Immunophenotypical changes of T lymphocytes in the elderly

Th17/IL-17 induces endothelial cell senescence via activation of NF-κB/p53/Rb signaling pathway

Cellular senescence is a key mechanism of age-related vascular endothelial dysfunction. Interleukin-17A (IL-17A) is an inflammatory cytokine produced by Th17 cells (a subgroup of helper T cells), which is a key factor in the development of atherosclerosis. However, the effect of IL-17A on the senescence of vascular endothelial cells is still unclear. In this study, we aimed to explore the role of IL-17A on endothelial cell senescence and its signaling pathways associated with senescence. The proportion of Th17 cells in the spleen and the expression levels of IL-17A, IL-6, and vascular cell adhesion molecule-1 (VCAM-1) in mice of different ages were increased with aging. In vitro experiments showed that proliferation was inhibited, senescent β-galactosidase and senescence-associated proteins (p16, p19, p21, and p53) of mouse aortic endothelial cells (MAECs) were increased with IL-17A treatment. Blocking the NF-κB pathway with ammonium pyrrolidinedithiocarbamate (PDTC) successfully inhibited IL-17A-induced expression of senescence-associated proteins. In conclusion, our data reveal a previously unsuspected link between IL-17A and endothelial cell senescence, which was mediated by the NF-κB /p53/Rb pathway.

CD158k and PD-1 expressions define heterogeneous subtypes of Sezary syndrome

SS can be divided into 3 subtypes, each with a different immune environment and response to treatment.

Sezary syndrome (SS) is a rare leukemic form of cutaneous T-cell lymphoma. Diagnosis mainly depends on flow cytometry, but results are not specific enough to be unequivocal. The difficulty in defining a single marker that could characterize Sezary cells may be the consequence of different pathological subtypes. In this study, we used multivariate flow cytometry analyses. We chose to investigate the expression of classical CD3, CD4, CD7, and CD26 and the new association of 2 markers CD158k and PD-1. We performed lymphocyte computational phenotypic analyses during diagnosis and follow-up of patients with SS to define new SS classes and improve the sensitivity of the diagnosis and the follow-up flow cytometry method. Three classes of SS, defined by different immunophenotypic profiles, CD158k⁺ SS, CD158k⁻PD-1⁺ SS, CD158k and PD-1 double-negative SS, showed different CD8⁺ and B-cell environments. Such a study could help to diagnose and define biological markers of susceptibility/resistance to treatment, including immunotherapy.

Immunosenescence: participation of T lymphocytes and myeloid-derived suppressor cells in aging-related immune response changes

Healthy aging is partly related to appropriate function of the immune system. As already reported, some changes in this system are observed, including reduced number and repertoire of T cells due to thymic involution, accumulation of memory T cells by chronic infections, homeostatic proliferation compensating for the number of naïve T cells, decreased proliferation of T cells against a stimulus, telomere shortening, replicative senescence of the T cells, and inflammaging, besides the accumulation of myeloid-derived suppressor cells. The purpose of this article is to clarify each of these changes, aiming to minimize limitations of immunosenescence. If such associations can be established, these cells may be used as early and less invasive markers of aging-related diseases, as well as to indicate interventions, evaluate the efficacy of interventions and be a tool to achieve longevity with quality of life.

Cryptococcal Meningitis in A Patient With Giant Cell Arteritis

Cryptococcal meningitis is a rare complication of giant cell vasculitis. Because its manifestations are very similar to those of giant cell vasculitis relapse, the diagnosis is often delayed and/or misdiagnosed. In this article, we present the case of a 65-year-old female patient who suffered from cryptococcal meningitis during high-dose steroid therapy for giant cell vasculitis.

HSC Aging and Senescent Immune Remodeling

Aging-associated changes in the function of the immune system are referred to as senescent immune remodeling (SIR). Here we review the current understanding on the cellular and molecular mechanisms underlying SIR. We focus on aging-associated changes in T and B cells, and discuss recent evidence supporting the notion that aging of the hematopoietic stem cell (HSC) compartment directly contributes to SIR due to aging-associated alterations in stem cell differentiation. We conclude by outlining strategies to attenuate SIR, including approaches to rejuvenate HSCs, which may open new avenues for targeting SIR in the clinic.

Splenic lymphoid subsets with less well-recognized phenotypes mimic aberrant antigen expression

OBJECTIVES

Flow cytometry can assist in the diagnosis of lymphoma by identifying aberrant antigen expression. Recognition of aberrancy requires knowledge of the phenotype of normal lymphoid cells.

METHODS

Lymphoid subsets were characterized in 20 spleens removed for traumatic rupture, using 8-color flow cytometry.

RESULTS

Normal variation in splenic lymphoid subsets was highlighted and several well-recognized subsets were identified: CD5+ B cells (20/20 specimens), CD7- T cells (20/20), and CD3 brightγδT cells (16/20). In addition, less well-recognized lymphoid subsets that resemble those described in lymphoma were identified in all specimens: CD5- T cells (4.5 ± 5.1% of T cells), CD2- natural killer (NK) cells (38 ± 7% of NK cells), and CD7dim+ NK cells. Similar populations were identified in 20 control peripheral blood specimens, where they represented a smaller proportion of total lymphoid cells.

CONCLUSIONS

Familiarity with the phenotype of normal lymphoid subsets can help prevent misinterpreting flow cytometric data. Furthermore, in the context of neoplastic cells, the phenotype may suggest expanded normal subsets rather than aberrant antigen expression.

Crosstalk between the circadian clock circuitry and the immune system

Various features, components, and functions of the immune system present daily variations. Immunocompetent cell counts and cytokine levels present variations according to the time of day and the sleep-wake cycle. Moreover, different immune cell types, such as macrophages, natural killer cells, and lymphocytes, contain a circadian molecular clockwork. The biological clocks intrinsic to immune cells and lymphoid organs, together with inputs from the central pacemaker of the suprachiasmatic nuclei via humoral and neural pathways, regulate the function of cells of the immune system, including their response to signals and their effector functions. Consequences of this include, for example, the daily variation in the response to an immune challenge (e.g., bacterial endotoxin injection) and the circadian control of allergic reactions. The circadian-immune connection is bidirectional, because in addition to this circadian control of immune functions, immune challenges and immune mediators (e.g., cytokines) were shown to have strong effects on circadian rhythms at the molecular, cellular, and behavioral levels. This tight crosstalk between the circadian and immune systems has wide-ranging implications for disease, as shown by the higher incidence of cancer and the exacerbation of autoimmune symptoms upon circadian disruption.

Attenuated response of aged mice to respiratory Francisella novicida is characterized by reduced cell death and absence of subsequent hypercytokinemia

Background

Pneumonia and pulmonary infections are major causes of mortality among the growing elderly population. Age associated attenuations of various immune parameters, involved with both innate and adaptive responses are collectively known as immune senescence. These changes are likely to be involved with differences in host susceptibility to disease between young and aged individuals.

Methodology/Principal Findings

The objective of this study was to assess potential age related differences in the pulmonary host response in mice to the Gram-negative respiratory pathogen, Francisella novicida. We intranasally infected mice with F. novicida and compared various immune and pathological parameters of the pulmonary host response in both young and aged mice.

Conclusions/Significance

We observed that 20% of aged mice were able to survive an intranasal challenge with F. novicida while all of their younger cohorts died consistently within 4 to 6 days post infection. Further experiments revealed that all of the aged mice tested were initially able to control bacterial replication in the lungs as well as at distal sites of replication compared with young mice. In addition, the small cohort of aged survivors did not progress to a severe sepsis syndrome with hypercytokinemia, as did all of the young adult mice. Finally, a lack of widespread cell death in potential aged survivors coupled with a difference in cell types recruited to sites of infection within the lung confirmed an altered host response to Francisella in aged mice.

Complex patterns of gene expression in human T cells during in vivo aging

Human aging is associated with complex alterations that contribute to remodelling of physiological processes and ultimately manifests in loss of tissue/organ function. Peripheral blood T cells do not escape this phenomenon and undergo profound remodelling with aging. Thus, investigating the effects of aging on T cells transcriptomics and identifying the underlying regulatory mechanisms can be of extreme importance to understand the aging process in the Immune System (IS). To this aim, we performed an analysis of gene expression data of T cells collected from peripheral blood of 25 healthy human donors of different age from 25 to more than 95 years, in order to characterize changes that occur throughout the entire adult lifespan. By means of microarray analysis, we observed large groups of genes exhibiting non-monotonic expression patterns over time: such behaviour, that could not be observed in typical "two-group" experiments (e.g. young vs. old people) highlights similarities in gene expression profiles of young and "successfully aged" individuals. Genes whose expression profiles change during lifespan were grouped into three main patterns (eigenmodes) to which different biological functions were significantly associated. The analysis of KEGG pathways to which these genes belong indicated that the biological processes altered in T cell aging are not only those typically associated with immune cells (Jak-STAT signalling, T cell receptor signalling, cytokine-cytokine receptor interactions, etc.) but also some not specific of immune cells, such as long-term depression, PPAR and mTOR signalling, glucose and glutathione metabolism, suggesting that T cell aging may be representative of a more generalised aging phenomenon. Thus, the T cell may represent a useful cellular model to study organismal aging. We further searched for over-represented transcription factor binding sites (TFBSs) in the promoter regions of genes clustered by similarity of their age-related patterns to evidence possible co-regulation. A comparison between over-representation of TFBSs and the time course of the corresponding transcription factor (TF) expression levels revealed that a restricted group of TFs may play a central role in driving aging-specific changes in gene expression of T cells.

Circadian variations of cortisol, melatonin and lymphocyte subpopulations in geriatric age

A number of age-related changes in the 24-hour hormonal and non-hormonal rhythms have been found in older human beings. Lymphocyte subpopulations present circadian variation of some of their subsets and this variation may influence magnitude and expression of the immune responses. Numerous interactions exist among the nervous, endocrine and immune systems, mediated by neurotransmitters, hormones and cytokines. The aim of this study is to evaluate circadian variations of some endocrine and immune factors in older adults. Cortisol and melatonin serum levels were measured and lymphocyte subpopulation analyses were performed on blood samples collected every four hours for 24 hours from ten healthy young and middle-aged subjects and from ten healthy elderly subjects. There was a statistically significant difference between the groups in the observed values of CD20 (higher in young and middle-aged subjects) and CD25 and DR+ T cells (higher in elderly subjects). In the group of young and middle-aged subjects a clear circadian rhythm was validated for the time-qualified changes of all the factors studied. In the group of elderly subjects a number of rhythms were absent or altered. The results of the current study show that aging is associated with enhanced responsiveness of T cell compartment and alterations of circadian rhythmicity.

Age-related differences in integrin expression in peripheral blood lymphocytes

Alpha integrins play an important role in cell to cell and cell to extra-cellular matrix interactions required for an effective T-lymphocyte-mediated immune response, however little is known about age related differences in expression of alpha integrins on T-cells in humans. We here measured alpha-4 (α4) integrin (CD49d) expression on T-lymphocytes via peripheral blood sampling, comparing parameters between cohorts of young and old adults. No age-related differences were found for the absolute numbers of T-cells, although the percentage of CD4+ T-cells in older adults was significantly greater and the percentage of CD8+ T-cells lower than in younger cohorts. Percentage and absolute numbers of CD3+ T-cells co-expressing CD49d were significantly lower in older adults compared to younger cohorts, and the percentage of gated CD4+ and CD8+ cells that co-labelled positively for CD49d was also reduced in this group. There were no age-related differences in circulating levels of cytokines (Type I interferons) that are known to regulate cell surface integrin expression. Reduced expression of alpha integrins on T-cells may be an early indicator of the loss of homeostatic control that occurs with ageing, contributing to diminished effector T-cell responses during senescence.

Aged mice display an altered pulmonary host response to Francisella tularensis live vaccine strain (LVS) infections

Aging is a complex phenomenon that has been shown to affect many organ systems including the innate and adaptive immune systems. The current study was designed to examine the potential effect of immunosenescence on the pulmonary immune response using a Francisella tularensis live vaccine strain (LVS) inhalation infection model. F. tularensis is a Gram-negative intracellular pathogen that can cause a severe pneumonia. In this study both young (8-12 week old) and aged (20-24 month old) mice were infected intranasally with LVS. Lung tissues from young and aged mice were used to assess pathology, recruitment of immune cell types and cytokine expression levels at various times post infection. Bacterial burdens were also assessed. Interestingly, the lungs of aged animals harbored fewer organisms at early time points of infection (day 1, day 3) compared with their younger counterparts. In addition, only aged animals displayed small perivascular aggregates at these early time points that appeared mostly mononuclear in nature. However, the kinetics of infiltrating polymorphonuclear neutrophils (PMNs) and increased cytokine levels measured in the bronchial alveolar lavage fluid (BALF) were delayed in infected aged animals relative to young infected animals with neutrophils appearing at day 5 post infection (PI) in the aged animals as opposed to day 3 PI in the young infected animals. Also evident were alterations in the ratios of mononuclear to PMNs at distinct post infection times. The above evidence indicates that aged mice elicit an altered immune response in the lung to respiratory F. tularensis LVS infections compared to their younger counterparts.

Immunophenotypical characterization in Andalusian horse: variations with age and gender

Assessment of lymphocyte subsets is an effective method for characterizing disorders such as leukemia, lymphomas, autoimmune and infectious diseases. In order to clinically interpret these parameters, normal reference values should be set, estimating age- and gender-related variations. This research aimed to: (1) characterize lymphocyte subpopulations in Andalusian horse, and (2) evaluate age and gender-related variations of lymphocyte subsets. Jugular blood samples were obtained from 159 animals, 77 males and 82 females, belonging to four age groups-1: 1-2 years (N=39; 21 males and 18 females), 2: 2-3 years (N=38; 16 males and 22 females), 3: 3-4 years (N=41; 19 males and 22 females) and 4: 4-7 years (N=41; 21 males and 20 females). T lymphocytes subsets were quantified by flow cytometry with monoclonal antibodies specific for CD2, CD4 and CD8 cell markers. B and NK cell counts were estimated by using a mathematical formula. No variations were found in T, B lymphocytes and NK cells between males and females. Animals of group 1 and 2 had a higher number of CD2, T, CD4+, CD8+, B lymphocytes and NK cells than animals of groups 3 and 4. The percentage of CD2 in group 1 was significantly lower than in group 4. The percentage of T and CD4+ lymphocytes in the group 1 were significantly higher than groups 2 and 3, respectively. Whereas the percentage of B cells calculated by flow cytometry was significantly lower in group 2 compared to group 4, the percentage of B cells calculated by a mathematical formula was higher in group 1. NK cells percentage was significantly lower in group 3 and 4 than in younger animals. In conclusion, in Andalusian horse, gender does not influence absolute numbers and percentages of T, B and NK. There is an age-related decline in absolute number of CD2, T, CD4+ and CD8+ lymphocytes, B lymphocytes and NK cells, with increasing percentage of CD2, T, CD4+ and B lymphocytes, and a decrease in NK with no differences in CD4/CD8 ratio. The decline of lymphocyte population numbers with age is a natural process in many animal species, and could be the origin for immune dysfunction observed in geriatric individuals.

CD7(-) T cells are late memory cells generated from CD7(+) T cells

CD7(-) T cells constitute a distinct subset within the CD4(+) and CD8(+) T cell populations; their developmental and functional relationship to the majority of CD7(+) T cells, however, remained so far unresolved. We here elucidate that CD7(-) cells represent aging T cells in late memory cell development characterized by a high activation threshold, low effector capacities, and high sensitivity to activation-induced cell death (AICD). In this regard, CD7(-) T cells highly express killer cell lectin-like receptor G1 (KLRG-1), harbor telomeres of shorter lengths, a decreased telomerase expression per cell, and less amounts of T cell receptor rearrangement excision circles (TRECs) compared to CD7(+) cells. CD7(-) T cells are generated in vitro from naive CD7(+) T cells upon repetitive TCR/CD28 engagement, a process that is unidirectional and requires multiple cell divisions. Consequently, clonal expansions of CD7(-) T cells in vivo are less frequent than of CD7(+) T cells, the former can be traced back to those of CD7(+) T cells.

Age-matched lymphocyte subpopulation reference values in childhood and adolescence: application of exponential regression analysis

BACKGROUND

Normal values of lymphocyte subpopulations for healthy children and adults have been published in defined age groups exclusively, which results in difficult data interpretation for patients close to the limit of contiguous age group ranges. In addition, normal values for a number of lymphocyte subpopulations have not been established to date.

OBJECTIVE

The aim of this study was to develop a model which provides continuous age-dependent reference values. This model was applied for lymphocyte subpopulations such as naïve and memory T cells as well as their activation profile with diagnostic relevance in children and adults.

STUDY DESIGN

A total of 100 blood samples, obtained from 80 healthy children and 20 adults were analysed by means of four colour-flow cytometry. Continuous age-dependent reference values were computed based on the residual values in an exponential regression model.

RESULTS

We calculated a continuous age-related regression model for both, absolute cell counts and percentages of CD3(+)CD4(+) T helper (T(H)) cells, CD3(+)CD8(+) cytotoxic T cells, CD56(+)CD3(-) natural killer (NK) cells, CD56(+)CD3(+) T cells, CD3(+)CD4(+)CD45RA(+) naïve T(H) cells, CD3(+)CD4(+)CD45RO(+) memory T(H) cells, CD3(+)CD8(+)CD45RA(+)CD28(+) naïve cytotoxic T cells, CD3(+)CD8(+)CD45RO(+) memory cytotoxic T cells, CD3(+)CD8(+)CD69(+) early activated cytotoxic T cells and CD3(+)CD8(+)HLA-DR(+) late activated cytotoxic T cells, respectively, to obtain reference values.

CONCLUSION

Based on an exponential regression model, the obtained reference values reflect the continuous maturation of lymphocyte subsets during childhood.

Review on immunosenescence

The improvements of socio-environmental conditions, medical care and quality of life have caused a general improvement in the health status of the population and a consequent reduction of morbidity and mortality, resulting in an overall increased life-expectancy. The role of immunosenescence was negligible in the past, when the human lifespan was 40–50 years, and its impact on morbidity and mortality has emerged in combination with the extension of lifespan. Immunosenescence results from multifactorial processes that act on all components of the immune system. The changes associated with immunosenescence are playing an increasingly important role in the emergence of a series of age-related pathologies, conditioning the present epidemiology of old people.

Redox regulation of the proteasome in T lymphocytes during aging

Proteasome is a major cellular organelle responsible for the regulated turnover of both normal and misfolded proteins. Recent reports from our laboratory have implicated lowered proteasomal chymotryptic activity to be responsible for decreased induction of the transcription factor NFkappaB in T lymphocytes during aging. In this study, we have further analyzed the basis for this decline in proteasomal function, by focusing on the role of oxidative stress. On exposure to the prooxidant BSO, both ATP-stimulatable 26S and ATP-independent 20S proteasomal catalytic activity could be down-regulated in T cells from young donors, mimicking the decline observed in T cells from the elderly. Loss in these catalytic activities, following exposure to prooxidant stimulus, also resulted in a decline in both activation-induced proliferation and degradation of the inhibitor IkappaBalpha, with concomitant increase in the accumulation of carbonylated proteins, mimicking responses seen in T cells from the elderly. Pretreatment with an antioxidant, NAC, could override prooxidant-mediated, but not age-associated, decrease in both 20S and 26S proteasomal activities. These results suggest that the decrease in proteasomal activities observed during aging may be secondary to oxidative stress and underlie immune senescence.

The descent of memory T-cell subsets

The immune system has evolved by continuously increasing its complexity to provide the host with an advantage over infectious agents. The development of immunological memory engenders long-lasting protection and lengthens the lifespan of the host. The generation of subsets of memory T cells with distinct homing and functional properties increases our defensive capabilities. However, the developmental relationship of memory T-cell subsets is a matter of debate. In this Opinion article, in light of recent developments, we suggest that it is probable that two distinct lineages comprise the memory CD8+ T-cell population generated in response to infection.

Inflammation markers predicting frailty and mortality in the elderly

Greater numbers of individuals are living to older ages. A major concern at both individual and population levels is how to live these years at a high functional level. If we had physiological markers to identify those at risk for progressive functional decline and impeding death, therapies could be targeted towards these individuals to prevent adverse outcomes. Senescence is presently considered as the consequence of lifelong antigenic stress impinging upon the individual genetic background. We might consider inflammation markers as synthetic measures of lifelong attrition combined with genetic tendency to develop an inflammatory phenotype. Such biomarkers are the most powerful predictors of frailty and mortality in the elderly available today. The aim of this review is to translate results from the research on ageing into a practical view, suggesting new tools for the clinical approach to older people.

Elevation of Immune Activation in Kenyan Women is Associated with Alterations in Immune Function: Implications for Vaccine Development

The infectious burden leading to immune activation can vary between different populations and lead to various immune dysfunctions. We compared the effect of immune activation on apoptosis and T cell function in HIV uninfected individuals from Nairobi, Kenya (n=34), and Winnipeg, Canada (n=10). Women from Nairobi had a significantly greater number of CD8+ T cells expressing the activation markers CD38 and HLA DR. Kenyan women also had significantly higher levels of CTLA-4+ CD4 and CD8+ T cells, and reduced levels of CD28+ CD8+ cells. Levels of CD95+ CD4+ T cells were higher in Kenyan women and, correspondingly, showed higher levels of spontaneous apoptosis. Kenyan women also demonstrated hyper-responsiveness to T cell activation as assessed by interferon gamma production. This study demonstrates that in a population of Kenyan women with high levels of T cell activation, there were also elevated levels of T cell apoptotic death and hyper-responsiveness. These differences may influence the efficacy of immune responses to pathogens and must be considered when testing candidate vaccines.

Phenotypic and functional changes of circulating monocytes and polymorphonuclear leucocytes from elderly persons

The function and phenotype of monocytes and granulocytes in the elderly is consistently remodelled. Because leucocyte adhesion molecules play important roles in mediating a wide variety of leucocyte functions, age-related changes in their expression on granulocyte and monocyte surfaces could be partially responsible for immune dysfunctions during senescence. Considering the central role of innate immunity in the process of immunosenescence and the involvement of cell adhesion molecules (CAM) in the great majority of leucocyte functions, we studied the expression of CD50 and CD62L adhesion molecules in peripheral blood granulocytes and monocytes from healthy elderly and young subjects. We show here that the percentage of granulocytes and monocytes expressing CD62L is decreased in the elderly, whereas its density expression is unchanged on both cell types. A downregulation of the density expression of CD50 at a per cell level characterizes granulocytes in the elderly, whereas CD50 expression on monocytes from old subjects shows a peculiar attitude: its density expression decreases whereas the number of positive cells is expanded. The downregulation of this receptor on granulocytes from aged people could determine a state of hyperactivation contributing to the proinflammatory status of the elderly, while the lower expression on monocytes could therefore contribute to the impaired antigen presentation in the elderly. On the other hand, the increased number of CD50 positive monocytes in the elderly, despite its decreased density expression at a per cell level, could be interpreted as an attempt to counteract the inability to mount strong immune responses. Both CD50 and CD62L changes in ageing polymorphonuclear (PMN) cells allow recognition as non-self or senescent self to permit macrophages in the liver and spleen to remove them from the circulation. The increased proportion of granulocytes and monocytes lacking CD62L and the downregulation of CD50 intensity expression on both cell types may suggest a state of in vivo activation. Therefore, CD50 and CD62L shedding from the cell surface of activated granulocytes and monocytes could be interpreted as a tentative to counteract the dangerous effects of an excessive chronic inflammation in the elderly. However, the increased proportion of CD62L negative granulocytes in the elderly leads to an impairment in cell adhesion which is the first line of response to acute inflammatory stimuli. This phenomenon likely contributes to the increased susceptibility to acute infections of elderly people.

Tyrosine phosphorylation-dependent activation of NFκB is compromised in T cells from the elderly

NFkappaB induction and gene regulation are compromised in T lymphocytes during aging. This has been attributed to altered proteasomal function resulting in decreased ubiquitin-mediated degradation of IkappaBalpha. However, little is known about the impact of aging on the mechanisms that lead to the release of active NFkappaB employing pro-oxidant pathways. Oxidant-mediated activation of NFkappaB has been previously shown to involve proteasome independent mechanisms and hence may be an important alternate conduit to the induction of this central transcription factor in aging. Employing H(2)O(2) and pervanadate we not only demonstrate lowered tyrosine phosphorylation of IkappaBalpha, but also compromised induction of nuclear NFkappaB in T cells from the elderly. Lowered tyrosine phosphorylation of IkappaBalpha may be due to a decrease in activity of p56(lck) and ZAP-70, since treatment with piceatannol, an inhibitor of syk and src family kinases, mimics age associated decline in tyrosine phosphorylation of IkappaBalpha in T cells from young donors. Thus, alternate pathways of NFkappaB induction are also impaired in T cells from the elderly and may underlie immune-deficit accompanying aging.

T-cell receptor BV gene segment polymorphisms in healthy elderly individuals from the south of Brazil

The ageing of the immune system (immunosenescence) is believed to be involved in both morbidity and mortality in elderly humans due to a higher incidence of infections, autoimmune diseases, cancers and other pathological situations. As any specific immune response involves recognition of antigens by T cells, the ability to develop a given immune response is also dependent on the T-cell repertoire available at a given time point. Different T-cell receptor beta variable segment (BV) (TCRBV) gene segment alleles have been associated with diseases in various human populations. In the present work we analysed the allelic frequencies of four biallelic polymorphisms in TCRBV gene segments (TCRBV3S1, TCRBV13S5, TCRBV13S6 and TCRBV18) in healthy elderly human subjects (80 years old or more) from the south of Brazil, where life expectancies reach similar levels to those observed in developed countries. Except for allele 2 of the TCRBV13S6 polymorphism, which was more frequent in elderly than in young individuals (P = 0.0105), there were no differences in allele or genotype frequencies between young and elderly individuals. The data suggest that there is no direct correlation between the TCRBV3S1, TCRBV13S5 and TCRBV18 polymorphisms analysed and healthy senescence in this particular group of elderly individuals. The higher frequency of TCRBV13S6 allele 2 in healthy elderly individuals should be confirmed in other samples to establish the significance of this finding.

Psychoneurodendocrine correlates of lymphocyte subsets during healthy ageing

Ageing has been associated with increased cortisol levels and absolute counts of T lymphocytes with memory phenotype. Although the mechanisms underlying these changes are still unknown, it has been speculated that this could be related to a dysfunction in FAS/CD95 expression in naive or memory cells. In this study, we investigated the role of psychoneuroendocrine variables in regulating CD95 expression on lymphocyte subsets. Forty-six elderly subjects (65-91 years) and 33 young adults (20-40 years) were recruited accordingly the SENIEUR protocol. The psychological status was measured by structured clinical interviews, salivary cortisol was assessed along the day (9, 12 and 22h) and peripheral blood lymphocytes were immunophenotyped. The elderly were more stressed, depressed and anxious than the young subjects. Cortisol levels were increased in the elderly, indicating an activation of the hypothalamic-pituitary-adrenal (HPA) axis. We observed reduced counts of CD45RA+CD95+ cells in the elderly compared to young adults. The elderly subjects also showed a reduced expression of CD3 and CD62L in contrast to increased CD95 expression in CD45RA+ cells. The emotional state was positively correlated with the lymphocyte markers. Our data suggest the healthy ageing is associated with psychoneuroendocrine alterations that may be implicated in the regulation of CD95 expression on peripheral T cells.

Changes in peripheral blood lymphocyte subsets in elderly subjects are associated with an impaired function of the hypothalamic-pituitary-adrenal axis

A growing body of evidence indicates that ageing brings a progressive disruption in the immune and endocrine systems. However, very few reports have correlated the changes in the immune system with the endocrine function in the elderly. The aim of the present study was to investigate the changes occurring in the peripheral blood lymphocyte subpopulations with age and correlate them with the hypothalamic-pituitary-adrenal (HPA) function. We determined the peripheral blood lymphocyte phenotype and the T cell receptor usage by flow cytometry analysis. The HPA function was evaluated by the basal serum levels of adrenal steroids and the response to stimulation with a low-dose ACTH. In the elderly, we observed a decrease of major T subsets together with an increase of NK cells and activated T cells. With regard to the HPA function, the most significant decline was found in dehydroepiandrosterone (DHEA) and dehydroepiandrosterone-sulphate (DHEAS). A close correlation between immune changes with ageing and DHEA response to ACTH stimulation was found. The present study showed an inverse correlation of lymphocyte changes with the plasma levels of steroids, especially DHEA and its metabolite, DHEAS. This association was not found for other steroids and points for the possibility of using DHEA to correct the immunological decline associated with ageing.

Ceramide mediates age-associated increase in macrophage cyclooxygenase-2 expression

Previously, we showed that macrophages (MØ) from old mice have significantly higher levels of lipopolysaccharide (LPS)-induced prostaglandin E(2) (PGE(2)) production than young mice, due to increased cyclooxygenase-2 (COX-2) mRNA levels. The aim of the current study was to determine the underlying mechanisms of age-associated increase in COX-2 gene expression. The results demonstrate that increased COX-2 mRNA expression in the old mice is due to a higher rate of transcription rather than increased stability of COX-2 mRNA. Furthermore, the results show that LPS-induced ceramide levels from the old mice are significantly higher than those of young mice, whereas there is no age-related difference in concentration of its down stream metabolite, sphingosine. The addition of ceramide in the presence or absence of LPS resulted in a significant increase in PGE(2) production in a dose- and time-dependent manner. Inhibition of ceramide conversion to sphingosine had no effect on this ceramide-induced effect. The ceramide-induced up-regulation in PGE(2) production was mediated through increase in COX activity and transcriptional up-regulation of COX-2 mRNA. Collectively, these data suggest that the age-associated increase in MØ COX-2 mRNA is due to transcriptional up-regulation. Furthermore, this increase in transcription is mediated by higher cellular ceramide concentration in old MØ compared with that of young MØ.

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

An expression of the surface co-stimulatory molecules-the CD152 and the CD28 has been compared between young and old individuals on the CD8(high+) lymphocytes. Sixty five elderly healthy (65-96 years old) and 31 young (19-40 years old) volunteers were examined. An expression of CD152 and CD28 surface antigens was analyzed by flow cytometry ex vivo and on whole blood cell cultures lymphocytes stimulated with interleukin 2 (IL2). The elderly population was characterized by a lower percentage of the CD8(high+) lymphocytes than the young population. The percentages of CD28(+) lymphocytes as well as those of CD8(high+)CD28(+) subpopulation were lower in the old group compared to the young group. The surface expression of CD152 antigen was similar to that of CD28 with a lower percentage of the CD152(+) lymphocytes and CD8(high+)CD152(+) cells in the old group. Stimulation of lymphocytes in vitro with IL2 resulted in an increase of the CD8(high+)CD152(+) cells in the elderly, while it had no effect on lymphocytes of the young group. Our results indicate that lymphocytes of the elderly population are characterized by a lower expression of the surface CD28 and CD152 molecules. An age-related decrease of an expression of the co-stimulatory molecules CD28 and CD152 on the surface of lymphocytes, found in our study, may be compatible with a hypothesis of a 'remodelling' of immune response in the healthy elderly.

Altered T cell signalling in ageing

T cell responses are altered in the aged in a manner usually interpreted as detrimental to host defences against infectious agents and possibly also against cancer. T cell dysregulation may be caused by any or a combination of stem cell deficits, compromised T cell differentiation, inefficient antigen processing and presentation by antigen presenting cells, suboptimal processing of the antigenic signal by T cells or inability of the T cell to respond appropriately thereafter. This review will focus on altered T cell signalling in ageing, encompassing not only alterations in signal transduction by the antigen-specific T cell receptor, but changes in the balance of positive and negative T cell costimulation and the resultant modified cytokine environment, the response to which is itself altered in ageing.

CD50 and CD62L adhesion receptor expression on naive (CD45RA+) and memory (CD45RO+) T lymphocytes in the elderly

A complex reshaping characterizes cellular immunity in the elderly. In particular, the hallmark of the "senescence" of the T cell compartment is a decrease in the proportion of CD45RA+ naive T lymphocytes concomitantly with an expansion of CD45RO+ memory T cells. However, in addition to age-dependent changes in their representation, phenotypical and functional anomalies also characterize naive and memory T cell populations in the elderly. Since cell adhesion molecules (CAMs) are multifunctional receptors which play important roles not only in cell-to-cell and cell-to-matrix interactions but also in signal transduction and cell activation, we analysed, by means of a three-colour flow cytometry method, the proportion, absolute number and density expression or mean fluorescence intensity (MFI) of CD50 (ICAM-3) and CD62L (L-selectin homing receptor) adhesion receptors on CD45RA+ and CD45RO+ peripheral blood CD3+ T cell subsets from 10 healthy elderly subjects and 10 young controls. Our aim was to investigate age-dependent changes in the expression pattern of these CAMs on naive and memory lymphocytes which might contribute to the remodelling of the immune system in the elderly. We considered the mean values +/- standard deviations of the percentage, absolute number and MFI of positive cells. The percentage of naive T cells expressing CD50 was not significantly modified in aged (94.8 +/- 5.0%) compared to young individuals (97.8 +/- 3.2%). On the contrary, the percentage of memory T cells exhibiting CD50 was lower in elderly than young donors (92.0 +/- 6.4 vs. 98.3 +/- 2.2%; p < 0.01). The percentage of naive T cells expressing CD62L was decreased in the elderly donors (53.3 +/- 18.8 vs. 80.8 +/- 11.0%; p < 0.001), whereas the proportion of CD62L+ memory T lymphocytes was substantially comparable between the two age groups (63.5 +/- 15.7 vs. 54.7 +/- 12.3%). The absolute number per mm(3) of CD50+ naive T cells from aged individuals was decreased (251.9 +/- 141.9 vs. 621.8 +/- 238.0/mm(3); p < 0.001), whereas memory peripheral blood T lymphocytes expressing CD50 were substantially unchanged (863.8 +/- 260.9 vs. 802.7 +/- 139.6/mm(3)). On the contrary, the absolute numbers per mm(3) of naive and memory peripheral blood T lymphocytes exhibiting CD62L were respectively decreased (190.8 +/- 133.4/mm(3)) and increased (515.1 +/- 146.8/mm(3)) in elderly donors compared to young controls (601.3 +/- 129.1 and 351.8 +/- 195.0/mm(3); p < 0.001 and p < 0.05, respectively). Finally, CD50 MFI values of naive as well as memory T cell subpopulations from aged subjects were increased compared to young donors (14.0 +/- 2.0 vs. 9.8 +/- 1.2 and 14.0 +/- 2.0 vs. 11.6 +/- 1.3; p < 0.001 and p < 0.01, respectively). CD62L was also overexpressed in both naive (8.4 +/- 1.6 vs. 6.7 +/- 1.4; p < 0.05) and memory (10.3 +/- 2.5 vs. 5.4 +/- 1.1; p < 0.001) T subsets in the elderly. CD50 and CD62L upregulation could be interpreted as a compensatory mechanism for a decreased responsiveness and a greater requirement for activation signals rather than an age-related anomaly.

Immunosenescence and infectious diseases

Infectious diseases are major causes, with malignancies, of morbidity and mortality in the elderly. Increased susceptibility to infections may result from underlying dysfunction of an aged immune system; moreover, inappropriate immunologic functions associated with aging can determine an insufficient response to vaccines. Impairments of cellular, humoral and innate immunity in the elderly, contributing to increased incidence of infectious diseases, are discussed in this review.

The CD7(-) subset of CD4(+) memory T cells is prone to accelerated apoptosis that is prevented by interleukin-15 (IL-15)

The CD7(-) subset of CD4(+) T cells reflects a stable differentiation state of post-thymic helper T cells with CD45R0(+)CD45RA(-) 'memory' phenotype. Here we report that CD4(+)CD7(-) T cells are prone to increased spontaneous apoptosis in vitro compared to CD4(+)CD7(+) T cells. Spontaneous apoptosis is prevented by IL-15, but not by IL-2. Moreover, IL-15 increases Bcl-2 and decreases CD95/Fas expression of CD7(-), but not of CD7(+) T cells. Because IL-15 is physiologically not secreted but expressed in a membrane-bound form, we cocultured T cells with TNF-alpha stimulated fibroblasts that expose membrane IL-15. TNF-alpha stimulated fibroblasts rescue CD4(+)CD7(-) T cells from apoptosis whereas unstimulated fibroblasts do not. Rescue from apoptosis requires cell-cell contact and is abolished by addition of neutralizing antibodies to IL-15. We conclude that membrane IL-15 prevents accelerated apoptosis of CD4(+)CD7(-) T cells. This mechanism may contribute to accumulation of CD7(-) T cells in chronic inflammatory skin lesions.