anti-CD19 CAR T-cell therapy. Unlike other immunotherapies, such as immune checkpoint inhibitors and bispecific antibodies, CAR T cells are unique as they are "living drugs," that is, gene-edited killer cells that can recognize and kill cancer. During these 30 years of development, the CAR construct, T-cell manufacturing process, and clinical patient management have gone through rounds of failures and successes that drove continuous improvement. Tisagenlecleucel was the first gene therapy to receive approval from the FDA for any indication. The initial approval was for relapsed or refractory (r/r) pediatric and young-adult B-cell acute lymphoblastic leukemia in August 2017 and in May 2018 for adult r/r diffuse large B-cell lymphoma. Here we review the preclinical and clinical development of what began as CART19 at the University of Pennsylvania and later developed into tisagenlecleucel.

Activation of miR-21-Regulated Pathways in Immune Aging Selects against Signatures Characteristic of Memory T Cells

Induction of protective vaccine responses, governed by the successful generation of antigen-specific anti-bodies and long-lived memory T cells, is increasingly impaired with age. Regulation of the T cell proteome by a dynamic network of microRNAs is crucial to T cell responses. Here, we show that activation-induced upregulation of miR-21 biases the transcrip-tome of differentiating T cells away from memory T cells and toward inflammatory effector T cells. Such a transcriptome bias is also characteristic of T cell responses in older individuals who have increased miR-21 expression and is reversed by antagonizing miR-21. miR-21 targets negative feedback circuits in several signaling pathways. The concerted, sustained activity of these signaling path-ways in miR-21^high T cells disfavors the induction of transcription factor networks involved in memory cell differentiation. Our data suggest that curbing miR-21 upregulation or activity in older individuals may improve their ability to mount effective vaccine responses.

A hallmark of the aging immune system is its failure to induce long-lived memory. Kim et al. report that increased expression of miR-21 in naive T cells from older individuals sustains signaling in the MAPK and AKT-mTORC pathways, disfavoring induction of transcription factor networks involved in memory cell generation.

Defects in Antiviral T Cell Responses Inflicted by Aging-Associated miR-181a Deficiency

Generation of protective immunity to infections and vaccinations declines with age. Studies in healthy individuals have implicated reduced miR-181a expression in T cells as contributing to this defect. To understand the impact of miR-181a expression on antiviral responses, we examined LCMV infection in mice with miR-181ab1-deficient T cells. We found that miR-181a deficiency delays viral clearance, thereby biasing the immune response in favor of CD4 over CD8 T cells. Antigen-specific CD4 T cells in mice with miR-181a-deficient T cells expand more and have a broader TCR repertoire with preferential expansion of high-affinity T cells than in wild-type mice. Importantly, generation of antigen-specific miR-181a-deficient CD8 effector T cells is particularly impaired, resulting in lower frequencies of CD8 T cells in the liver even at time points when the infection has been cleared. Consistent with the mouse model, CD4 memory T cells in individuals infected with West Nile virus at older ages tend to be more frequent and of higher affinity.

Cell generation dynamics underlying naive T-cell homeostasis in adult humans

Thymic involution and proliferation of naive T cells both contribute to shaping the naive T-cell repertoire as humans age, but a clear understanding of the roles of each throughout a human life span has been difficult to determine. By measuring nuclear bomb test–derived ¹⁴C in genomic DNA, we determined the turnover rates of CD4⁺ and CD8⁺ naive T-cell populations and defined their dynamics in healthy individuals ranging from 20 to 65 years of age. We demonstrate that naive T-cell generation decreases with age because of a combination of declining peripheral division and thymic production during adulthood. Concomitant decline in T-cell loss compensates for decreased generation rates. We investigated putative mechanisms underlying age-related changes in homeostatic regulation of CD4+ naive T-cell turnover, using mass cytometry to profile candidate signaling pathways involved in T-cell activation and proliferation relative to CD31 expression, a marker of thymic proximity for the CD4+ naive T-cell population. We show that basal nuclear factor κB (NF-κB) phosphorylation positively correlated with CD31 expression and thus is decreased in peripherally expanded naive T-cell clones. Functionally, we found that NF-κB signaling was essential for naive T-cell proliferation to the homeostatic growth factor interleukin (IL)-7, and reduced NF-κB phosphorylation in CD4⁺CD31⁻ naive T cells is linked to reduced homeostatic proliferation potential. Our results reveal an age-related decline in naive T-cell turnover as a putative regulator of naive T-cell diversity and identify a molecular pathway that restricts proliferation of peripherally expanded naive T-cell clones that accumulate with age.

Our pool of naive T cells is critical for protection against new infections and cancers. By measuring remnant 14C from 1960s nuclear bomb blasts that has been incorporated into cellular DNA, this study defines the average age of the naive T-cell pool in healthy adults, revealing the slow, regulated turnover of the naive T-cell pool, supporting its maintenance for a human lifetime.

Metabolic reprogramming in memory CD4 T cell responses of old adults

To determine whether aging affects the ability of T cells to undergo metabolic reprogramming upon activation, we compared CD4 T cell responses after polyclonal in vitro stimulation. Compared to younger adults, CD4 memory T cells from healthy older individuals exhibited a higher upregulation of oxidative phosphorylation with increased production of reactive oxygen species and intracellular and secreted ATP. Increased ATP secretion led to increased purinergic signaling and P2X7-dependent increases in cytoplasmic calcium. The increased mitochondrial activity was not due to a difference in activation-induced mitochondrial biogenesis. Expression of carnitine palmitoyl transferase 1 was higher, conversely that of fatty acid synthase was reduced in older T cells, resulting in increased fatty acid oxidation, while depleting intracellular lipid stores. The aged CD4 memory T cells therefore maintain a more catabolic state in lipid metabolism, while their ability to upregulate glycolysis upon activation is preserved.

Expression and regulation of telomerase in human T cell differentiation, activation, aging and diseases

Telomeres are essential for chromosomal integrity. Telomere shortening during cell division restricts cellular proliferative capacity and leads to cellular senescence when critically shortened telomere lengths are reached. Similar to hematopoietic stem cells, T cells can upregulate telomerase activity to compensate for telomere loss incurred during proliferation in response to engagement of the T cell antigen receptor (TCR) or exposure to homeostatic cytokines. However, this compensation for telomere loss by telomerase in T cells is imperfect or limited, as shortening of T cell telomeres is observed in human aging and during in vitro longterm culture. In this review, we summarize the current state of knowledge regarding the expression and regulation of telomerase in human T cells and changes of telomerase expression during development, activation, differentiation, aging and disease conditions. In conclusion, we discuss how controlled enhancement of telomerase activity could be a potential strategy to improve T cell function in the elderly and in immunotherapy.

Defective Transcriptional Programming of Effector CD8 T Cells in Aged Mice Is Cell-Extrinsic and Can Be Corrected by Administration of IL-12 and IL-18

In response to infection with intracellular microorganisms, old mice mobilize decreased numbers of antigen-specific CD8 T cells with reduced expression of effector molecules and impaired cytolytic activity. Molecular mechanisms behind these defects and the cell-intrinsic (affecting naïve CD8 T cells themselves) vs. extrinsic, microenvironmental origin of such defects remain unclear. Using reciprocal transfer experiments of highly purified naïve T cells from adult and old transgenic OT-1 mice, we decisively show that the dominant effect is cell-extrinsic. Naïve adult OT-1 T cells failed to expand and terminally differentiate in the old organism infected with Listeria-OVA. This defect was preceded by blunted expression of the master transcription factor T-bet and impaired glycolytic switch when T cells are primed in the old organism. However, both old and adult naïve CD8 T cells proliferated and produced effector molecules to a similar extent when stimulated in vitro with polyclonal stimuli, as well as when transferred into adult recipients. Multiple inflammatory cytokines with direct effects on T cell effector differentiation were decreased in spleens of old animals, particularly IL-12 and IL-18. Of note, in vivo treatment of mice with IL-12 and IL-18 on days 4–6 of Listeria infection reconstituted cytotoxic T cell response of aged mice to the level of adult. Therefore, critical cytokine signals which are underproduced in the old priming environment can restore proper transcriptional programming of old naïve CD8 T cells and improve immune defense against intracellular microorganisms.

Immunology of the ageing kidney

Immunosenescence involves a series of ageing-induced alterations in the immune system and is characterized by two opposing hallmarks: defective immune responses and increased systemic inflammation. The immune system is modulated by intrinsic and extrinsic factors and undergoes profound changes in response to the ageing process. Immune responses are therefore highly age-dependent. Emerging data show that immunosenescence underlies common mechanisms responsible for several age-related diseases and is a plastic state that can be modified and accelerated by non-heritable environmental factors and pharmacological intervention. In the kidney, resident macrophages and fibroblasts are continuously exposed to components of the external environment, and the effects of cellular reprogramming induced by local immune responses, which accumulate with age, might have a role in the increased susceptibility to kidney disease among elderly individuals. Additionally, because chronic kidney disease, especially end-stage renal disease, is often accompanied by immunosenescence, which affects these patients independently of age, and many kidney diseases are strongly age-associated, treatment approaches that target immunosenescence might be particularly clinically relevant.

Cytokines, growth factors and proteases in medium and large vessel vasculitis

Giant cell arteritis and Takayasu arteritis are autoimmune vasculitides that cause aneurysm formation and tissue infarction. Extravascular inflammation consists of an intense acute phase response. Deeper understanding of pathogenic events in the vessel wall has highlighted the loss of tissue protective mechanisms, the intrusion of immune cells into "forbidden territory", and the autonomy of self-renewing vasculitic infiltrates. Adventitial vasa vasora critically control vessel wall access and drive differentiation of tissue-invasive T cells. Selected T cells establish tissue residency and build autonomous, self-sufficient inflammatory lesions. Pathogenic effector T cells intrude and survive due to failed immune checkpoint inhibition. Vasculitis-sustaining T cells and macrophages provide a broad portfolio of effector functions, involving heterogeneous populations of pro-inflammatory T cells and diverse macrophage subsets that ultimately induce wall capillarization and intimal hyperplasia. Redirecting diagnostic and therapeutic strategies from control of extravascular inflammatory markers to suppression of vascular inflammation will improve disease management.

Mechanisms underlying T cell ageing

T cell ageing has a pivotal role in rendering older individuals vulnerable to infections and cancer and in impairing the response to vaccination. Easy accessibility to peripheral human T cells as well as an expanding array of tools to examine T cell biology have provided opportunities to examine major ageing pathways and their consequences for T cell function. Here, we review emerging concepts of how the body attempts to maintain a functional T cell compartment with advancing age, focusing on three fundamental domains of the ageing process, namely self-renewal, control of cellular quiescence and cellular senescence. Understanding these critical elements in successful T cell ageing will allow the design of interventions to prevent or reverse ageing-related T cell failure.

Human T Cell Differentiation Negatively Regulates Telomerase Expression Resulting in Reduced Activation-Induced Proliferation and Survival

Maintenance of telomeres is essential for preserving T cell proliferative responses yet the precise role of telomerase in human T cell differentiation, function, and aging is not fully understood. Here we analyzed human telomerase reverse transcriptase (hTERT) expression and telomerase activity in six T cell subsets from 111 human adults and found that levels of hTERT mRNA and telomerase activity had an ordered decrease from naïve (TN) to central memory (TCM) to effector memory (TEM) cells and were higher in CD4+ than their corresponding CD8+ subsets. This differentiation-related reduction of hTERT mRNA and telomerase activity was preserved after activation. Furthermore, the levels of hTERT mRNA and telomerase activity were positively correlated with the degree of activation-induced proliferation and survival of T cells in vitro. Partial knockdown of hTERT by an anti-sense oligo in naïve CD4+ cells led to a modest but significant reduction of cell proliferation. Finally, we found that activation-induced levels of telomerase activity in CD4+ TN and TCM cells were significantly lower in old than in young subjects. These findings reveal that hTERT/telomerase expression progressively declines during T cell differentiation and age-associated reduction of activation-induced expression of hTERT/telomerase mainly affects naïve CD4+ T cells and suggest that enhancing telomerase activity could be a strategy to improve T cell function in the elderly.

Aging promotes reorganization of the CD4 T cell landscape toward extreme regulatory and effector phenotypes

Age-associated changes in CD4 T-cell functionality have been linked to chronic inflammation and decreased immunity. However, a detailed characterization of CD4 T cell phenotypes that could explain these dysregulated functional properties is lacking. We used single-cell RNA sequencing and multidimensional protein analyses to profile thousands of CD4 T cells obtained from young and old mice. We found that the landscape of CD4 T cell subsets differs markedly between young and old mice, such that three cell subsets-exhausted, cytotoxic, and activated regulatory T cells (aTregs)-appear rarely in young mice but gradually accumulate with age. Most unexpected were the extreme pro- and anti-inflammatory phenotypes of cytotoxic CD4 T cells and aTregs, respectively. These findings provide a comprehensive view of the dynamic reorganization of the CD4 T cell milieu with age and illuminate dominant subsets associated with chronic inflammation and immunity decline, suggesting new therapeutic avenues for age-related diseases.

Transcription factor networks in aged naïve CD4 T cells bias lineage differentiation

With reduced thymic activity, the population of naïve T cells in humans is maintained by homeostatic proliferation throughout adult life. In young adults, naïve CD4 T cells have enormous proliferative potential and plasticity to differentiate into different lineages. Here, we explored whether naïve CD4 T-cell aging is associated with a partial loss of this unbiased multipotency. We find that naïve CD4 T cells from older individuals have developed a propensity to develop into TH9 cells. Two major mechanisms contribute to this predisposition. First, responsiveness to transforming growth factor β (TGFβ) stimulation is enhanced with age due to an upregulation of the TGFβR3 receptor that results in increased expression of the transcription factor PU.1. Secondly, aged naïve CD4 T cells display altered transcription factor profiles in response to T-cell receptor stimulation, including enhanced expression of BATF and IRF4 and reduced expression of ID3 and BCL6. These transcription factors are involved in TH9 differentiation as well as IL9 transcription suggesting that the aging-associated changes in the transcription factor profile favor TH9 commitment.

T-cell aging in end-stage renal disease: an evolving story with CMV

Established evidence from the last decade has suggested that chronic cytomegalovirus infection has strong impact on the human immune system, resulting in aggravated aging-associated T-cell changes that are associated with poorer vaccination responses, cardiovascular disease and shortened survival. Patients with end-stage renal disease (ESRD), the most severe form of chronic kidney disease, exhibit premature aging phenotypes in almost all organ systems, including the immune system. Longitudinal studies of T-cell aging in healthy humans have been scanty because it requires a large number of study subjects and a study duration for decades. In recent years, it became clear that ESRD patients with cytomegalovirus (CMV) infection exhibit enhanced aging-related immune changes than CMV-seropositive individuals without renal disease, including chronic inflammation, decreased numbers of naïve CD4+ and CD8+ T cells, increased clonality of memory T cells with skewed repertoire and shortened telomeres. These findings lead to the hypothesis that the uremic milieu and treatment for renal failure can lead to premature aging of T cells independent from CMV infection and suggest that ESRD can be an important disease model for studying human aging. Future studies deciphering the underlying mechanisms of accelerated T cell aging in ESRD patients may eventually reveal additional insights into T-cell persistence and function during aging in CMV-seropositive, non-ESRD individuals.

The natural history of naive T cells from birth to maturity

Generating and maintaining a diverse repertoire of naive T cells is essential for protection against pathogens, and developing a mechanistic and quantitative description of the processes involved lies at the heart of our understanding of vertebrate immunity. Here, we review the biology of naive T cells from birth to maturity and outline how the integration of mathematical models and experiments has helped us to develop a full picture of their life histories.

Mitochondrial Dysfunction and the Aging Immune System

Mitochondria are ancient organelles that have co-evolved with their cellular hosts, developing a mutually beneficial arrangement. In addition to making energy, mitochondria are multifaceted, being involved in heat production, calcium storage, apoptosis, cell signaling, biosynthesis, and aging. Many of these mitochondrial functions decline with age, and are the basis for many diseases of aging. Despite the vast amount of research dedicated to this subject, the relationship between aging mitochondria and immune function is largely absent from the literature. In this review, three main issues facing the aging immune system are discussed: (1) inflamm-aging; (2) susceptibility to infection and (3) declining T-cell function. These issues are re-evaluated using the lens of mitochondrial dysfunction with aging. With the recent expansion of numerous profiling technologies, there has been a resurgence of interest in the role of metabolism in immunity, with mitochondria taking center stage. Building upon this recent accumulation of knowledge in immunometabolism, this review will advance the hypothesis that the decline in immunity and associated pathologies are partially related to the natural progression of mitochondrial dysfunction with aging.

Impaired Tip60-mediated Foxp3 acetylation attenuates regulatory T cell development in rheumatoid arthritis

In rheumatoid arthritis (RA), imbalanced T cells subsets play a critical role in sustaining chronic inflammatory responses in the synovium. Naïve T cells in RA patients undergo maldifferentiation, including an increase in the effector Th1/Th17 lineage and a reduction in regulatory T (Treg) cells. Upon stimulation, naïve CD4⁺CD45RO^- T cells from RA patients exhibited insufficient expression of Foxp3, which induced a deficiency in Tregs production and an imbalance of Treg/Th17 differentiation. Further mechanistic study indicated that RA T cells failed to produce sufficient levels of the histone acetyltransferase Tip60, leading to reduced acetylation of Foxp3; this, in turn, decreased Foxp3 expression, impaired Treg commitment, and promoted Th17 production. Moreover, in human synovium chimeric mice, suppression of Tip60 activity in healthy T cells promoted tissue infiltration and arthritogenesis, while reconstitution of Tip60 in RA T cells suppressed synovitis and effector T cell infiltration. Our findings link T cell maldifferentiation and tissue infiltration with Tip60-mediated Foxp3 acetylation and identify Tip60 as a potential therapeutic target for suppression of tissue inflammation and autoimmunogenesis in RA.

TCR repertoire evolution during maintenance of CMV-specific T-cell populations

During infections and cancer, the composition of the T-cell receptor (TCR) repertoire of antigen-specific CD8⁺ T cells changes over time. TCR avidity is thought to be a major driver of this process, thereby interacting with several additional regulators of T-cell responses to form a composite immune response architecture. Infections with latent viruses, such as cytomegalovirus (CMV), can lead to large T-cell responses characterized by an oligoclonal TCR repertoire. Here, we review the current status of experimental studies and theoretical models of TCR repertoire evolution during CMV infection. We will particularly discuss the degree to which this process may be determined through structural TCR avidity. As engineered TCR-redirected T cells have moved into the spotlight for providing more effective immunotherapies, it is essential to understand how the key features of a given TCR influence T-cell expansion and maintenance in settings of infection or malignancy. Deeper insights into these mechanisms will improve our basic understanding of T-cell immunology and help to identify optimal TCRs for immunotherapy.

An injectable bone marrow-like scaffold enhances T cell immunity after hematopoietic stem cell transplantation

The use of allogeneic hematopoietic stem cell transplantation (HSCT) to cure multiple disorders is limited by deficiency and dysregulation of T-cells. Here we report a biomaterial-based scaffold that mimics features of T-cell lymphopoiesis in the bone marrow. The bone marrow cryogel (BMC) releases bone morphogenetic protein-2 to recruit stromal cells, and presents the Notch ligand Delta-like ligand-4 to facilitate T-cell lineage specification of mouse and human hematopoietic progenitor cells. BMCs subcutaneously injected in mice at the time of HSCT enhanced T-cell progenitor seeding of the thymus, T-cell neogenesis and diversification of the T-cell receptor repertoire. Peripheral T-cell reconstitution increased ~6-fold in mouse HSCT and ~2-fold in human xenogeneic HSCT. Furthermore, BMCs promoted donor CD4⁺ regulatory T-cell generation and improved survival after allogeneic HSCT. Compared with adoptive transfer of T-cell progenitors, BMCs increased donor chimerism, T-cell generation and antigen-specific T-cell responses to vaccination. BMCs may provide an off-the-shelf approach for enhancing T-cell regeneration and mitigating graft-versus-host disease in HSCT.

Epigenomic drivers of immune dysfunction in aging

Aging inevitably leads to reduced immune function, leaving the elderly more susceptible to infections, less able to respond to pathogen challenges, and less responsive to preventative vaccinations. No cell type is exempt from the ravages of age, and extensive studies have found age-related alterations in the frequencies and functions of both stem and progenitor cells, as well as effector cells of both the innate and adaptive immune systems. The intrinsic functional reduction in immune competence is also associated with low-grade chronic inflammation, termed "inflamm-aging," which further perpetuates immune dysfunction. While many of these age-related cellular changes are well characterized, understanding the molecular changes that underpin the functional decline has proven more difficult. Changes in chromatin are increasingly appreciated as a causative mechanism of cellular and organismal aging across species. These changes include increased genomic instability through loss of heterochromatin and increased DNA damage, telomere attrition, and epigenetic alterations. In this review, we discuss the connections between chromatin, immunocompetence, and the loss of function associated with mammalian immune aging. Through understanding the molecular events which underpin the phenotypic changes observed in the aged immune system, it is hoped that the aged immune system can be restored to provide youthful immunity once more.

Functional pathways regulated by microRNA networks in CD8 T-cell aging

One of the most prominent immunological changes during human aging is the alteration in CD8 T-cell subset distribution, predominated by a loss of naïve CD8 T cells. The molecular mechanisms that contribute to the loss of naïve CD8 T-cells during aging remain unclear. Considering that many CD8 T-cell functions are influenced by microRNAs (miRNAs), we explored miRNA expression profiling to identify novel dysfunctions that contribute to naïve CD8 T-cell loss during aging. Here, we describe age-dependent miRNA expression changes in naïve, central memory, and effector memory CD8 T-cell subsets. Changes in old naïve CD8 T-cells partially resembled those driven by an underlying shift in cellular differentiation toward a young central memory phenotype. Pathways enriched for targets of age-dependent miRNAs included FOXO1, NF-κB, and PI3K-AKT signaling. Transcriptome analysis of old naïve CD8 T-cells yielded corresponding patterns that correlated to those seen with reduced FOXO1 or altered NF-κB activities. Of particular interest, IL-7R expression, controlled by FOXO1 signaling, declines on naïve CD8 T cells with age and directly correlates with the frequencies of naïve CD8 T cells. Thus, age-associated changes in miRNA networks may ultimately contribute to the failure in CD8 T-cell homeostasis exemplified by the loss in naïve cells.

Dissecting alterations in human CD8+ T cells with aging by high-dimensional single cell mass cytometry

We investigated the effect of aging on the multi-dimensional characteristics and heterogeneity of human peripheral CD8⁺ T cells defined by the expression of a set of molecules at the single cell level using the recently developed mass cytometry or Cytometry by Time-Of-Flight (CyTOF) and computational algorithms. CD8⁺ T cells of young and older adults had differential expression of molecules, especially those related to cell activation and migration, permitting the clustering of young and older adults through an unbiased approach. The changes in the expression of individual molecules were collectively reflected in the altered high-dimensional profiles of CD8⁺ T cells in older adults as visualized by the dimensionality reduction analysis tools principal component analysis (PCA) and t-distributed stochastic neighbor embedding (t-SNE). A combination of PhenoGraph clustering and t-SNE analysis revealed heterogeneous subsets of CD8⁺ T cells that altered with aging. Furthermore, intermolecular quantitative relationships in CD8⁺ T cells appeared to change with age as determined by the computational algorithm conditional-Density Resampled Estimate of Mutual Information (DREMI). The results of our study showed that heterogeneity, multidimensional characteristics, and intermolecular quantitative relationships in human CD8⁺ T cells altered with age, distinctively clustering young and older adults through an unbiased approach.

DNA Damage Response Signals Transduce Stress From Rheumatoid Arthritis Risk Factors Into T Cell Dysfunction

Rheumatoid arthritis (RA) is an autoimmune-mediated disease that is associated with significant cartilage damage and immunosenescence. Despite decades of research, the major signal pathways that initiate RA are still unclear. The DNA damage response (DDR) is a specific and hierarchical network that includes cell cycle checkpoints, DNA repair, and DNA-damage tolerance pathways. Recent studies suggest that this condition is associated with deficits in telomere maintenance and overall genomic instability in the T cells of RA patients. Analysis of the underlying mechanisms has revealed defects in DDR pathways. Particularly, the DNA repair enzyme, ataxia telangiectasia mutated (ATM), is downregulated, which leaves the damaged DNA breaks in RA-associated T cells unrepaired and pushes them to apoptosis, exhausts the T cell pool, and promotes the arthritogenesis effector function of T cells. This review discusses recent advancements and illustrates that risk factors for RA, such as viral infections, environmental events, and genetic risk loci are combat with DDR signals, and the impaired DDR response of RA-associated T cells, in turn, triggers disease-related phenotypes. Therefore, DDR is the dominant signal that converts genetic and environmental stress to RA-related immune dysfunction. Understanding the orchestration of RA pathogenesis by DDR signals would further our current knowledge of RA and provide novel avenues in RA therapy.

Aging of Antiviral CD8+ Memory T Cells Fosters Increased Survival, Metabolic Adaptations, and Lymphoid Tissue Homing

Aging of established antiviral T cell memory can foster a series of progressive adaptations that paradoxically improve rather than compromise protective CD8⁺ T cell immunity. We now provide evidence that this gradual evolution, the pace of which is contingent on the precise context of the primary response, also impinges on the molecular mechanisms that regulate CD8⁺ memory T cell (T_M) homeostasis. Over time, CD8⁺ T_M generated in the wake of an acute infection with the natural murine pathogen lymphocytic choriomeningitis virus become more resistant to apoptosis and acquire enhanced cytokine responsiveness without adjusting their homeostatic proliferation rates; concurrent metabolic adaptations promote increased CD8⁺ T_M quiescence and fitness but also impart the reacquisition of a partial effector-like metabolic profile; and a gradual redistribution of aging CD8⁺ T_M from blood and nonlymphoid tissues to lymphatic organs results in CD8⁺ T_M accumulations in bone marrow, splenic white pulp, and, particularly, lymph nodes. Altogether, these data demonstrate how temporal alterations of fundamental homeostatic determinants converge to render aged CD8⁺ T_M poised for greater recall responses.

Integrative Physiology of Pneumonia

Pneumonia is a type of acute lower respiratory infection that is common and severe. The outcome of lower respiratory infection is determined by the degrees to which immunity is protective and inflammation is damaging. Intercellular and interorgan signaling networks coordinate these actions to fight infection and protect the tissue. Cells residing in the lung initiate and steer these responses, with additional immunity effectors recruited from the bloodstream. Responses of extrapulmonary tissues, including the liver, bone marrow, and others, are essential to resistance and resilience. Responses in the lung and extrapulmonary organs can also be counterproductive and drive acute and chronic comorbidities after respiratory infection. This review discusses cell-specific and organ-specific roles in the integrated physiological response to acute lung infection, and the mechanisms by which intercellular and interorgan signaling contribute to host defense and healthy respiratory physiology or to acute lung injury, chronic pulmonary disease, and adverse extrapulmonary sequelae. Pneumonia should no longer be perceived as simply an acute infection of the lung. Pneumonia susceptibility reflects ongoing and poorly understood chronic conditions, and pneumonia results in diverse and often persistent deleterious consequences for multiple physiological systems.

Defective respiration and one-carbon metabolism contribute to impaired naïve T cell activation in aged mice

T cell-mediated immune responses are compromised in aged individuals, leading to increased morbidity and reduced response to vaccination. Finding new ways to boost T cell immunity in the elderly is key for enhancing their immune competence. In this work, we performed a systematic analysis of proteins and metabolites in young versus aged T cells. Metabolic rewiring occurs in young T cells following stimulation but is dampened in aged T cells. Moreover, we show that aged T cell functions can be enhanced by metabolite addition.

T cell-mediated immune responses are compromised in aged individuals, leading to increased morbidity and reduced response to vaccination. While cellular metabolism tightly regulates T cell activation and function, metabolic reprogramming in aged T cells has not been thoroughly studied. Here, we report a systematic analysis of metabolism during young versus aged naïve T cell activation. We observed a decrease in the number and activation of naïve T cells isolated from aged mice. While young T cells demonstrated robust mitochondrial biogenesis and respiration upon activation, aged T cells generated smaller mitochondria with lower respiratory capacity. Using quantitative proteomics, we defined the aged T cell proteome and discovered a specific deficit in the induction of enzymes of one-carbon metabolism. The activation of aged naïve T cells was enhanced by addition of products of one-carbon metabolism (formate and glycine). These studies define mechanisms of skewed metabolic remodeling in aged T cells and provide evidence that modulation of metabolism has the potential to promote immune function in aged individuals.

Age-Related Changes on CD40 Promotor Methylation and Immune Gene Expressions in Thymus of Chicken

One hundred and twenty one-day-old breeder cocks, included 15 cages of 8 birds each, were fed to learn the aging's effect on chicken's thymus immunity. At 2 (2-W) and 40 (40-W) weeks of age, one chicken each cage was randomly chosen and slaughtered to get the thymus sample. The results showed that thymus weight and morphology of 40-W group were far different from that of 2-W group, and exhibited a property of degeneration. Considering this phenotype variance, we analyzed the thymus' transcriptome to investigate the molecular mechanism that had been implicated in this phenotype diversity with age. Pearson correlation coefficients and principal component analysis indicated that two major populations corresponding to 40-W and 2-W group were identified, and 1949 differentially expressed genes (DEGs, 1722 up-regulated and 127 down-regulated) were obtained. Results of GO and KEGG pathway enrichment found that 4 significantly enriched KEGG pathways (Cytokine-cytokine receptor interaction, Intestinal immune network for IgA production, Toll-like receptor signaling pathway, AGE-RAGE signaling pathway in diabetic complications) related to immunoregulation were screened between 40-W and 2-W group. These results confirmed that thymus immunity of chickens had a strong age-related correlation. DEGs related to these 4 enriched KEGG pathways were suppressed in the thymus of 2-W group, this indicated that thymus immunity of 2-weeks-age chick was down-regulated. CD40 is involved in 3 of the 4 significantly enriched pathways, and it is critical for thymus immune-regulation. CD40 promoter methylation level of 2-W group was higher than that of 40-W group, it is consistent with the transcriptional differences of the gene. Our study concluded that thymus immunity of chicken was varied with age. Compared to the 40-W group, thymus immunity of 2-W group was down-regulated, and in a status of hypo-activation on the whole, and these effects might be related to CD40 suppression induced by promoter hyper-methylation of the gene.

A comprehensive characterization of aggravated aging-related changes in T lymphocytes and monocytes in end-stage renal disease: the iESRD study

Background

Patients with end-stage renal disease (ESRD) exhibit a premature aging phenotype of the immune system. Nevertheless, the etiology and impact of these changes in ESRD patients remain unknown.

Results

Compared to healthy individuals, ESRD patients exhibit accelerated immunosenescence in both T cell and monocyte compartments, characterized by a dramatic reduction in naïve CD4+ and CD8+ T cell numbers but increase in CD8+ T_EMRA cell and proinflammatory monocyte numbers. Notably, within ESRD patients, aging-related immune changes positively correlated not only with increasing age but also with longer dialysis vintage. In multivariable-adjusted logistic regression models, the combination of high terminally differentiated CD8+ T cell level and high intermediate monocyte level, as a composite predictive immunophenotype, was independently associated with prevalent coronary artery disease as well as cardiovascular disease, after adjustment for age, sex, systemic inflammation and presence of diabetes. Levels of terminally differentiated CD8+ T cells also positively correlated with the level of uremic toxin p-cresyl sulfate.

Conclusions

Aging-associated adaptive and innate immune changes are aggravated in ESRD and are associated with cardiovascular diseases. For the first time, our study demonstrates the potential link between immunosenescence in ESRD and duration of exposure to the uremic milieu.

Electronic supplementary material

The online version of this article (10.1186/s12979-018-0131-x) contains supplementary material, which is available to authorized users.

Age-related tumor growth in mice is related to integrin α 4 in CD8+ T cells

Cancer incidence increases with age, but paradoxically, cancers have been found to grow more quickly in young mice compared with aged ones. The cause of differential tumor growth has been debated and, over time, attributed to faster tumor cell proliferation, decreased tumor cell apoptosis, and/or increased angiogenesis in young animals. Despite major advances in our understanding of tumor immunity over the past 2 decades, little attention has been paid to comparing immune cell populations in young and aged mice. Using mouse colon adenocarcinoma model MC38 implanted in young and mature mice, we show that age substantially influences the number of tumor-infiltrating cytotoxic CD8+ T cells, which control cancer progression. The different tumor growth pace in young and mature mice was abrogated in RAG1null mice, which lack mature T and B lymphocytes, and upon selective depletion of endogenous CD8+ cells. Transcriptome analysis further indicated that young mice have decreased levels of the Itga4 gene (CD49d, VLA-4) in tumor-infiltrating lymphocytes when compared with mature mice. Hypothesizing that VLA-4 can have a tumor-protective effect, we depleted the protein, which resulted in accelerated tumor growth in mature mice. These observations may explain the paradoxical growth rates observed in murine cancers, point to the central role of VLA-4 in controlling tumor growth, and open new venues to therapeutic manipulation.

T cell receptor sequencing of activated CD8 T cells in the blood identifies tumor-infiltrating clones that expand after PD-1 therapy and radiation in a melanoma patient

PD-1-targeted therapy has dramatically changed advanced cancer treatment. However, many questions remain, including specificity of T cells activated by PD-1 therapy and how peripheral blood analysis correlates to effects at tumor sites. In this study, we utilized TCR sequencing to dissect the composition of peripheral blood CD8 T cells activated upon therapy, comparing it with tumor-infiltrating lymphocytes. We report on a nonagenarian melanoma patient who showed a prominent increase in peripheral blood Ki-67 + CD8 T cells following brain stereotactic radiation and anti-PD-1 immunotherapy. Proliferating CD8 T cells exhibited an effector-like phenotype with expression of CD38, HLA-DR and Granzyme B, as well as expression of the positive costimulatory molecules CD28 and CD27. TCR sequencing of peripheral blood CD8 T cells revealed a highly oligoclonal repertoire at baseline with one clonotype accounting for 30%. However, the majority of dominant clones-including a previously identified cytomegalovirus-reactive clone-did not expand following treatment. In contrast, expanding clones were present at low frequencies in the peripheral blood but were enriched in a previously resected liver metastasis. The patient has so far remained recurrence-free for 36 months, and several CD8 T cell clones that expanded after treatment were maintained at elevated levels for at least 8 months. Our data show that even in a nonagenarian individual with oligoclonal expansion of CD8 T cells, we can identify activation of tumor-infiltrating CD8 T cell clones in peripheral blood following anti-PD-1-based immunotherapies.