Immunosenescence

Long-lasting alterations of the immune system by ionizing radiation exposure: implications for disease development among atomic bomb survivors

PURPOSE

The immune systems of the atomic-bomb (A-bomb) survivors were damaged proportionately to irradiation levels at the time of the bombing over 60 years ago. Although the survivor's immune system repaired and regenerated as the hematopoietic system has recovered, significant residual injury persists, as manifested by abnormalities in lymphoid cell composition and function. This review summarizes the long-lasting alterations in immunological functions associated with atomic-bomb irradiation, and discusses the likelihood that damaging effects of radiation on the immune system may be involved partly in disease development so frequently observed in A-bomb survivors.

CONCLUSIONS

Significant immunological alterations noted include: (i) attrition of T-cell functions, as reductions in mitogen-dependent proliferation and interleukin-2 (IL-2) production; (ii) decrease in helper T-cell populations; and (iii) increase in blood inflammatory cytokine levels. These findings suggest that A-bomb radiation exposure perturbed one or more of the primary processes responsible for T-cell homeostasis and the balance between cell renewal and survival and cell death among naive and memory T cells. Such perturbed T-cell homeostasis may result in acceleration of immunological aging. Persistent inflammation, linked in some way to the perturbation of T-cell homeostasis, is key in addressing whether such noted immunological changes observed in A-bomb survivors are in fact associated with disease development.

Designing ageing conditions in tumour microenvironment-a new possible modality for cancer treatment

While tumour incidence is known to augment with age, paradoxically tumour growth and metastasis were often found to proceed at a slower rate at late ages. This age-related biological behaviour of tumours actually imposes a differential therapeutic approach to the old cancer patient. Several mechanisms of the age-related reduced tumour progression have been demonstrated: decreased tumour cell proliferation, increased apoptotic cell death, decreased angiogenesis and anti-tumoural immune response changes. We postulated that it might be possible to design age-adjusted treatment modalities based on the mechanisms responsible for the reduced tumour progression rate in the aged. Based on these mechanisms, we compared the effect of different treatments (apoptosis-inducing agents, Hydrocortisone and Adriamycin, anti-angiogenic agent, TNP-470, and immunomodulators-Levamisole and BCG) on two experimental tumours (B16 melanoma and AKR lymphoma) growing in young and old mice. Most treatments showed, in both tumours, a higher inhibitory effect on tumours growing in old mice than on those developing in young ones, to our knowledge, a feature not described before for anti-tumoural agents. We suggest that designing ageing conditions in tumours of young patients might possibly alleviate neoplastic aggressiveness in these patients as well.

Differential effects of age on circulating and splenic leukocyte populations in C57BL/6 and BALB/c male mice

BACKGROUND

Despite several reports on age-related phenotypic changes of the immune system's cells, studies that use a multipoint age comparison between the specific and innate immune cell populations of prototypical Th1- and Th2-type polarized mouse strains are still lacking.

RESULTS

Using a multipoint age comparison approach, cells from the two major immune system compartments, peripheral blood and spleen, and flow cytometry analysis, we found several principal differences in T cell and professional antigen presenting cell (APC) populations originating from a prototypical T helper (Th) 1 mouse strain, C57BL/6, and a prototypical Th2 strain, BALB/c. For example, regardless of age, there were strain differences in both peripheral blood mononuclear cells (PBMC) and spleens in the proportion of CD4+ (higher in the BALB/c strain), CD8+ T cells and CD11b+/CD11c+ APC (greater in C57BL/6 mice). Other differences were present only in PBMC (MHC class II + and CD19+ were greater in C57BL/6 mice) or differences were evident in the spleens but not in circulation (CD3+ T cells were greater in C57BL/6 mice). There were populations of cells that increased with age in PBMC and spleens of both strains (MHC class II+), decreased in the periphery and spleens of both strains (CD11b+) or did not change in the PBMC and spleens of both strains (CD8+). We also found strain and age differences in the distribution of naïve and memory/activated splenic T cells, e.g., BALB/c mice had more memory/activated and less naive CD8+ and CD4+ T cells and the C57BL/6 mice.

CONCLUSION

Our data provide important information on the principal differences, within the context of age, in T cell and professional APC populations between the prototypical Th1 mouse strain C57BL/6 and the prototypical Th2 strain BALB/c. Although the age-related changes that occur may be rather subtle, they may be very relevant in conditions of disease and stress. Importantly, our data indicate that age and strain should be considered in concert in the selection of appropriate mouse models for immunological research.

Immunosupportive therapies in aging

The primary role of the immune system is to protect the organism against pathogens, but age-associated alterations to immunity increase the susceptibility of the elderly to infectious disease. The exact nature of these changes is still controversial, but the use of screening procedures, such as the SENIEUR protocol to exclude underlying illness, helped to better characterize the changes actually related to physiological aging rather than pathology. It is generally agreed that the most marked changes occur in the cellular immune response reflecting profound alterations in T cells. Much of this is due to thymic involution as well as changes in the proportions of T cell subpopulations resulting from antigen exposure, and altered T cell activation pathways. However, a body of data indicates that innate immune responses, including the critical bridge between innate and adaptive immunity, and antigen presenting capacity are not completely resistant to senescence processes. The consequences of all these alterations are an increased incidence of infections, as well as possibly cancers, autoimmune disorders, and chronic inflammatory diseases. The leading question is what, if anything, can we do to prevent these deleterious changes without dangerously dysregulating the precarious balance of productive immunity versus immunopathology? There are many potential new therapeutic means now available to modulate immunosenescence and many others are expected to be available shortly. One main problem in applying these experimental therapies is ethical: there is a common feeling that as ageing is not a disease; the elderly are not sick and therefore do not require adventurous therapies with unpredictable side-effects in mostly frail individuals. Animal models are not helpful in this context. In this chapter we will first briefly review what we think we know about human immunosenescence and its consequences for the health status of elderly individuals. We will then discuss possible interventions that might one day become applicable in an appropriate ethical environment.

Aging and the dendritic cell system: implications for cancer

The immune system shows a decline in responsiveness to antigens both with aging, as well as in the presence of tumors. The malfunction of the immune system with age can be attributed to developmental and functional alterations in several cell populations. Previous studies have shown defects in humoral responses and abnormalities in T cell function in aged individuals, but have not distinguished between abnormalities in antigen presentation and intrinsic T cell or B cell defects in aged individuals. Dendritic cells (DC) play a pivotal role in regulating immune responses by presenting antigens to naïve T lymphocytes, modulating Th1/Th2/Th3/Treg balance, producing numerous regulatory cytokines and chemokines, and modifying survival of immune effectors. DC are receiving increased attention due to their involvement in the immunobiology of tolerance and autoimmunity, as well as their potential role as biological adjuvants in tumor vaccines. Recent advances in the molecular and cell biology of different DC populations allow for addressing the issue of DC and aging both in rodents and humans. Since DC play a crucial role in initiating and regulating immune responses, it is reasonable to hypothesize that they are directly involved in altered antitumor immunity in aging. However, the results of studies focusing on DC in the elderly are conflicting. The present review summarizes the available human and experimental animal data on quantitative and qualitative alterations of DC in aging and discusses the potential role of the DC system in the increased incidence of cancer in the elderly.

Zinc-bound metallothioneins and immune plasticity: lessons from very old mice and humans

The capacity of the remodelling immune responses during stress (named immune plasticity) is fundamental to reach successful ageing. We herein report two pivotal experimental models in order to demonstrate the relevance of the immune plasticity in ageing and successful ageing. These two experimental models will be compared with the capacity in remodelling the immune response in human centenarians. With regard to experimental models, one model is represented by the circadian rhythms of immune responses, the other one is the immune responses during partial hepatectomy/liver regeneration (pHx). The latter is suggestive because it mimics the immunosenescence and chronic inflammation 48 h after partial hepatectomy in the young through the continuous production of IL-6, which is the main cause of immune plasticity lack in ageing. The constant production of IL-6 leads to abnormal increments of zinc-bound Metallothionein (MT), which is in turn unable in zinc release in ageing. As a consequence, low zinc ion bioavailability appears for thymic and extrathymic immune efficiency, in particular of liver NKT cells bearing TCR γδ. The remodelling during the circadian cycle and during pHx of zinc-bound MT confers the immune plasticity of liver NKT γδ cells and NK cells in young and very old mice, not in old mice. With regard to human centenarians and their capacity in remodelling the immune response with respect to elderly, these exceptional individuals display low zinc-bound MT associated with: a) satisfactory intracellular zinc ion availability, b) more capacity in zinc release by MT, c) less inflammation due to low gene expression of IL-6 receptor (gp130), d) increased levels of IFN-gamma and number of NKT cell bearing TCR γδ. Moreover, some polymorphisms for MT tested in PBMCs from human donors are related to successful ageing. In conclusion, zinc-bound MT homeostasis is fundamental to confer the immune plasticity that is a condition "sine qua non" to achieve healthy ageing and longevity.

SELDI-TOF-MS ProteinChip array profiling of T-cell clones propagated in long-term culture identifies human profilin-1 as a potential bio-marker of immunosenescence

Background

The adaptive immune response requires waves of T-cell clonal expansion on contact with pathogen and elimination after clearance of the source of antigen. However, lifelong persistent infections with common viruses cause chronic antigenic stimulation which takes its toll on adaptive immunity in late life. Chronic antigenic stress results in deregulation of the T-cell response and accumulation of anergic cells. Longitudinal studies of the elderly show that this impacts on survival. Identifying the nature of the defects in chronically-stimulated T-cells and protein bio-markers of these dysfunctional cells would help to understand age-associated compromised T-cell function (immunosenescence) and facilitate the development of targeted intervention strategies.

The purpose of this work was to use surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS) to analyse proteins associated with T-cell senescence in order to identify potential bio-markers. Clonal populations of T-cells isolated from elderly octogenarian and centenarian donors were grown in vitro until senescence, and early passage and late passage (pre-senescent) cells were analysed using SELDI-TOF-MS ProteinChip arrays.

Results

Discriminant analysis identified several protein or peptide peaks in the region of 14.5–16.5 kDa that were associated with T-cell clone senescence. Human profilin-1, a ubiquitous protein associated with actin remodelling and cellular motility was unambiguously identified. Altered expression of profilin-1 in senescent T-cell clones was confirmed by Western blot analysis.

Conclusion

Due to the proposed roles of profilin-1 in cellular survival, cytoskeleton remodelling, motility, and proliferation, it is hypothesised that differential expression of profilin-1 in ageing may contribute directly to immunosenescence.

Nutritional formula improved immune profiles of seniors living in nursing homes

OBJECTIVES

To assess whether an experimental nutritional formula (EXP) supports immune function in seniors living in long-term care facilities.

DESIGN

Prospective, randomized, double-blind, controlled trial conducted September 2002 through January 2003.

SETTING

North central Florida nursing homes.

PARTICIPANTS

Subjects aged 65 and older (n = 157).

INTERVENTION

Subjects received 240 mL/d of EXP or standard liquid nutrition (CON) for 4 weeks before and 6 weeks after an influenza vaccination.

MEASUREMENTS

Influenza vaccine antibody responses, immunophenotyping, lymphocyte activation, cytokines, and clinical measures (fever, number of prescribed antibiotics).

RESULTS

Ninety-two subjects (n = 40, CON; n = 52, EXP) completed the study. Geometric mean antibody titers were similar between groups, yet the percentage of subjects with H1N1 antibody titers greater than 100 postvaccination was higher in the EXP group than in the CON group (43% vs 23%, P=.047). Similar trends were found for the percentage of subjects (intent to treat) with fourfold increases against the B/Hong Kong component (64% vs 46%, P = .09) or with H3N2 antibody titers of 40 or more (97% vs 89%, P=.06). EXP subjects had higher levels of influenza-activated lymphocytes (CD69+ and CD25+). Cytokine production after mitogen activation was lower in EXP than CON subjects (interleukin (IL)-6: 20+/-3 vs 29+/-3 ng/mL, P = .045; IL-10: 310+/-60 vs 603+/-140 pg/mL, P = .06). Fewer EXP subjects were treated for fever (5% vs 16%, P = .02) or prescribed antibiotics (7 vs 11 new antibiotics/100 days of study, P = .06).

CONCLUSION

Seniors consuming the EXP formula demonstrated enhanced immune function, indicated by increased influenza vaccine response and lymphocyte activation, less fever, and fewer newly prescribed antibiotics than those consuming a standard ready-to-drink nutritional supplement.

MacrophAging: a cellular and molecular review

Aging is associated with the deterioration of several physiological functions, which leads to aged-related pathologies and, ultimately, to death. The immune system is affected by aging, causing an increased susceptibility to infections and mortality, as well as a major incidence of immune diseases and cancer in the elderly. Because macrophages are an essential component of both innate and adaptive immunity, altered function of these phagocytic cells with aging may play a key role in immunosenescence. Here we summarize data about the effects of aging on macrophages and we discuss the molecular events that could be involved in this process.

Humoral immune response and B-cell functions including immunoglobulin class switch are downregulated in aged mice and humans

Vaccinations are powerful tools for combating infections. Because of the age-related impairment in immune functions, the currently available vaccines are protecting only a small proportion of the elderly population. We, here, provide an overview of age-related changes in innate and adaptive immunity with particular emphasis to changes in antibody production with aging. We also summarize our results showing that the E2A-encoded transcription factor E47, which regulates many B cell functions including class switch recombination (CSR) and somatic hypermutation (SHM), is downregulated in splenic B cells from old mice. This leads to a reduction in the activation-induced cytidine deaminase (AID), which directly induces CSR and SHM, and, in turn, to reduced amounts of switched antibodies produced by splenic activated B cells. Our preliminary results in humans indicate similar reductions: we show herein that the expression of E2A and AID progressively decline with age. Our results provide a possible molecular basis for a decrease in the humoral immune response in aging mice and humans.

Telomerase reverse transcriptase mRNA expression in peripheral lymphocytes of patients with chronic HBV and HCV infections

Telomerase activity is present at low levels in peripheral lymphocytes (PL) and is upregulated upon activation, possibly protecting PL from telomere shortening. As decreased telomere length is considered a sign of cellular senescence, telomerase may, therefore, play an important role on immune function, organ regeneration and carcinogenesis. So far, quantification of human telomerase reverse transcriptase levels (hTERT) in PL, has not been reported. We determined hTERT mRNA levels in PL of hepatitis B virus (HBV) and hepatitis C virus (HCV) patients, in an attempt to address whether hTERT transcripts in PL are altered in these viral diseases, which are characterized by immune dysfunction and increased incidence of hepatocarcinogenesis. hTERT mRNA levels in PL of HBV (n = 17), HCV (n = 24) patients and healthy controls (n = 22) were quantified by real-time polymerase chain reaction. We observed significantly lower hTERT mRNA levels in HBV and HCV patients compared with healthy individuals (P < 0.05). hTERT mRNA levels were not associated with the patients' clinical status (inactive, hepatitis and cirrhosis). Also no correlation was observed between hTERT mRNA expression, and HBV and HCV replicative activity. In the inactive group (n = 18) we observed a negative correlation between hTERT mRNA expression and disease duration (rs = -0.52, P < 0.03). We performed for the first time an accurate quantification of hTERT mRNA expression in PL of HBV and HCV patients. The observed low levels of hTERT mRNA expression in the above patients may suggest its involvement in the immunopathogenesis of chronic viral hepatitis.

Skewed representation of functionally distinct populations of Vgamma9Vdelta2 T lymphocytes in aging

We recently demonstrated that numerical and functional alterations of gammadelta T cells are present in healthy elderly. Here we observed that the decreased absolute number of Vgamma9Vdelta2 T cells present in old subjects in comparison with young/adult and middle aged donors is due to the reduction of naive and central memory Vgamma9Vdelta2 T cells bearing CD27 and CCR7 antigens. The proportion of effector/memory Vgamma9Vdelta2 T cells lacking CD27 or CCR7 markers was significantly increased in the peripheral blood of old subjects in comparison with younger donors. Moreover, the percentage of CD69+ gammadelta T cells was significantly increased in old subjects in comparison with younger donors after overnight activation, confirming that more effector cells are available in aged people. A functional analysis in young/adult and middle aged donors revealed that effector/memory CD27- Vgamma9Vdelta2 T cells are increased after 10-days of in vitro colture in the presence of isopentenylpyrophosphate (IPP) and IL-2. In contrast, the IPP+IL-2 mediated differentiation and expansion of CD27- effector/memory cells was absent in old subjects, confirming a lack of naive and central memory cells responding to IL-2. Accordingly, the expansion index of effector/memory CD27- Vgamma9Vdelta2 T cells was negatively correlated with the donor age. Finally, terminally differentiated Vgamma9Vdelta2 T cells measured as perforin content after 10-day in vitro expansion showed no age-related difference. These data demonstrated a shift of the circulating gammadelta T cell population towards CD27- and CCR7- effector T cells in the elderly with the reduction of immature CD27+ and CCR7+ T cell precursors.

Age-related CD8 T cell clonal expansions constrict CD8 T cell repertoire and have the potential to impair immune defense

Peripheral T cell diversity is virtually constant in the young, but is invariably reduced in aged mice and humans. CD8+ T cell clonal expansions (TCE) are the most drastic manifestation of, and possible contributors to, this reduced diversity. We show that the presence of TCE results in reduced CD8+, but not CD4+, T cell diversity, and in functional inability to mobilize parts of the CD8+ T cell repertoire affected by TCE. In the model of herpes simplex virus (HSV)-1 infection of B6 mice, >90% of the responding CD8+ T cells use Vbeta10 or Vbeta8 and are directed against a single glycoprotein B (gB498-505) epitope, gB-8p. We found that old animals bearing CD8+ TCE within Vbeta10 or Vbeta8 families failed to mount an effective immune response against HSV-1, as judged by reduced numbers of peptide-major histocompatibility complex tetramer+ CD8 T cells and an absence of antiviral lytic function. Furthermore, Vbeta8 TCE experimentally introduced into young mice resulted in lower resistance to viral challenge, whereas Vbeta5+ TCE induced in a similar fashion did not impact viral resistance. These results demonstrate that age-related TCE functionally impair the efficacy of antiviral CD8+ T cell immunity in an antigen-specific manner, strongly suggesting that TCE are not the mere manifestation of, but are also a contributing factor to, the immunodeficiency of senescence.

Immunoprevention and immunotherapy of cancer in ageing

Over the last few years there has been a growing interest in geriatric oncology, mainly because of the evidence that advanced age is the greatest risk factor for the development of cancer and that, since the elderly population is rapidly expanding, so too will the number of cancer patients. This forecast necessitates the development of new and more specific strategies for the prevention and cure of cancer in the elderly and as a result an ever-increasing need for oncologists, geriatricians and researchers to work closely together. The increased incidence of cancer in elderly people has been related to the age-associated changes occurring in the immune system, the so-called immunosenescence. This phenomenon is best characterised by a remodelling of the immune system, which appears early on and progresses throughout a person's life and mainly involves a decrease in cellular functions. This review aims to provide a rationale for the development of specific immunotherapeutic and immunopreventive regimens for the elderly. We also include a discussion on the influence that immunosenescence has on the growth of tumours and the effectiveness of immunogene therapy and cancer vaccination following a brief analysis of the age-related alterations of the cell populations involved in antitumour immunity.

Age-dependent differences in the efficacy of cancer immunotherapy in C57BL and AKR mouse strains

While tumor incidence increases with age, tumor growth and metastasis often proceed at a slower rate in aged organisms. The mechanisms underlying this age-related reduced tumor development may suggest therapeutic modalities appropriate for the aged. Decreased tumor aggressiveness in the old was shown to be related to altered immune response. Consequently, the aim of the present study was to assess whether cancer immunotherapy has an age-dependent effect. Only a few studies have compared cancer immunotherapy efficiency as a function of age, most showing lower inhibition in older animals. In the present study, we tested the effect of two immunomodulators, levamisole and BCG, on two tumors, B16 melanoma and AKR lymphoma, in mice of different ages. We demonstrated a higher efficiency of immunotherapy in aged as compared to young mice, particularly at low immunomodulator doses. While decreased T cell function during aging is apparently established, nonspecific immunity is more preserved or even enhanced in later life. We found an increased number of macrophages in tumors of old compared to young mice and an increase in MAC-1+ cells in old levamisole-treated compared to non-treated mice. The stronger therapeutic effect of this immunomodulator in old mice might thus be due to an increased macrophage-mediated anti-tumoral effect.

Moderate exercise may attenuate some aspects of immunosenescence

BACKGROUND

Immunosenescence is related to the deterioration of many immune functions, which may be manifested in increased susceptibility to infection, cancer, and autoimmunity. Lifestyle factors, such as diet or physical activity, may influence the senescence of the immune system. It is widely accepted that moderate physical activity may cause beneficial effects for physical and psychological health as well as for the immune system activity in aged people.

METHODS

Thirty elderly women aged 62 to 86 were subjected to a two-years authorized physical activity program. Peripheral blood lymphocytes distribution and the production of cytokines involved in the immune response development and regulation (IL-2, IL-4 and IFN-gamma) were investigated. The same parameters were evaluated in two control groups of women: a sedentary group of 12 elderly women selected for the second round of the physical activity program and in a group of 20 sedentary young women. Flow cytometry methods were used for the examination of surface markers on peripheral blood lymphocytes and intracellular cytokines expression.

RESULTS

The distribution of the main lymphocytes subpopulations in the peripheral blood of elderly women did not show changes after long-term moderate physical training. The percentage of lymphocytes expressing intracellular IL-2 was higher in the group of women attending 2-years physical activity program than in the control group of elderly sedentary women, and it was similar to the value estimated in the group of young sedentary women. There was no difference in the intracellular expression of IL-4 and IFN-gamma between the active and elderly sedentary women.

CONCLUSIONS

Our results suggest that moderate, long-term physical activity in elderly women may increase the production of IL-2, an important regulator of the immune response. This may help ameliorate immunosenescence in these women.

Zinc, immune plasticity, aging, and successful aging: role of metallothionein

The capacity of the remodeling immune responses during stress (immune plasticity) is fundamental to reach successful aging. We herein report two pivotal models to demonstrate the relevance of the immune plasticity in aging and successful aging. One model is represented by the circadian rhythms of immune responses; the other one is the immune responses during partial hepatectomy/liver regeneration (pHx). The latter is suggestive because it mimics the immunosenescence and chronic inflammation 48 hours after partial hepatectomy in the young through the continuous production of IL-6, which is the main cause of immune plasticity lack in aging. The constant production of IL-6 leads to abnormal increments of zinc-bound metallothionein (MT), which is, in turn, unable in zinc release in aging. As a consequence, low zinc ion bioavailability appears for thymic and extrathymic immune efficiency, in particular, of liver NKT cells bearing TCR gd. The remodeling during the circadian cycle and during pHx of zinc-bound MT confers the immune plasticity of liver NKT gamma delta cells and NK cells in young and very old age, not in old age. Therefore, zinc-bound MT homeostasis is crucial in conferring liver immune plasticity with subsequent successful aging.

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.

Stress responses and innate immunity: aging as a contributory factor

Evolutionary pressure has selected individuals with traits that allow them to survive to reproduction, without consideration of the consequences for the post-child rearing years and old age. In the 21st century, society is populated increasingly by the elderly and with the falling birth rate and improved health care this trend is set to continue for the foreseeable future. To minimize the potential burden on health services one would hope that 'growing old gracefully' should also mean 'growing old healthily'. However, for too many the aging process is accompanied by increasing physical and mental frailty producing an elevated risk of physical and psychological stress in old age. Stress is a potent modulator of immune function, which in youth can be compensated for by the presence of an optimal immune response. In the elderly the immune response is blunted as a result of the decline in several components of the immune system (immune senescence) and a shifting to a chronic pro-inflammatory status (the so-called 'inflamm-aging' effect). We discuss here what is known of the effects of both stress and aging upon the innate immune system, focusing in particular upon the age-related alterations in the hypopituitary-adrenal axis. We propose a double hit model for age and stress in which the age-related increase in the cortisol/sulphated dehydroepiandrosterone ratio synergizes with elevated cortisol during stress to reduce immunity in the elderly significantly.

Regulation of dendritic cell expansion in aged athymic nude mice by FLT3 ligand

This report describes age-related alterations of dendritic cells (DC) distribution in nude athymic mice in vivo and reversal of certain age-dependent defects by an in vivo administration of hematopoietic growth factor FLT3 ligand (FLT3L). There are decreased percentages of CD11c(+) DC in the bone marrow and spleen and a reduced expression of MHC class II and CD86 molecules on DC in old nude mice. The decreased levels of CD11c(+) DC were due to the CD8alpha(-) DC subset. The distribution of CD11c(+) CD8alpha(+) DC in the lymphoid tissues was not different in young and old mice. The effect of in vivo administration of FLT3L on the generation and distribution of DC in the lymphoid tissues in young and old nude mice was also evaluated. Although, FLT3L had a higher inductive potential on the expansion of DC from the bone marrow in the elderly mice, the total level of CD11c(+) DC in the young animals was still significantly higher as compared to the old animals. Interestingly, FLT3L induced a pronounced redistribution and accumulation of MHC class II(+) DC in the lymphoid tissues in old mice, markedly increased the accumulation of CD8alpha(-) DC in the bone marrow in both young and old nude mice, and elevated both CD8alpha(-) and CD8alpha(+) DC in the spleen in young mice. However, only the level of CD8alpha(+) DC was up regulated in the spleen in old athymic mice after FLT3L-based therapy. In summary, abnormalities in DC generation and distribution in old athymic mice could be, in part, circumvented by the in vivo administration of FLT3L.

Selective T cell receptor decrease in peripheral blood T lymphocytes of patients with polymyalgia rheumatica and giant cell arteritis

OBJECTIVES

To investigate the phenotype and T cell receptor (TCR) use in peripheral blood T cells in patients with polymyalgia rheumatica (PMR) and giant cell arteritis (GCA).

METHODS

Circulating T lymphocyte phenotype and TCR repertoire were studied by flow cytometry using specific monoclonal antibodies in 23 healthy controls and 37 patients with PMR/GCA.

RESULTS

Patients with active PMR/GCA showed an inverse relation between naive and memory CD4+ T cells and unchanged expression of activation surface markers compared with controls. CD4+ TCR BV expansions were seen in 12 (52%) controls and in 8 (22%) patients with active disease (p = 0.03). Within the CD8+ subset, the frequency of expansions was similar between groups. Most T cell expansions remained stable over time. Seventeen of the 23 patients with active PMR/GCA disclosed a simultaneous CD4+ and CD8+ T cell depletion for at least one particular BV family with a clear predominance of BV5S2/S3.

CONCLUSIONS

The phenotype of circulating T cells in patients with PMR/GCA is similar to that found in aged healthy subjects, except for the surface markers of naive and memory cells and a striking non-activated phenotype. Specific BV expansions in CD4+ and CD8+ T cells, which remain stable over time, are frequent in aged subjects, including patients with PMR/GCA. TCR BV changes in patients with active disease seem to be also age related, except for the significant decrease in certain BV families in both CD4+ and CD8+ T cell subsets, which may favour the participation of a superantigen stimulation in PMR/GCA.

Longitudinal follow-up study of adenoviral vector-mediated gene transfer of dopamine d2 receptors in the striatum in young, middle-aged, and aged rats: a positron emission tomography study

Overexpression of dopamine D(2) receptors by adenoviral vector-mediated gene transfer in the rat striatum was evaluated by positron emission tomography in vivo and by ex vivo autoradiography in 5-, 13-, and 24-month-old Fischer 344 rats. Each rat had hemilateral gene transfer of D(2) receptors mediated by adenoviral vectors (AdCMV.DopD(2)R) in the striatum with contralateral striatal injection of control vectors (AdCMV.LacZ). At day 2 or 3 after vector injection positron emission tomography or ex vivo autoradiography was performed. The binding potential of a radiolabeled D(2) receptors ligand, [11C]raclopride, was significantly higher in the D(2) receptors gene-transferred striatum than the control side in each age group at a similar degree. The binding potential in the AdCMV.DopD(2)R-injected striatum of 24-month-old rats was similar to that in the AdCMV.LacZ-injected striatum of 5-month-old rats (0.99+/-0.14 versus 0.91+/-0.08). A significant age-associated decrease of the binding potential of [11C]raclopride was found in the control vector-injected side, and a significant increase of the binding potential in the adenoviral vector-injected side in all three age groups, suggesting no aging effect on the overexpression of D(2) receptors. A group of rats underwent follow-up assessment by positron emission tomography. The overexpression of D(2) receptors decreased with time in all three groups; however, the decrease rate of the D(2) receptors expression was significantly smaller in the 24-month-old group than in the 5-month-old group. We confirmed that the adenoviral vector-mediated gene transfer of D(2) receptors compensated the decreased density of striatal D(2) receptors in the 24-month-old rats up to the level in the control striatum of 5-month-old rats, and the decrease rate of the overexpression was significantly smaller in aged rats.

Hypothalamic-pituitary-adrenocortical and gonadal functions in rheumatoid arthritis

Rheumatoid arthritis (RA) as well as most autoimmune disorders results from a combination of several predisposing factors including the relations between epitopes of the trigger agent (i.e., virus, self-antigens) and histocompatibility epitopes (i.e., HLA), the status of the stress response system including the hypothalamic-pituitary-adrenocortical axis (HPA) and the sympathetic nervous system (SNS), as well as the gonadal hormones (hypothalamic-pituitary-gonadal axis, HPG), with estrogens implicated as enhancers of the immune response and androgens and progesterone as natural suppressors. The regular observation of reduced cortisol and adrenal androgen secretion during testing in RA patients not treated with glucocorticoids should clearly be regarded as "relative adrenal insufficiency" in the setting of a sustained inflammatory process, as shown by high interleukin (IL)-6 levels. In polymyalgia rheumatica, several pathogenetic and clinical aspects of the disease might well overlap RA, at least with elderly onset RA (EORA). Therefore, reduced production of adrenal hormones (i.e., cortisol, DHEAS) at baseline in active and untreated patients with polymyalgia rheumatica was detected. The defect was mainly related to altered adrenal responsiveness to ACTH stimulation (i.e., increased 17-OHP), at least in untreated patients with polymyalgia rheumatica. Finally, normal serum estrogen and low androgen levels, but high synovial fluid estrogen and much lower androgen levels, have been found in RA patients, supporting the fundamental role of the peripheral sex hormone metabolism in the manifestations of the disease.

HLA haplotypes and TNF polymorphism do not associate with longevity in the Irish

Polymorphism of the human leukocyte antigen has been implicated in a number of autoimmune disorders including ageing. In the course of the present study, no association of the human leukocyte antigen (HLA)-A1, B8, DR3 haplotype with a male Irish aged population, as previously reported, was observed. Two polymorphic nucleotides in the TNF cluster (G-308A TNF-alpha and G+252A TNF-beta), associated with increased TNF-alpha production, were shown to be in tight linkage disequilibrium with the class I and II HLA loci, generating HLA haplotypes with extended linkage disequilibrium. However, no age-related allele or genotype frequencies were observed for either polymorphic nucleotide.

Low effectiveness of DNA vaccination against HER-2/neu in ageing

We evaluated the effectiveness of vaccination with a HER-2/neu DNA plasmid to induce protective immunity against HER-2/neu overexpressing syngeneic TUBO tumour cells in old ages. Young and old Balb/c mice received three immunizations with a pCMVneuNT DNA plasmid and, successively, were challenged with TUBO cells. Young mice were completely protected whereas less than 60% protection was observed in old mice. Anti-p185(neu) antibodies were found in the sera from both young and old immunized mice, even if antibody production was significantly higher in young in comparison with old mice. Similarly, higher anti-p185(neu) lymphocyte proliferation was induced in young than in old mice. No anti-p185(neu) cytotoxicity was found in lymphocytes from old animals. We conclude that anticancer DNA vaccination has a lower effectiveness in old than in young ages.

Stress-associated immunomodulation and its implications for responses to vaccination

The rapidly growing field of psychoneuroimmunology involves the elucidation of the complex interactions between the CNS, the endocrine system and the immune system and its effects on health. Although the mechanisms involved in this bidirectional communication is not yet fully understood, studies in psychoneuroimmunology have shown that stress, through the hypothalamic-pituitary-adrenal and the sympathetic-adrenal-medullary axes, can induce modulation of the immune system. In this review, we discuss human studies and animal models, which focus on psychological stress and its effects on the immune response to vaccination, emphasizing the implications of these effects on health.

Proliferation requirements of cytomegalovirus-specific, effector-type human CD8+ T cells

Two prototypic types of virus-specific CD8(+) T cells can be found in latently infected individuals: CD45R0(+)CD27(+)CCR7(-) effector-memory, and CD45RA(+)CD27(-)CCR7(-) effector-type cells. It has recently been implied that CD45RA(+)CD27(-)CCR7(-) T cells are terminally differentiated effector cells and as such have lost all proliferative capacity. We show in this study, however, that stimulation of CMV-specific CD45RA(+)CD27(-)CCR7(-) T cells with their cognate peptide in concert with either CD4(+) help or IL-2, IL-15, or IL-21 in fact induces massive clonal expansion. Concurrently, these stimulated effector T cells change cell surface phenotype from CD45RA to CD45R0 and regain CCR7, while effector functions are maintained. Our data imply that CD45RA(+)CD27(-)CCR7(-) effector-type T cells contribute to immunity not only by direct execution of effector functions, but also by yielding progeny in situations of viral reinfection or reactivation.

A diet supplemented with thiolic anti-oxidants improves leucocyte function in two strains of prematurely ageing mice

1. According to previous studies, Swiss mice of the same age showed striking interindividual differences in behaviour when exposed to a T-maze test, with a slow performance being linked to an impaired immune function, hyperemotional response to stress and a shorter life span compared with mice that quickly explore the maze. These facts led us to propose the slow mice as a model of prematurely ageing mice (PAM). 2. In the present study, we investigated whether this prematurely ageing model could be found in other strains of mice, such as BALB/c mice, by analysing several lymphocytes functions, such as adherence, chemotaxis, proliferative response to the mitogen concanavalin A (Con A), interleukin (IL)-2 release and natural killer (NK) activity. In addition, we tested the probable beneficial effects on these functions of dietary supplementation with thioproline (TP) plus N-acetylcysteine (NAC; 0.1% w/w of each anti-oxidant) in female Swiss and BALB/c mice. 3. Our model of premature ageing, previously reported in Swiss mice, has also been reproduced in the inbred BALB/c mouse strain, in which PAM showing an immunosenescence in several lymphocyte functions, such as lower chemotaxis, proliferative response to Con A, IL-2 release and NK activity, as well as higher adherence, were observed. A short-term (5 week) ingestion of TP + NAC by female Swiss and BALB/c mice improved leucocyte function, increasing chemotaxis, the proliferative response to Con A, IL-2 release and NK activity and decreasing the adherence of lymphocytes. These effects are greatest in cells from PAM of both strains. 4. In conclusion, our model of premature ageing has been reproduced in an inbred strain. In addition, the ingestion of a diet supplemented with two thiolic anti-oxidants, such as NAC and TP, has been shown to be beneficial to the immune response in PAM.

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

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

Phenotype, antigen-presenting capacity, and migration of antigen-presenting cells in young and old age

In the present paper, we investigated whether the phenotype, the antigen-presenting capacity, and the migration of antigen-presenting cells (APCs), are affected by the aging process. APCs were obtained incubating peritoneal monocyte-macrophage cells with granulocyte-macrophage colony-stimulating factor (GM-CSF) (immature APCs) or GM-CSF and IFNgamma (mature APCs). Phenotypically, after 8 days incubation, APCs cultures were composed of CD11c and Mac-3 cells, with a similar representation, both in young and old mice. The absolute number and the expression of MHC I and II, CD80, and CD86 both on immature and mature APCs were not significantly different in young and old mice. APCs from old mice induced similar lymphocyte proliferative responses but lower lymphocyte cytotoxicity and a reduced number of CD8(+) T cells producing IFNgamma in comparison with APCs from young animals. Lymphocyte responses were antigen-specific, since TS/A pulsed APCs induced lymphocyte cytotoxicity against TS/A but not against syngeneic TUBO tumor cells. The low expression of the mRNA for the migratory CCR7 chemokine receptor present in immature APCs from old mice was greatly increased in mature APCs up to the levels found in APCs from young animals. The in vivo migration of APCs was higher in old than in young mice. These results demonstrate that some alterations in APCs function are present in aging, suggesting that an increased migratory capacity of old APCs may be required to balance their reduced antigen presentation to cytotoxic lymphocytes.

Age-dependent effects of repeated immunization with a first generation adenovirus vector on the immune response and transgene expression in young and old rats

We evaluated the kinetics of transgene expression and humoral and cellular immune responses against viral antigens and the product of the reporter gene LacZ in young (4 months) and old (20 months) Wistar rats. Animals received the intramuscular injection of a recombinant E1-deleted human type 5 adenovirus encoding beta-gal (Ad-LacZ) on days 0 and 30. The transgene expression evaluated on day 2 after infection revealed a significantly higher beta-gal activity in young than in old animals (1.9-fold increase, p<0.05). beta-gal expression decreased on day 6, and on day 15 transgene activity was undetectable in muscles from both groups. Ad-LacZ inoculation was repeated on day 30 in both animal groups. However, after the second adenovirus administration, no increase in beta-gal activity was observed. Humoral and cellular immune responses, evaluated after the first and second Ad-LacZ injection, developed with similar kinetics in young and old rats. In particular, the antigen specific antibodies were able to kill adenovirus-infected tumor cells in both complement-dependent cytotoxicity (CDC) and antibody-mediated cell-dependent cytotoxicity (ADCC) assays. Lymphocyte proliferation in response to the in vitro stimulation with specific antigens was significantly lower in old than in young animals whereas no difference was found in cytotoxic T lymphocyte activity against adenovirus-infected tumor cells. Our results demonstrate that repeated immunization with AdCMV.LacZ induces minor age-related differences in immune response which precludes gene expression both in young and old animals.

Aging-dependent exclusion of antigen-inexperienced cells from the peripheral B cell repertoire

Aging is accompanied by greatly reduced B cell production in the bone marrow, yet peripheral B cell numbers do not decline. We hypothesize that this may reflect filling of the peripheral pool with B cells that are long-lived as a consequence of specificity for, and chronic stimulation by, environmental Ags. To begin to explore this possibility, we analyzed the effects of aging on B cell population dynamics in the anti-H2(k/b) 3-83 mu-delta Ig-transgenic mouse. We predicted that, because they presumably do not bind environmental Ags, B cells bearing the transgenic receptor may be lost in aged animals. As seen in nontransgenic animals, total splenic B cell numbers remained constant with age in the Ig-transgenic animals despite reduced B cell production. Importantly, although the few newly produced B cells in the bone marrow of aged mice are 3-83 positive, the peripheral compartment of these mice is dominated by B cells that express endogenous Ig genes rather than the transgenes. This population includes large numbers of marginal zone-like and CD21(low/-)CD23(low/-)IgM(low) B cells, as well as elevated numbers of CD5+ B cells. Many of these cells express only non-B220 CD45 isoforms, suggesting that they may be memory cells. A significant proportion of aged transgenic animals produce autoantibodies that are reactive with ssDNA, dsDNA, or histones. Results support the hypothesis that, in the face of severely reduced production with age, B cells are selected based on reactivity to environmental Ags, accumulate, and display activated phenotypes. Cells bearing 3-83-transgenic receptors are excluded from this population due to their specificity. Beyond their importance in aging, these findings define a novel form of receptor revision in which B cells are selected rather than deleted based on Ag reactivity.

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

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

Defect in ERK2 and p54(JNK) activation in aging mouse splenocytes

We have previously reported on a defect in both extracellular signal-regulated protein kinase (ERK) and c-jun N-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) activation in splenocytes obtained from old rats. In order to investigate whether these effects are conserved across species, we have now used mouse splenocytes to measure the effect of aging on the activation of the same two MAPK families: ERK and JNK. Our results demonstrate that, as in rats, both MAPK signal transduction pathways are affected by aging in mice, indicating the existence of a further defect located downstream of the receptor-proximal events. Whereas ERK1 and p46(JNK) activation were not significantly modified, the kinetics of both ERK2 and p54(JNK) activation and inactivation were affected in splenocytes from old animals. Specifically, by analyzing the kinetics of activation and inactivation of these enzymes, we found a nearly 50% decrease in the fold of activation of both ERK2 and p54(JNK). These defects result in an overall diminution of enzyme activities without changes in the steady-state levels of relevant proteins. The impaired activity of these two MAPK pathways is likely to play a role in the reduced expression of interleukin-2 and diminished lymphoproliferation observed in old animals.

Stress-induced immunomodulation and the implications for health

There are complex bi-directional interactions among the central nervous system (CNS), the endocrine system, and the immune system. Although the mechanisms of this bi-directional communication is not yet fully understood, studies in the field of psychoneuroimmunology (PNI) have shown that stress, through the hypothalamic-pituitary-adrenal (HPA) and the sympathetic-adrenal medullary (SAM) axes, can result in the dysregulation of the immune system. In this review, we discuss human studies and animal models, which focuses on psychological stress emphasizing the implications of these effects on wound healing and infectious diseases.

Valpha24+ NKT cells are decreased in elderly humans

Natural killer T (NKT) cells represent a novel cell lineage characterized by the restricted expression of an invariant TCRalpha chain encoded by Valpha24/JalphaQ gene segments in humans and Valpha14/Jalpha281+ in mice. Different aspects of the immune response are severely affected by age. Thus, we have studied the effect of aging on NKT cells from healthy elderly individuals. Our results demonstrated a decreased percentage of CD3+Valpha24+ cells in peripheral blood from elderly donors, whereas mainstream T lymphocytes showed an age-associated decrease in the expression of CD28, the vast majority of CD3+Valpha24+ cells from old individuals were CD28+. A significant increase in the percentage of Valpha24+ cells with the CD4-CD8+ phenotype was also found in the elderly, indicating a redistribution of Valpha24+ subsets according to the CD4/CD8 phenotype. Given the important immunoregulatory role of these cells, the decrease of NKT cells will contribute to the deleterious immune response in the elderly.

Value of immunological markers in predicting responsiveness to influenza vaccination in elderly individuals

Elderly individuals are at high risk for morbidity and mortality when infected with influenza virus. Vaccinations with inactivated virus are less effective in the elderly due to the declining competency of the aging immune system. We have explored whether immunological parameters predict poor anti-influenza virus vaccine responses and can be used as biological markers of immunosenescence. One hundred fifty-three residents of community-based retirement facilities aged 65 to 98 years received a trivalent influenza vaccine. Vaccine-induced antibody responses were determined by comparing hemagglutination inhibition titers before and 28 days after immunization. The composition of the T-cell compartment was analyzed by flow cytometry and the sizes of three T-cell subsets, CD4(+) CD45RO(+) cells, CD4(+) CD28(null) cells, and CD8(+) CD28(null) cells, were determined. Only 17% of the vaccine recipients were able to generate an increase in titers of antibody to all three vaccine components, and 46% of the immunized individuals failed to respond to any of the three hemagglutinins. The likelihood of successful vaccination declined with age and was independently correlated with the expansion of a particular T-cell subset, CD8(+) CD28(null) T cells. The sizes of the CD4(+) CD45RO(+) memory T-cell and CD4(+) CD28(null) T-cell subsets had no effect on the ability to mount anti-influenza virus antibody responses. Frequencies of CD8(+) CD28(null) T cells are useful biological markers of compromised immunocompetence, identifying individuals at risk for insufficient antibody responses.

The process of aging changes the interplay of the immune, endocrine and nervous systems

The immune, endocrine and nervous systems interact with each other by means of cytokines, hormones and neurotransmitters. Interaction is dependent on specific receptors and respective signaling pathways in target cells. During aging, changes occur on many levels of these global systems which depend on oxidative damage, non-enzymatic glycosylation, mitochondrial mutations, defects in cell cycle control, mitotic dysregulation, genome instability, telomere shortening and other chromosomal pathologies. An alteration of the numerical value of a parameter of one system can lead to changes of the numerical value of a variable of another system. In a non-linear dynamic process these changes can contribute to the aging phenotype. Although it is extremely difficult to dissect linear interrelations of three global systems during aging, this review attempts to identify some simple linear pathways. Furthermore, it is demonstrated that chronic inflammatory diseases may accelerate the aging process. This review also reveals that new statistical and computational methods are necessary to unravel the complexity of the aging process.

Acute myeloid leukemia in the elderly: biology and therapeutic strategies

Age represents one of the most important adverse prognostic factors in acute myeloid leukemia (AML). The therapeutic results for patients older than 60 years accrued into clinical trials of intensive chemotherapy are largely unsatisfactory (complete remission rates rarely superior to 50-60%; median relapse-free survival usually less than 12 months). Because only 30-40% of elderly patients are actually entered into these trials, the overall failure of current treatments appear even more disappointing when considered in the context of the whole population of older individuals with AML. This appears primarily due to intrinsic differences in the biology of leukemia itself and to host-related factors (i.e. reduced tolerance to chemotherapy and comorbidity). AMLs of older subjects display several biological overlaps with secondary AMLs including multilineage involvement, phenotype, unfavorable cytogenetics and elevated activity of multidrug resistance genes. The clinical application of biologically-based prognostic factors may enable to separate patients who may actually benefit from aggressive chemotherapy from those who should be offered attenuated/palliative treatments or enrolled upfront into experimental trials of new drugs or biologic/immunologic treatments. This may hopefully result in a 'risk-adapted' strategy aimed at improving disease free survival and/or quality of life for patients with differing risk profiles.

Immunosenescence and infectious diseases

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

Changes in the expression of surface receptors on lymphocyte subsets in the elderly: quantitative flow cytometric analysis

The immunophenotype of circulating lymphocytes, including the intensity expression of surface receptors, changes with ageing. Until now, no results of systematic studies on age-dependent changes with respect to the expression of the major lymphocyte surface receptors in healthy elderly subjects have been reported. In order to identify age-related changes in both representation and immunophenotype of lymphocyte populations, we investigated, by means of triple-color whole-blood immunostaining and quantitative flow cytometry, the percent values and the absolute numbers, as well as the levels of surface antigen expression or antigen molecules per cell (ABC values x 10(3)), of different peripheral blood lymphocyte subsets from 23 healthy elderly subjects and 13 young donors. Naive (CD45RA+CD3+) T cells, total B cells, and CD5+ B lymphocytes are decreased (22%, 6%, 0.8% vs. 30%, 12%, 1.4%, respectively), whereas activated (HLA-DR+CD3+) and memory (CD45RO+CD3+) T cells, CD3+CD7- T lymphocytes, and lymphocytes expressing the NK marker CD56 are expanded in the elderly (2%, 53%, 13%, 6% vs. 0.8%, 45%, 8%, 8%, respectively). Moreover, T lymphocytes from elderly individuals express lower CD3 (61 +/- 10) compared to young (69 +/- 10). Considering the different T-cell populations, CD3 antigen is respectively decreased on CD45RO+ T cells (55 +/- 14 vs. 66 +/- 14) and up-regulated on CD56+ T lymphocytes (62 +/- 21 vs. 45 +/- 20). Increased CD8 expression characterizes CD3+CD7- lymphocytes (70 +/- 34 vs. 44 +/- 17) while HLA-DR on activated T cells is lower in old (39 +/- 7) than young (46 +/- 9) donors. CD7 is down-regulated both in T (22 +/- 3 vs. 28 +/- 3) and NK (48 +/- 18 vs. 71 +/- 18) cells, whereas CD2 expression, unchanged on NK cells, is up-regulated on T lymphocytes (54 +/- 10 vs. 41 +/- 8). Age-related changes in B-cell antigen expressions were also found: CD20 is increased (124 +/- 23 vs. 105 +/- 16) whereas, despite the unchanged CD5 expression of T cells, CD5 intensity on the B-cell subset co-expressing this antigen is higher in old (49 +/- 37) than in young (22 +/- 4) people. The observed changes in the expression of functionally important cellular receptors can contribute to the remodeling of immune function characteristic of the elderly. Moreover, since quantitative flow cytometry is becoming widely employed in clinical practice, our results also contribute to the assessment of specific age-dependent antigen expression changes to be considered for diagnostic approaches in the elderly.

Dendritic cells in old age--neglected by gerontology?

Dendritic cells (DC) are known as the most efficient antigen-presenting cell type to activate T cells and are key modulators of the immune response. Due to their central role in immunology, DC have been considered as a useful tool for immunotherapy. They may also compensate failing T cell reactivity in aged persons. Despite numerous recent advances in the molecular and cell biology of DC, only very few groups have addressed the topic of DC and aging. It is the aim of the present contribution to give a short overview on what is known on DC in old age.

Zinc, infections and immunosenescence

Infections may cause mortality in old age due to damaged immune responses. As zinc is required as a catalyst, structural (zinc fingers) and regulatory ion, it is involved in many biological functions, including immune responses. Low zinc ion bioavailability and impaired cell-mediated immunity are common in ageing and may be restored by physiological supplementation with zinc for 1-2 months, impacting upon morbidity and survival. This article reviews the role of zinc in immune efficacy during ageing, and also describes the main biochemical pathways involved in the role of zinc in resistance to infections in ageing in order to better understand the possible causes of immunosenescence.

Increased expression of NK cell markers on T lymphocytes in aging and chronic activation of the immune system reflects the accumulation of effector/senescent T cells

In humans, CD56, CD161, CD16, CD94 or CD57 represent prototypic markers of NK cells, although they are also found on a subset of CD8+ T cells. We propose here that the expression of NK receptors on CD8+ T cells can be considered a marker of cytotoxic effector T cells that are expanded in vivo after antigenic activation leading to extensive proliferation. The persistence of antigen will lead to loss of co-stimulatory molecules, telomere shortening and defective IL-2 production, changes that define the state replicative senescence in T lymphocytes. The majority of these "effector/senescent" T lymphocytes are CD8+, CD45RA+, CD11a(bright), CD28-, CD27-, CD62L- and CCR7-. They are cytotoxic T cells with strong expression of intracytoplasmic perforin and granzyme, but with low proliferative capacity and defective IL-2 production. Many of these characteristics are shared by the recently defined "effector/memory" T cells, being mainly distinguished by the absence of CD45RA expression on the memory cells. The expression of NK receptor in these effector cells will probably contribute to the regulation of their cytotoxic function. Expansion of cells with these characteristics can be found not only in the elderly but also in other clinical conditions involving chronic activation of the immune system such as viral infections, rheumatic and autoimmune diseases or tumors. Another subset of T cells that expresses the NK receptors is the alpha-galactosyl-ceramide specific T cell subset defined by the expression of canonical Valpha24JalphaQ TCR, recognition of CD1d and secretion of high amounts of IL-4 and IFN-gamma. However, the changes observed in the expression of NK-R on T cells associated to immunosenescence can not be attributed to expansion of this particular T cell subset, although alterations in the number and function of these cells have been demonstrated in some autoimmune diseases.