Lower percentage of CD8(high+)CD152(+) but not CD8(high+)CD28(+) T lymphocytes in the elderly may be reverted by interleukin 2 in vitro

A silver bullet for ageing medicine?: clinical relevance of T-cell checkpoint receptors in normal human ageing

Immunosenescence describes dysregulation of the immune system with ageing manifested in both the innate and adaptive immunity, including changes in T-cell checkpoint signaling. Through complex and nuanced process, T-cells lose excitatory signaling pathways and upregulate their inhibitory signaling, leading to ineffective immune responses that contribute to the formation of the ageing phenotype. Here we expand on the expression, function, and clinical potential of targeting the T-cell checkpoint signaling in age and highlight interventions offering the most benefits to older adults' health. Notably, modifications in vaccination such as with mTOR inhibitors show immediate clinical relevance and good tolerability. Other proposed treatments, including therapies with monoclonal antibodies fail to show clinical efficacy or tolerability needed for implementation at present. Although T-cell co-signaling fits a valuable niche for translational scientists to manage immunosenescence, future study would benefit from the inclusion of older adults with multiple long-term conditions and polypharmacy, ensuring better applicability to actual patients seen in clinical settings.

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.

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.

Intraindividual variability and the effect of acute illness on immune senescence markers

OBJECTIVES

To determine the intraindividual variability and effect of acute illness on two markers of immune senescence.

DESIGN

Cohort study with repeated measures.

SETTING

Clinical research center and emergency department at two academic medical centers.

PARTICIPANTS

Seventy-three subjects aged 65 and older enrolled in three groups: chronic underlying conditions but no acute illness, acutely ill with infection (community-acquired pneumonia), and acutely ill without infection.

MEASUREMENTS

CD16 density on polymorphonuclear neutrophils (PMNs) and the proportion of CD8+ T cells that express CD28 determined twice in the nonacutely ill group and three times (Days 0, 30, and 60) in the acute illness groups.

RESULTS

In the nonacutely ill group, PMN CD16 density demonstrated wide intraindividual variation, but there was a strong correlation for repeated measures of the percentage of CD8+ T cells expressing CD28 (correlation coefficient (r)=0.77, P<.001). Acute illness markedly affected both measures, regardless of whether the illness was due to infection; there was no correlation between measures obtained on Day 0 versus Day 30 for either immune marker. In contrast, a strong correlation existed between Day 30 and Day 60 values, particularly for CD8+/CD28+ percentage (r=0.58-0.86; P=.006 to <.001).

CONCLUSION

The percentage of CD8+ T cells that express CD28 is a highly reproducible marker of immune senescence. Although acute illness affects this marker, 30 to 60 days of convalescence appears adequate for it to return to baseline.