The impairment of natural killer function in the healthy aged is due to a postbinding deficient mechanism

Immunosenescence as a convergence pathway in neurodegeneration

Immunity refers to the body's defense mechanism to protect itself against illness or to produce antibodies against pathogens. Senescence is a cellular phenomenon that integrates a sustainable growth restriction, other phenotypic abnormalities and including a pro-inflammatory secretome. It is highly involved in regulating developmental stages, tissue homeostasis, and tumor proliferation monitoring. Contemporary experimental reports imply that abolition of senescent cells employing evolved genetic and therapeutic approaches augment the chances of survival and boosts the health span of an individual. Immunosenescence is considered as a process in which dysfunction of the immune system occurs with aging and greatly includes remodeling of lymphoid organs. This in turn causes fluctuations in the immune function of the elderly that has strict relation with the expansion of autoimmune diseases, infections, malignant tumors and neurodegenerative disorders. The interaction of the nervous and immune systems during aging is marked by bi-directional influence and mutual correlation of variations. The enhanced systemic inflammatory condition in the elderly, and the neuronal immune cell activity can be modulated by inflamm-aging and peripheral immunosenescence resulting in chronic low-grade inflammatory processes in the central Nervous system known as neuro-inflammaging. For example, glia excitation by cytokines and glia pro-inflammatory productions contribute significantly to memory injury as well as in acute systemic inflammation, which is associated with high levels of Tumor necrosis factor -α and a rise in cognitive decline. In recent years its role in the pathology of Alzheimer's disease has caught research interest to a large extent. This article reviews the connection concerning the immune and nervous systems and highlights how immunosenescence and inflamm-aging can affect neurodegenerative disorders.

Aging of the Immune System: Focus on Natural Killer Cells Phenotype and Functions

Aging is the greatest risk factor for nearly all major chronic diseases, including cardiovascular diseases, cancer, Alzheimer’s and other neurodegenerative diseases of aging. Age-related impairment of immune function (immunosenescence) is one important cause of age-related morbidity and mortality, which may extend beyond its role in infectious disease. One aspect of immunosenescence that has received less attention is age-related natural killer (NK) cell dysfunction, characterized by reduced cytokine secretion and decreased target cell cytotoxicity, accompanied by and despite an increase in NK cell numbers with age. Moreover, recent studies have revealed that NK cells are the central actors in the immunosurveillance of senescent cells, whose age-related accumulation is itself a probable contributor to the chronic sterile low-grade inflammation developed with aging (“inflammaging”). NK cell dysfunction is therefore implicated in the increasing burden of infection, malignancy, inflammatory disorders, and senescent cells with age. This review will focus on recent advances and open questions in understanding the interplay between systemic inflammation, senescence burden, and NK cell dysfunction in the context of aging. Understanding the factors driving and enforcing NK cell aging may potentially lead to therapies countering age-related diseases and underlying drivers of the biological aging process itself.

Interconnections between Inflammageing and Immunosenescence during Ageing

Acute inflammation is a physiological response to injury or infection, with a cascade of steps that ultimately lead to the recruitment of immune cells to clear invading pathogens and heal wounds. However, chronic inflammation arising from the continued presence of the initial trigger, or the dysfunction of signalling and/or effector pathways, is harmful to health. While successful ageing in older adults, including centenarians, is associated with low levels of inflammation, elevated inflammation increases the risk of poor health and death. Hence inflammation has been described as one of seven pillars of ageing. Age-associated sterile, chronic, and low-grade inflammation is commonly termed inflammageing-it is not simply a consequence of increasing chronological age, but is also a marker of biological ageing, multimorbidity, and mortality risk. While inflammageing was initially thought to be caused by "continuous antigenic load and stress", reports from the last two decades describe a much more complex phenomenon also involving cellular senescence and the ageing of the immune system. In this review, we explore some of the main sources and consequences of inflammageing in the context of immunosenescence and highlight potential interventions. In particular, we assess the contribution of cellular senescence to age-associated inflammation, identify patterns of pro- and anti-inflammatory markers characteristic of inflammageing, describe alterations in the ageing immune system that lead to elevated inflammation, and finally assess the ways that diet, exercise, and pharmacological interventions can reduce inflammageing and thus, improve later life health.

NK cells: A double edge sword against SARS-CoV-2

Natural killer (NK) cells are pivotal effectors of the innate immunity protecting an individual from microbes. They are the first line of defense against invading viruses, given their substantial ability to directly target infected cells without the need for specific antigen presentation. By establishing cellular networks with a variety of cell types such as dendritic cells, NK cells can also amplify and modulate antiviral adaptive immune responses. In this review, we will examine the role of NK cells in SARS-COV2 infections causing the ongoing COVID19 pandemic, keeping in mind the controversial role of NK cells specifically in viral respiratory infections and in inflammatory-driven lung damage. We discuss lessons learnt from previous coronavirus outbreaks in humans (caused by SARS-CoV-1 and MERS-COV).

Hepatic lipid metabolism and non-alcoholic fatty liver disease in aging

Aging is associated with dysregulation of glucose and lipid metabolism. Various factors that contribute to the dysregulation include both modifiable (e.g. obesity, insulin resistance) and non-modifiable risk factors (age-associated physiologic changes). Although there is no linear relationship between aging and prevalence of non-alcoholic fatty liver disease, current data strongly suggests that advanced age leads to more severe histological changes and poorer clinical outcomes. Hepatic lipid accumulation could lead to significant hepatic and systemic consequences including steatohepatitis, cirrhosis, impairment of systemic glucose metabolism and metabolic syndrome, thereby contributing to age-related diseases. Insulin, leptin and adiponectin are key regulators of the various physiologic processes that regulate hepatic lipid metabolism. Recent advances have expanded our understanding in this field, highlighting the role of novel mediators such as FGF 21, and mitochondria derived peptides. In this review, we will summarize the mediators of hepatic lipid metabolism and how they are altered in aging.

Synergistic anti-pancreatic cancer immunological effects by treatment with reduced expression in immortalized cells/dickkopf-3 protein and peripheral blood mononuclear cells

BACKGROUND AND AIM

Reduced expression in immortalized cells/dickkopf-3 (REIC/DKK3) is a reported tumor suppressor gene and has potential to become an innovative therapy for various cancers. We examined the antitumor immunological effects of human REIC/DKK3 protein against pancreatic cancer.

METHODS

Activation of extracellular signal-regulated kinases 1 and 2, mammalian target of rapamycin, and signal transducer and activator of transcription 3 by REIC/DKK3 protein was assessed in human peripheral blood mononuclear cells using immunoblotting. Pancreatic cancer cell lines (AsPC-1 and MIA Paca-2) were cocultured with peripheral blood mononuclear cells, and the anticancer effects of REIC/DKK3 protein were assessed using the methyl thiazole tetrazolium, cytotoxicity, and enzyme-linked immunospot assays. The antitumor immunological effects of the combined treatment with REIC/DKK3 protein and peripheral blood mononuclear cells were also assessed in a pancreatic cancer model using non-obese diabetic/severe combined immunodeficiency mice.

RESULTS

The REIC/DKK3 protein activated extracellular signal-regulated kinases 1 and 2, mammalian target of rapamycin, and signal transducer and activator of transcription 3 in peripheral blood mononuclear cells. REIC/DKK3 protein inhibited in vitro cancer cell viability and enhanced cytotoxicity when incubated with peripheral blood mononuclear cells. REIC/DKK3 protein induced significant production of interferon gamma from lymphocytes incubated with pancreatic cancer cells, indicating that CD8+ T cells were activated in the peripheral blood mononuclear cells when cocultured with AsPC-1 and MIA Paca-2 in the presence of REIC/DKK3 protein. Combined treatment with REIC/DKK3 protein and peripheral blood mononuclear cells produced in vivo anticancer immunostimulatory effects on pancreatic cancer cells.

CONCLUSIONS

The REIC/DKK3 protein and peripheral blood mononuclear cells synergistically enhanced anticancer immunological effects against pancreatic cancer cells. The observed immunomodulatory effect of combined treatment likely occurs in adenovirus-mediated REIC/DKK3 gene therapy and provides important clues to the therapeutic mechanisms involving immune cells.

Effects of yogurt containing Lactobacillus plantarum HOKKAIDO on immune function and stress markers

Lactobacillus plantarum HOKKAIDO (HOKKAIDO strain) was isolated from well-pickled vegetables in Hokkaido, Japan. We report a randomized, double-blind, placebo-controlled study evaluating the effects of L. plantarum HOKKAIDO on immune function and stress markers in 171 adult subjects. Subjects were divided into three groups: the L. plantarum HOKKAIDO yogurt group, the placebo-1 group who ingested yogurt without the HOKKAIDO strain, and the placebo-2 group who ingested a yogurt-like dessert without the HOKKAIDO strain. Hematological tests and body composition measurements were performed before and after 4 and 8 weeks of blinded ingestion. Although no significant differences in natural killer cell activity were observed, it was found that neutrophil ratio significantly decreased and lymphocytes tended to increase in the HOKKAIDO strain yogurt group compared with the yogurt-like dessert group. In addition, the neutrophil-to-lymphocyte ratio, a stress marker, tended to improve in the HOKKAIDO strain yogurt group compared with the yogurt-like dessert group. These results suggest that the ingestion of HOKKAIDO strain yogurt tends to improve immune activity and decrease stress markers.

Age-related increase of VGF-expression in T lymphocytes

VGF is a protein expressed by neurons and processed into several peptides. It plays a role in energy homeostasis and promotes growth and survival. Recently, VGF mRNA was detected in peripheral leukocytes. Since it is known that aging is associated with a decrease in the development and function of neuronal as well as immune cells, we addressed the question whether a peripheral expression of VGF by CD3+ T cells and CD56+ NK cells is correlated with age. Therefore, the frequency of VGF+CD3+ and VGF+CD56+ cells was determined in mentally healthy volunteers aged between 22 and 88. We found an age-dependent increase in the number of VGF+CD3+ T cells that correlated with HbA1c and the body mass index (BMI). VGF-expression by NK cells was age-independent. Blockade of VGF reduced proliferation and secretion of cytokines such as IL-2, IL-17A, IL-1β, IL-10 and TNF by CD3+ T cells and PBMCs. Rapamycin-mediated T cell blockade significantly reduced the frequency of VGF-expressing T cells. We conclude that VGF contributes to survival and function of peripheral T cells. The age-dependent increase in VGF-expression could serve as mechanism that counterregulates the decrease in functionality of T lymphocytes.

Natural killer cell development and maturation in aged mice

The effect of aging on natural killer cell homeostasis is not well studied in humans or in animal models. We compared natural killer (NK) cells from young and aged mice to investigate age-related defects in NK cell distribution and development. Our findings indicate aged mice have reduced NK cells in most peripheral tissues, but not in bone marrow. Reduction of NK cells in periphery was attributed to a reduction of the most mature CD11b(+) CD27(-) NK cells. Apoptosis was not found to explain this specific reduction of mature NK cells. Analysis of NK cell development in bone marrow revealed that aged NK cells progress normally through early stages of development, but a smaller percentage of aged NK cells achieved terminal maturation. Less mature NK cells in aged bone marrow correlated with reduced proliferation of immature NK cells. We propose that advanced age impairs bone marrow maturation of NK cells, possibly affecting homeostasis of NK cells in peripheral tissues. These alterations in NK cell maturational status have critical consequences for NK cell function in advanced age: reduction of the mature circulating NK cells in peripheral tissues of aged mice affects their overall capacity to patrol and eliminate cancerous and viral infected cells.

Does aging affect the immune status? A comparative analysis in 300 healthy volunteers from France, Austria and Spain

Background

As the European population is getting older, there is growing need in scientific data on how to achieve healthy and successful aging. A decline in immune function with age is unanimously supported by many epidemiological and clinical observations, with a decrease in T-cell mediated function encompassing a large part of this alteration. In the EU-funded VITAGE project, the effects of aging on biomarkers of immune status are being studied in three European countries. According to strict inclusion/exclusion criteria, a cohort of 300 healthy male non-smoking 20–75 years old volunteers were enrolled in France (n = 99), Spain (n = 100) and Austria (n = 101). In each country, the volunteers were classified as a function of age (one age group per decade). Biomarkers of immune status were determined including delayed-type hypersensitivity tests, measurement of lymphocyte surface markers, and serum determinations of interleukin-2, complement fractions and immunoglobulins.

Results

There were moderate differences in the biomarkers of immune status of the VITAGE study volunteers among the three European centres. The percentage of Natural Killer (NK) cells was 156% and 142% higher in Spain as compared to France and Austria, respectively (p < 0.0001), and this increase was observed at any age group above 30 years. Comparison between age-groups showed that in Spain, but not in France or Austria, older individuals had significantly a lower B lymphocyte distribution and conversely, a higher NK cell distribution. Moreover, the CD4/CD8 ratio was positively correlated with age in Austrian subjects (p < 0.0001).

Conclusion

Our results provide evidence of an increased NK cell distribution in the elderly, especially in the Spanish population. NK cell status may predict morbidity and mortality in the elderly, emphasizing the importance of innate as well as adaptive immunity in ensuring healthy longevity and cancer resistance, possibly in link with the Mediterranean diet.

The impact of ageing on natural killer cell function and potential consequences for health in older adults

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Roles are emerging for natural killer (NK) cells beyond removing transformed cells.

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These include immune regulation and the elimination of senescent cells.

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Human ageing is associated with a decline in NK cell function.

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We propose some aspects of human ageing are due in part to reduced NK cell function.

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These include reduced vaccination efficacy and delayed resolution of inflammation.

Forming the first line of defence against virally infected and malignant cells, natural killer (NK) cells are critical effector cells of the innate immune system. With age, significant impairments have been reported in the two main mechanisms by which NK cells confer host protection: direct cytotoxicity and the secretion of immunoregulatory cytokines and chemokines. In elderly subjects, decreased NK cell activity has been shown to be associated with an increased incidence and severity of viral infection, highlighting the clinical implications that age-associated changes in NK cell biology have on the health of older adults. However, is an increased susceptibility to viral infection the only consequence of these age-related changes in NK cell function? Recently, evidence has emerged that has shown that in addition to eliminating transformed cells, NK cells are involved in many other biological processes such as immune regulation, anti-microbial immune responses and the recognition and elimination of senescent cells, novel functions that involve NK-mediated cytotoxicity and/or cytokine production. Thus, the decrease in NK cell function that accompanies physiological ageing is likely to have wider implications for the health of older adults than originally thought. Here, we give a detailed description of the changes in NK cell biology that accompany human ageing and propose that certain features of the ageing process such as: (i) the increased reactivation rates of latent Mycobacterium tuberculosis, (ii) the slower resolution of inflammatory responses and (iii) the increased incidence of bacterial and fungal infection are attributable in part to an age-associated decline in NK cell function.

Immunosenescence and age-related viral diseases

Immunosenescence is described as a decline in the normal functioning of the immune system associated with physiologic ageing. Immunosenescence contributes to reduced efficacy to vaccination and increased susceptibility to infectious diseases in the elderly. Extensive studies of laboratory animal models of ageing or donor lymphocyte analysis have identified changes in immunity caused by the ageing process. Most of these studies have identified phenotypic and functional changes in innate and adaptive immunity. However, it is unclear which of these defects are critical for impaired immune defense against infection. This review describes the changes that occur in innate and adaptive immunity with ageing and some age-related viral diseases where defects in a key component of immunity contribute to the high mortality rate in mouse models of ageing.

Improving immunogenicity and effectiveness of influenza vaccine in older adults

Aging is associated with a decline in immune function (immunosenescence) that leads to progressive deterioration in both innate and adaptive immune functions. These changes contribute to the subsequent increased risk for infectious diseases and their sequelae. Vaccination is the most effective and inexpensive public health strategy for prevention of infection, despite the decreased efficacy of vaccines in older adults due to immunosenescence. The rapid rise in the older adult population globally represents a great challenge for vaccination programs. This article first addresses the status of innate and adaptive immune functions in aging and then focuses on influenza vaccine. The development history of influenza vaccines, current status, and potential strategies to improve the immunogenicity and vaccine effectiveness in older adults are discussed.

Age-related changes in natural killer cell receptors from childhood through old age

Most studies on natural killer (NK) cells and aging have focused on overall cell numbers and global cytotoxic activity. NK cell functions are controlled by surface receptors belonging to three major families: killer cell immunoglobulin-like receptors (KIRs), natural cytotoxicity receptors (NCRs), and C-type lectins. The expression of these receptors was investigated from childhood through old age in T, NKT- and NK cells and also in the CD56(dim) (cytotoxic) and CD56(bright) (responsible for cytokine production) NK cell subsets. A decrease in the expression of activating receptors (NKp30 and NKp46) was observed in NK cells in elderly individuals. KIR expression was increased only in the CD56(bright) subset. Children presented similar results regarding expression of NKp30 and KIR, but not NKp46. NKG2D expression was decreased in T cells of elderly subjects. Analysis of KIR genotype revealed that KIR2DL5 and KIR2DS3 were significantly associated with old age. Cytotoxic activity was preserved from childhood through old age, suggesting that the increase of the absolute number of CD56(dim), observed in elderly, may represent a compensatory mechanism for the receptor expression alterations. This initial study provides the framework for more focused studies of this subject, which are necessary to determine whether the changing balance of NK receptor expression may influence susceptibility to infectious, inflammatory, and neoplastic diseases.

Human innate immunosenescence: causes and consequences for immunity in old age

The past decade has seen an explosion in research focusing on innate immunity. Through a wide range of mechanisms including phagocytosis, intracellular killing and activation of proinflammatory or antiviral cytokine production, the cells of the innate immune system initiate and support adaptive immunity. The effects of aging on innate immune responses remain incompletely understood, particularly in humans. Here we review advances in the study of human immunosenescence in the diverse cells of the innate immune system, including neutrophils, monocytes, macrophages, natural killer and natural killer T (NKT) cells and dendritic cells-with a focus on consequences for the response to infection or vaccination in old age.

Pathophysiology of ageing, longevity and age related diseases

On April 18, 2007 an international meeting on Pathophysiology of Ageing, Longevity and Age-Related Diseases was held in Palermo, Italy. Several interesting topics on Cancer, Immunosenescence, Age-related inflammatory diseases and longevity were discussed. In this report we summarize the most important issues. However, ageing must be considered an unavoidable end point of the life history of each individual, nevertheless the increasing knowledge on ageing mechanisms, allows envisaging many different strategies to cope with, and delay it. So, a better understanding of pathophysiology of ageing and age-related disease is essential for giving everybody a reasonable chance for living a long and enjoyable final part of the life.

Establishment of a microplate assay for flow cytometric assessment and it is use for the evaluation of age-related phenotypic changes in canine whole blood leukocytes

The effectiveness of flow cytometric assays for canine use is still requiring standardization. Despite several studies using purified mononuclear cells, no methodology or reference ranges are available for immunophenotyping of whole blood leukocytes (WBL). Fresh and pre-fixed WBL were used to identify cell-subsets, (Thy-1(+)/CD5(+)/CD4(+)/CD8(+)/CD21(+) and CD14(+)) and measure MHC-II, CD45RA/CD45RB expression. We described here an efficient method for fast quantification of canine-WBL, using pre-fix in a microplate assay, which allows long-term sample storage prior to phenotyping. Decreased percentage of CD5(+)-T-cells within the lymphocyte-gate and increased percentage of CD21(+)-B-cells were observed in young animals, which led to higher T/B cell ratios in middle-aged dogs. Lower numerical counts of Thy-1(+), CD4(+), CD8(+) and CD21(+) lymphocyte were observed when compared to young animals. In addition, we identified an age-related decline of MHC-II/CD45RA expression by lymphocytes. We proposed an improved method for phenotyping of canine peripheral blood mononuclear cells (PBMC) that has significant use for researchers and veterinary clinicians. The hematological changes of senescence previously identified on PBMC could be adequately reproduced on features identified by whole blood. Furthermore, this study supplies normal range references as baseline standards for clinical purposes, besides specific immunological parameters to monitor canine aging process.

Effect of a traditional Japanese herbal medicine, hochu-ekki-to (Bu-Zhong-Yi-Qi Tang), on immunity in elderly persons

In general, the elderly show a significant age-related decline in their immune response, thus leading to an increased vulnerability to infections or to an increase in the occurrence of malignant tumors. In this study, we examined the effect of Hochu-ekki-to (HOT or TJ-41) on the immunological capacity of the elderly. A group of elderly patients complaining of general fatigue or weakness were orally administered 7.5 g of HOT everyday for at least 120 days (4 months), whereas another group of aged patients mainly complaining of a loss of appetite were daily given 7.5 g of Anchu-san (TJ-5) during the same period and served as a control group. From the immunological point of view, the total number of circulating leukocytes remained unchanged, during the observation period both in the HOT and Anchu-san groups, as well as the ratios between CD3(+) T and CD20(+) B cells and between CD4(+) T and CD8(+) T cells. In addition, no differences were observed in the expression of CD25 antigen, which represents an activated state of T cells. However, as verified on day 30 as well as on day 120 after the administration of HOT, the natural killer (NK) activity against K562 target cells was significantly enhanced, in comparison to the results on day 0 in the HOT group, as well as to that activity on days 0, 30 and 120 in the Anchu-san group. In addition, on days 30 and 120 in the HOT group, there was a significant increase in the serum IFN-gamma level, which is thought to be associated with the NK activity, whereas no significant changes in that level were observed in the Anchu-san group, during the study period. From these results, it may be concluded that the administration of HOT to elderly people may help them improve, at least to some degree, their immunological capacity.

Aging and innate immune cells

The innate immune system serves an important role in preventing microbial invasion. However, it experiences significant changes with advancing age. Among the age-associated changes are: Aged macrophages and neutrophils have impaired respiratory burst and reactive nitrogen intermediates as a result of altered intracellular signaling, rendering them less able to destroy bacteria. Aged neutrophils are also less able to respond to rescue from apoptosis. Aged dendritic cells (DC) are less able to stimulate T and B cells. The altered T cell stimulation is a result of changes in human leukocyte antigen expression and cytokine production, and lower B cell stimulation is a result of changes in DC immune complex binding. Natural killer (NK) cells from the elderly are less capable of destroying tumor cells. NK T cells increase in number and have greater interleukin-4 production with age. Levels of various complement components are also altered with advancing age.

The influence of age and gender on the immune system: a longitudinal study in Labrador Retriever dogs

While aging studies employing a cross-sectional design have been informative in documenting many age-related alterations in immune function between different age cohorts within a population, longitudinal studies are invaluable for verifying changes at the level of the individual and for defining the precise periods of life during which particular changes occur. In the present study, a battery of immunological parameters were evaluated in a group of Labrador Retrievers as part of a comprehensive longitudinal aging study. Twenty-three dogs (14 females, 9 males; from 4 to 11 years of age) were evaluated annually for total WBC counts, lymphocyte subset distributions, natural killer cell activity and neutrophil phagocytic activity, and biannually for lymphoproliferative activity. An age-related decline in absolute numbers of lymphocytes, T-cells, CD4-cells and CD8-cells was observed in both genders. The distribution of lymphocyte subsets shifted with age, most dramatically in the females; percentages of B-cells declined while those of T-cells increased. Changes in percentages of CD4- and CD8-cells over the 8-year period were not dramatic; in females, percentages of CD8-cells increased significantly in early- to mid-life and then stabilized. Lymphoproliferative responses to mitogens declined over time in both genders. Males demonstrated higher levels of NK cytolytic activity than females; a marginal decline in activity with age was observed. No significant age-related changes in the phagocytic capacity of PMN were observed. These longitudinal findings help to discriminate between those immune parameters which change most dramatically in early-life versus those which either change more dramatically later in life or change gradually over the entire span of life. In addition they identify significant gender differences in several parameters and corroborate our previously published cross-sectional aging data in the same species.

Effects of housing relocation on immunocompetence and psychosocial functioning in older adults

BACKGROUND

The psychological and physical response to moderate life stressors among older adults has not been well characterized. This research examines effects of voluntary housing relocation on distress and immune function in healthy older adults as a model for studying the effects of moderate life stress.

METHODS

Thirty older adults moving to congregate living facilities were assessed 1 month premove, 2 weeks postmove, and 3 months postmove. Twenty-eight nonmoving control subjects were assessed at similar time points. Subjects completed psychosocial questionnaires and had early morning blood draws in their homes. Blood samples were assayed for natural killer cell cytotoxicity (NKCC), interleukin-6 (IL-6), and IgG antibody titers to the Epstein Barr virus (EBV) viral capsid antigen.

RESULTS

Movers demonstrated decreased vigor and elevated thought intrusion 1 month premove and 2 weeks postmove. By the 3-month follow-up, vigor increased, and intrusion decreased to levels commensurate with the controls. Averaged across all time points, movers showed lower NKCC than controls; however, post-hoc analyses indicate that by the 3-month follow-up time point, these differences were no longer significant. There were no differences between groups in IL-6 or in EBV antibody titers. Independent of the effects of group, higher levels of vigor were associated with greater NKCC at all assessments and with lower EBV titers at 2 weeks postmove.

CONCLUSIONS

Findings suggest that in general, healthy older adults recover well psychologically from moderate. temporary life stressors such as moving. Whereas movers showed generally lower NKCC than controls, IL-6 and EBV antibody titers appeared not to be strongly affected by the stress of moving.

NK and NK/T cells in human senescence

Natural killer (NK) cells are cytotoxic cells that play a critical role in the innate immune response against infections and tumors. Recent studies on NK cell biology have demonstrated that besides their cytotoxic function, NK cells express cytokine and chemokine receptors and also that they secrete other immunoregulatory cytokines and chemokines, supporting their relevance in the regulation of the immune response by promoting downstream adaptive, Th1 mediated, responses against infections. Immunosenescence is the deterioration of the immune response associated with aging. It is characterized mainly by a defective T cell response, but includes changes in the number and function of other cells of the innate immune system. Age-associated alterations in the number and function of NK cells have been reported. There is a general consensus that a progressive increase in the percentage of NK cells with a mature phenotype occurs in elderly donors associated with an impairment of their cytotoxic capacity when considered on a "per cell" basis. The response of NK cells from elderly individuals to IL-2 or other cytokines is also decreased in terms of proliferation, expression of CD69 and killing of NK-resistant cell lines. Furthermore early IFN-gamma and chemokine production in response to IL-2 or IL-12 is also decreased. However aging does not significantly alter other NK cell functions such as TNF-alpha production or perforin induction in response to IL-2. The percentage of T cells that co-express NK cell markers is also increased in aging. These results indicate that the increase in the number of "classical" mature NK and NK/T cells in aging is associated with a defective functional capacity of NK cells. Low NK cell number or function in elderly individuals is associated with increased mortality risk and increased incidence of severe infections, supporting the role of NK cells in the defense against infections in the elderly.

Immune function did not decline with aging in apparently healthy, well-nourished women

Nutrition plays a crucial role in immune function. Most studies on age-associated changes in immunocompetence in healthy adults did not examine the nutritional status of participants extensively. Inadequate nutritional status may confound the relationship of aging and immune response. The purpose of this study was to examine age-related changes in parameters of acquired and innate immunity in healthy and generally well-nourished older (62-88 years) versus younger (20-40 years) women. Subjects were screened for participation using the health criteria of the SENIEUR protocol as well as a number of nutrition criteria related to undernutrition, and protein, iron, vitamin B12, and folate status. Young and old women did not differ in total T (CD3+), T-helper (CD4+), or T-cytotoxic (CD8+) cell number. However, older women tended to have lower T-cell proliferation response to concanavalin A (P < 0.10) and significantly reduced response to phytohemagglutinin (P < 0.05). No age-related changes were noted in natural killer cell number or cytotoxicity. Phagocytosis and subsequent oxidative burst activity also did not differ between young and old women. Most immune parameters were not compromised with aging in this cohort of apparently healthy, well-nourished women. These findings highlight the importance of simultaneous examination of health and nutritional status in studies of immune function with aging.

Natural killer cells in healthy aging

Immunosenescence is a process that affects all cell compartments of the immune system. Age-associated changes have been demonstrated not only on T lymphocytes but also in different aspects of the innate immunity including natural killer (NK) cells. A significant expansion in the percentage of NK cells showing a mature phenotype has been found in healthy elderly donors, and the NK-cytotoxic capacity of total peripheral blood lymphocytes is well preserved in these individuals. However, NK-cell killing of K562 is impaired when considered on a per-cell basis. Furthermore, NK cells from elderly people show a decreased proliferative response to interleukin 2 and a parallel impaired expression of the CD69 activation antigen. The response to interleukin 2 of NK cells from aged donors is also impaired in terms of their capacity to kill NK-resistant cell lines, but not when K562 killing, perforin synthesis, or tumor necrosis factor alpha production are considered. Therefore phenotypic and functional alterations can be shown in NK cells in healthy aging. These changes are compatible with the expansion of a mature NK subset.

Effects of 6 months of moderate aerobic exercise training on immune function in the elderly

The purpose of this study was to determine the effects of 6 months of moderate aerobic exercise on age-dysregulated measures of T lymphocyte and natural killer (NK) cell number and function. Previously sedentary elderly (age = 65 +/- 0.8 years) subjects were randomly assigned to supervised 3 time/week exercise intervention group (EXC, n = 14) or flexibility/toning control group (FT-CON, n = 15). Fasting resting blood samples were drawn prior to and after the 6 month intervention. The EXC group exhibited a significant (P < 0.05) 20% increase in VO2 max, whereas the FT-CON group had a smaller non-significant (P = 0.07) increase (9%). Immune results revealed that, in general, changes in immune function in response to 6 months of exercise training at an average intensity of 52% heart rate reserve (HRR) were similar when compared to FT-CON who exercised at approximately 21% HRR. There were no intervention-induced changes in total white blood cell, neutrophil, lymphocyte, monocyte, eosinophil, or basophil blood counts. Furthermore, the percentage and number of CD3+, CD4+ and CD8+ T cells in the blood remained unchanged. There was a tendency for the percentage and number of CD4+ and CD8+ näive cells (CD45RA+) to increase and for CD4+ memory cells (CD45RO+) to decrease post-intervention, especially in FT-CON. Both groups exhibited a small intervention-induced increase in the T-cell proliferative response to mitogenic stimulation: the percentage change of which was higher in the EXC group at several doses of Con A. Unstimulated NK cell cytolysis versus K562 cells tended to increase (P < 0.1) in the EXC group with little change in FT-CON. We conclude that 6 months of supervised exercise training can lead to nominal increases in some measures of immune function, while not affecting others, in previously sedentary elderly.

Vitamin D, thyroid hormones and muscle mass influence natural killer (NK) innate immunity in healthy nonagenarians and centenarians

Increasing evidence has demonstrated that the immune system closely interacts with other physiological systems, whose communications are mediated by circulating cytokines and hormones. The aim of our study was to test whether the number and cytolytic activity of NK cells in a group of relatively healthy Italian nonagenarians and centenarians were affected by the modifications of endocrine, metabolic and functional parameters that occur during ageing. Because of the extreme age of the study population, a cross-sectional analysis was performed. This study revealed that the group of oldest subjects with the highest number of NK cells and the best preserved cytolytic function also presented a preserved metabolism of thyroid hormones and vitamin D and integrity of muscle mass. In fact, the NK cell number and/or cytolytic activity of healthy subjects > 90 years old was positively associated with serum levels of vitamin D, while T3, FT4, i-PTH hormones and lean body mass were associated only with NK cell number. In conclusion, our results stress the paramount importance of nutritional evaluation in the clinical assessment of elderly people.

NK phenotypic markers and IL2 response in NK cells from elderly people

Immunosenescence is a process that primarily affects the T cell compartment of the immune system, although age-associated immunological alterations have also been demonstrated in the NK cell phenotype and function. A significant expansion in the number of NK cells is found in aging. The NK cytotoxic capacity of total peripheral blood lymphocytes is also well preserved, not only in healthy elderly people but also in centenarians. However, NK cell killing of K562 is impaired when considered in a per-cell basis, and this defect is associated with defective signal transduction after activation more than a diminished conjugate formation or killing capacity. We have studied the phenotype of NK cells in elderly donors fulfilling the Senieur criteria. We have also studied the capacity of these cells to be activated by IL2 when different NK cell functions, other than cytotoxicity, are considered. Our results confirm the increased percentage of NK cells in the elderly due to the expansion of the CD56dim subset that also show an altered pattern of activation markers, whereas no differences were found in the CD56bright subset. The response of NK cells to IL2 was found to be impaired when proliferation, expression of CD69, and Ca2+ mobilization were considered, whereas TNF-alpha production was not significantly affected. These results suggest that human NK cells do not escape the aging process, although senescence have a differential effect on distinct NK cell biological functions, ranging from severe to negligible impairment, depending on the parameters considered.

Granulocyte and natural killer activity in the elderly

The deterioration of the immune system in ageing, 'immunosenescence', is thought to contribute to increased morbidity and mortality from infections and possibly autoimmune diseases and cancer. The most profound changes involve effector and immunoregulatory T-cell functions. Immunosenescence appears also to be related to changes in non specific immunity as well. In the present study we have assessed superoxide production, chemotaxis and the expression of the apoptosis-related molecule APO1/Fas (CD95) on neutrophils (PMN) from young and old subjects. Furthermore, we have measured the basal natural killer (NK) activity of young and elderly subjects and we have compared the number of CD16+ cells found in these two groups. We observed a significant decrease age-related both of formation of O2- and chemotaxis whereas no significant correlation between age and the expression of CD95 on granulocyte membrane was demonstrated, suggesting that an increase age-related of CD95-linked apoptosis of PMN should be not an important determinant in the decreased PMN function. We also observed a significant correlation between age and NK activity. The decreased NK cell function was not due to a decreased number of NK cells in effector cell preparations since the number of CD16+ cells was significantly increased in old subjects. In conclusion, our results show that in the elderly there is also a deficit of the aspecific immunity that might play a role in the pathogenic mechanisms of the immunosenescence.

Natural immunity and bone and muscle remodelling hormones in the elderly

Increasing evidence has demonstrated that the immune system is closely integrated with two other physiological systems: endocrine and nervous. They communicate through circulating humoral factors such as cytokines, hormones and neurotransmitters. We undertook a cross-sectional analysis in a group of elderly subjects over 90 years to demonstrate that a functional relationship exists among the number and cytolytic activities of NK cells, bone and muscle remodelling hormones, anthropometric parameters and physical ability. Peripheral blood samples collected from 62, 90-106 years-old subjects underwent biochemical (bone and muscle remodelling hormone levels) and immunological determinations (Natural Killer cell distribution and activity), anthropometric and functional assessment. Significant associations were found among NK cell number and cytolytic activity and serum concentrations of vitamin D, anthropometric parameters, while functional independence in daily activity was only associated with NK cell number. In general a high level of physical ability was correlated with preserved body stores and vitamin D levels. In conclusion, our results stress the importance of nutritional evaluation in the clinical assessment of elderly people. The magnitude of the NK immune response, which constitutes the first line of defence against infected and neoplastic cells, is best preserved in oldest-old people with the best hormonal parameters and nutritional measures.

Natural killer cells in the late decades of human life

We examined the lymphocyte subsets and indices of natural killer (NK) cell activity (lytic unit (LU), index of absolute NK cell activity in vivo (ALU), and NK cell activity on a per-cell basis (PCNK)) in 82 people (age, 30-99 years) who were immunologically normal. Although the number of NK cells was maintained throughout the examined age range, the ALU and PCNK values correlated negatively with age. We then examined whether any of the various immunologic parameters, including the function and cell counts of NK cells, T cells, and neutrophils, related to past infectious episodes and death in the follow-up period in 44 elderly subjects (age, 63-98 years). Only low ALU and PCNK values correlated with a past history of severe infection, while low LU, ALU, and PCNK values were the only parameters which correlated with death due to infection during the follow-up period. We propose that human NK cells do not escape the aging process and that a low NK cell function relates to the development of severe infections, which may be fatal, in elderly subjects.

Altered thymic endocrine activity along with impairments of peripheral zinc metabolism and T-lymphocyte populations are associated with myasthenia gravis: a follow-up study

Thymic endocrine activity was assessed by a bioassay to determine the basal activity of thymulin (TH), a zinc dependent hormone, and its in vitro reactivation in two different age groups of patients with myasthenia gravis (MG). Before thymectomy, basal TH plasma levels were increased in patients over the age of 50 years. Plasma zinc levels were increased in all patients, this increment being very high in old patients. One year after thymectomy both TH and zinc plasma levels decreased. While zinc plasma levels were within the normal ranges for their respective ages, TH levels were lower in young and higher in old patients than in age comparable controls. Young patients with MG showed increased CD3,DR positive peripheral T-cells as well as lymphocytes with the CD16,CD56 phenotype. An increment of CD3 positive cells along with CD4 and CD16,CD56 positive cells were found in older patients. Thymectomy partially affected blood lymphocyte representation only in young patients, since CD3,DR T-cells decreased one year after surgery. No significant variations in T-cell representation were found in old patients after thymectomy. Immunosuppression in thymectomized patients did not significantly affected TH and zinc plasma levels. Very high levels of TH and the presence of additional alterations in T-lymphocyte subsets in old patients suggested that differential age related pathogenetic immunological mechanisms might be associated with the disease.

Influence of aging and chemoradiotherapy on leucocyte function in oral cancer patients

Leucocyte functions and the influence of chemoradiotherapy were examined in three age groups of patients with oral cancer. The groups consisted of 66 patients below 65 years old (group A): 40 patients between 65 and 80 years old (group B); 20 patients over 80 years old (group C). 20 healthy individuals (45.8 +/- 9.6 years old) were chosen as controls. Originally, no significant differences in leucocyte count, CD3 population, CD4/CD8 ratio, natural killer activity or phagocytosis of polymorphonuclear leucocytes (PMNL) were found in the patients. However, T cell blastogenesis, lymphokine-activated killer cell activity and superoxide production of PMNL were all suppressed. These functions were further suppressed by cancer therapy, the greatest suppression being seen in group C. Compared to controls and group A, the generation of interleukin-1, interleukin-6, tumour necrosis factor-alpha and granulocyte-macrophage colony-stimulating factor were markedly suppressed in group C. These results show that very old cancer patients are already in an immunologically suppressed condition and that the leucocyte functions of these patients are further impaired by cancer therapy.

Distribution and lytic activity of NK cell subsets in the elderly

Old subjects present an increased number of NK cells associated with a decreased lytic activity of isolated and cloned CD16 cells. Recently, two new surface molecules of 58 kDa, identified by the monoclonal antibodies GL183 and EB6, have been described. The presence of these molecules, which can be coexpressed on CD16+ cells allows the recognition of the NK cell subsets whose cytolytic activity is restricted to different allospecificities. This study investigated a group of old subjects to determine whether a particular distribution or a different lytic activity of NK subsets, defined by MoAbs GL183 and EB6, is involved in the altered cytolytic activity found during ageing. Further, we investigated whether the ageing process might be responsible for a restriction of the NK cell repertoire involved in the recognition of allogenic cells. We found that old and young subjects have a similar proportion of double positive and double negative GL183/EB6 cells, while in the old group single positive subsets were increased. The lytic activity of sorted NK subsets isolated from old and young subjects was similar, although double positive and double negative cells from the old presented a lower cytotoxic activity. The addition of IFN-beta or rIL-2 to the culture medium restored the lytic activity to the level found in young subjects. These data show that the decreased NK lytic activity found in the old subjects is shared out among the different NK subsets and normal aged subjects do not lose the NK repertoire found in the young.