Association between natural killer cell activity and infection in immunologically normal elderly people

[Immunological markers of ageing]

Ageing is a process involving morphological and physiological modifications that gradually appear with time and lead to death. Given the heterogeneous nature of the process among individuals and among the different organs, tissues, and systems in the same individual, the concept of <<biological age>> has been developed. The search for parameters that enable us to evaluate biological age--and therefore longevity--and the analysis of the efficacy of strategies to retard the ageing process are the objectives of gerontology. At present, one of the most important theories of ageing is the <<oxidative-inflammatory>> theory. Given that immune cell function is an excellent marker of health, we review the concepts that enable different functional and oxidative stress parameters in immune cells to be identified as markers of biological age and longevity. None of these parameters is universally accepted as a biomarker of ageing, although they are becoming increasingly important.

Immunological biomarkers of ageing in man: changes in both innate and adaptive immunity are associated with health and longevity

Scientific and clinical advances in the last century have led to increased numbers of individuals living to older ages. Thus a major concern is how to live these years with a high quality of life. The ageing immune system is less well able to cope with infectious diseases than the youthful immune system probably as a consequence of altered immune response to pathogens. Thus, both innate and adaptive immune responses show age-related changes that could be decisive for healthy ageing and survival. Longitudinal studies in healthy elderly have allowed the definition of the ''immune risk phenotype" (IRP) a predictor of mortality in elderly individuals that is based on several parameters of the adaptive immune response. Here, we hypothesize that failures in innate immunity observed in frail elderly are related to those alterations described in adaptive immunity defined as the IRP. It will be important to include assays of NK cell markers and functions in future longitudinal studies in order to investigate this point in detail as well as to consider the trace element zinc as an essential co-factor for optimal NK cell activity.

Psychosocial and biochemical interactions in aging: preliminary results from an Italian old sample of "Zincage" project

The study of the interactions among biological factors and psychosocial conditions is a very innovative field, because data are lacking in the scientific literature. Among biological aspects, zinc is an essential element in the elderly, especially in relation to one of the proteins, such as albumin, involved in zinc transport into the cells. In this study, the aim is the assessment of the interrelationship between albumin value (used as an index of the body zinc status) and some psychosocial dimensions in elderly Italian sample recruited for ZINCAGE project, supported by the European Commission in the "Sixth Framework Programme". Some tests and questionnaires were administered to older people included in the trial: the "life-style questionnaire"; the mini mental state examination (MMSE); the geriatric depression scale (GDS-15 items). On the basis of the Senieur Protocol for gerontological studies, a sample of 291 Italian healthy old subjects has been recruited in Central Italy and divided into 3 age groups: (a) 125 subjects aged from 65 to 74 years, (b) 89 subjects aged from 75 to 84 years, (c) 77 subjects aged >or=85 years (classified like successful old people). No cognitive impairment assessed by MMSE was observed in 67.5% of the sample; 64.0% had GDS score less than 5, indicating no depression, whereas the prevalence of biological albumin deficiency (<3.5 g/dl) found in Italian old people was 21.0%. Sixty one percent of subjects with albumin deficiency displayed higher values of GDS (>or=5). These preliminary results showed an interrelationship among serum albumin value and psychosocial aspects in Italian old population, suggesting that low albumin values may be involved in impaired psychological dimensions.

NK cell compartment in patients with coronary heart disease

Background

Viral and bacterial infections have been considered as a risk factor for Coronary Heart Disease (CHD). NK cells, as a first line of defense against those infections, may play a role in CHD development. Thus, the main aim of our study was to determine NK cell compartment in patients with CHD undergoing coronary artery by-pass grafting.

Results

Ninety three patients with CHD were included into the study; the control group consisted of 49 healthy volunteers. As compared to controls, CHD patients had lower NK cytotoxic activity. CHD group had also a decreased absolute number and percentage of total NK cells and CD3-CD56dim cytotoxic NK subset. In addition, we observed tendency toward lower percentage of the CD3-CD56bright regulatory NK subset and CD3-CD56+IFN-γ+ cells in CHD patients.

Conclusion

These data indicate that CHD is associated with an impairment of NK cells compartment.

Stress and exercise: Getting the balance right for aging immunity

Age-related immunological and endocrinological changes may have implications for resilience to stress in older adults. We hypothesize that the combination of adrenopause and immunosenescence may leave this population particularly vulnerable to the negative effects of stress on immunity. We propose that exercise may be an effective intervention to limit the impact of stress on immunity in chronically stressed older populations.

Markers to measure immunomodulation in human nutrition intervention studies

Normal functioning of the immune system is crucial to the health of man, and diet is one of the major exogenous factors modulating individual immunocompetence. Recently, nutrition research has focused on the role of foods or specific food components in enhancing immune system responsiveness to challenges and thereby improving health and reducing disease risks. Assessing diet-induced changes of immune function, however, requires a thorough methodological approach targeting a large spectrum of immune system parameters. Currently, no single marker is available to predict the outcome of a dietary intervention on the resistance to infection or to other immune system-related diseases. The present review summarises the immune function assays commonly used as markers in human intervention studies and evaluates their biological relevance (e.g. known correlation with clinically relevant endpoints), sensitivity (e.g. within- and between-subject variation), and practical feasibility. Based on these criteria markers were classified into three categories with high, medium or low suitability. Vaccine-specific serum antibody production, delayed-type hypersensitivity response, vaccine-specific or total secretory IgA in saliva and the response to attenuated pathogens, were classified as markers with high suitability. Markers with medium suitability include natural killer cell cytotoxicity, oxidative burst of phagocytes, lymphocyte proliferation and the cytokine pattern produced by activated immune cells. Since no single marker allows conclusions to be drawn about the modulation of the whole immune system, except for the clinical outcome of infection itself, combining markers with high and medium suitability is currently the best approach to measure immunomodulation in human nutrition intervention studies. It would be valuable to include several immune markers in addition to clinical outcome in future clinical trials in this area, as there is too little evidence that correlates markers with global health improvement.

Immunological parameters: what do they mean?

The immune system acts to protect the host from infectious agents that exist in the environment and from other noxious insults. It is constantly active, acting to discriminate "nonself" from "self." The immune system has 2 functional divisions: the innate and the acquired. Both involve various blood-borne factors and cells. A number of methodologies exist to assess aspects of immune function; many of these rely on studying cells in culture ex vivo. There are large interindividual variations in many immune functions even among the healthy. Many factors, including genetics, gender, age, nutrient status, and gut flora, contribute to the observed variation. Individuals with immune responses significantly below "normal" are more susceptible to infectious agents and exhibit increased infectious morbidity and mortality. However, it is not clear how the variation in immune function among healthy individuals relates to variation in susceptibility to infection.

Attachment security and immunity in healthy women

BACKGROUND

Attachment security is associated with health and possibly autonomic and endocrine reactivity to stress, however the relationship between attachment style and immune function has not yet been investigated.

METHODS

A random sample of 61 female nurses provided a blood sample and completed the Perceived Stress Scale, the Multidimensional Scale of Perceived Social Support, the 20-item Toronto Alexithymia Scale, and the Experiences in Close Relationships questionnaire. Immune measures included immunophenotypic analysis, lymphocyte proliferative response to Phytohemagglutinin, and NK cell cytotoxicity (NKCC). Statistical analysis focused on the relationship between attachment-related anxiety or avoidance and immune measures. Multiple regression was used to control for perceived stress and support, alexithymia, health-related behaviors possibly influencing immunity, and use of anti-inflammatory drugs, tobacco or alcohol.

RESULTS

Attachment-related anxiety was not associated with any immune parameter. Attachment-related avoidance was associated with lower NKCC. This association was independent from the number of circulating NK cells, which suggests a change in cell functionality. Perceived stress was also associated with lower NKCC.

CONCLUSIONS

This study suggests a link between attachment security and immunity. While our findings should be interpreted with great caution and need replication, they are consistent with previous work suggesting that insecure attachment may be a risk factor for health and may relate to biological processes relevant to health.

Interleukin-12 is involved in the enhancement of human natural killer cell activity by Lactobacillus casei Shirota

We conducted a placebo-controlled, cross-over trial to examine the effect of Lactobacillus casei Shirota (LcS) on natural killer (NK) cell activity in humans. NK cell activity exhibited a declining trend during the period of placebo ingestion, but NK cell activity increased after intake for 3 weeks of fermented milk containing 4 x 10(10) live LcS. When human peripheral blood mononuclear cells were cultured in the presence of heat-killed LcS, NK cell activity was enhanced. The ability of LcS to enhance NK cell activity and induce interleukin (IL)-12 production was correlated, and the addition of anti-IL-12 monoclonal antibody reduced the enhancement of NK cell activity triggered by LcS. In addition, separation of NK cells from LcS-stimulated monocytes with membrane filter reduced NK cell activity to the intermediate level and almost deprived monocytes of the ability to produce IL-12. These results demonstrate that LcS can enhance NK cell activity in vivo and in vitro in humans, and IL-12 may be responsible for enhancement of NK cell activity triggered by LcS.

Aging and innate immunity

Adaptive immunity undergoes severe deterioration with age and represents the main problem in the elderly. However, evidence accumulated over the last decade supports the hypothesis that aging also has a profound impact on innate immunity, which in turn markedly impacts the health and longevity of older people.

Increased natural killer cell activity in patients with an abdominal aortic aneurysm

BACKGROUND

Natural killer (NK) cells have an emerging role in the development of chronic disease and in the direction and maintenance of inflammatory responses. Abdominal aortic aneurysms (AAA) is a chronic inflammatory disorder of unknown aetiology. The aim was to investigate whether NK cells showed altered function in patients with an AAA.

METHODS

The presence, phenotype and function of peripheral blood and tissue NK cells from patients with an AAA, peripheral vascular disease (PVD) and healthy age-sex-matched controls were assessed before and after surgery.

RESULTS

Patients with an AAA had significantly higher (P < 0.010) percentages of peripheral blood NK cells (mean (95 per cent c.i.) 23.8 (2.6) per cent) than patients with PVD (17.4 (2.9) per cent) and control subjects (16.2 (2.8) per cent). The NK cells from patients with an AAA had increased cytotoxicity on a per cell basis towards both an NK-sensitive target cell line and human aortic smooth muscle cells. Increased NK cell proportions (22.7 (3.5) per cent) and cytotoxic activity, together with higher C-reactive protein values, persisted after successful AAA repair.

CONCLUSION

These data support the hypothesis that increased NK cytotoxicity could be a contributing factor in the generation or potentiation of inflammation in patients with an AAA.

Depressive symptoms and life satisfaction in elderly women are associated with natural killer cell number and cytotoxicity

Well-preserved natural killer (NK) cell cytotoxicity (NKCC) is associated with healthy aging. The objective of the survey was to investigate psychological factors related to NKCC and NK cell populations in elderly women. A cross-sectional study involving 181 participants was conducted using the Japanese version of the 28-item General Health Questionnaire (GHQ) and additional questions assessing psychological status and lifestyle. Spearman's rank test revealed a significant negative correlation between NKCC and the GHQ depression subscale (GHQ-D) scores. Significantly reduced NKCC was found in participants presenting high GHQ-D scores (12 < or = GHQ-D, n = 58) compared with those showing middle (8 < or = GHQ-D < or = 11, n = 55) or low (GHQ-D = 7, n = 68) scores. Adjusting for covariates regarding lifestyle, multiple logistic regression analysis was applied; consequently, significant associations were found between reduced NKCC and high depressive symptoms and between increased NK cell numbers and life satisfaction. These results indicated a clue to longitudinal studies in the future.

Assessing immune function changes in exercise and diet intervention studies

PURPOSE OF REVIEW

To discuss the advantages and limitations of the methods currently available to assess changes in human immune function in response to interventions such as changes in diet or exercise.

RECENT FINDINGS

Much recent research has focused on the effect of regular moderate exercise and the role of foods or specific food components in enhancing immune system responsiveness to challenge and thereby improving health and reducing disease risk. The present review summarizes the issues in experimental design that need to be considered in human intervention studies, the immune function variables commonly used as markers in such studies and the biological relevance (e.g. known correlation with clinically relevant endpoints) of the markers. In-vivo markers appear to be the best. Markers of peripheral blood leukocyte function are also of value since they may provide information on the mechanism(s) of change caused by an intervention.

SUMMARY

Currently, no single marker of human immune function is available to predict the outcome of an exercise or dietary intervention on the resistance to infection or to other immune system-related diseases. There is too little evidence at present that correlates individual markers with global health improvement and therefore assessing changes of immune function requires a thorough methodological approach targeting a large spectrum of parameters.

Modulation of natural killer cell activity by supplementation of fermented milk containing Lactobacillus casei in habitual smokers

BACKGROUND

Habitual smoking significantly reduces natural killer (NK) cell activity. To clarify whether the intake of fermented milk containing lactic acid bacteria restores NK cell activity in habitual smokers, we conducted a placebo-controlled double-blind test.

METHODS

Ninety-nine subjects with smoking habits were randomly divided into two groups and daily for 3 weeks were given fermented milk containing Lactobacillus casei or placebo. NK cell activity in the peripheral blood mononuclear cells (PBMNC) was determined before and after the intake. Average number of cigarettes smoked and number of cigarettes that the subjects smoked before giving blood after getting up on the inspection day were asked, and these data were used to adjust the influence of smoking on NK cell activity.

RESULTS

NK cell activity in individuals was inversely correlated to numbers of cigarettes smoked. Averaged NK cell activity adjusted by the numbers of cigarettes was significantly higher in individuals drinking fermented milk containing L. casei than those drinking a placebo. However, the proportion of NK cells was not different between individuals drinking either fermented milk containing L. casei or the placebo.

CONCLUSIONS

Intake of fermented milk containing lactic acid bacteria was considered effective for restoring the NK cell activity of habitual smokers.

Natural killer cells and exercise training in the elderly: a review

Consistent reports of the positive relationship between regular physical activity and immunosenescence have generated much excitement in the field of exercise immunology. It is generally accepted that natural killer (NK) cell activity per NK cell decreases with age; decreases in NKCA have been associated with infection and death in the aged. The effects of exercise and training on natural killer cells, components of the innate immune system, have been studied extensively in young people. However, the published research on the elderly population is limited. Generally it has been found that training increases or does not change natural killer cell activity or counts in the elderly. The clinical relevance of these results is yet to be fully explored. In addition, the limitations of these studies on immune function have been many, and studies are often difficult to compare due to differences in their methods and presentation of results.

Reciprocal age related change in natural killer cell receptors for MHC class I

Natural killer (NK) cells are essential for healthy aging. NK cell activation is controlled by MHC class I-specific CD94/NKG2 receptors and killer immunoglobulin-like receptors (KIR). To assess NK cytotoxic function in isolation from MHC receptor engagement, we measured the ability of purified NK cells to kill mouse P815 target cells in the presence of anti-CD16 mAb. CD16-mediated cytotoxicity did not change with age, indicating that NK activation and cytotoxic granule release remained functional. We then investigated MHC class I receptor expression on NK cells. There was an age related decrease in CD94 and NKG2A expression and a reciprocal age related increase in KIR expression. NKG2A expression also declined with age on CD56(+) T cells. CD94/NKG2A receptor function was proportional to expression, indicating that NK cell inhibitory signaling pathways were intact. NKG2A and KIR expression were complementary, suggesting that CD94/NKG2A function could substitute for inhibitory KIR function during polyclonal NK cell development in both young and elderly adults. The distinct roles of CD94/NKG2A and KIR receptors suggest that shifting MHC class I receptor expression patterns reflect age related changes in NK cell and CD56(+) T cell turnover and function in vivo.

Immunomodulating effect of influenza vaccination in the elderly differing in health status

The aim of this study was to analyse whether split influenza vaccine may elicit NK cytotoxic response in the vaccinated elderly people and whether this effect may be maintained over few weeks after vaccination. It was also worth investigating the relation between NK activity in the vaccinated and specific immune protection against influenza and non-specific against other infections. Two groups of volunteers were vaccinated with trivalent split viron influenza vaccine in two consecutive seasons (1999/2000; 2000/2001). The elderly group consisted of 142 people (65-92 years old) in the first season and 110 in the second; while the young (16-44 years old) of 98 and 67 people, respectively. An analysis of NK cytotoxic activity had been done before vaccination, two days, one month and fifth months thereafter. The results revealed that vaccination with the influenza vaccine had an augmenting effect on NK activity, in all groups examined, in both epidemic seasons, visible at two days and 1 month after the vaccination. In the elderly high pre- and post-vaccination NK activity was related to higher titers of anti-hemagglutinin, better health status and lower incidence of all cause respiratory tract infections. At the second vaccination, most of the elderly with chronic medical conditions and high NK activity, who did not attain the protective level of anti-hemagglutinins in the first season, converted into the protected. High pre- and post-vaccination NK activity predisposes elderly people to the protective humoral anti-hemagglutinin response and gives better protection from respiratory tract infections.

Investigation of KIR diversity in immunosenecence and longevity within the Irish population

Natural killer (NK) cells play a pivotal role in the innate immune response. During the ageing process, variations occur in NK cell number and function. The cytolytic activity of NK cells is controlled by an array of activating and inhibitory cell surface receptors, including the killer cell immunoglobulin-like receptors (KIRs). In the present study, genetic diversity of the KIR loci was analysed with respect to successful ageing in the Irish population. A PCR-SSOP KIR gene identification system was employed to determine the frequency of the named KIR genes/pseudogenes and KIR genotypes within a healthy aged cohort and young control group. Although, two KIR genes (2DS3, 2DL5) displayed an initial increased frequency in the aged group, the significance of this association was lost when repeated in a second cohort. In view of the lack of studies to date, investigating the role of the KIR gene system in healthy ageing, further analysis of KIR diversity is required to fully elucidate it's role in respect to age-related disease and longevity.

Hypothetical soluble KIR2DS4 natural killer cell receptor molecule does not associate with successful ageing in the Irish

The identification of immunogenetic longevity markers is a major area of molecular gerontological research. A number of genetic loci have been examined, e.g. the HLA and cytokine networks. This study investigated a genetic marker within the highly polymorphic KIR gene system with successful ageing in the Irish population. A 22 bp deletion was identified in the KIR2DS4 gene that predicts a truncated soluble KIR molecule with one intact Ig-like domain. The frequency of this variant was determined using a specific-primer PCR methodology. There was no observed association between this common polymorphic variation within this activatory KIR gene and the aged Irish population. This is the first study of KIR polymorphism in ageing and although no association was identified, the importance of the KIR network in the immune response and its polymorphic nature warrants more detailed analysis to ascertain its role in immunosenescence.

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.

Natural killer cells and their receptors

Natural killer (NK) cells have been known for a long time to be a very important component of the innate immune system. However, it is only during the last 10 years that knowledge of their receptors has emerged. Described in the present review are those receptor families killer inhibitory receptor (KIR) (belonging to the immunoglobulin superfamily), and killer lectin like receptor (KLR) CD94/NKG2, that both use HLA as a ligand and have inhibiting and activating types of receptors, and natural cytotoxic receptors (NCR) which do not associate with HLA. Association of the receptor gives rise to either an inhibiting or activating signal leading to either failure or success in lysing a target cell. The KIR receptors are very polymorphic both in the number of genes expressed in an individual and the alleles present for a gene. They would appear to have had a rapid evolution compared to the CD94/NKG2 receptors. The roles that NK cells and their receptors have with various facets of transplantation, disease, pregnancy and control of virus infection in humans are described.

Cell-mediated immune response in MDMA users after repeated dose administration: studies in controlled versus noncontrolled settings

Acute administration of 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") produces time-dependent immune dysfunction in humans. Recreational use of MDMA generally includes repeated drug consumption, often in association with other drugs, such as alcohol and cannabis. In the laboratory setting, repeated MDMA administration to healthy MDMA consumers produced a time-dependent immune dysfunction similar to that observed with the ingestion of a single dose, and the first of the two administrations paralleled the time-course of MDMA-induced cortisol stimulation kinetics and MDMA plasma concentrations. A significant decrease in CD4 T-helper cells with simultaneous increase in natural killer (NK) cell and a decrease in functional responsiveness of lymphocytes to mitogenic stimulation was observed. Response to the second dose was either long-lasting compared with the first dose or disproportionate and did not show any parallelism with cortisol and MDMA plasma concentrations. This circumstance extended the critical period during which immunocompetence is highly impaired as a result of MDMA use. Accumulation of MDMA in the body of a poor metabolizer induced higher immunomodulatory effects with statistically significant differences in NK cell function compared with extensive metabolizers. When basal values of lymphocyte subsets were examined in a population of recreational MDMA users participating in different clinical trials, alterations in several immunological parameters were observed. The absolute number of lymphocytes, in particular T lymphocytes and CD4 T-helper cell subsets, showed a trend toward reduced values, although cell counts were within normal limits. By contrast, NK cells in MDMA consumers were reduced to one-third of those from healthy persons. A statistically significant decrease in affected immune parameters was recorded during a 2-year observation period in a subgroup of recreational MDMA users. These permanent alterations in immunologic homeostasis may result in impairment of general health and subsequent increased susceptibility to infection and immune-related disorders.