Cellular aging and senescence characteristics of human T-lymphocytes

Nonlinear Dynamics of TNFR1 and TNFR2 Expression on Immune Cells: Genetic and Age-Related Aspects of Inflamm-Aging Mechanisms

Introduction: Immunosenescence alters TNF receptor expression (TNFR1 and TNFR2), contributing to chronic inflammation (inflamm-aging) and age-related diseases. Polymorphisms in TNFRSF1A and TNFRSF1B may influence receptor expression; however, their role in age-dependent modulation remains unclear. This study examines TNFR1/TNFR2 expression dynamics on T cells, B cells, and monocytes across different ages and evaluates the impact of genetic polymorphisms. Methods: PBMCs from 150 donors (18-60 years) were isolated via density-gradient centrifugation and cultured under spontaneous and LPS-stimulated conditions. TNFR1 and TNFR2 expression on immune cell subsets was quantified using flow cytometry with BD QuantiBRITE PE beads. SNP genotyping in TNFRSF1A and TNFRSF1B was performed via PCR with restriction analysis. Nonlinear age-related trends were assessed using polynomial approximation and inflection point analysis (Tukey's method). Results: Among the 23 analyzed TNF system parameters, the proportion of TNFR2+CD3+ T cells increased with age, whereas TNFR1+ and TNFR2+ monocyte populations showed significant negative correlations (p < 0.05). Inflection points (~27, 34-36, and 44-45 years) indicated nonlinear dynamics in TNFRs expression during aging. TNFR2 expression on T cells gradually increased and stabilized at later ages, whereas TNFR1 and TNFR2 expression on monocytes followed distinct declining trajectories. Genetic polymorphisms influenced correlation strength, but did not alter direction, demonstrating a conserved pattern of age-related receptor expression shifts. Conclusions: TNFR expression exhibits nonlinear, age-dependent alterations across immune cells, shaped by immunosenescence and genetic variability. The identified critical age intervals represent key phases of immune remodeling, where assessing TNFR expression may provide insights into inflamm-aging mechanisms and potential targets for immune modulation.

Markers of immunosenescence in CMV seropositive healthy elderly adults

A significant increase in life expectancy has accompanied the growth of the world's population. Approximately 10% of the global population are adults over 60, and it is estimated that 2050 this figure will double. This increase in the proportion of older adults leads to a more significant burden of age-related diseases. Immunosenescence predisposes elderly individuals to a higher incidence of infectious and chronic non-communicable diseases with higher mortality rates. Despite advances in research, it is necessary to evaluate the cellular characteristics of the aging immune system in populations with a high incidence of latent viruses such as cytomegalovirus (CMV). In this sense, this work aimed to identify senescence markers in cells of the innate and adaptive immune system in healthy older adults with CMV infection. We observed that older adults present an increase in the population of CD14+CD16+ intermediate monocytes, an expansion of CD56neg NK cells with an increase in the expression of CD57, as well as a decrease in the naïve CD4+ and CD8+ T cells, accompanied by an increased expression of senescence markers CD57 and KLRG1 in effector CD8+ T cells.

Herpesvirus Antibodies Are Correlated With Greater Expression of p16 in the T Cells of Humans

Background

There is an increasing awareness that aging of the immune system, or immunosenescence, is a key biological process underlying many of the hallmark diseases of aging and age-related decline broadly. While immunosenescence can be in part due to normal age-related changes in the immune system, emerging evidence posits that viral infections may be biological stressors of the immune system that accelerate the pace of immunosenescence.

Methods

We used a convenience sample of 42 individuals aged 65 years and older to examine correlations between antiviral immunoglobulin G (IgG) levels for 4 human herpesviruses (cytomegalovirus [CMV], herpes simplex virus [types 1 and 2], and Epstein-Barr virus) and multiple indicators of T-cell immunosenescence.

Results

We found that most of the sample (n = 33) was antiviral IgG positive for 2 or more of the 4 herpesvirus infections. We also examined correlations between both the total number of viruses for which an individual had antiviral IgG and each individual virus and multiple indicators of T-cell immunosenescence, particularly p16 expression. The strongest correlations were observed between the total number of viruses for which an individual had detectable antiviral IgG and p16 mean fluorescent intensity (MFI) among CD27-CD28-CD57+ CD4+ cells (r = 0.60; P < .001) and between anti-CMV IgG and p16 MFI of CD27-CD57+ CD4+ cells (r = 0.59; P < .001).

Conclusions

Broadly, our findings offer compelling preliminary evidence for future investigations to incorporate multiple indicators of persistent viral infections and a more comprehensive set of markers of T-cell immunosenescence in population-based studies of aging.

Dysregulation of peripheral and intratumoral KLRG1+ CD8+T cells is associated with immune evasion in patients with non-small-cell lung cancer

OBJECTIVES

Killer cell lectin like receptor G1 (KLRG1) is identified as a co-inhibitory receptor for NK cells and antigen-experienced T cells. The role of KLRG1 in immune regulation in patients with non-small cell lung cancer (NSCLC) remains poorly understood.

MATERIALS AND METHODS

We measured the proportion and immune function of KLRG1+CD8+T cells derived from peripheral blood in patients with NSCLC by flow cytometry. Besides, using data from the gene expression profiles and single-cell sequencing, we explored the expression and immune role of KLRG1 in tumor tissues of patients with NSCLC. We further determined the prognostic value of KLRG1 in terms of overall survival (OS) in NSCLC patients.

RESULTS

We found that the proportion of KLRG1+CD8+T cells in peripheral blood significantly increased in patients with NSCLC as compared to those with benign pulmonary nodules and healthy donors. Peripheral KLRG1+CD8+T cell proportion was increased in elder subjects compared to that in younger ones, implying an immunosenescence phenotype. Moreover, the KLRG1+CD8+T cell levels were positively correlated with tumor size and TNM stage in the NSCLC cohort. In vitro stimulation experiments demonstrated that the KLRG1+CD8+T cells from peripheral blood expressed higher levels of Granzyme B and perforin than the KLRG1-CD8+ T cells. However, single-cell RNA sequencing data revealed that the KLRG1+CD8+ T cells were less infiltrated in tumor microenvironment and exhibited impaired cytotoxicity. The KLRG1 gene expression levels were significantly lower in tumor tissues than that in normal lung tissues, and were inversely correlated with CDH1 expression levels. Moreover, higher expression of CDH1 in tumor tissues predicted worse overall survival only in patients with KLRG1-high expression, but not in the KLRG1-low subset.

CONCLUSION

This study demonstrates that KLRG1+CD8+T cells were associated with tumor immune evasion in NSCLC and suggests KLRG1 as a potential immunotherapy target.

T-cell senescence: A crucial player in autoimmune diseases

Senescent T cells are proliferative disabled lymphocytes that lack antigen-specific responses. The development of T-cell senescence in autoimmune diseases contributes to immunological disorders and disease progression. Senescent T cells lack costimulatory markers with the reduction of T cell receptor repertoire and the uptake of natural killer cell receptors. Senescent T cells exert cytotoxic effects through the expression of perforin, granzymes, tumor necrosis factor, and other molecules without the antigen-presenting process. DNA damage accumulation, telomere damage, and limited DNA repair capacity are important features of senescent T cells. Impaired mitochondrial function and accumulation of reactive oxygen species contribute to T cell senescence. Alleviation of T-cell senescence could provide potential targets for the treatment of autoimmune diseases.

Neoadjuvant chemotherapy modulates exhaustion of T cells in breast cancer patients

Breast cancer is the leading cause of cancer deaths in women worldwide. It has been observed that the incidence of breast cancer increases linearly with age after 45, which suggest a link between cancer, aging, and senescence. A growing body of evidence indicates that the immunosuppressive tumor network in breast cancer patients can lead to T-cell exhaustion and senescence. Cytotoxic chemotherapy is a common treatment for many cancers, and it is hypothesized that its efficacy may be related to immune activation. However, the effects of neoadjuvant chemotherapy on T-cell dysfunction in breast cancer patients are not fully understood. This study aimed to evaluate the impact of neoadjuvant chemotherapy on the expression of exhaustion and senescence markers in T cells in women with breast cancer. Our results showed that T cells from breast cancer patients have a reduced ability to respond to stimulation in-vitro and an increased expression of senescence and exhaustion-associated markers, such as TIM-3, LAG3, and CD57. Furthermore, we found that neoadjuvant chemotherapy has an immunomodulatory effect and reduces the expression of exhaustion markers. Our observations of the immune phenotype of T cells during neoadjuvant chemotherapy treatment highlight its ability to stimulate the immune system against cancer. Therefore, monitoring the response of T cells during chemotherapy may enable early prediction of clinical response.

Senescent-like Blood Lymphocytes and Disease Progression in Amyotrophic Lateral Sclerosis

BACKGROUND AND OBJECTIVES

Aging is known to exacerbate neuroinflammation, and in the neurodegenerative disorder amyotrophic lateral sclerosis (ALS), an older age is associated with a worse prognosis. We have previously shown the activation of cell senescence pathways in the proteome of peripheral blood mononuclear cells and the increase of proinflammatory cytokines in blood from individuals living with ALS. In this single-center, retrospective study, we investigated the expression of senescent-like blood mononuclear cells in ALS.

METHODS

We first applied multidimensional cytometry by time-of-flight (CyTOF) to study the senescent immunophenotype of blood mononuclear cells from 21 patients with ALS and 10 healthy controls (HCs). We then used targeted flow cytometry (FC) to investigate frequencies of senescent blood lymphocytes in 40 patients with ALS and 20 HCs. Longitudinal analysis included 2 additional time points in 17 patients with ALS. Frequencies of senescent-like lymphocytes were analyzed in relation to survival.

RESULTS

Unsupervised clustering of CyTOF data showed higher frequencies of senescent CD4+CD27-CD57+ T cells in patients with ALS compared with those in HCs (p = 0.0017, false discovery (FDR)-adjusted p = 0.029). Moderate to strong negative correlations were identified between CD4 T central memory-cell frequencies and survival (R = -061, p = 0.01; FDR-adjusted p < 0.1) and between CD95 CD8 cells and ALS functional rating scale revised at baseline (R = -0.72, p = 0.001; FDR-adjusted p < 0.1).Targeted FC analysis showed higher memory T regulatory cells (p = 0.0052) and memory CD8+ T cell (M-Tc; p = 0.0006) in bulbar ALS (A-B) compared with those in limb ALS (A-L), while late memory B cells (LM-B) were also elevated in A-B and fast-progressing ALS (p = 0.0059). Higher M-Tc levels separated A-B from A-L (AUC: 0.887; p < 0.0001). A linear regression model with prespecified clinical independent variables and neurofilament light chain plasma concentration showed that higher frequencies of LM-B predicted a shorter survival (hazard ratio: 1.094, CI: 1.026-1.167; p = 0.006).

DISCUSSION

Our data suggest that a systemic elevation of senescent and late memory T and B lymphocytes is a feature of faster progressing ALS and of ALS individuals with bulbar involvement. Lymphocyte senescence and their memory state may be central to the immune dysregulation known to drive disease progression in ALS and a target for biomarkers and therapeutics discovery.

Assessment of cell cycle regulators in human peripheral blood cells as markers of cellular senescence

Cellular senescence has gained increasing interest during recent years, particularly due to causal involvement in the aging process corroborated by multiple experimental findings. Indeed, cellular senescence considered to be one of the hallmarks of aging, is defined as a stable growth arrest predominantly mediated by cell cycle regulators p53, p21 and p16. Senescent cells have frequently been studied in the peripheral blood of humans due to its accessibility. This review summarizes ex vivo studies describing cell cycle regulators as markers of senescence in human peripheral blood cells, along with detection methodologies and associative studies examining demographic and clinical characteristics. The utility of techniques such as the quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), microarray, RNA sequencing and nCounter technologies for detection at the transcriptional level, along with Western blotting, enzyme-linked immunosorbent assay and flow cytometry at the translational level, will be brought up at salient points throughout this review. Notably, housekeeping genes or proteins serving as controls such as GAPDH and β-Actin, were found not to be stably expressed in some contexts. As such, optimization and validation of such genes during experimental design were recommended. In addition, the expression of cell cycle regulators was found to vary not only between different types of blood cells such as T cells and B cells but also between stages of cellular differentiation such as naïve T cells and highly differentiated T cells. On the other hand, the associations of the presence of cell cycle regulators with demographics (age, gender, ethnicity, and socioeconomic status), clinical characteristics (body mass index, specific diseases, disease-related parameters) and lifestyle vary in groups of participants. One envisions that increased understanding and insights into the assessment of cell cycle regulators as markers of senescence in human peripheral blood cells will help inform prognostication and clinical intervention in elderly individuals.

Immunosuppressive network promotes immunosenescence associated with aging and chronic inflammatory conditions

The functional competence of the immune system gradually declines with aging, a process called immunosenescence. The age-related remodelling of the immune system affects both adaptive and innate immunity. In particular, a chronic low-grade inflammation, termed inflammaging, is associated with the aging process. Immunosenescence not only is present in inflammaging state, but it also occurs in several pathological conditions in conjunction with chronic inflammation. It is known that persistent inflammation stimulates a counteracting compensatory immunosuppression intended to protect host tissues. Inflammatory mediators enhance myelopoiesis and induce the generation of immature myeloid-derived suppressor cells (MDSC) which in mutual cooperation stimulates the immunosuppressive network. Immunosuppressive cells, especially MDSCs, regulatory T cells (Treg), and M2 macrophages produce immunosuppressive factors, e.g., TGF-β, IL-10, ROS, arginase-1 (ARG1), and indoleamine 2,3-dioxygenase (IDO), which suppress the functions of CD4/CD8T and B cells as well as macrophages, natural killer (NK) cells, and dendritic cells. The immunosuppressive armament (i) inhibits the development and proliferation of immune cells, (ii) decreases the cytotoxic activity of CD8T and NK cells, (iii) prevents antigen presentation and antibody production, and (iv) suppresses responsiveness to inflammatory mediators. These phenotypes are the hallmarks of immunosenescence. Immunosuppressive factors are able to control the chromatin landscape, and thus, it seems that the immunosenescence state is epigenetically regulated.

Critically ill COVID-19 patients exhibit hyperactive cytokine responses associated with effector exhausted senescent T cells in acute infection

COVID-19 can progress to severe pneumonia with respiratory failure and is aggravated by the deregulation of the immune system causing an excessive inflammation including the cytokine storm. We herein report that severe acutely infected patients have high levels of both type-1 and type-2 cytokines. Our results show abnormal cytokine levels upon T cell stimulation, in a non-polarized profile. Furthermore, our findings indicate that this hyperactive cytokine response is associated with a significantly increased frequency of late-differentiated T cells with particular phenotype of effector exhausted/senescent CD28 ^-CD57 ⁺ cells. Interestingly, we demonstrated for the first time an increased frequency of CD3 ⁺CD4 ⁺CD28 ^-CD57 ⁺ T cells with expression of programmed death 1 (PD-1), one of the hallmarks of T cell exhaustion. These findings reveal that COVID-19 is associated with acute immunodeficiency, especially within the CD4 ⁺ T cell compartment and points to possible mechanisms of loss of clonal repertoire and susceptibility to viral relapse and reinfection events.

The old guard: Age-related changes in microglia and their consequences

Among all major organs, the brain is one of the most susceptible to the inexorable effects of aging. Throughout the last decades, several studies in human cohorts and animal models have revealed a plethora of age-related changes in the brain, including reduced neurogenesis, oxidative damage, mitochondrial dysfunction and cell senescence. As the main immune effectors and first responders of the nervous tissue, microglia are at the center of these events. These cells experience irrevocable changes as a result from cumulative exposure to environmental triggers, such as stress, infection and metabolic dysregulation. The age-related immunosenescent phenotype acquired by microglia is characterized by profound modifications in their transcriptomic profile, secretome, morphology and phagocytic activity, which compromise both their housekeeping and defensive functions. As a result, aged microglia are no longer capable of establishing effective immune responses and sustaining normal synaptic activity, directly contributing to age-associated cognitive decline and neurodegeneration. This review discusses how lifestyle and environmental factors drive microglia dysfunction at the molecular and functional level, also highlighting possible interventions to reverse aging-associated damage to the nervous and immune systems.

Hallmarks and detection techniques of cellular senescence and cellular ageing in immune cells

The ageing of the global population brings about unprecedented challenges. Chronic age-related diseases in an increasing number of people represent an enormous burden for health and social care. The immune system deteriorates during ageing and contributes to many of these age-associated diseases due to its pivotal role in pathogen clearance, tissue homeostasis and maintenance. Moreover, in order to develop treatments for COVID-19, we urgently need to acquire more knowledge about the aged immune system, as older adults are disproportionally and more severely affected. Changes with age lead to impaired responses to infections, malignancies and vaccination, and are accompanied by chronic, low-degree inflammation, which together is termed immunosenescence. However, the molecular and cellular mechanisms that underlie immunosenescence, termed immune cell senescence, are mostly unknown. Cellular senescence, characterised by an irreversible cell cycle arrest, is thought to be the cause of tissue and organismal ageing. Thus, better understanding of cellular senescence in immune populations at single-cell level may provide us with insight into how immune cell senescence develops over the life time of an individual. In this review, we will briefly introduce the phenotypic characterisation of aged innate and adaptive immune cells, which also contributes to overall immunosenescence, including subsets and function. Next, we will focus on the different hallmarks of cellular senescence and cellular ageing, and the detection techniques most suitable for immune cells. Applying these techniques will deepen our understanding of immune cell senescence and to discover potential druggable pathways, which can be modulated to reverse immune ageing.

Immunosenescence Study of T Cells: A Systematic Review

Background

Aging is accompanied by alterations in immune response which leads to increased susceptibility to infectious diseases, cancer, autoimmunity, and inflammatory disorders. This decline in immune function is termed as immunosenescence; however, the mechanisms are not fully elucidated. Experimental approaches of adaptive immunity, particularly for T cells, have been the main focus of immunosenescence research. This systematic review evaluates and discusses T cell markers implicated in immunosenescence.

Objective

To determine the best flow cytometry markers of circulating T cells associated with immunosenescence.

Methods

We systematically queried PubMed, MEDLINE, EBSCO, and BVS databases for original articles focused on two age groups of healthy humans: 18–44 (young adults) and >60 (older adults) years. In accordance with the Cochrane methodology, we synthesized data through qualitative descriptions and quantitative random effects meta-analysis due to extensive heterogeneity.

Results

A total of 36 studies conducted in the last 20 years were included for the qualitative analysis and four out of these studies were used to perform the meta-analysis. A significant decrease in naïve T cell subset was observed in older adults compared to young adults. Primary markers used to identify senescent cells were loss of CD28 and increased expression of CD57 and KLRG1 in terminally-differentiated memory T cell subset in older adults. Moreover, we observed an increase in proinflammatory cytokines and decrease in telomere length in old adult T cells. It was not possible to perform quantitative synthesis on cell markers, cytokines, and telomere length because of the significant variations between the groups, which is attributed to differences in protocols and unreported measurements, thus generating a high risk of bias.

Conclusions

Heterogeneity among studies in terms of data report, measurement techniques and high risk of bias were major impediments for performing a robust statistical analysis that could aid the identification of eligible flow cytometry markers of immunosenescence phenotype in T cells.

Comparative Study of Senescent Th Biomarkers in Healthy Donors and Early Arthritis Patients. Analysis of VPAC Receptors and Their Influence

Pro-inflammatory CD4⁺CD28⁻ T cells are characteristic of immunosenescence, but also of several autoimmune/inflammatory diseases. Vasoactive intestinal peptide (VIP) acts as an anti-inflammatory and immunomodulatory mediator on these cells. Our objective was to study the mutual influence between senescent Th cells and VIP axis in early arthritis (EA), comparing with non-EA donors. We characterized the correlation between senescent Th cells and clinic parameters of EA as well as the behavior of senescent Th biomarkers by real-time PCR. Clinical data were systematically recorded at baseline and after 6 months of follow-up. The number of CD4⁺CD28⁻ T cells measured by sorting is higher in patients who initially meet ACR classification criteria for rheumatoid arthritis (RA) compared to those who were classified as undifferentiated arthritis (UA). A slight positive correlation between EA CD4⁺CD28⁻ T cells and CRP or ESR and a negative correlation with bone mineral density were found. Th senescent biomarkers in EA CD4⁺CD28⁻ T cells were similar to donors, however some of them increased after 6 months of follow-up. VPAC receptors were analyzed by real-time PCR and immunofluorescence, and CD4⁺CD28⁻ T cells showed higher expression of VPAC₂ and lower of VPAC₁, VPAC₂ showing a significant increased expression in EA cells. Sorted CD4⁺CD28⁻ T cells were in vitro expanded in presence of VIP, wherein VIP increased senescent biomarker CD27, while it diminished CD57 or NKG2 senescent biomarkers. Our study demonstrates for the first time the existence of a link between senescent Th cells and the VIP axis.

Quantitative and time-resolved miRNA pattern of early human T cell activation

T cells are central to the immune response against various pathogens and cancer cells. Complex networks of transcriptional and post-transcriptional regulators, including microRNAs (miRNAs), coordinate the T cell activation process. Available miRNA datasets, however, do not sufficiently dissolve the dynamic changes of miRNA controlled networks upon T cell activation. Here, we established a quantitative and time-resolved expression pattern for the entire miRNome over a period of 24 h upon human T-cell activation. Based on our time-resolved datasets, we identified central miRNAs and specified common miRNA expression profiles. We found the most prominent quantitative expression changes for miR-155-5p with a range from initially 40 molecules/cell to 1600 molecules/cell upon T-cell activation. We established a comprehensive dynamic regulatory network of both the up- and downstream regulation of miR-155. Upstream, we highlight IRF4 and its complexes with SPI1 and BATF as central for the transcriptional regulation of miR-155. Downstream of miR-155-5p, we verified 17 of its target genes by the time-resolved data recorded after T cell activation. Our data provide comprehensive insights into the range of stimulus induced miRNA abundance changes and lay the ground to identify efficient points of intervention for modifying the T cell response.

I mmunosenescence and Inflammaging: Risk Factors of Severe COVID-19 in Older People

Old individuals are more susceptible to various infections due to immunological changes that occur during the aging process. These changes named collectively as "immunosenescence" include decreases in both the innate and adaptive immune responses in addition to the exacerbated production of inflammatory cytokines. This scenario of immunological dysfunction and its relationship with disease development in older people has been widely studied, especially in infections that can be fatal, such as influenza and, more recently, COVID-19. In the current scenario of SARS-CoV-2 infection, many mechanisms of disease pathogenesis in old individuals have been proposed. To better understand the dynamics of COVID-19 in this group, aspects related to immunological senescence must be well elucidated. In this article, we discuss the main mechanisms involved in immunosenescence and their possible correlations with the susceptibility of individuals of advanced age to SARS-CoV-2 infection and the more severe conditions of the disease.

Functional recreation of age-related CD8 T cells in young mice identifies drivers of aging- and human-specific tissue pathology

Mitigating effects of aging on human health remains elusive because aging impacts multiple systems simultaneously, and because experimental animals exhibit critical aging differences relative to humans. Separation of aging into discrete processes may identify targetable drivers of pathology, particularly when applied to human-specific features. Gradual homeostatic expansion of CD8 T cells dominantly alters their function in aging humans but not in mice. Injecting T cells into athymic mice induces rapid homeostatic expansion, but its relevance to aging remains uncertain. We hypothesized that homeostatic expansion of T cells injected into T-deficient hosts models physiologically relevant CD8 T cell aging in young mice, and aimed to analyze age-related T cell phenotype and tissue pathology in such animals. Indeed, we found that such injection conferred uniform age-related phenotype, genotype, and function to mouse CD8 T cells, heightened age-associated tissue pathology in young athymic hosts, and humanized amyloidosis after brain injury in secondary wild-type recipients. This validates a model conferring a human-specific aging feature to mice that identifies targetable drivers of tissue pathology. Similar examination of independent aging features should promote systematic understanding of aging and identify additional targets to mitigate its effects on human health.

Intracellular Tenofovir and Emtricitabine Concentrations in Younger and Older Women with HIV Receiving Tenofovir Disoproxil Fumarate/Emtricitabine

The altered immune states of aging and HIV infection may affect intracellular metabolism of tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC); increased cellular senescence decreases FTC-triphosphate (FTCtp) concentrations. The effects of age and inflammation on the ratio of intracellular metabolites (IMs; tenofovir diphosphate [TFVdp] and FTCtp) to their endogenous nucleotides (ENs; dATP and dCTP), a potential treatment efficacy marker, were assessed among participants of the Women's Interagency HIV Study (WIHS), who ranged from 25 to 75 years. Samples from women receiving TDF-FTC with viral loads of <200 copies/ml were dichotomized by age at collection into two groups (≤45 years and ≥60 years). IM/EN concentrations were measured in peripheral blood mononuclear cell (PBMC) pellets; interleukin-6 (IL-6) and sCD163 were measured in plasma; senescent CD8⁺ T cells were measured in viable PBMCs. The TFVdp:dATP and FTCtp:dCTP ratios had statistically significantly different distributions in older and younger women (log-rank test, P = 0.0023 and P = 0.032, respectively); in general, IM and EN concentrations were higher in the older women. After adjusting for potential confounders, these findings were not significant. In women aged ≤45 years, TFVdp was negatively associated with IL-6 and sCD163, while FTCtp was positively associated with sCD163 and IL-6 in women aged ≥60 years. Body mass index (BMI) was positively associated with IL-6 in both age groups and negatively associated with TFVdp in women aged ≤45 years. After adjustment, age remained significant for sCD163, while black race, BMI, and renal function remained significant for several IMs and ENs, suggesting that factors associated with aging, but not age itself, govern intracellular TDF-FTC pharmacology.

Strength Endurance Training but Not Intensive Strength Training Reduces Senescence-Prone T Cells in Peripheral Blood in Community-Dwelling Elderly Women

Aging is characterized by a progressive decline in immune function known as immunosenescence. Although the causes of immunosenescence are likely to be multifactorial, an age-associated accumulation of senescent T cells and decreased naive T-cell repertoire are key contributors to the phenomenon. On the other hand, there is a growing consensus that physical exercise may improve immune response in aging. However, the optimum training modality required to obtain beneficial adaptations in older subjects is lacking. Therefore, we aimed to investigate the effects of exercise modality on T-cell phenotypes in older women. A total of 100 women (aged ≥ 65 years) were randomized to either intensive strength training (80% of one-repetition maximum ), strength endurance training (40% one-repetition maximum), or control (stretching exercise) for 2-3 times per week during 6 weeks. The T-cell percentages and absolute counts were determined using flow cytometry and a hematology analyzer. C-reactive protein was measured using immunonephelometry. We report for the first time that 6 weeks of strength endurance training significantly decreased the basal percentage and absolute counts of senescence-prone T cells, which was positively related to the number of training sessions performed. Conceivably, training protocols with many repetitions-at a sufficiently high external resistance-might assist the reduction of senescence-prone T cells in older women.

Six weeks of strength endurance training decreases circulating senescence-prone T-lymphocytes in cytomegalovirus seropositive but not seronegative older women

Background

Ageing is associated with a decline in immune function termed immunosenescence. This process is characterized amongst others by less naive T-cells and more senescent phenotypes, which have been implicated in the pathogenesis of many age-related diseases. Thus far, reports regarding the long-term adaptation effects of exercise on T-cell phenotypes are scant and largely equivocal. These inconsistencies may be due to potential contributors to immunosenescence, particularly cytomegalovirus infection, which is considered a hallmark of T-cell senescence. Therefore, we sought to investigate the impact of cytomegalovirus serostatus on the distribution of peripheral T-cell subsets following long-term exercise in older women.

Methods

One hundred women (aged 65 years and above) were randomized to 3 times/weekly training at either intensive strength training (3 × 10 repetitions at 80% of one-repetition maximum, n = 31), strength endurance training (2 × 30 repetitions at 40% of one-repetition maximum, n = 33), or control (passive stretching exercise, n = 36) for 6 weeks. All training sessions were supervised by trained instructors to minimize the risk of injury and to ensure that the participants adhered to the training protocol throughout the entire range of motion. The T-cell percentages and absolute blood counts were determined before and after 6 weeks (24 h–48 h after the last training session) using flow cytometry and a haematology analyser. Cytomegalovirus antibodies were measured in serum using Architect iSystem and cytomegalovirus serostatus was balanced in the three intervention groups. C-reactive protein was measured using immunonephelometry.

Results

We report for the first time that 6 weeks of strength endurance training significantly decreased senescence-prone T-cells along with a small increase in the number of CD8– naive T-cells in blood. The absolute counts of senescent-like T-cells decreased by 44% (from 26.03 ± 35.27 to 14.66 ± 21.36 cells/μL, p < 0.01) and by 51% (from 6.55 ± 12.37 to 3.18 ± 6.83 cells/μL, p < 0.05) for the CD8+ and CD8– T-cell pools, respectively. Intriguingly, these changes were observed in cytomegalovirus seropositive, but not cytomegalovirus seronegative individuals.

Conclusions

In conclusion, the present study shows that strength endurance training leads to a reduction in circulating senescence-prone T-cells in cytomegalovirus seropositive older women. It remains to be established if monitoring of peripheral senescence-prone T-cells may have utility as cellular biomarkers of immunosenescence.

Electronic supplementary material

The online version of this article (10.1186/s12979-019-0157-8) contains supplementary material, which is available to authorized users.

Phenotypic Evidence of T Cell Exhaustion and Senescence During Symptomatic Plasmodium falciparum Malaria

T cells play significant roles during Plasmodium falciparum infections. Their regulation of the immune response in symptomatic children with malaria has been deemed necessary to prevent immune associated pathology. In this study, we phenotypically characterized the expression of T cell inhibitory(PD-1, CTLA-4) and senescent markers (CD28(-), CD57) from children with symptomatic malaria, asymptomatic malaria and healthy controls using flow cytometry. We observed increased expression of T cell exhaustion and senescence markers in the symptomatic children compared to the asymptomatic and healthy controls. T cell senescence markers were more highly expressed on CD8 T cells than on CD4 T cells. Asymptomatically infected children had comparable levels of these markers with healthy controls except for CD8+ PD-1+ T cells which were significantly elevated in the asymptomatic children. Also, using multivariate regression analysis, CTLA-4 was the only marker that could predict parasitaemia level. The results suggest that the upregulation of immune exhaustion and senescence markers during symptomatic malaria may affect the effector function of T cells leading to inefficient clearance of parasites, hence the inability to develop sterile immunity to malaria.

Modulation of age related protein expression changes by gelam honey in cardiac mitochondrial rats

Aging is characterized by progressive decline in biochemical and physiological functions. According to the free radical theory of aging, aging results from oxidative damage due to the accumulation of excess reactive oxygen species (ROS). Mitochondria are the main source of ROS production and are also the main target for ROS. Therefore, a diet high in antioxidant such as honey is potentially able to protect the body from ROS and oxidative damage. Gelam honey is higher in flavonoid content and phenolic compounds compared to other local honey. This study was conducted to determine the effects of gelam honey on age related protein expression changes in cardiac mitochondrial rat. A total of 24 Sprague-Dawley male rats were divided into two groups: the young group (2 months old), and aged group (19 months old). Each group were then subdivided into two groups: control group (force-fed with distilled water), and treatment group (force-fed with gelam honey, 2.5 g/kg), and were treated for 8 months. Comparative proteomic analysis of mitochondria from cardiac tissue was then performed by high performance mass spectrometry (Q-TOF LCMS/MS) followed by validation of selected proteins by Western blotting. Proteins were identified using Spectrum Mill software and were subjected to stringent statistical analysis. A total of 286 proteins were identified in the young control group (YC) and 241 proteins were identified in the young gelam group (YG). In the aged group, a total of 243 proteins were identified in control group (OC), and 271 proteins in gelam group (OG). Comparative proteome profiling identified 69 proteins with different abundance (p < 0.05) in OC when compared to YC, and also in YG when compared to YC. On the other hand, 55 proteins were found to be different in abundance when comparing OG with OC. In the aged group, gelam honey supplementation affected the relative abundance of 52 proteins with most of these proteins showing a decrease in the control group. Bioinformatics analysis showed that the majority of the affected proteins were involved in the respiratory chain (OXPHOS) which play an important role in maintaining mitochondrial function.

Innate and adaptive immune dysregulation in critically ill ICU patients

This study aimed to evaluate whether ICU patients who developed persistent critical illness displayed an immune profile similar to an aged immune phenotype and any associations with patient outcomes. Twenty two critically ill ICU patients (27–76 years, 15 males), at day 5 of mechanical ventilation, and 22 healthy age-matched controls (27–77 years, 13 males) were recruited. Frequency and phenotype of innate and adaptive immune cells and telomere length in peripheral blood mononuclear cells (PBMCs) were measured. An elevated granulocyte count (p < 0.0001), increased numbers of immature granulocytes (p < 0.0001), increased CD16^++ve monocytes (p = 0.003) and CD14^+ve HLADR^dim/low monocytes (p = 0.004) and lower NK cell numbers (p = 0.007) were observed in ICU patients compared to controls. Critically ill patients also had lower numbers of total T lymphocytes (p = 0.03), naïve CD4 T cells (p = 0.003) and PTK7^+ve recent thymic emigrants (p = 0.002), and increased senescent CD28^−ve CD57^+ve CD4 T cells (p = 0.02), but there was no difference in PBMC telomere length. Regulatory immune cell frequency was affected with reduced circulating CD19^+veCD24^hiCD38^hi regulatory B cells (p = 0.02). However, only a raised neutrophil:lymphocyte ratio and reduced frequency of CD14^+ve HLADR^dim/low monocytes were associated with poor outcomes. We conclude that persistent critical illness results in changes to immune cell phenotype only some of which are similar to that seen in physiological ageing of the immune system.

Major features of immunesenescence, including reduced thymic output, are ameliorated by high levels of physical activity in adulthood

It is widely accepted that aging is accompanied by remodelling of the immune system including thymic atrophy and increased frequency of senescent T cells, leading to immune compromise. However, physical activity, which influences immunity but declines dramatically with age, is not considered in this literature. We assessed immune profiles in 125 adults (55-79 years) who had maintained a high level of physical activity (cycling) for much of their adult lives, 75 age-matched older adults and 55 young adults not involved in regular exercise. The frequency of naïve T cells and recent thymic emigrants (RTE) were both higher in cyclists compared with inactive elders, and RTE frequency in cyclists was no different to young adults. Compared with their less active counterparts, the cyclists had significantly higher serum levels of the thymoprotective cytokine IL-7 and lower IL-6, which promotes thymic atrophy. Cyclists also showed additional evidence of reduced immunesenescence, namely lower Th17 polarization and higher B regulatory cell frequency than inactive elders. Physical activity did not protect against all aspects of immunesenescence: CD28^-ve CD57^+ve senescent CD8 T-cell frequency did not differ between cyclists and inactive elders. We conclude that many features of immunesenescence may be driven by reduced physical activity with age.

Signal transduction changes in CD4+ and CD8+ T cell subpopulations with aging

The innate and adaptive branches of the immune system display changes with aging, a fact referred to as immunosenescence. Furthermore, it has been established that adaptive immunity is more susceptible to age-related changes than innate immunity. The most prominent phenotypic changes that reflect the specific differentiation and role of each T cell subpopulation are two-fold. They are a decreased number of naïve T cells that parallels an increase in memory T cells, mainly in the cytotoxic CD8⁺ T cell population, which can be subdivided into naïve, central, effector memory and TEMRA cells. The two main T cell properties that are the most affected with aging are the altered clonal expansion and decreased cytokine production, especially IL-2. These T cell functions have been shown to be affected in the early events of signaling. The aim of the present study was to investigate the influence of age on TCR- and CD28-dependent activation of the downstream signaling effectors Lck, SHP-1, Akt, PI3K p85α and mTOR in differentiated subpopulations of CD4⁺ and CD8⁺ T cells. Results showed that lymphocytes of elderly subjects were already in an activated state that could not be upregulated by external stimulation. Results also showed that the age-related signal transduction changes were more important than phenotype in the CD4⁺ and CD8⁺ T subpopulations. These observations suggested that age-related molecular and biochemical changes have a more significant influence on T cell functions than T cell phenotype.

Effects of Physical Exercise on Markers of Cellular Immunosenescence: A Systematic Review

Aging affects negatively the immune system, defined as immunosenescence, which increases the susceptibility of elderly persons to infection, autoimmune disease, and cancer. There are strong indications that physical exercise in elderly persons may prevent the age-related decline in immune response without significant side effects. Consequently, exercise is being considered as a safe mode of intervention to reduce immunosenescence. The aim of this review was to appraise the existing evidence regarding the impact of exercise on surface markers of cellular immunosenescence in either young and old humans or animals. PubMed and Web of Science were systematically screened, and 28 relevant articles in humans or animals were retrieved. Most of the intervention studies demonstrated that an acute bout of exercise induced increases in senescent, naïve, memory CD4⁺ and CD8⁺ T-lymphocytes and significantly elevated apoptotic lymphocytes in peripheral blood. As regards long-term effects, exercise induced increased levels of T-lymphocytes expressing CD28⁺ in both young and elderly subjects. Few studies found an increase in natural killer cell activity following a period of training. We can conclude that exercise has considerable effects on markers of cellular aspects of the immune system. However, very few studies have been conducted so far to investigate the effects of exercise on markers of cellular immunosenescence in elderly persons. Implications for immunosenescence need further investigation.

Shifts in subsets of CD8+ T-cells as evidence of immunosenescence in patients with cancers affecting the lungs: an observational case-control study

Background

Shifts in CD8+ T-cell subsets that are hallmarks of immunosenescence are observed in ageing and in conditions of chronic immune stimulation. Presently, there is limited documentation of such changes in lung cancer and other malignancies affecting the lungs.

Methods

Changes in CD8+ T-cell subsets, based on the expression of CD28 and CD57, were analysed in patients with various forms of cancer affecting the lungs, undergoing chemotherapy and in a control group over six months, using multi-colour flow cytometry.

Results

The differences between patients and controls, and the changes in the frequency of CD8+ T-cell subpopulations among lung cancer patients corresponded to those seen in immunosenescence: lower CD8-/CD8+ ratio, lower proportions of CD28+CD57- cells consisting of naïve and central memory cells, and higher proportions of senescent-enriched CD28-CD57+ cells among the lung cancer patients, with the stage IV lung cancer patients showing the most pronounced changes. Also observed was a tendency of chemotherapy to induce the formation of CD28+CD57+ cells, which, in line with the capacity of chemotherapy to induce the formation of senescent cells, might provide more evidence supporting CD28+CD57+ cells as senescent cells.

Conclusion

Immunosenescence was present before the start of the treatment; it appeared to be pronounced in patients with advanced cases of malignancies affecting the lungs, and might not be averted by chemotherapy.

Immunosenescence in renal transplantation: a changing balance of innate and adaptive immunity

PURPOSE OF REVIEW

With global demographic changes and an overall improved healthcare, more older end-stage renal disease (ESRD) patients receive kidney transplants. At the same time, organs from older donors are utilized more frequently. Those developments have and will continue to impact allocation, immunosuppression and efforts improving organ quality.

RECENT FINDINGS

Findings mainly outside the field of transplantation have provided insights into mechanisms that drive immunosenescence and immunogenicity, thus providing a rationale for an age-adapted immunosuppression and relevant clinical trials in the elderly. With fewer rejections in the elderly, alloimmune responses appear to be characterized by a decline in effectiveness and an augmented unspecific immune response.

SUMMARY

Immunosenescence displays broad and ambivalent effects in elderly transplant recipients. Those changes appear to compensate a decline in allospecific effectiveness by a shift towards an augmented unspecific immune response. Immunosuppression needs to target those age-specific changes to optimize outcomes in elderly transplant recipients.

Age-Related Differences in Percentages of Regulatory and Effector T Lymphocytes and Their Subsets in Healthy Individuals and Characteristic STAT1/STAT5 Signalling Response in Helper T Lymphocytes

The dynamic process of the development of the immune system can in itself result in age-related immune malfunctions. In this study, we analysed lymphocyte subsets in the peripheral blood of 60 healthy donors, divided into groups of children, adolescents, and adults, focusing on effector (Teff) and regulatory (Treg) T lymphocytes and STAT1/STAT5 signalling response in helper T lymphocytes (Th) in adults, using flow cytometry. Our results demonstrate a decrease in the percentage of total Tregs and an increase in the percentage of total Teffs with age and a consequential immense increase in the Teff/Treg ratio. The increase of Teffs was most apparent in Th1, Th1Th17, and Th17CD161- subsets. Significant Th lymphocyte STAT1 expression differences were observed between children and adolescents, which were associated with the decrease in activated Tregs. Higher expression of STAT1 was found in FoxP3hi than in FoxP3low Th lymphocytes, while significant IL-2 induced STAT5 phosphorylation differences were found among the subsets of Th lymphocytes in adults. Our study demonstrates age-related changes in circulating Teff and Treg, as well as significant differences in STAT5/STAT1 signalling among FoxP3+ Th lymphocytes, providing new advances in the understanding of immunosenescence.

Aging-associated subpopulations of human CD8+ T-lymphocytes identified by their CD28 and CD57 phenotypes

BACKGROUND

During organismal aging, human T-cells shift towards less functional phenotypes, often called senescent cells. As these cells have not been well characterized, we aimed to relate surface markers of human T-cell senescence with characteristics of in vitro cellular aging and to further characterize these cells.

METHODS

We identified, by flow cytometry, subpopulations of CD8+ T-cells based on CD57 and CD28 expression, and tested them for some markers of cellular senescence, apoptosis, differentiation and homing.

RESULTS

Elderly persons presented significantly higher proportions not only of CD28-CD57+, but also of CD28+CD57+ cells. CD28+CD57+ cells had the highest expression of p16, p21, Bcl-2, CD95, CD45RO, CCR5 and PD-1, thereby arguing in favor of a senescent phenotype.

CONCLUSION

Among CD8+ T-lymphocytes, CD28+CD57+ cells represent a subset with some senescent features that are distinct from the CD28-CD57+ cells.

CD58/CD2 Is the Primary Costimulatory Pathway in Human CD28-CD8+ T Cells

A substantial proportion of CD8(+) T cells in adults lack the expression of the CD28 molecule, and the aging of the immune system is associated with a steady expansion of this T cell subset. CD28(-)CD8(+) T cells are characterized by potent effector functions but impaired responses to antigenic challenge. CD28 acts as the primary T cell costimulatory receptor, but there are numerous additional receptors that can costimulate the activation of T cells. In this study, we have examined such alternative costimulatory pathways regarding their functional role in CD28(-)CD8(+) T cells. Our study showed that most costimulatory molecules have a low capacity to activate CD28-deficient T cells, whereas the engagement of the CD2 molecule by its ligand CD58 clearly costimulated proliferation, cytokine production, and effector function in this T cell subset. CD58 is broadly expressed on APCs including dendritic cells. Blocking CD58 mAb greatly reduced the response of human CD28(-)CD8(+) T cells to allogeneic dendritic cells, as well as to viral Ags. Our results clearly identify the CD58/CD2 axis as the primary costimulatory pathway for CD8 T cells that lack CD28. Moreover, we show that engagement of CD2 amplifies TCR signals in CD28(-)CD8(+) T cells, demonstrating that the CD2-CD58 interaction has a genuine costimulatory effect on this T cell subset. CD2 signals might promote the control of viral infection by CD28(-)CD8(+) T cells, but they might also contribute to the continuous expansion of CD28(-)CD8(+) T cells during chronic stimulation by persistent Ag.

Proteome analysis in the assessment of ageing

Based on demographic trends, the societies in many developed countries are facing an increasing number and proportion of people over the age of 65. The raise in elderly populations along with improved health-care will be concomitant with an increased prevalence of ageing-associated chronic conditions like cardiovascular, renal, and respiratory diseases, arthritis, dementia, and diabetes mellitus. This is expected to pose unprecedented challenges both for individuals and societies and their health care systems. An ultimate goal of ageing research is therefore the understanding of physiological ageing and the achievement of 'healthy' ageing by decreasing age-related pathologies. However, on a molecular level, ageing is a complex multi-mechanistic process whose contributing factors may vary individually, partly overlap with pathological alterations, and are often poorly understood. Proteome analysis potentially allows modelling of these multifactorial processes. This review summarises recent proteomic research on age-related changes identified in animal models and human studies. We combined this information with pathway analysis to identify molecular mechanisms associated with ageing. We identified some molecular pathways that are affected in most or even all organs and others that are organ-specific. However, appropriately powered studies are needed to confirm these findings based in in silico evaluation.

CD28-, CD45RA(null/dim) and natural killer-like CD8+ T cells are increased in peripheral blood of women with low-grade cervical lesions

Background

In response to antigen naive CD8+, T cells differentiate into effector cells, which express Natural killer (NK) receptors, lose CD28 expression, and die by apoptosis. However, in smaller quantities, the cells are retained for subsequent exposure to the same antigen. Knowledge is limited regarding whether the percentages of CD28-, Effector memory (EMRA^null/dim), and the CD16+/CD56 + CD8+ T cells of women with low-grade cervical lesions are altered at a systemic level.

Methods

We enrolled in this study women controls and women with Human papilloma virus infection (HPV-I) without associated cellular neoplastic changes and with Cervical Intraepithelial Neoplastic-I (CIN-I). Flow cytometry (FC) was performed for measurement of CD28-, memory subset, and NK-like CD8 + T cells, and IL-17, IFN-gamma, Tumor necrosis factor (TNF)-alpha, Interleukin (IL)-10, IL-6, IL-4, and IL-2. Finally, we genotyped the HPV.

Results

The CIN-I group increased the CD8 + CD28− and CD16+/56+ T cell percentage compared with that of HPV-I and controls (p <0.01), and CD8 + CCR7-CD45RA^null/dim (EMRA^null/dim) T cells were also increased in the CIN-I group compared with the controls (p <0.01). These two study groups were HPV- genotyped; 49% were HPV18+, and we did not observe differences in cytokine levels among all groups.

Conclusions

Increased levels of CD28-, EMRA^null/dim, and CD16+/CD56 + CD8+ T cells of peripheral blood in women with CIN-I may be associated with persistent HPV infection and could exert an influence on progression to cervical cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12935-014-0097-5) contains supplementary material, which is available to authorized users.

Ageing and myeloid-derived suppressor cells: possible involvement in immunosenescence and age-related disease

Infections, cancer and autoimmune diseases occur more frequently in the elderly, and although many factors contribute to this, the age-related remodelling of the immune system, termed immunosenescence, plays a major role. Over the last two decades, studies have evaluated the effect of ageing on both the adaptive and innate arms of the immune system and demonstrated compromised function in several cells including lymphocytes (naïve, effector and memory), regulatory T and B cells, monocytes, neutrophils and NK cells. In addition, a well-documented feature of ageing is the increase in systemic inflammatory status (inflammageing), with raised serum levels of IL6, TNFα and CRP as well as reduced IL10. Recently, myeloid-derived suppressor cells have been the focus of many reports as these cells show immunosuppressive properties and are present in higher frequency during infections, cancer and autoimmunity. Importantly, there have been publications showing increased numbers of myeloid-derived suppressor cells in aged mice and humans. In this review, we discuss the current literature on myeloid-derived suppressor cells, their possible role in altered immune function in the elderly, and whether it may be possible to manipulate these cells to alleviate age-related immune dysfunction.

Is HIV a model of accelerated or accentuated aging?

BACKGROUND

Antiretroviral therapy has reduced the incidence of adverse events and early mortality in HIV-infected persons. Despite these benefits, important comorbidities that increase with age (eg, diabetes, cardiovascular disease, cancer, liver disease, and neurocognitive impairment) are more prevalent in HIV-infected persons than in HIV-uninfected persons at every age, and geriatric syndromes such as falls and frailty occur earlier in HIV-infected persons. This raises a critical research question: Does HIV accelerate aging through pathways and mechanisms common to the aging process or is HIV simply an additional risk factor for a wide number of chronic conditions, thus accentuating aging?

METHODS

Extensive literature review.

RESULTS

The purpose of this review is to briefly outline the evidence that age-related clinical syndromes are exacerbated by HIV, examine the ways in which HIV is similar, and dissimilar from natural aging, and assess the validity of HIV as a model of premature aging. Specific biomarkers of aging are limited in HIV-infected hosts and impacted by antiretroviral therapy, and a high rate of modifiable life style confounders (eg, smoking, substance abuse, alcohol) and coinfections (eg, hepatitis) in HIV-infected participants.

CONCLUSIONS

There is a need for validated biomarkers of aging in the context of HIV. Despite these differences, welldesigned studies of HIV-infected participants are likely to provide new opportunities to better understand the mechanisms that lead to aging and age-related diseases.

T-cell subset distribution in HIV-1-infected patients after 12 years of treatment-induced viremic suppression

OBJECTIVE

Residual immune activation and skewed T cell maturation may contribute to excess comorbidity and mortality in successfully treated HIV-infected patients, and long-term effects of combination antiretroviral therapy (cART) on immune reconstitution remain a debated issue. Quantitative T cell reconstitution and activation and its association with residual viremia in patients with 12 years of viremic suppression were investigated.

DESIGN

Blood samples collected cross-sectionally from 71 HIV-infected patients with cART-induced viremic suppression through 12 years were compared with samples from 16 healthy controls.

METHODS

Several different subsets of naive, memory, and activated T cells were analyzed in fresh whole blood by 6-color flowcytometry, and ultrasensitive quantification of HIV RNA was performed.

RESULTS

HIV-infected patients had lower absolute and relative CD4 T cell counts and higher absolute and relative CD8 T cell counts than controls. HIV-infected patients had lower concentrations of naive CD4 cells than controls, but proportions were similar. HIV-infected patients had higher concentrations of CD8 T cells than controls in all the examined subsets but only a higher proportion of CD8 cells in the intermediately differentiated and activated subsets. Residual viremia did not correlate to proportions of naive CD4, CD4 recent thymic emigrants, or activated CD8 T cells.

CONCLUSIONS

This study demonstrated some degree of T cell imbalance even after 12 years of successful cART. Large longitudinal studies are needed to establish whether these discrete changes have clinical relevance.

Translational research in immune senescence: assessing the relevance of current models

Advancing age is accompanied by profound changes in immune function; some are induced by the loss of critical niches that support development of naïve cells (e.g. thymic involution), others by the intrinsic physiology of long-lived cells attempting to maintain homeostasis, still others by extrinsic effects such as oxidative stress or long-term exposure to antigen due to persistent viral infections. Once compensatory mechanisms can no longer maintain a youthful phenotype the end result is the immune senescent milieu - one characterized by chronic, low grade, systemic inflammation and impaired responses to immune challenge, particularly when encountering new antigens. This state is associated with progression of chronic illnesses like atherosclerosis and dementia, and an increased risk of acute illness, disability and death in older adults. The complex interaction between immune senescence and chronic illness provides an ideal landscape for translational research with the potential to greatly affect human health. However, current animal models and even human investigative strategies for immune senescence have marked limitations, and the reductionist paradigm itself may be poorly suited to meet these challenges. A new paradigm, one that embraces complexity as a core feature of research in older adults is required to address the critical health issues facing the burgeoning senior population, the group that consumes the majority of healthcare resources. In this review, we outline the major advantages and limitations of current models and offer suggestions for how to move forward.