A longitudinal study of the stability, variability, and interdependencies among late-differentiated T and NK cell subsets in older adults

Potential relationship between cytomegalovirus and immunosenescence: Evidence from observational studies

Immunosenescence (IS) occurs as a natural outcome of ageing and may be described as a decline in immune system flexibility and adaptability to sufficiently respond to new, foreign antigens. Potential factors that may precipitate IS include persistent herpesvirus infections, such as cytomegalovirus (CMV). Here, we conducted a review of the literature evaluating the potential association between CMV and IS. Twenty-seven epidemiologic studies that included direct comparisons between CMV-seropositive and CMV-seronegative immunocompetent individuals were analysed. The majority of these studies (n = 20) were conducted in European populations. The strength of evidence supporting a relationship between CMV, and various IS-associated immunologic endpoints was assessed. T-cell population restructuring was the most prominently studied endpoint, described in 21 studies, most of which reported a relationship between CMV and reduced CD4:CD8 T-cell ratio or modified CD8+ T-cell levels. Telomere length (n = 4) and inflammageing (n = 3) were less frequently described in the primary literature, and the association of these endpoints with CMV and IS was less pronounced. An emergent trend from our review is the potential effect modification of the CMV-IS relationship with both sex and age, indicating the importance of considering various effector variables when evaluating associations between CMV and IS. Our analysis revealed plausible mechanisms that may underlie the larger epidemiologic trends seen in the literature that support the indirect effect of CMV on IS. Future studies are needed to clarify CMV-associated and IS-associated immunologic endpoints, as well as in more diverse global and immunocompromised populations.

Lifespan Socioeconomic Context Is Associated With Cytomegalovirus and Late-Differentiated CD8 + T and Natural Killer Cells: Initial Results in Older Adults

OBJECTIVE

Lower socioeconomic status (SES) can accelerate immune aging; however, it is unknown whether and how lifespan socioeconomic context (SEC)-the relative wealth and quality of the communities an individual lives in across their lifespan-impacts immune aging. We examined the effects of childhood and adulthood SEC on late-differentiated immune cells and investigated the mediating and moderating role of cytomegalovirus (CMV), a key driver of immune aging.

METHODS

Adults 60 years and older ( N = 109) reported their addresses from birth to age 60 years, which were coded for county-level employment, education, and income to construct a latent SEC variable, averaged across ages 0 to 18 years (childhood SEC) and 19 to 60 years (adulthood SEC). Blood was drawn semiannually for 5 years for CMV serostatus and flow cytometry estimates of late-differentiated CD8 + T and natural killer cells. Models were adjusted for chronological age, time, sex, and individual SES (current income and education).

RESULTS

Lower childhood SEC was associated with higher percentages of late-differentiated CD8 + T and natural killer cells via CMV seropositivity (indirect effects, p values = .015-.028). In addition, an interaction between CMV serostatus and SEC on CD8 + T-cell aging ( p = .049) demonstrated that adulthood SEC was negatively associated with immune aging among CMV- but not CMV+ adults.

CONCLUSIONS

Beyond current SES, SEC related to immune aging in distinct patterns by lifespan phase. Lower childhood SEC importantly may influence who acquires CMV, which in turn predicts higher levels of immune aging, whereas higher adulthood SEC was protective against immune aging among CMV- older adults. These initial results need to be explored in larger samples.

Biomarkers of Aging and Relevant Evaluation Techniques: A Comprehensive Review

The risk of developing chronic illnesses and disabilities is increasing with age. To predict and prevent aging, biomarkers relevant to the aging process must be identified. This paper reviews the known molecular, cellular, and physiological biomarkers of aging. Moreover, we discuss the currently available technologies for identifying these biomarkers, and their applications and potential in aging research. We hope that this review will stimulate further research and innovation in this emerging and fast-growing field.

Counteracting Immunosenescence-Which Therapeutic Strategies Are Promising?

Aging attenuates the overall responsiveness of the immune system to eradicate pathogens. The increased production of pro-inflammatory cytokines by innate immune cells under basal conditions, termed inflammaging, contributes to impaired innate immune responsiveness towards pathogen-mediated stimulation and limits antigen-presenting activity. Adaptive immune responses are attenuated as well due to lowered numbers of naïve lymphocytes and their impaired responsiveness towards antigen-specific stimulation. Additionally, the numbers of immunoregulatory cell types, comprising regulatory T cells and myeloid-derived suppressor cells, that inhibit the activity of innate and adaptive immune cells are elevated. This review aims to summarize our knowledge on the cellular and molecular causes of immunosenescence while also taking into account senescence effects that constitute immune evasion mechanisms in the case of chronic viral infections and cancer. For tumor therapy numerous nanoformulated drugs have been developed to overcome poor solubility of compounds and to enable cell-directed delivery in order to restore immune functions, e.g., by addressing dysregulated signaling pathways. Further, nanovaccines which efficiently address antigen-presenting cells to mount sustained anti-tumor immune responses have been clinically evaluated. Further, senolytics that selectively deplete senescent cells are being tested in a number of clinical trials. Here we discuss the potential use of such drugs to improve anti-aging therapy.

Life stressors and immune aging: Protective effects of cognitive reappraisal

Stressful life events may accelerate aspects of immune aging, but habitual use of an adaptive emotion regulation strategy, cognitive reappraisal, may attenuate these effects. This study examined whether cognitive reappraisal moderates the associations between life stressor frequency and stressor desirability on aspects of immune aging, including late-differentiated CD8+ T and natural killer (NK) cells and inflammatory markers (IL-6, TNF-α, and CRP), both between and within people in a longitudinal sample of 149 older adults (mean age = 77.8, range: 64-92 years). Participants reported stressful life events, use of cognitive reappraisal, and provided blood semiannually for up to 5 years to assess aspects of immune aging. Multilevel models, adjusted for demographic and health covariates, tested the between-person (stable, trait-like differences) and within-person associations (dynamic fluctuations) among life stressors and reappraisal on immune aging. Experiencing more frequent life stressors than usual was associated with higher levels of late-differentiated NK cells within person, but this effect was accounted for by experiencing health-related stressors. Unexpectedly, experiencing more frequent and less desirable stressors were associated with lower average levels of TNF-α. As expected, reappraisal moderated the associations between life stressors and late-differentiated NK cells between people and IL-6 within people. Specifically, older adults who experienced less desirable stressors but also used more reappraisal had significantly lower proportions of late-differentiated NK cells on average and lower levels of IL-6 within-person. These results suggest cognitive reappraisal may play a protective role in attenuating the effects of stressful life events on aspects of innate immune aging in older adults.

Resources and lymphocyte terminal maturity among older adults

OBJECTIVE

Women's financial resources were associated with more terminal maturity in natural killer lymphocytes, generally associated with loss of proliferative potential, during the "Great Recession". This preregistered analysis expanded on that finding in a longitudinal design including both genders and examining the role of cytomegalovirus (CMV) serostatus.

METHOD

Older adults (N = 138, 57% women) were assessed longitudinally during 2012-2017; including self-reported psychological, social, financial, and status-skill resources, CMV antibody titers and serostatus, and assessment of T and natural killer lymphocyte terminal maturity (LTM).

RESULTS

Neither total nor financial resources were associated with LTM. Adjusting only for age, more psychological resources (e.g., meaning, hope, humor) were associated with lower T LTM (percent: γ = -1.11 [-1.78, -.44]; number: γ = -.99 [-1.70, -.27]). There were no significant interactions with age, gender, or CMV serostatus; however, additionally adjusting for serostatus reduced the effect of psychological resources (percent: γ = -.41 [-93, .12]; number: (γ = -.40 [-.94, .13]).

CONCLUSIONS

Outside the context of the "Great Recession", psychological resources but not financial resources were associated with terminal maturity in T cells, a relationship related to CMV serostatus. Further studies in different and more diverse samples, and in different eras, are needed to understand what resources are most protective against immunological aging, when, and for whom. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

The diseased kidney: aging and senescent immunology

Immunosenescence is the deterioration of the innate and adaptive immune systems associated with aging and is primarily characterized by a reduction in T cell production and accumulation of atypical subsets. Age-related immunological dysfunction leads to impaired immune protection and persistent low-grade chronic inflammation, resulting in a decreased vaccination response and increased vulnerability to infection, cancer, cardiovascular disease, and autoimmune disease in the elderly. As the elderly constitute a growing proportion of the population with renal disease, immunosenescence is a normal aging process that is prevalent among older people. In addition, immunosenescence seems to be more pronounced in patients with kidney diseases than in healthy controls, as shown by severe chronic inflammation, accumulation of immune cells with the senescent phenotype (CD28− T cells, CD14+CD16+ monocytes), and proinflammatory cytokine production. Immunosenescence inhibits immunological clearance and renal tissue regeneration, thereby increasing the risk of permanent renal damage, infection, and cardiovascular events in patients with kidney disease, lowering the prognosis, and even influencing the efficacy of renal replacement treatment. Biological drugs (senomorphics and senolytics) target the aging immune system and exert renoprotective effects. This review aims to emphasize the features of immunosenescence and its influence on kidney diseases and immunotherapy, highlighting the future directions of kidney disease treatment using senescence-focused techniques.

Single-cell transcriptomics reveal a unique memory-like NK cell subset that accumulates with ageing and correlates with disease severity in COVID-19

Background

Natural killer (NK) cells are innate lymphoid cells that mediate antitumour and antiviral responses. However, very little is known about how ageing influences human NK cells, especially at the single-cell level.

Methods

We applied single-cell sequencing (scRNA-seq) to human lymphocytes and NK cells from 4 young and 4 elderly individuals and then analysed the transcriptome data using Seurat. We detected the proportion and phenotype of NK cell subsets in peripheral blood samples from a total of 62 young and 52 elderly healthy donors by flow cytometry. We also used flow cytometry to examine the effector functions of NK cell subsets upon IFN-α/IL-12+IL-15/K562/IL-2 stimulation in vitro in peripheral blood samples from a total of 64 young and 63 elderly healthy donors. We finally studied and integrated single-cell transcriptomes of NK cells from 15 young and 41 elderly COVID-19 patients with those from 12 young and 6 elderly healthy control individuals to investigate the impacts of ageing on NK cell subsets in COVID-19 disease.

Results

We discovered a memory-like NK subpopulation (NK2) exhibiting the largest distribution change between elderly and young individuals among lymphocytes. Notably, we discovered a unique NK subset that was predominantly CD52⁺ NK2 cells (NK2.1). These memory-like NK2.1 cells accumulated with age, exhibited proinflammatory characteristics, and displayed a type I interferon response state. Integrative analyses of a large-cohort COVID-19 dataset and our datasets revealed that NK2.1 cells from elderly COVID-19 patients are enriched for type I interferon signalling, which is positively correlated with disease severity in COVID-19.

Conclusions

We identified a unique memory-like NK cell subset that accumulates with ageing and correlates with disease severity in COVID-19. Our results identify memory-like NK2.1 cells as a potential target for developing immunotherapies for infectious diseases and for addressing age-related dysfunctions of the immune system.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13073-022-01049-3.

Immunosenescence evaluation of peripheral blood lymphocyte subsets in 957 healthy adults from 20 to 95 years old

Immunosenescence is characterized by an age-related decline in immune system function. Major efforts have been made to identify changes in peripheral blood lymphocyte subsets accompanying immunosenescence in elderly adults. However, the change trends of some lymphocyte subsets with age are still controversial, and populations of advanced ages, such as people in their 80s or 90s, have not yet been thoroughly investigated. To provide further insight, we recruited 957 healthy donors without certain diseases with ages ranging from 20 to 95 years. Peripheral lymphocyte subsets, including T cells, CD4 T cells, CD8 T cells, B cells and NK cells, and the CD4/CD8 ratio were measured by flow cytometry. Additionally, regulatory CD4 T cells with inhibitory functions marked by CD3⁺CD4⁺CD25^hi and the expression of the costimulatory molecule CD28 on CD8 T cells were evaluated. Sex was considered at the same time. The data indicated that in elderly people, peripheral T (p < 0.001), CD4 T (p < 0.001) and B (p < 0.001) lymphocyte subsets decreased, but the NK cell population (p < 0.001) increased. More regulatory CD4 T cells may imply stronger inhibition in the elderly population. The decreased CD28 expression with age in females verified CD28 to be an immunosenescence marker and the sharply decreased CD28 expression after 75 years in males indicated a rapid immunosenescence at the late life span of the male populations. In addition, our study established reference values for peripheral lymphocyte subsets at different age stages in males and females, which are urgently needed for the clinical management and treatment of geriatric diseases.

Influence of Exercise on Exhausted and Senescent T Cells: A Systematic Review

The impaired effector function of exhausted and senescent T cells is implicated in cancer progression and inadequate vaccine responses. Exercise has been shown to improve cancer therapy and vaccine efficacy, most likely by improving immune function. However, given inconsistent terminology and definitions, the interactions between exercise and exhausted and senescent T cells remain unclear. We therefore performed a systematic review to investigate the effect of exercise on senescent and exhausted CD8⁺ T cell populations clearly defined by protein surface markers. Thirty articles were included, with the majority (n = 24) reporting senescent T cell populations defined according to a variety of surface markers. Repeated exercise was shown to be beneficial through limiting the accumulation of senescent and exhausted CD8⁺ T cells. This outcome is likely related to exercise-induced preferential mobilization of senescent T cells promoting apoptosis in the peripheral blood compartment. Future studies need to determine the clinical relevance of this effect in cancer prevention and vaccine efficacy. Data regarding exercise and exhausted T cells are limited due to a lack of available high-quality studies. Future studies require the control of confounding variables such as sex and cytomegalovirus (CMV) status, and consistent definitions of exhausted and senescent T cell populations to improve comparisons between studies and interventions.

In-Depth Profiling of T-Cell Responsiveness to Commonly Recognized CMV Antigens in Older People Reveals Important Sex Differences

The impact of biological sex on T-cell immunity to Cytomegalovirus (CMV) has not been investigated in detail with only one published study comparing CMV-specific T-cell responses in men and women. Many studies, however, have shown an association between CMV infection and immunosenescence, with broad effects on peripheral blood lymphocyte subsets as well as the T and B-cell repertoires. Here, we provide a detailed analysis of CMV-specific T-cell responses in (n=94) CMV+ older people, including 47 women and 47 men aged between 60 and 93 years. We explore sex differences with respect to 16 different CMV proteins arranged in 14 peptide pools (overlapping peptides). Following ex vivo stimulation, CD4 and CD8 T-cells producing IFN-γ, TNF, and IL-2 were enumerated by flow-cytometry (intracellular cytokine staining). T-cell responses were evaluated in terms of each cytokine separately or in terms of cytokines produced simultaneously (polyfunctionality). Surface memory phenotype and CD3 downmodulation were assessed in parallel. The polyfunctionality index and a memory subset differentiation score were used to identify associations between response size, cytokine production, polyfunctionality, and memory subset distribution. While no significant sex differences were found with respect to overall CMV target protein selection, the T-cell response in men appeared more focused and accompanied by a more prominent accumulation of CMV-specific memory CD4 and CD8 T-cells. T-cell polyfunctionality and differentiation were similar in the sexes, however, CMV-specific T-cells in men produced more pro-inflammatory cytokines. Particularly, TNF production by CD4 T-cells was stronger in men than in women. Also, compared with women, men had larger responses to CMV proteins with immediate-early/early kinetics than women, which might have been driven by CMV reactivation. In conclusion, the CMV-specific T-cell response in men was larger and more pro-inflammatory than in women. Our findings may help explain sex differences in CMV-associated pathologies.

Sex-Differential Impact of Human Cytomegalovirus Infection on In Vitro Reactivity to Toll-Like Receptor 2, 4 and 7/8 Stimulation in Gambian Infants

Human cytomegalovirus (HCMV) infection rates approach 100% by the first year of life in low-income countries. It is not known if this drives changes to innate immunity in early life and thereby altered immune reactivity to infections and vaccines. Given the panoply of sex differences in immunity, it is feasible that any immunological effects of HCMV would differ in males and females. We analysed ex vivo innate cytokine responses to a panel of toll-like receptor (TLR) ligands in 108 nine-month-old Gambian males and females participating in a vaccine trial. We found evidence that HCMV suppressed reactivity to TLR2 and TLR7/8 stimulation in females but not males. This is likely to contribute to sex differences in responses to infections and vaccines in early life and has implications for the development of TLR ligands as vaccine adjuvants. Development of an effective HCMV vaccine would be able to circumvent some of these potentially negative effects of HCMV infection in childhood.

Diagnosis-independent loss of T-cell costimulatory molecules in individuals with cytomegalovirus infection

Major depressive disorder (MDD) is associated with physiological changes commonly observed with increasing age, such as inflammation and impaired immune function. Age-related impaired adaptive immunity is characterized by the loss of naive T-cells and the reciprocal accumulation of memory T-cells together with the loss of T-cell co-stimulatory molecules. Additionally, the presence and activity of cytomegalovirus (CMV) alters the architecture of the T-cell compartment in a manner consistent with premature aging. Because CMV is also thought to reactivate with psychological stress, this study tested whether MDD influences age-related phenotypes of T-cell populations in the context of CMV infection in young and middle-aged adults. Morning blood samples from volunteers with a DSM-IV diagnosis of MDD (n = 98, mean age(SD) = 36(10) years, 74.5% female, 57.1% CMV⁺) and comparison controls (n = 98, mean age(SD) = 34(10) years, 68.4% female, 51.0% CMV⁺) were evaluated for CMV IgG antibody status and the distribution of late differentiated (CD27^-CD28^-) cells within CD4⁺ and CD8⁺ T-cell subsets, i.e. naive (CCR7⁺CD45RA⁺), effector memory (EM, CCR7^-CD45RA^-), central memory (CM, CCR7⁺CD45RA^-) and effector memory cells re-expressing CD45RA (EMRA, CCR7^-CD45RA⁺). Mixed linear regression models controlling for age, sex, ethnicity and flow cytometry batch showed that CMV seropositivity was associated with a reduction in naive T-cells, expansion of EMRA T-cells, and a greater percent distribution of CD27^-CD28^- cells within CD4⁺ and CD8⁺ memory T-cell subsets (p's < 0.004), but there was no significant effect of MDD, nor any significant interaction between CMV and diagnosis. Unexpectedly, depressed men were less likely to be CMV⁺ and depressed women were more likely to be CMV⁺ than sex-matched controls suggesting a possible interaction between sex and MDD on CMV susceptibility, but this three-way interaction did not significantly affect the T-cell subtypes. Our findings suggest that depression in young and middle-aged adults does not prematurely advance aging of the T-cell compartment independently of CMV, but there may be significant sex-specific effects on adaptive immunity that warrant further investigation.

Aging, sex, inflammation, frailty, and CMV and HIV infections

Aging is characterized by significant immune remodeling at both cellular and molecular levels, also known as immunosenescence. Older adults often manifest a chronic low-grade inflammatory phenotype. These age-related immune system changes have increasingly been recognized not only to lead to immune functional decline and increased vulnerability to infections, but also to play an important role in many chronic conditions such as frailty in older adults. In addition to sex as an important biological factor, chronic viral infections including that by human immunodeficiency virus (HIV) and cytomegalovirus (CMV) are all known to have major impact on the aging immune system. This article provides an overview of our current understanding of aging immunity, sex, inflammation, frailty, and HIV and CMV infections.

Perceived stress, cytomegalovirus titers, and late-differentiated T and NK cells: Between-, within-person associations in a longitudinal study of older adults

Cytomegalovirus (CMV) and psychological stress are implicated as drivers of immunological aging. It is unknown, however, whether associations among CMV titers, stress, and immune aging are more stable or dynamic over time. The present investigation tested the between-person (stable differences) and within-person (dynamic fluctuations) associations of CMV titers and perceived stress on late-differentiated T and natural killer (NK) peripheral blood cells in a longitudinal study of older adults aged 64-92 years (N = 149). Participants reported stress levels and provided blood biannually for 2.5 years (up to 5 waves per person) to assess CMV IgG titers and composites of late-differentiated CD8 T cells (CD28- and CD57 + subsets) and CD56dim NK cells (CD57+, NKG2C+, and FcεRIγ- subsets). In multilevel models that controlled for demographic variables, higher CMV titers were associated with higher proportions and counts of aged T and NK cells between people and lower counts of aged T cells within people. Perceived stress was associated with higher counts of aged T cells between people, but was not associated with aged NK cells. A significant interaction between stress and CMV titers on T cells between people indicated that older adults with lower stress levels and lower CMV titers had the lowest proportions of late-differentiated T cells, whereas those with higher stress levels had high proportions, regardless of CMV control. Our results provide evidence for longer-term, between-person associations among CMV titers, stress, and immunological aging, rather than dynamic within-person associations. We propose that targeting factors that promote low, stable perceived stress in older adults may retard T cell differentiation and ultimately support healthy aging.