A comprehensive analysis of peripheral blood lymphocytes in healthy aged humans by flow cytometry

The association between incarceration and housing insecurity and advanced immune age during late life

Emerging evidence suggests that psychosocial stress ages the immune system. Accordingly, immune aging may be an important potential mechanism linking psychosocial stress to aging-related decline and disease. Incarceration and housing insecurity represent severe and complex experiences of a multitude of psychosocial stressors, including discrimination, violence, and poverty. In this study, we investigated the association between incarceration and/or housing insecurity and advanced immune age in adults aged 55 and older. Our sample was derived from the Health and Retirement Survey (HRS), with n = 7003 individuals with valid housing insecurity data and n = 7523 with valid incarceration data. From 2016 Venous Blood Study data, we assessed immune aging using a comprehensive set of immune markers including inflammatory markers (IL-6, CRP, s-TNFR1), markers of viral control (CMV IgG antibodies), and ratios of T cell phenotypes (CD8+:CD4+, CD+ Memory: Naïve, CD4+ Memory: Naïve, CD8+ Memory: Naïve ratios). We found that both incarceration and housing insecurity were strongly associated with more advanced immune aging as indicated by increased inflammation, reduced viral control, and reduction in naïve T cells relative to memory T cells. Given that those who experienced incarceration, housing insecurity, and/or are racialized minorities were less likely to be included in this study, our results likely underestimated these associations. Despite these limitations, our study provided strong evidence that experiencing incarceration and/or housing insecurity may accelerate the aging of the immune system.

PTSD is associated with an increase in aged T cell phenotypes in adults living in Detroit

BACKGROUND

Psychosocial stress is thought to play a key role in the acceleration of immunological aging. This study investigated the relationship between lifetime and past-year history of post-traumatic stress disorder (PTSD) and the distribution of T cell phenotypes thought to be characteristic of immunological aging.

METHODS

Data were from 85 individuals who participated in the community-based Detroit Neighborhood Health Study. Immune markers assessed included the CD4:CD8 ratio, the ratio of late-differentiated effector (CCR7-CD45RA+CD27-CD28-) to naïve (CCR7+CD45RA+CD27+CD28+) T cells, the percentage of KLRG1-expressing cells, and the percentage of CD57-expressing cells.

RESULTS

In models adjusted for age, gender, race/ethnicity, education, smoking status, and medication use, we found that past-year PTSD was associated with statistically significant differences in the CD8+ T cell population, including a higher ratio of late-differentiated effector to naïve T cells, a higher percentage of KLRG1+ cells, and a higher percentage of CD57+ cells. The percentage of CD57+ cells in the CD4 subset was also significantly higher and the CD4:CD8 ratio significantly lower among individuals who had experienced past-year PTSD. Lifetime PTSD was also associated with differences in several parameters of immune aging.

CONCLUSIONS

PTSD is associated with an aged immune phenotype and should be evaluated as a potential catalyzer of accelerated immunological aging in future studies.

The emerging role of epigenetics in rheumatic diseases

Epigenetics is a key mechanism regulating the expression of genes. There are three main and interrelated mechanisms: DNA methylation, post-translational modification of histone proteins and non-coding RNA. Gene activation is generally associated with lower levels of DNA methylation in promoters and with distinct histone marks such as acetylation of amino acids in histones. Unlike the genetic code, the epigenome is altered by endogenous (e.g. hormonal) and environmental (e.g. diet, exercise) factors and changes with age. Recent evidence implicates epigenetic mechanisms in the pathogenesis of common rheumatic disease, including RA, OA, SLE and scleroderma. Epigenetic drift has been implicated in age-related changes in the immune system that result in the development of a pro-inflammatory status termed inflammageing, potentially increasing the risk of age-related conditions such as polymyalgia rheumatica. Therapeutic targeting of the epigenome has shown promise in animal models of rheumatic diseases. Rapid advances in computational biology and DNA sequencing technology will lead to a more comprehensive understanding of the roles of epigenetics in the pathogenesis of common rheumatic diseases.

Proportions of CD4+ memory T cells are altered in individuals chronically infected with Schistosoma haematobium

Characterisation of protective helminth acquired immunity in humans or experimental models has focused on effector responses with little work conducted on memory responses. Here we show for the first time, that human helminth infection is associated with altered proportions of the CD4+ memory T cells, with an associated alteration of T_H1 responses. The reduced CD4+ memory T cell proportions are associated with a significantly lower ratio of schistosome-specific IgE/IgG4 (marker for resistance to infection/re-infection) in uninfected older people. Helminth infection does not affect the CD8+ memory T cell pool. Furthermore, we show for the first time in a helminth infection that the CD4+ memory T cell proportions decline following curative anti-helminthic treatment despite increased CD4+ memory cell replication. Reduced accumulation of the CD4+ memory T cells in schistosome-infected people has implications for the development of natural or vaccine induced schistosome-specific protective immunity as well as for unrelated pathogens.

Broad cross-reactive TCR repertoires recognizing dissimilar Epstein-Barr and influenza A virus epitopes

Memory T cells cross-reactive with epitopes encoded by related or even unrelated viruses may alter the immune response and pathogenesis of infection by a process known as heterologous immunity. Because a challenge virus epitope may react with only a subset of the T cell repertoire in a cross-reactive epitope-specific memory pool, the vigorous cross-reactive response may be narrowly focused, or oligoclonal. We show in this article, by examining human T cell cross-reactivity between the HLA-A2-restricted influenza A virus-encoded M1(58-66) epitope (GILGFVFTL) and the dissimilar Epstein-Barr virus-encoded BMLF1(280-288) epitope (GLCTLVAML), that, under some conditions, heterologous immunity can lead to a significant broadening, rather than a narrowing, of the TCR repertoire. We suggest that dissimilar cross-reactive epitopes might generate a broad, rather than a narrow, T cell repertoire if there is a lack of dominant high-affinity clones; this hypothesis is supported by computer simulation.

Lasting effects of an impairment of Th1-like immune response in γ-irradiated mice: A resemblance between irradiated mice and aged mice

Although one of the several chronic effects of ionizing radiation is aging, there are no experimental data on radiation-induced immunological aging. The most interesting change in aging was a helper T (Th) 1/Th2 imbalance. We investigated chronic effect on immune responses after ionizing radiation and its effects in irradiated mice were compared with those of aged mice. The 2-month-old mice received a whole-body irradiation of 5Gy. At 6months after irradiation, we compared the immune functions of the irradiated mice with those of normal mice of the same age and with those of older. Interferon (IFN)-γ and antigen-specific immunoglobulin (Ig)G2a level were lower in the irradiated mice than in normal mice of same age, showing similar levels to those of old normal mice. In contrast, interleukin (IL)-4 and IL-5 and antigen-specific IgG1 level were increased in irradiated mice when compared with the same aged-normal mice. Next, we investigated the low expression of IL-12p70, IL-12 receptors and IL-18 receptors in irradiated and old mice. Also, the decrease of natural killer cell activity was intensified in the irradiated mice, showing lower than values to those of old mice. Interestingly, in irradiated mice, the absolute numbers and the percentages of natural killer (NK) cells was extremely decreased. But the absolute numbers of Th cells and cytotoxic T (Tc) cells in old mice were significantly decreased. In conclusion, an immunological imbalance by the whole-body irradiation of 5Gy induces to persist in the long term, resulting in the similar results with aging. Our results suggest that the downregulation of the Th1-like immune response shown in old mice rapidly occurred through exposure of ionizing radiation.

Low zinc status: a new risk factor for pneumonia in the elderly?

Low zinc status may be a risk factor for pneumonia in the elderly. This special article reviews the magnitude of the problem of pneumonia (its prevalence, morbidity, and mortality) in the elderly, pneumonia's etiology, and the dysregulation of the immune system associated with increasing age. In addition, recent evidence from the literature is presented demonstrating that low zinc status (commonly reported in the elderly) impairs immune function, decreases resistance to pathogens, and is associated with increased incidence and duration of pneumonia, increased use and duration of antimicrobial treatment, and increased overall mortality in the elderly. Inadequate stores of zinc might, therefore, be a risk factor for pneumonia in the elderly. Randomized, double-blind, controlled studies are needed to determine the efficacy of zinc supplementation as a potential low-cost intervention to reduce morbidity and mortality due to pneumonia in this vulnerable population.

Calorie restriction enhances T-cell-mediated immune response in adult overweight men and women

Calorie restriction (CR) enhances immune response and prolongs life span in animals. However, information on the applicability of these results to humans is limited. T-cell function declines with age. We examined effects of CR on T-cell function in humans. Forty-six overweight, nonobese participants aged 20-42 years were randomly assigned to 30% or 10% CR group for 6 months. Delayed-type hypersensitivity (DTH), T-cell proliferation (TP), and prostaglandin E(2) (PGE(2)) productions were determined before and after CR. DTH and TP to T-cell mitogens were increased in both groups over baseline (p < or = .019). However, number of positive responses to DTH antigens (p = .016) and TP to anti-CD3 reached statistical significance only after 30% CR (p = .001). Lipopolysaccharide-stimulated PGE(2) was reduced in both groups but reached statistical significance after 30% CR (p < or = .029). These results, for the first time, show that 6-month CR in humans improves T-cell function.

Restoration of the immune functions in aged mice by supplementation with a new herbal composition, HemoHIM

The effect of a new herbal composition, HemoHIM, on immune functions was examined in aged mice, in which various immune responses had been impaired. The composition HemoHIM was prepared by adding the ethanol-insoluble fraction to the total water extract of a mixture of three edible herbs, Angelica Radix, Cnidium Rhizoma and Paeonia Radix. Supplementation to the aged mice with HemoHIM restored the proliferative response and cytokine production of splenocytes with a response to ConA. Also, HemoHIM recovered the NK cell activity which had been impaired in the aged mice. Meanwhile aging is known to reduce the Th1-like function, but not the Th2-like function, resulting in a Th1/Th2 imbalance. HemoHIM restored the Th1/Th2 balance in the aged mice through enhanced IFN-gamma and IgG2a production, and conversely a reduced IL-4 and IgG1 production. It was found that one factor for the Th1/Th2 imbalance in the aged mice was a lower production of IL-12p70. However, HemoHIM restored the IL-12p70 production in the aged mice. These results suggested that HemoHIM was effective for the restoration of impaired immune functions of the aged mice and therefore could be a good recommendation for immune restoration in elderly humans.

Immune cell variations in patients with hip fracture

Hip fracture is an increasing pathology in the patients with increasing age. Immunological response differences may appear between different age groups. The purpose of this study was to investigate the immune response in patients with subcapital hip fracture and the relationship with age. Prospective study of 100 patients with displaced subcapital femoral fracture between 2000 and 2004, divided into three age groups: over 90 years (13), 80-90 (56) and under 80 years (27). The chi(2)-test, analysis of variance and Student's t-test were applied. Correlation coefficient and the Spearman test were used to study linear correlation. The T helper cells decreased with age, this inverse correlation was significant. There was a direct correlation between CD16% and age. IgA, IgG and IgM levels did not show any significant relationship with age in our study. Nevertheless, the IgE levels in peripheral blood showed a significant direct correlation with age. Basophils percentage presented an inverse correlation with age. Age is associated to some immune changes in patients suffering hip fracture.

Tissue detection of natural killer cells in colorectal adenocarcinoma

BACKGROUND

Natural killer (NK) cells represent a first line of defence against a developing cancer; however, their exact role in colorectal cancer remains undetermined. The aim of the present study was to evaluate the expression of CD16 and CD57 [immunohistochemical markers of natural NK cells] in colorectal adenocarcinoma.

METHODS

Presence of NK cells was investigated in 82 colorectal adenocarcinomas. Immunohistochemical analysis was performed, using 2 monoclonal antibodies (anti-Fc Gamma Receptor II, CD16 and an equivalent to Leu-7, specific for CD-57). The number of immunopositive cells (%) was evaluated by image analysis. The cases were characterized according to: patient gender and age, tumor location, size, grade, bowel wall invasion, lymph node metastases and Dukes' stage.

RESULTS

NK cells were detected in 79/82 cases at the primary tumor site, 27/33 metastatic lymph nodes and 3/4 hepatic metastases; they were detected in levels similar to those reported in the literature, but their presence was not correlated to the clinical or pathological characteristics of the series, except for a negative association with the patients' age (p = 0.031).

CONCLUSIONS

Our data do not support an association of NK cell tissue presence with clinical or pathological variables of colorectal adenocarcinoma, except for a negative association with the patients' age; this might possibly be attributed to decreased adhesion molecule expression in older ages.

The effect of age and gender on cytokine production by human peripheral blood mononuclear cells and markers of bone metabolism

BACKGROUND

Aging has been associated with various alterations of immune functions, the musculoskeletal system and a decline of sex hormone levels. Estradiol has a central role in the regulation of bone turnover and also modulates the production of cytokines such as interleukin-1 and -6 and tumor necrosis factor-alpha. We therefore studied the effect of age and gender on cytokine production by mononuclear cells and markers of bone metabolism.

METHODS

Peripheral blood mononuclear cells were isolated from young and elderly subjects; intracellular detection of cytokine production after stimulation with ionomycine and PMA (T cells) or LPS (monocytes) was performed by four color flow cytometry. Sex hormone levels and markers of bone metabolism were measured by RIA or ELISA:

RESULTS

When we compared elderly to young women we found an increased proportion of T cells that were positive for interferon-gamma, interleukin-2, -4, -10 and -13. Also the percentage of cells producing interleukin-4 or interferon-gamma within the CD8(+) population was higher in the group of elderly women. In contrast, proportionally fewer monocytes of elderly women were positive for tumor necrosis factor-alpha or interleukin-6 than those of young women. In elderly men a higher percentage of T cells produced interleukin-2, -4 and -13. In the group of aged men we found a higher frequency of cells that produced interleukin-4 within the CD4(+) or CD8(+) population. Moreover, within monocytes of elderly men we found an increased percentage of cells positive for both interleukin-1beta and tumor necrosis factor-alpha. The data on markers of bone metabolism indicated an increase of bone turnover in old age.

CONCLUSION

Our data demonstrate that aging is associated with significant alterations of bone metabolism and cytokine production by T cells and monocytes. For particular cytokines (interferon-gamma and interleukin-10 in T cells, interleukin-6 and tumor necrosis factor-alpha in monocytes) these changes are gender specific.

Lymphocyte modulation in a baboon model of immunosenescence

The age-related modulation of lymphocyte number and function was assessed in a nonhuman primate model consisting of healthy olive baboons (Papio cynocephalus anubis) of ages encompassing the entire life span of this species. The objectives of this study were to characterize an animal model of immunosenescence and to assess whether or not age should be considered when designing studies for the evaluation of vaccine candidates in baboons. Specifically the following parameters were assessed in baboons from 6 months to 26 years of age: relative numbers of B lymphocytes, CD4+ and CD8+ T lymphocytes, and T lymphocytes expressing CD28, CD25, and phytohemagglutinin-stimulated lymphoproliferative activity; and concentrations of total immunoglobulin, soluble interleukin-2 receptor alpha, and soluble CD30 in serum. There was a statistically significant effect of age on lymphocyte numbers. As age increased, relative B-cell numbers (ranging from 6 to 50%) decreased (P < 0.001) and relative T-cell numbers (ranging from 28 to 80%) increased (P < 0.001). The increase in T-cell numbers involved both the CD4+ and CD8+ subsets. In addition, there was a significant negative correlation of age with levels of soluble interleukin-2 receptor alpha in serum. Modulation of lymphocyte numbers appears to occur gradually during the entire baboon life span, thus suggesting the presence of an age-related developmentally regulated process. These findings indicate that baboons represent a potentially useful model to study selected phenomena related to immunosenescence. These findings also indicate that, when using the baboon model for vaccine or other experimental protocols requiring the assessment of immune responses, it would be appropriate to take into account the age of the animals in the study design.

Aging, immunity, and cancer

BACKGROUND

The prime function of the immune system is to protect the entire organism from a variety of insults and illnesses, including the development of cancer. The question of how age-related declines in immune function contribute to an increasing incidence of malignancies continues to be a focus of discussion and speculation.

METHODS

The recent literature from the National Library of Medicine database (1990 through the present) was searched for articles using the medical subject headings (MeSH terms) of aging, immunity, cancer, senescence, and apoptosis. Bibliographies of articles retrieved were also scanned.

RESULTS

Data from in vitro and in vivo animal and human studies demonstrate clear age-related alterations in both the cellular and humoral components of the immune system, but there is little evidence supporting direct causal links between immune senescence and most malignancies.

CONCLUSIONS

Senescent decline in immune surveillance leads to the accumulation of cellular and DNA mutations that could be a significant factor in the development of malignancy and programmed cell death or apoptosis observed in the elderly.

Immunology and aging

Aging is accompanied by numerous functional and phenotypic changes in T cells, B cells and monocytes/macrophages; moreover, increases in autoimmunity, infections and occurrence of cancer have been reported in aged people. Healthy elderly persons, defined according to the criteria of the SENIEUR protocol, show various alterations in immunocompetent cells. Recent data have shown that the distribution of the subsets of peripheral blood, T-cell subtypes, is influenced by age. With increasing age, CD45RA(+) naive cells are replaced by CD45RA(-) memory CD4(+) T cells. In the CD8(+) T-cell subset, we found an increased proportion of cells co-expressing CD57. In monocytes also, some alterations of the immunophenotype, for example the expression of the adhesion molecule CD54, were observed. A relative deficit of transendothelial migration with aging was found in T cells, whereas this function was not impaired in monocytes. The immunophenotype and the function of dendritic cells do no t appear to be affected by aging. Due to their capacity to present antigens to T cells and to induce T-cell proliferation, dendritic cells may provide a useful tool for immunotherapy. In conclusion, investigations of immune functions in aging people reveal that there is an alteration of the immunophenotype of T cells and monocytes. Several functions of T-cell accompanying mechanisms, for example cytokine production and cell migration, are also affected by aging. In contrast, dendritic cells do not seem to be influenced by the aging process.

Review article: ageing and the neutrophil: no appetite for killing?

In the armoury of the immune system developed to combat the various micro-organisms that could invade the host, the neutrophil forms the first line of defence against rapidly dividing bacteria and fungi. However, as humans age they become more susceptible to infection with these microbes and this has been ascribed to a decline in immune status, termed immune senescence. Here we summarize the literature specifically concerning the attenuation of neutrophil function with age and the possible mechanisms underlying their reduced response to infectious agents.

Distinct categories of immunologic changes in frail elderly

Immune changes and their relationships in a frail elderly population (N=116, age 70-103, median 86 years) were defined in comparison to a healthy younger group. Previous immune studies in the elderly have generally focused on one or few parameters without correlation analyses. Furthermore, the study populations have been active elderly in relatively small numbers. A total of 33 immune parameters representing many aspects of the immune system were quantified. Most changes in the frail elderly were parallel to those reported in active elderly. A classification tree analysis revealed that increased plasma activation markers (neopterin and sTNF-R) and increased CD28 expression on CD8 T cells and proliferative response separated the aged and control populations. Statistical procedures utilizing principal components analyses, partial correlations and exploratory factor analyses all indicated that immunologic parameters in frail elderly are grouped in three major clusters of immunologic results. These involved (a) increased plasma levels of neopterin and sTNF receptor indicating elevated IFNgamma and TNF cytokine activity; (b) increased proportion of mature (CD45RO) versus naïve (CD45RA) T cells; and (c) a diverse group of related changes including impaired proliferative response, reduced T cells, CD28 and CD25 expression, B cell percentage and lower CD4:CD8 ratios and increased HLA-DR expression. These findings emphasize that several different groups of immune parameters but not 33 independent immune changes, occurred in the aged population.

Surface markers and transendothelial migration of dendritic cells from elderly subjects

Age-related changes of immune functions have been extensively investigated in both humans and animal models; nevertheless, the literature on potential alterations of dendritic cells, potent antigen presenting cells responsible for initiating immune responses, with aging is very scarce. We studied the immuno-phenotype of peripheral blood dendritic cells of elderly and young subjects by three-color flow cytometry. In addition, the capacity of transendothelial migration, an important step in inflammatory reactions, of peripheral blood dendritic cells of elderly subjects was investigated in an in vitro model. The expression of HLA-DR in the peripheral blood dendritic cells of the elderly subjects was significantly decreased when compared to the young control subjects. The expression of various other surface markers was similar in the young and elderly subjects. The ability of transendothelial migration of dendritic cells was found to be unimpaired in the elderly subjects. Both in the young and elderly subjects a significantly higher expression of CD29, CD86, HLA-DR, and HLA-DQ in the dendritic cells that had migrated through the endothelium in comparison to nonadherent, nonmigrating cells was found. In the migrating dendritic cells of the elderly subjects a significantly increased expression of CD11c was observed, whereas the expression of CD54 was significantly enhanced in the migrating dendritic cells of the young subjects only. In conclusion, our results demonstrate intact functions and a normal immunophenotype of dendritic cells derived from elderly subjects. Dendritic cells thus seem to be functional and therefore are not responsible for the well-known decline of T cell functions with aging.

Effect of micronutrient status on natural killer cell immune function in healthy free-living subjects aged >/=90 y

BACKGROUND

Natural killer (NK) cells play a role in natural immunity against tumor and infected cells. Advanced aging is associated with functional impairment of NK cells and increased susceptibility to nutritional deficiencies.

OBJECTIVE

Our objective was to test whether micronutrient status affects NK cell activity in an older population.

DESIGN

The relations between NK cell variables (percentage of leukocytes and cytotoxicity) and blood concentrations of selected micronutrients were studied in 62 healthy, free-living northern Italian subjects (25 men, 37 women) aged 90-106 y. Anthropometric measurements were also made.

RESULTS

All subjects were well nourished according to age-specific anthropometric norms but many of them had micronutrient deficiencies. The prevalence of micronutrient deficiency was highest for selenium (in approximately 50% of both sexes), zinc (in 52% of men and 41% of women), and vitamin B-6 (in 40% of men and 59% of women), followed by vitamin A (in 16% of men and 27% of women) and vitamin E, vitamin B-12, and folate (each in <10% of both sexes). Ubiquinone-10 status was inadequate in 40% of women and 24% of men (P = 0.02). The percentage of NK cells was associated with serum zinc (men: r = 0.573, P = 0. 007; women: r = 0.373, P = 0.031) and selenium (women: r = 0.409, P = 0.018) concentrations. In women only, NK cell cytotoxicity at different effector-target cell ratios was positively associated with plasma vitamin E and ubiquinone-10 concentrations (P < 0.05). No significant associations with NK cell variables were found for the other measured nutrients.

CONCLUSIONS

The results of this study strengthen the hypothesis that individual micronutrients may affect the number and function of NK cells in old age. The study also confirms the high prevalence of micronutrient deficiencies in healthy and apparently well-nourished persons aged >/=90 y.

Phenotypic and functional characteristics of circulating monocytes of elderly persons

Aging is associated with impairment of immune functions. Age-dependent alterations in T-cells are well known. Although the pivotal role of monocytes in immune regulation by their production of proinflammatory and inhibitory cytokines is acknowledged, limited information is available on monocyte changes in aging. The present study focused on phenotypic changes in circulating monocytes in elderly subjects and in the level of cytokines they produce. The results demonstrated a significant expansion of CD14dim/CD16bright circulating monocytes in elderly. In contrast, the majority of circulating monocytes of healthy young individuals were CD14bright/CD16dim. The CD14dim/CD16bright monocytes are considered to have phenotypic evidence for activation. Furthermore, significant increases of constitutive production of monocytic cytokines including interleukin (IL)-1beta. IL-1 receptor antagonist, and IL-6 by nonstimulated monocytes from elderly was also indicative of activation. This was also observed when monocytes from elderly were cultured with autologous lymphocytes. However, after stimulation, significantly lowered IL-1beta production was observed and IL-6 and IL-10 tended to be higher in the elderly. Collectively, these results indicate that monocytes of aged individuals, in contrast to a younger population exhibit in vivo activation as well as imbalanced production of cytokines. Such age-related alterations in monocytes may contribute to impaired immune competence of aging.

Exercise and the immune system--influence of nutrition and ageing

In essence, the immune system is enhanced during moderate and severe exercise, and only intense long-duration exercise is followed by impairment of the immune system. The latter includes suppressed concentration of lymphocytes, suppressed natural killer cell activity, lymphocyte proliferation and secretory IgA in saliva. During the time of immune impairment, referred to as "the open window", microbial agents, especially viruses may invade the host and infections may be established. One reason for the "overtraining effect" seen in elite athletes could be that this window of opportunism for pathogens is longer and the degree of immunosuppression more pronounced. Alterations in metabolism and metabolic factors may contribute to exercise-associated changes in immune function. Reductions in plasma-glutamine concentrations, altered plasma-glucose level, free oxygen radicals and prostaglandins (PG) released by the elevated number of neutrophils and monocytes may influence the function of lymphocytes and contribute to the impaired function of the later cells. Thus, nutritional supplementation with glutamine, carbohydrate, anti-oxidants or PG-inhibitors may, in principle, influence exercise-associated immune function. Although several intervention studies have been performed, it is premature to make recommendations regarding nutritional supplementation to avoid post-exercise impairment of the immune system.

Exercise and immune function: effect of ageing and nutrition

Strenuous exercise is followed by lymphopenia, neutrophilia, impaired natural immunity, decreased lymphocyte proliferative responses to mitogens, a low level of secretory immunoglobulin A in saliva, but high circulating levels of pro- and anti-inflammatory cytokines. These exercise-induced immune changes may provide the physiological basis of altered resistance to infections. The mechanisms underlying exercise-induced immune changes are multifactorial and include neuroendocrinological and metabolic mechanisms. Nutritional supplementation with glutamine abolishes the exercise-induced decline in plasma glutamine, but does not influence post-exercise immune impairment. However, carbohydrate loading diminishes most exercise effects of cytokines, lymphocyte and neutrophils. The diminished neutrophilia and elastase (EC 3.4.21.37) responses to eccentric exercise in elderly subjects were enhanced to levels comparable with those of young subjects by fish oil or vitamin E supplements. However, although vitamin C supplementation may diminish the risk of contracting an infection after strenuous exercise, it is not obvious that this effect is linked to an effect of vitamin C on exercise-induced immune changes. In conclusion, it is premature to make recommendations regarding nutritional supplementation to avoid post-exercise impairment of the immune system.

CD69, CD25, and HLA-DR activation antigen expression on CD3+ lymphocytes and relationship to serum TNF-alpha, IFN-gamma, and sIL-2R levels in aging

Aging is associated with changes in lymphocyte subsets and unexplained HLA-DR upregulation on T-lymphocytes. We further investigated this activation, by measuring early (CD69), middle (CD25), and late (HLA-DR) T-lymphocyte activation markers on CD3+ lymphocytes, across subjects (20-100 years) together with serum tumor necrosis factor (TNF-alpha), interferon-gamma (IFN-gamma), and soluble interleukin-2 receptor (sIL-2R). HLA-DR was present as a CD3+ HLA-DR+ subset that constituted 8% of total lymphocytes, increased twofold with age and included CD4+, CD8+, and CD45RA+ phenotypes. HLA-DR was also expressed on a CD8+ CD57+ subset. The CD3+ CD25+ subset constituted 13% of lymphocytes, fell with age but was weakly associated with the CD3+ HLA-DR+ subset especially in older subjects. A small 3-5% CD3+ CD69+ subsets showed no age effect. Serum sIL-2R, TNF-alpha, but not IFN-gamma, were associated with CD3+ HLA-DR+ lymphocytes, TNF-alpha with CD8+ CD57+ count and sIL-2R and IFN-gamma with the CD3+ CD25+/CD3+ CD4+ ratio. The study confirms age-related upregulation of HLA-DR on CD3+ lymphocytes, shows some evidence for associated upregulation of CD25 on CD3+ cells in older subjects, and links serum TNF-alpha, IFN-gamma, and sIL2-R to T-lymphocyte activation.

Age-related changes in the absolute number of CD95 positive cells in T cell subsets in the blood

Comparison of the absolute number of cells in distinct T cells subsets expressing CD95 (Fas) was carried out in two populations of healthy female volunteers. In one population, the average age was 30 +/- 5 years, and in the second population the average age was 73 +/- 13 years. No significant difference was noted in the total number of lymphocytes, CD3+, CD4+, or CD8+ cells per microL of blood between the two age groups, but major differences were noted in the number of cells expressing CD95. A significant reduction was seen in the number of cells per microL of blood in both the CD4+ CD45RA+ CD95+ and CD8+ CD45RA+ CD95+ populations in the older group compared with the younger group. Within the memory pool significantly fewer CD8+ CD45RO+ CD95+ cells were found in the older population compared with the younger group. No such difference were found in the number of CD4+ CD45RO+ CD95+ cells between groups. Such a significant decline in the number of CD95+ cells, whose expression is known to be linked with activation, may be implicated as a mechanism by which cells that have reached a stage of replicative senescence remain in the peripheral T cell pool. Anti-CD3-mediated activation of cells from both groups revealed much lower proliferative responses from the older group, supporting the idea that there is an age-associated increase in the number of cells that have reached their replicative limit. These cells may not be lost from the peripheral pool because they fail to express CD95.

T cell receptor V-segment frequencies in peripheral CD8+ T cells in aging

Infections are a major cause of illness and death amongst elderly people. Peripheral blood CD8+ T lymphocytes --which play a crucial role in host defence against viral infections--, are divided in subsets based upon the expression of several cell and activation markers. In senescence changes and variations in peripheral CD8+ T lymphocyte compartment have been described, and such a decrease in the CD8+CD45RA+ lymphocytes. In this report the T V alpha and Vbeta cell specificities repertoire usage in aging subjects were studied by the use of seven different monoclonal antibodies specific for defined regions of the TCR. Except for the Vbeta6subfamily, no differences between old and control subjects in frequency of T cells bearing selected V alphabeta epitopes, were observed.

Altered cytokine production in the elderly

Elderly persons are more susceptible to bacterial and virus infections and neoplasias than young adults. This is related to an impaired immune response. Lymphocytes of the elderly show a decreased proliferation after induction with mitogens. The decreased proliferation is correlated to a decreased release of interleukin (IL)-2 and soluble IL-2 receptor (sIL-2R). However, IL-2R expression on the cell surface is normal. Interferon (IFN)-gamma as the main T-helper-1 (TH1) cytokine is produced less by lymphocytes of the elderly, whereas the TH2 cytokines IL-4 and IL-10 are produced in higher amounts as compared to stimulated lymphocytes of young donors. The decreased production of IFN-gamma is correlated to a decreased number of CD45RO+/CD8+ T cells. Therefore in the elderly there seems to be a dysregulation in the TH1/TH2-system which is predominated by TH2-functions. Monocyte function seems to be increased in the elderly. Leukocytes of elderly persons produce higher amounts of IL-1, IL-6, IL-8 and tumor necrosis factor (TNF)-alpha after induction with lipopolysaccharide (LPS) than leukocytes from young donors. In contrast, in vitro induction of IFN-alpha by viruses is decreased in the elderly compared to the young. In conclusion, there are cellular defects and dysfunctions in the elderly resulting in an altered immune response.

Susceptibility to apoptosis of T lymphocytes from elderly humans is associated with increased in vivo expression of functional Fas receptors

We recently showed that mature T lymphocytes derived from elderly humans were more susceptible to activation-induced cell death than similar cells from young individuals. Because this excessive apoptosis is unrelated to either the age-associated decrease in IL-2 production, a differential Bcl-2 expression or to a modification of the antioxidant pathway, we examined the possibility that the Fas receptor (FasR) is directly implicated in the generation of the unwarranted death signal. We investigated the expression and the function of FasR on T lymphocyte populations from healthy young and elderly individuals. We found that the frequency of FasR+ T cells increases as a function of age. The FasR expressed at the surface of freshly isolated T lymphocytes from elderly donors appear to be fully functional since their ligation by a cytocidal IgM anti-Fas mAb leads to a significant increase in DNA fragmentation in this cell population. Conversely, exposure of T cells derived from aged individuals to an antagonistic anti-FasR mAb partially prevents the age-related increase in apoptotic cell death. The population of FasR+ T lymphocytes is essentially constituted of previously activated CD45RO+ cells and also includes recently activated lymphocytes bearing the CD25 and CD69 activation markers. The accumulation of chronically and recently in vivo activated T-cells with age probably contributes to the amplification of the process of Fas-mediated cell death in T lymphocytes isolated from senescent organisms.

Age- and radiation-dependent changes in carbonyl content, susceptibility to proteolysis, and antigenicity of soluble rat liver proteins

Soluble liver proteins (SLP) from old and gamma-irradiated young rats were studied with respect to their carbonyl content, the rates of autolysis and degradation by proteinase K, and their antigenicity for mice and compared with SLP from non-irradiated young animals. A significant increase in the carbonyl level was found in SLP from old and gamma-irradiated young rats as compared to SLP from intact young rats. The rates of SLP autolysis and proteolysis by proteinase K were increased in the same animal groups but did not correlate the carbonyl level. At the same time, whereas the antigenicity for mice of SLP from old rats was significantly higher than that of SLP from young rats, the antigenicity of SLP from gamma-irradiated rats did not differ from non-irradiated animals. Enrichment of the diet with antioxidant and vitamin supplements (AVS) during one month before the irradiation caused a decrease in the radiation-induced carbonyl level in rat SLP. However, this raised antioxidant level in animal diet did not influence the rates of SLP autolysis and degradation by proteinase K and also did not alter the antigenicity of these proteins. The data allow us to suggest that the increase in autolysis, degradation by the exogenous proteinase, and antigenicity of SLP from old rats are determined not only by carbonyl formation in these proteins due to action of oxygen radicals but also by other age-specific protein modifications.

Decreased proliferative capacity and increased susceptibility to activation-induced cell death in late-passage human CD4+ TCR2+ cultured T cell clones

The growth characteristics in vitro of interleukin 2 (IL 2)-dependent human CD4+ alpha beta-T cell receptor-positive helper T cell clones (TCC) were studied in relation to alterations in surface phenotype, cytokine responsiveness, and susceptibility to activation-induced cell death (AICD). TCC derived from peripheral blood T cells had finite lifespans averaging 33 population doublings (PD) with a recorded maximum lifespan of 80 PD (n = 208). First analyses of the TCC were undertaken at ca. 25 PD, at which time all cells of all TCC expressed high intensity CD45RO and low intensity CD45RA, as well as high intensity CD95 (fas) and MHC class II antigens. The expression of these molecules remained elevated throughout the proliferative lifespan of the clones, but for those TCC which were initially CD28+ (the majority), the density of expression of the latter was diminished in most late-passage clones. Concomitant with this, late-passage cells showed reduced responsiveness to CD28-mediated costimulation by CHO transfectants expressing human CD80 compared to early-passage cells. Additionally, the level of expression of IL 2R gamma c and IL 7R chains was commonly reduced, as was the response to IL 2 and IL 7. Despite unchanged levels of fas expression on TCC with time, late-passage cells were more susceptible to AICD than early, passage cells. These observations further document functional and phenotypic alterations in long-term cultured human T helper cells, which may be considered as biomarkers of immunosenescence. This may contribute to an improved understanding of the mechanisms underlying depressed T cell function in old age.

Excessive apoptosis of mature T lymphocytes is a characteristic feature of human immune senescence

Recent evidence suggests that apoptotic deletion of activated mature lymphocytes is an essential physiological process implicated in both the regulation of the immune response and the control of the overall number of immunocompetent cells. Tightly interrelated signaling mechanisms convey either activation or death messages, achieving the necessary equilibrium between cell proliferation and cell deletion. During the course of aging, numerous alterations of these signaling pathways may shift the balance toward cell death. In the present investigation, the reduced DNA synthesis of anti-CD3 activated T lymphocytes isolated from elderly individuals is associated with an important and early cell deletion from the cultures. Visualization of DNA fragmentation in the remaining activated cells argues in favour of the apoptotic nature of the cell deletion. Quantification of histone-associated DNA fragments shows that the apoptotic process is greatly amplified in activated lymphocytes derived from senescent organisms. Further analysis reveals that IL-2 deprivation does not play a significant role in the age-related increase in apoptosis. Partial correction of this excessive apoptosis by products that bypass the early steps of the signaling cascade suggests that transmembrane signaling defects are involved in this process. Exploration of the antioxidant pathway reveals that the increased susceptibility of lymphocytes from senescent organisms to apoptosis is not explained by a decreased Bcl-2 expression and is not influenced by a modification of the intracellular concentration of glutathione (GSH).

Dysregulation between TH1 and TH2 T cell subpopulations in the elderly

We investigated the influence of zinc and its binding proteins on the immune system in 21 elderly and 20 young subjects. We detected a deficiency of zinc in the serum of the elderly. Albumin levels were within physiological range, but alpha 2-macroglobulin was significantly increased in the serum of elderly subjects. Using a whole blood assay, we found decreased production of interferon-gamma (IFN-gamma) and soluble interleukin-2 receptors (SIL-2R) in the elderly, whereas interleukin-10 (IL-10) production was greater than in the young controls. To exclude cellular defects, we measured lymphocyte subpopulations. In elderly subjects, we detected lower quantities of CD8+, CD8+/CD45RA+ and CD4+/CD45RO+ cells, but not CD4+ cells, than in young subjects. Other lymphocyte subpopulations were comparable for both groups. These findings suggest a dysregulation between TH1 cells and TH2 cells in the elderly, which may be a result of long-term zinc deficiency. Zinc reconstitution showed no beneficial effects as measured by T cell activity.

CD8+ T cell subsets in aging

Infections are major cause of illness and death amongst elderly people. Peripheral blood CD8+ T lymphocytes -which play a crucial role in host defence against viral infections-. are divided in subsets based upon the expression of several cell and activation markers. Since in senescence changes in peripheral blood CD8+ T lymphocyte compartment have been described, studies were performed to determine whether in aging there are variations in the peripheral blood CD8+CD38+, CD8+CD57+, CD8+HLA-DR+, CD8+CD45RA+ and CD8+CD45RO+ cell subset. A decrease in the CD8+CD45RA+ lymphocytes was observed, indicating that variations in the CD8+ compartment can take place with ageing.

Cytokine production and lymphocyte subpopulations in aged humans. An assessment during nocturnal sleep

The view of a general impairment of immune functions associated with aging has been challenged by recent studies including a more detailed evaluation of various cytokines and lymphocyte subsets. In the present human study, effects of age on the production of cytokines by T cells and monocytes were assessed, together with age-dependent changes in subset populations of mononuclear cells (MNC). Blood was collected every 30 min during nocturnal sleep in 16 aged (mean: 79.6 +/- 7.5 years) and in 16 young controls (mean: 24.6 +/- 3.1 years). Nocturnal sleep was chosen as a well-defined period within the 24-h cycle with minimal exogenous influences. The in vitro production of interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) was measured after mitogen stimulation with lipopolisaccharide from E. coli (LPS). Production of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) was measured after stimulation with phytohemagglutinin (PHA). Regarding MNC subsets, monocytes, lymphocytes, CD3+, CD4+, CD8+, HLA-DR, CD16+, CD25+, and CD19+ were determined. Advanced age was associated with a decreased number of T cells (CD3+) and decreases in the major T cell subsets (CD4+, CD8+, P < 0.001). Production of IL-2 was not affected. However, production of IFN-gamma tended to be enhanced, and numbers of activated T cells (HLA-DR/CD3+), natural killer cells (CD16+), and T cells expressing IL-2 receptors (CD25+/CD3+) were markedly increased in the aged. While monocyte counts were unchanged in the elderly production of IL-1 beta and TNF-alpha mainly derived from these cells, was enhanced (p < 0.05). Results indicate a state of enhanced responsiveness of the T cell compartment and of monocytes in aged which may compensate for the substantial decrease in T cells.

Differential expression of various T cell surface markers in young and elderly subjects

The purpose of this study was to investigate the expression of lymphocyte markers in the peripheral blood of aged individuals and of young healthy blood donors. Results showed significant changes in the distribution of various T cell subpopulations. The CD3, CD4 and CD8 surface expression was not different in the elderly patients when compared to the young subjects. The number of CD4+ T cells expressing CD45 RO isoform (memory cells) was increased in aged people; CD45 RA+ CD4+ cells (naive cells) were decreased. The expression of the CD45 RB on the CD4+ cells was significantly lower in the elderly when compared to the young subjects. In contrast, the surface expression of CD45 RO and CD45 RB in the CD8+ cells was not statistically different in the young and aged subjects. The proportion of CD8+ cells coexpressing CD57 was significantly increased in the elderly subjects. These results indicate age-dependent alterations of various surface markers of T cells. These observations may be of importance in the investigation of immunoregulatory mechanisms in geriatric patients with infection, autoimmune disease or cancer.

Changes in CD45 isoform expression vary according to the duration of T-cell memory after vaccination

Healthy young (< 40 years) and elderly (< 60 years) adults were immunized with the 1992-1993 preparation of trivalent influenza vaccine, and changes in CD45 isoform expression on peripheral blood lymphocytes were measured in the pre- and postvaccination periods. Fluorescence-activated cell sorter analysis was used to study T-cell subsets in fresh peripheral blood lymphocytes (day 0) and after 6 days of culture with live influenza virus. We have reported previously that the interleukin-2 response to the stimulating strain of virus, A/Texas/16/89, did not decline until 26 weeks postvaccination. In ex vivo CD4+ subsets, this interleukin-2 response was paralleled by a > 10% increase in the proportion of cells expressing the CD45RO+ phenotype following vaccination (p < 0.0001). In vitro stimulation had no effect on CD4+ subsets prior to vaccination but, after vaccination, was associated with a > 10% increase in CD45RA+RO+ cells (P < 0.0001). In addition, we have identified a change in the population of cells that express a CD45 isoform that is neither CD45RA nor CD45RO (CD45RA-RO-). At 26 weeks postvaccination, the proportion of CD45RA-RO- cells in ex vivo CD4+ peripheral blood mononuclear cells increased by approximately 15% from that measured at the earlier postvaccination time points (P < 0.0001). In vitro stimulation with influenza virus resulted in a further 20% increase in the proportion of CD45RA-RO- cells (P < 0.0001). The CD45RA-RO- phenotype may identify a population of cells undergoing apoptosis (programmed cell death) that limits the duration of helper T-cell (CD4+) memory after vaccination.