CMV-Specific T-cell Responses at Older Ages: Broad Responses With a Large Central Memory Component May Be Key to Long-term Survival

Cytomegalovirus (CMV) infection sometimes causes large expansions of CMV-specific T cells, particularly in older people. This is believed to undermine immunity to other pathogens and to accelerate immunosenescence. While multiple different CMV proteins are recognized, most publications on age-related T-cell expansions have focused on dominant target proteins UL83 or UL123, and the T-cell activation marker interferon-γ (IFN-γ). We were concerned that this narrow approach might have skewed our understanding of CMV-specific immunity at older ages. We have, therefore, widened the scope of analysis to include in vitro-induced T-cell responses to 19 frequently recognized CMV proteins in "young" and "older" healthy volunteers and a group of "oldest old" long-term survivors (>85 years of age). Polychromatic flow cytometry was used to analyze T-cell activation markers (CD107, CD154, interleukin-2 [IL-2], tumor necrosis factor [TNF], and IFN-γ) and memory phenotypes (CD27, CD45RA). The older group had, on average, larger T-cell responses than the young, but, interestingly, response size differences were relatively smaller when all activation markers were considered rather than IFN-γ or TNF alone. The oldest old group recognized more proteins on average than the other groups, and had even bigger T-cell responses than the older group with a significantly larger central memory CD4 T-cell component.

Centenarians' offspring as a model of healthy aging: a reappraisal of the data on Italian subjects and a comprehensive overview

Within the scenario of an increasing life expectancy worldwide it is mandatory to identify determinants of healthy aging. Centenarian offspring (CO) is one of the most informative model to identify trajectories of healthy aging and their determinants (genetic and environmental), being representative of elderly in their 70th whose lifestyle can be still modified to attain a better health. This study is the first comprehensive investigation of the health status of 267 CO (mean age: 70.2 years) and adopts the innovative approach of comparing CO with 107 age-matched offspring of non-long-lived parents (hereafter indicated as NCO controls), recruited according to strict inclusion demographic criteria of Italian population. We adopted a multidimensional approach which integrates functional and cognitive assessment together with epidemiological and clinical data, including pro- and anti-inflammatory cytokines and adipokines, lipid profile, and insulin resistance. CO have a lower prevalence of stroke, cerebral thrombosis-hemorrhage, hypertension, hypercholesterolemia, and other minor diseases, lower BMI and waist circumference, a better functional and cognitive status and lower plasma level of FT4 compared to NCO controls. We conclude that a multidimensional approach is a reliable strategy to identify the health status of elderly at an age when interventions to modify their health trajectory are feasible.

Functional Diversity of Cytomegalovirus-Specific T Cells Is Maintained in Older People and Significantly Associated With Protein Specificity and Response Size

Background. Parallel upregulation of several T-cell effector functions (ie, polyfunctionality) is believed to be critical for the protection against viruses but thought to decrease in large T-cell expansions, in particular at older ages. The factors determining T-cell polyfunctionality are incompletely understood. Here we revisit the question of cytomegalovirus (CMV)–specific T-cell polyfunctionality, including a wide range of T-cell target proteins, response sizes, and participant ages.

Methods. Polychromatic flow cytometry was used to analyze the functional diversity (ie, CD107, CD154, interleukin 2, tumor necrosis factor, and interferon γ expression) of CD4⁺ and CD8⁺ T-cell responses to 19 CMV proteins in a large group of young and older United Kingdom participants. A group of oldest old people (age >85 years) was included to explore these parameters in exceptional survivors. Polyfunctionality was assessed for each protein-specific response subset, by subset and in aggregate, across all proteins by using the novel polyfunctionality index.

Results. Polyfunctionality was not reduced in healthy older people as compared to young people. However, it was significantly related to target protein specificity. For each protein, it increased with response size. In the oldest old group, overall T-cell polyfunctionality was significantly lower.

Discussion. Our results give a new perspective on T-cell polyfunctionality and raise the question of whether maintaining polyfunctionality of CMV-specific T cells at older ages is necessarily beneficial.

Optical design of a light-emitting diode lamp for a maritime lighthouse

Traffic signaling is an emerging field for light-emitting diode (LED) applications. This sustainable power-saving illumination technology can be used in maritime signaling thanks to the recently updated norms, where the possibility to utilize LED sources is explicitly cited, and to the availability of high-power white LEDs that, combined with suitable lenses, permit us to obtain well-collimated beams. This paper describes the optical design of a LED-based lamp that can replace a traditional lamp in an authentic marine lighthouse. This source recombines multiple separated LEDs realizing a quasi-punctual localized source. Advantages can be lower energy consumption, higher efficiency, longer life, fewer faults, slower aging, and minor maintenance costs. The proposed LED source allows us to keep and to utilize the old Fresnel lenses of the lighthouse, which very often have historical value.

Longitudinal changes of trabecular bone score after estrogen deprivation: effect of menopause and aromatase inhibition

PURPOSE

To examine the effects of the menopausal transition and treatment with aromatase inhibitors (AI) on trabecular bone score (TBS, a newly proposed index of bone architecture derived from DXA vertebral scans) and vertebral bone mineral density (BMD).

METHODS

Retrospective cohort study on 29 women who became postmenopausal during a mean follow-up of 2.9 years (MP group) and 34 women treated with AI during a mean follow-up of 2.1 years (AI group). BMD was measured by DXA and TBS with a specific software.

RESULTS

TBS decreased after menopause, but the change was significantly lower than that of the lumbar BMD (-4.6 vs. -6.8 %; mean difference: 2.2 %; p = 0.016). An even larger difference was observed in the AI group (-2.1 vs. -5.9 %; mean difference: 3.8 %; p = 0.002).

CONCLUSIONS

The decrease of TBS induced by menopause or treatment with AI is significantly lower than that of lumbar BMD.

New advances in CMV and immunosenescence

Immunosenescence, defined as the age-associated dysregulation and dysfunction of the immune system, is characterized by impaired protective immunity and decreased efficacy of vaccines. An increasing number of immunological, clinical and epidemiological studies suggest that persistent Cytomegalovirus (CMV) infection is associated with accelerated aging of the immune system and with several age-related diseases. However, current evidence on whether and how human CMV (HCMV) infection is implicated in immunosenescence and in age-related diseases remains incomplete and many aspects of CMV involvement in immune aging remain controversial. The attendees of the 4th International Workshop on "CMV & Immunosenescence", held in Parma, Italy, 25-27th March, 2013, presented and discussed data related to these open questions, which are reported in this commentary.

Naïve and memory CD8 T cell pool homeostasis in advanced aging: impact of age and of antigen-specific responses to cytomegalovirus

Alterations in the circulating CD8+ T cell pool, with a loss of naïve and accumulation of effector/effector memory cells, are pronounced in older adults. However, homeostatic forces that dictate such changes remain incompletely understood. This observational cross-sectional study explored the basis for variability of CD8+ T cell number and composition of its main subsets: naïve, central memory and effector memory T cells, in 131 cytomegalovirus (CMV) seropositive subjects aged over 60 years. We found great heterogeneity of CD8+ T cell numbers, which was mainly due to variability of the CD8 + CD28- T cell subset regardless of age. Analysis, by multiple regression, of distinct factors revealed that age was a predictor for the loss in absolute number of naïve T cells, but was not associated with changes in central or effector memory CD8+ T cell subsets. By contrast, the size of CD8+ T cells specific to pp65 and IE-1 antigens of CMV, predicted CD28 - CD8+ T cell, antigen-experienced CD8+ T cell, and even total CD8+ T cell numbers, but not naïve CD8+ T cell loss. These results indicate a clear dichotomy between the homeostasis of naïve and antigen-experienced subsets of CD8+ T cells which are independently affected, in human later life, by age and antigen-specific responses to CMV, respectively.

Immune parameters identify Italian centenarians with a longer five-year survival independent of their health and functional status

Centenarians are rare and exceptional individuals characterized by a peculiar phenotype. They are the best example of healthy aging in humans as most of them have escaped or substantially delayed the onset of major age-related diseases. Within this scenario, the purpose of the present work was to understand if immune status is associated with survival and health status in centenarians. To this aim, 116 centenarians were concomitantly characterized for their immunological, health and functional status, and followed-up for five-year survival. On the basis of previous knowledge we focused on a core of fundamental and basic immune parameters (number of leukocytes, monocytes, total lymphocytes, CD3(+) T lymphocytes, CD4(+) helper T lymphocytes, CD8(+) cytotoxic T lymphocytes, CD19(+) B lymphocytes and plasma levels of IgM), and the most important findings can be summarized as follows: i. a hierarchical cluster analysis was able to define Cluster1 (88 centenarians) and Cluster2 (28 centenarians) characterized by low and high values of all these immune parameters, respectively; ii. centenarians of Cluster2 showed a statistically longer five-year survival and more favorable values of other important immune (naïve, activated/memory and effector/memory T cells) and metabolic (glycemia, insulin and HOMA-IR) parameters, in accord with previous observations that centenarians have a peculiar immune profile, a preserved insulin pathway and a lower incidence of type 2 diabetes; and iii. unexpectedly, parameters related to frailty, as well as functional and cognitive status, did not show any significant correlation with the immune clustering, despite being capable per se of predicting survival. In conclusion, high values of basic immunological parameters and important T cell subsets correlate with five-year survival in centenarians, independent of other phenotypic characteristics. This unexpected biological scenario is compatible with the general hypothesis that in centenarians a progressive disconnection and loss of biological coherence among the different functions of the body occur, where survival/mortality result from the failure of any of these domains which apparently follow an independent age-related trajectory.

Cytomegalovirus infection modulates the phenotype and functional profile of the T-cell immune response to mycobacterial antigens in older life

Infection with Cytomegalovirus is associated with accelerated immunosenescence. Expansions of CMV-specific T cell responses have previously been demonstrated to affect the ability of T cells to respond to other infections. Most people above 60 years of age display M. tuberculosis-specific immunity because of vaccination, exposure, or both. T-cell responses can be assessed by measuring intracellular IFN-γ in vitro after tuberculin stimulation. Here we investigated tuberculin-specific CD4 T-cell responses in independently living healthy older people in the South of England using flow-cytometry. Individuals were investigated for tuberculin and CMV-specific T-cell immunity using in vitro antigen stimulation followed by intracellular staining for IFN-γ, TNF-α, IL2, as well as degranulation and CD154 upregulation. We also examined a control group of younger individuals (20–35 years of age). There was no significant difference between older and young people in regards to tuberculin responsiveness of CD4 T-cells; however, older people seemed to show more outliers. Increased responsiveness to tuberculin was significantly correlated to CMV responsiveness but not age. In older donors, the memory phenotype of tuberculin-induced T-cells was significantly skewed towards a more terminal differentiation phenotype in CMV-infected compared to uninfected individuals and the degree of skewing correlated quantitatively with the size of the CMV-specific CD4 T-cell response. This is a fundamental advance over previous reports of changes of the tuberculin-specific CD4 T-cell response with CMV serostatus. Our results show that how the immune system responds to CMV has a fundamental impact on the phenotype and function of the immune response to mycobacterial antigens in older life.

•

We examine the CD4 T-cell response to tuberculosis antigens in older people.

•

The CD4 T-cell response to Cytomegalovirus is explored in parallel.

•

CMV infection changes the profile of the tuberculin-specific-response.

•

The size of the CMV T-cell response is linked to these changes in a quantitative way.

•

The way we respond to CMV (‘mode’) affects our T-cell immunity to other pathogens.

Broad-spectrum activity of a novel antibiotic peptide against multidrug-resistant veterinary isolates

The emergence of multidrug resistant (MDR) and extensively drug resistant (XDR) bacteria has become a medical and veterinary problem. Antimicrobial peptides (AMPs) show potential to overcome antibiotic resistance and could be used therapeutically. A novel AMP (AMP2041) was developed in silico and its microbiocidal activity against MDR clinical strains isolated from cattle (n=6), dogs (n=8), and pigs (n=20) was evaluated. AMP2041 showed strong antimicrobial activity against all Gram-positive and Gram-negative MDR clinical strains tested. Within 20 min of incubation, there was complete killing of Pseudomonas aeruginosa ATCC 27953 and a 90% reduction of colony count for Escherichia coli ATCC 25922. For Staphylococcus aureus ATCC 25923, a 90% reduction of colony count was observed within 120 min of incubation.

Does the longevity of one or both parents influence the health status of their offspring?

According to the findings of some recent studies, the centenarians' offspring appear to represent a promising model for research on longevity and healthy aging. This study compares the health status and the functional status of three groups of subjects: 1. individuals with two long-lived parents (one of whom centenarian), 2. individuals with only one long-lived (centenarian) parent, and 3. individuals with no long-lived parents. The goal is to verify whether the centenarians' offspring display any advantage over the offspring of both non-long-lived parents and to evaluate whether the longevity of the non-centenarian parent provides a further advantage. A total of 374 subjects (mean age approximately 70 years) was examined. A threshold for longevity was established for non-centenarian parents through demographic data available for Italy (males surviving to at least 81 years of age and females to 87 years). The participants were assessed for their health and functional status by means of a standardized questionnaire and tests of physical performance. Data were analyzed using multivariate regression models adjusted for socio-demographic characteristics and risk factors for age-related pathologies. The results of the study show that centenarians' offspring have a better functional status, a reduced risk for several age-related pathologies and reduced drug consumption than the offspring of non-long-lived parents. In addition, the health status of centenarians' offspring does not appear to be influenced by the longevity of the second parent. It therefore seems possible to conclude that at ages around 70 years the genetic contribution to health status deriving from having one centenarian parent is not substantially improved if the other parent is also long-lived.

CMV and Immunosenescence: from basics to clinics

Alone among herpesviruses, persistent Cytomegalovirus (CMV) markedly alters the numbers and proportions of peripheral immune cells in infected-vs-uninfected people. Because the rate of CMV infection increases with age in most countries, it has been suggested that it drives or at least exacerbates “immunosenescence”. This contention remains controversial and was the primary subject of the Third International Workshop on CMV & Immunosenescence which was held in Cordoba, Spain, 15-16^th March, 2012. Discussions focused on several main themes including the effects of CMV on adaptive immunity and immunosenescence, characterization of CMV-specific T cells, impact of CMV infection and ageing on innate immunity, and finally, most important, the clinical implications of immunosenescence and CMV infection. Here we summarize the major findings of this workshop.

Report from the second cytomegalovirus and immunosenescence workshop

The Second International Workshop on CMV & Immunosenescence was held in Cambridge, UK, 2-4^th December, 2010. The presentations covered four separate sessions: cytomegalovirus and T cell phenotypes; T cell memory frequency, inflation and immunosenescence; cytomegalovirus in aging, mortality and disease states; and the immunobiology of cytomegalovirus-specific T cells and effects of the virus on vaccination. This commentary summarizes the major findings of these presentations and references subsequently published work from the presenter laboratory where appropriate and draws together major themes that were subsequently discussed along with new areas of interest that were highlighted by this discussion.

Endothelial dysfunction and high cardiovascular risk profile in severe alcoholics improve only partially following a medium-term alcohol withdrawal

BACKGROUND

Little is known about brachial artery flow-mediated vasodilatation (FMD) in active and medium-term withdrawing heavy alcoholics (HA).

METHODS

FMD and some parameters of cardiovascular (CV) risk were measured in 29 HA (average alcohol intake 135, range 86 to 215 g per day) at baseline and after a 9 ± 7 months withdrawal and in 35 teetotalers.

RESULTS

HA showed baseline impaired maximal % FMD (8.5 ± 5.4 SD vs. 14.9 ± 7.4, <0.001 vs. teetotalers), higher systolic (SBP) and diastolic (DBP) blood pressure (+24 mm Hg, <0.001; +15 mm Hg, <0.01), uric acid (5.3 ± 1.1 vs. 4.4 ± 0.8 mg/dl, <0.05), high-sensitivity C-reactive protein (hs-CRP; 2.7 ± 2.0 vs. 1.0 ± 0.9 mg/l, <0.02), endothelin-1 (ET-1, 0.88 ± 0.36 vs. 0.37 ± 0.10 pg/ml,<0.001), asymmetric dimethylarginine (ADMA, 0.50 ± 0.21 vs. 0.41 ± 0.12 μmol/l, p < 0.001), homeostasis model assessment of insulin resistance (HOMA-IR) (2.3 ± 1.1 vs. 1.2 ± 0.4, <0.001), and urinary 8-isoprostane (U8-iso-PGF2α) (237.2 ± 172.4 vs. 168.5 ± 96.6 pg/mg creatinine, <0.05). After withdrawal, SBP fell by 15 mm Hg, DBP by 11 mm Hg (p < 0.001), and hs-CRP by 0.94 mg/l (p < 0.02), all remaining still higher than teetotalers (<0.05, 0.01, 0.05 respectively). ET-1, HOMA-IR, and U8-iso-PGF2α were unchanged (p = NS vs. baseline, <0.05 to 0.001 vs. teetotalers). Maximal % FMD rose (to 10.6 ± 6.2, p < 0.04), but it still remained impaired (<0.04 vs. teetotalers). ADMA increased further to 0.64 ± 0.15 μmol/l (<0.05 vs. baseline, <0.02 vs. teetotalers).

CONCLUSIONS

HA show marked endothelial dysfunction (ED) and high BP, impaired insulin sensitivity, inflammation, increased oxidative stress, and elevated ET-1 and ADMA, which are unaffected or only partially reversed by a medium-term alcohol withdrawal. ED and related abnormalities persist in detoxified alcoholics, thus contributing to a greater CV morbidity and mortality.

Carbon nanohorns-based nanofluids as direct sunlight absorbers

The optimization of the poor heat transfer characteristics of fluids conventionally employed in solar devices are at present one of the main topics for system efficiency and compactness. In the present work we investigated the optical and thermal properties of nanofluids consisting in aqueous suspensions of single wall carbon nanohorns. The characteristics of these nanofluids were evaluated in view of their use as sunlight absorber fluids in a solar device. The observed nanoparticle-induced differences in optical properties appeared promising, leading to a considerably higher sunlight absorption. We found that the thermal conductivity of the nanofluids was higher than pure water. Both these effects, together with the possible chemical functionalization of carbon nanohorns, make this new kind of nanofluids very interesting for increasing the overall efficiency of the sunlight exploiting device.

Intense antiextracellular adaptive immune response to human cytomegalovirus in very old subjects with impaired health and cognitive and functional status

Human aging is characterized by expanded and altered adaptive immune responses to human CMV (HCMV). It is unclear whether this expansion has its origins in age-related homeostatic disturbances or viral reactivation, whether anti-CMV immune surveillance may still be effective, and what are the consequences of this expanded immune response for health and longevity. We conducted an observational cross-sectional study in groups of HCMV-seropositive subjects aged >or=65 y of variable health status to compare the intensity of Ab responses against HCMV with those against EBV and with CD4(+) and CD8(+) T cell proinflammatory effector responses directed to HCMV-derived pp65 and immediate-early protein 1 synthetic peptides. Ab responses to HCMV, but not to EBV, and anti-HCMV CD4(+), but not CD8(+), T cell responses were more intense in elderly subjects aged >or=85 y in poor health and were inversely correlated with markers of functional activity and cognitive function. Therefore, humoral and CD4(+) T cell anti-HCMV responses were specifically intensified in advanced aging associated with comorbidity and cognitive and functional impairments. Such a distinctive pattern of adaptive immunity indicates that immune responses targeting the extracellular phase of HCMV are increased in these elderly subjects and could represent an indirect effect of localized and undetectable HCMV reactivation. This study demonstrates that the oldest subjects in poor health with physical and mental impairment express intense functional immune responses to extracellular HCMV and suggests that they may be at risk for direct pathogenic effects by HCMV reactivation as well as indirect pathogenic effects linked to proinflammatory anti-HCMV effector responses.

Human longevity within an evolutionary perspective: The peculiar paradigm of a post-reproductive genetics

The data we collected on the genetics of human longevity, mostly resulting from studies on centenarians, indicate that: (1) centenarians and long-living sib-pairs are a good choice for the study of human longevity, because they represent an extreme phenotype, i.e., the survival tail of the population who escaped neonatal mortality, pre-antibiotic era illnesses, and fatal outcomes of age-related complex diseases. (2) The model of centenarians is not simply an additional model with respect to well-studied organisms, and the study of humans has revealed characteristics of ageing and longevity (geographical and sex differences, role of antigenic load and inflammation, role of mtDNA variants) which did not emerge from studies in laboratory model systems and organisms. (3) All the phenotypic characteristics of nonagenarians and centenarians fit the hypothesis that ageing is a remodelling process where the body of survivors progressively adapts to internal and external damaging agents they are exposed to during several decades, largely unpredicted by evolution. (4) Such a remodelling process, which can be considered a Darwinian process occurring at the somatic level within the framework of the evolutionary constraints, established by evolution for Homo sapiens as a species, may explain why the same gene polymorphism can have different (beneficial or detrimental) effects at different ages. (5) Geographic and demographic evidence suggest that longevity can be achieved by different combinations of genes, environment, and chance quantitatively and qualitatively different in many geographic areas, and that population-specific genetic factors, play a role on the longevity trait. (6) The concomitant and integrated use of new in silico and high throughput strategies will greatly accelerate the identification of new longevity genes in humans.

Massive Load of Functional Effector CD4+and CD8+T Cells against Cytomegalovirus in Very Old Subjects

A progressive, systemic, and low-grade proinflammatory status is one of the major characteristics of immunosenescence. Emerging data suggest a possible contribution of CMV, known to chronically infect a large proportion of humans, lifelong from newborns to centenarians. To test this hypothesis, we evaluated functional T cell responses to two CMV immunogenic proteins, pp65 and IE-1, in 65 chronically infected subjects aged 25-100 years. PBMC were stimulated with mixtures of peptides spanning the entire sequence of both proteins, and Ag specificity and magnitude of intracellular IFN-gamma- and TNF-alpha-positive cells were then analyzed within both CD4+ and CD8+ T cells. Results indicate that pp65 and, to a lesser extent, IE-1 constitute major Ags against which aged people target functionally efficient T cell effector responses with massive production of Th1 cytokines and exhibition of CD107a degranulation marker. As a result, the production of IFN-gamma induced in T cells by both Ags was seven to eight times greater in very old than in young subjects. The comparative analysis of pp65-specific responses in these very long-term carriers revealed a reciprocal relationship between CD4+ and CD8+ producing IFN-gamma in the same individuals. These results indicate that CMV represents an important pathogen responsible for a strong immune activation in human aging. Such a remarkable burden of effector CD4+ and CD8+ T cells may be necessary to protect the elderly from CMV endogenous reactivation, but can turn detrimental by giving a substantial contribution to the proinflammatory status that accompanies the main age-related diseases.

Pathophysiology of ageing, longevity and age related diseases

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

Immunomodulatory Effects of IFN-β1a Treatment Alone or Associated with Pentoxifylline in Patients with Relapsing-Remitting Multiple Sclerosis (RRMS)

Interferon-beta1a (IFN-beta1a) and pentoxifylline (PTX) are reported to be active in relapsing-remitting multiple sclerosis (RRMS), but the mechanisms are not completely understood. In two groups of RRMS patients, we studied the phenotype of peripheral lymphocytes and the level of several cytokines both in sera and in supernatants of activated peripheral blood mononuclear cells (PBMC) before and after 8 months of therapy with IFN-beta1a alone or associated with PTX. Our data indicate that patients with RRMS, treated with IFN-beta1a, exhibited a significant increase in CD4(+)CD25(++) T suppressor cells, accompanied by a significant decrease in cytotoxic lymphocytes (CD8(+)CD28(-) and natural killer [NK] cells) and IFN-gamma production, which could both contribute to an explanation of the previously described beneficial effects of IFN-beta treatment in MS. The addition of PTX to IFN-beta1a treatment did not modify the immunomodulatory effects obtained with IFN-beta1a alone. Future studies are needed to demonstrate which immunologic parameters correlate with the clinical benefit of IFN-beta1a treatment.

Different contribution of EBV and CMV infections in very long-term carriers to age-related alterations of CD8+ T cells

Aging is accompanied by a complex dynamics of CD8+ T cell subsets whose origin is unclear. To evaluate the impact of Epstein-Barr virus (EBV) and cytomegalovirus (CMV) chronic infections on CD8+ T cells in far advanced age, we studied CD8+ T cells frequencies and phenotype in nonagenarians and centenarians by HLA-A*0201- and HLA-B*0702-tetramers incorporating epitopes specific of both viruses along with viral replication. The results demonstrate that EBV and CMV infections induce quantitatively and qualitatively different CD8+ T-cell responses in advanced aging. The frequency and absolute number of CD8+ T cells specific for one lytic and two latent EBV-epitopes, were relatively low and mostly included within CD8+ CD28+ cells. By contrast, CMV infection was characterized by highly variable numbers of CD8+ T cells specific for two differently restricted CMV-epitopes that, in some subjects, were strikingly expanded. Moreover, the great majority of anti-CMV CD8+ T cells did not bear CD28 antigen. Notwithstanding the expansion of CMV-specific CD8+ lymphocytes, CMV-DNA detection in blood samples was invariably negative. Altogether, we suggest that CMV, but not EBV, can sustain chronic activation of the HLA-class I restricted effector arm in elderly that might have detrimental effects on age-associated diseases.

Low vitamin D status, high bone turnover, and bone fractures in centenarians

The oldest olds, including centenarians, are increasing worldwide and, in the near future, will represent a consistent part of the population. We have studied bone status and metabolism in 104 subjects over 98 yr of age to evaluate possible interventions able to avoid fragility fractures and disability. Ninety females and 14 males not affected by any acute disease were considered. After a complete clinical assessment, blood was drawn for evaluating bone turnover markers, and performance tests together with skeletal ultrasonography (either at the phalanges or at the heel) were performed. We found that 38 subjects had sustained a total of 55 fractures throughout their lives, and 75% of these were fragility fractures. Twenty-eight fractures occurred at the proximal femur, with 14 after the age of 94 yr. Serum 25-hydroxyvitamin D was undetectable in 99 of 104 centenarians. PTH and serum C-terminal fragment of collagen type I were elevated in 64 and 90% of centenarians, respectively, with a trend toward hypocalcemia. Bone alkaline phosphatase levels were close to the upper limit. Serum IL-6 was elevated in 81% of centenarians and was positively correlated with PTH and negatively correlated with serum calcium. Serum creatinine was not correlated with PTH. Bone ultrasonography showed that most centenarians had low values, and ultrasonographic parameters were correlated with resorption markers. We conclude that the extreme decades of life are characterized by a pathophysiological sequence of events linking vitamin D deficiency, low serum calcium, and secondary hyperparathyroidism with an increase in bone resorption and severe osteopenia. These data offer a rationale for the possible prevention of elevated bone turnover, bone loss, and consequently the reduction of osteoporotic fractures and fracture-induced disability in the oldest olds through the supplementation with calcium and vitamin D.

Marked increase with age of type 1 cytokines within memory and effector/cytotoxic CD8+ T cells in humans: a contribution to understand the relationship between inflammation and immunosenescence

The ageing process is characterized by a progressive exhaustion of the naïve T cell reservoir that is accompanied by a compensatory expansion of effector/cytotoxic CD8+CD28- T cells. However, the origin and function of this subpopulation is not completely clarified. In this study, we examined the intracellular cytokine profile in purified CD8+ T cells obtained from 29 healthy subjects of different ages. Type 1 (IFN-gamma IL-2 and TNF-alpha) and type 2 (IL-4, IL-6 and IL-10) cytokines were determined in three CD8+ T subsets, i.e. CD95-CD28+ (naïve), CD95+CD28- (effector/cytotoxic), and CD95+CD28+ (memory). As a general trend, we observed, in aged subjects, an increase of type 1 and type 2 intracellular cytokines within the three CD8+ subsets. In particular, we showed that type 1 cytokine-positive cells significantly increased, with age, among all the CD8+ subsets, while a marked increase of type 2 producing cells was observed only in memory CD8+ T cells. These profound changes are compatible with inflame-aging, an hypothesis which suggest that immunosenescence is mainly driven by a chronic antigenic load which not only induces an enormous expansion of CD28- T cells, but also increases their functional activity, exemplified by an high frequency of cells positive for pro-inflammatory cytokines.

Dendritic cells are functionally defective in multiple myeloma: the role of interleukin-6

We studied concentration, phenotype, and function of peripheral blood (PB) dendritic cells (DCs) from patients with multiple myeloma (MM). The absolute number of circulating precursors of myeloid and plasmacytoid DCs was significantly lower in MM patients than in healthy subjects. After maturation, PBDCs from MM patients showed significantly lower expression of HLA-DR, CD40, and CD80 antigens and impaired induction of allogeneic T-cell proliferation compared with controls. Remarkably, they were not capable of presenting the patient-specific tumor idiotype to autologous T cells. Conversely, DCs generated in vitro from CD14(+) monocytes from the same patients, and PBDCs freshly isolated from healthy donors efficiently stimulated allogeneic and autologous T cells. To clarify the mechanism of PBDC deficiency in MM, we investigated the effects of the main plasma cell growth factor, interleukin-6 (IL-6), on the development of DCs from CD34(+) cells. IL-6 inhibited the colony growth of CD34(+) DC progenitors and switched the commitment of CD34(+) cells from DCs to CD14(+) CD1a(-) CD86(-)CD80(-) CD40(+/-)HLA-DR +/- monocytic cells exerting potent phagocytic activity but no antigen-presentation capacity. This effect was reversed by anti-IL-6 antibodies. Growing CD34(+) cells in the presence of autologous serum (without IL-6) also suppressed the development of functional DCs. This study demonstrates that PBDCs from MM patients are functionally defective, partially because of IL-6-mediated inhibition of development. This brings into question the advisability of using PBDCs as antigen carriers for immunotherapy trials in MM. The results also suggest a novel mechanism whereby myeloma cells escape immune recognition.

T-cell dynamics after high-dose chemotherapy in adults: elucidation of the elusive CD8+ subset reveals multiple homeostatic T-cell compartments with distinct implications for immune competence

Recovery of total T cell numbers after in vivo T-cell depletion in humans is accompanied by complex perturbation within the CD8+ subset. We aimed to elucidate the reconstitution of CD8+ T cells by separate analysis of putative naïve CD95- CD28+, memory CD95+ CD28+ and CD28- T cell compartments after acute maximal depletion by high-dose chemotherapy (HD-ChT) in women with high-risk breast cancer. We found that recovery of putative naïve CD8+ CD95- CD28+ and CD4+ CD95- CD28+ T cells, was compatible with a thymus-dependent regenerative pathway since their recovery was slow and time-dependent, their values were tightly related to each other, and their reconstitution patterns were inversely related to age. By analysing non-naïve T cells, a striking diversion between putative memory T cells and CD28- T cells was found. These latter increased early well beyond normal values, thus playing a pivotal role in total T-cell homeostasis, and contributed to reduce the CD4 : CD8 ratio. In contrast, putative memory T cells returned to values not significantly different from those seen in patients at diagnosis, indicating that this compartment may recover after HD-ChT. At 3-5 years after treatment, naïve T cells persisted at low levels, with expansion of CD28- T cells, suggesting that such alterations may extend further. These findings indicate that CD28- T cells were responsible for 'blind' T-cell homeostasis, but support the notion that memory and naïve T cells are regulated separately. Given their distinct dynamics, quantitative evaluation of T-cell pools in patients undergoing chemotherapy should take into account separate analysis of naïve, memory and CD28- T cells.

A stochastic model for CD8(+)T cell dynamics in human immunosenescence: implications for survival and longevity

We propose here a stochastic model for the CD 8(+)T lymphocyte dynamics on the long time-scale of the human lifespan. Our purpose has been to test the hypothesis, recently proposed on the basis of our experimental data (Fagnoni et al., 2000), that the depletion of virgin CD8(+)T lymphocytes can be considered a reliable biomarker related to the risk of death. This hypothesis is embedded in a more general theory of immunosenescence according to which the accumulation of antigen experienced (AE) T cells and the concomitant exhaustion of antigen non-experienced (ANE) T cells with age, mostly due to the chronic lifelong exposure to antigens, is a major characteristic of the remodeling of the human immune system with age. In our model we considered a deterministic balance of ANE and AE T cell concentrations plus a stochastic forcing, which describes the chronic antigenic stress fluctuations, assuming a mean genetically determined capability of individuals to respond to antigens. The major results of our model is the validation of the above-mentioned hypothesis, since the model is capable of fitting the experimental data concerning the changes of ANE T cell concentration over age, and at the same time to reproduce survival curves similar to the demographic ones. Furthermore, the stochastic process results in being responsible for the peculiar shape of the survival curves.

Circulating CD33+ large mononuclear cells contain three distinct populations with phenotype of putative antigen-presenting cells including myeloid dendritic cells and CD14+ monocytes with their CD16+ subset

BACKGROUND

In peripheral blood, myeloid markers identify a heterogeneous mixture of cells in transit from the bone marrow to peripheral tissues. Similarly, HLA-class II DR expression usually identifies mononuclear cells with the potential for developing antigen-presenting activity. We gathered putative antigen presenting cells bearing myeloid markers (My-APC) to study their composition by cell surface phenotype.

METHODS

To gather and dissect My-APC phenotype while excluding lymphocytes and granulocytes, we developed a strategy based on staining red cell-lysed peripheral blood and gating cells bearing myeloid markers and physical parameters of large mononuclear cells.

RESULTS

Phenotypic analysis within the My-APC gate showed three distinct populations. The largest fraction was constituted by CD14+ monocytes that extended into the other two populations, each expressing gradually lower levels of CD14 surface antigen along with increasing levels of CD16 and CD2, respectively. The CD16 and CD2 expression patterns extended from CD16+CD14+ or CD2+CD14+ double- positive intermediate cells toward each single positive subset, but they were reciprocally exclusive. Interestingly, CD2+CD14- cells within the My-APC gate were equivalent to myeloid dendritic cell precursors (pre-DC) defined previously by the absence of lineage markers and expression of HLA-DR and myeloid markers. Phenotypic analysis of each population revealed differences in the expression of costimulatory molecules and CD62L.

CONCLUSIONS

This novel analytical approach allowed us to distinguish circulating My-APC in three subsets and to identify relationships between monocytes and other related myeloid populations including DC.

Serum interleukin-6, soluble interleukin-6 receptor and soluble gp130 exhibit different patterns of age- and menopause-related changes

Growing evidence suggests that interleukin-6 (IL-6) may play a pathogenetic role in postmenopausal bone loss and in other age-related pathological conditions. In this study, we have examined the age-related changes in the serum levels of IL-6 and the soluble receptors that modulate its biological activity--soluble IL-6 receptor (sIL-6R) and soluble gp130 (sgp130)--in 220 women (from 25 to 104yr old), including 22 centenarians. Serum IL-6 rose exponentially with age (r=0.74, p<0.0001). The median level of IL-6 increased almost ten-fold with age, from 1.16pg/ml in premenopausal women to 10.27pg/ml in centenarians. Serum sIL-6R and sgp130 showed an increase until the seventh decade and a progressive decrease in older ages (r=0.39, p<0.0001 and r=0.26, p=0.008, respectively). IL-6, sIL-6R and sgp130 were significantly higher in women within 10yr of menopause as compared to premenopausal subjects (1.51 vs. 1.16pg/ml, p=0.012; 41.9 vs. 35.7ng/ml, p=0.002; and 253.4 vs. 230.7ng/ml, p=0.008, respectively). In postmenopausal women, a negative correlation was found between sIL-6R and the lumbar bone mineral density (BMD) (r=-0.28, p=0.002) even after adjusting for age and weight. Furthermore, sIL-6R levels were higher in osteoporotic compared to normal women (47.9 vs. 39.5ng/ml, p=0.001). In conclusion, our results show that the serum levels of IL-6, sIL-6R and sgp130 exhibit different patterns of age- and menopause-related changes, and that the biological activity of IL-6 may be increased with age with potential implications in the age-related diseases such as osteoporosis.

Identification of Fas-L-expressing apoptotic T lymphocytes in normal human peripheral blood : in vivo suicide

Fas-L molecules expressed by in vitro stimulated T cells may be critically involved in suicidal activation-induced cell death (AICD) of such cells through engagement of their Fas receptors. A similar suicide of T cells was postulated to occur even in vivo, to eliminate dangerous activated lymphocytes; however, the demonstration of suicidal AICD of T cells in healthy humans in vivo is still lacking. We therefore investigated the possible occurrence of Fas-L-linked suicidal apoptosis of T cells in normal human peripheral blood. For this purpose, we took advantage of immunoelectron microscopy, which allows simultaneous visualization of the morphological apoptotic cellular changes together with surface expression of Fas-L molecules. Very few T lymphocytes were observed showing the ultrastructural features of apoptotic lymphocytes; these occasional apoptotic T cells, together with the majority of the normal T cell population, expressed the Fas molecule on the plasma membrane, as expected. Interestingly, the apoptotic cells were also Fas-L-positive, whereas normal T cells were Fas-L-negative. Such Fas-L-associated T cell suicide operating in vivo in healthy individuals is presumably able to suppress immune responses and prevent autoreactivity, thus maintaining the homeostasis of human blood.

Efficient presentation of tumor idiotype to autologous T cells by CD83(+) dendritic cells derived from highly purified circulating CD14(+) monocytes in multiple myeloma patients

To generate mature and fully functional CD83(+) dendritic cells derived from circulating CD14(+) cells highly purified from the leukapheresis products of multiple myeloma patients.CD14(+) monocytes were selected by high-gradient magnetic separation and differentiated to immature dendritic cells with granulocyte-macrophage colony-stimulating factor and interleukin-4 for 6-7 days and then induced to terminal maturation by the addition of tumor necrosis factor-alpha or stimulation with CD40 ligand. Dendritic cells were characterized by immunophenotyping, evaluation of soluble antigens uptake, cytokine secretion, capacity of stimulating allogeneic T cells, and ability of presenting nominal antigens, including tumor idiotype, to autologous T lymphocytes. Phenotypic analysis showed that 90% +/- 6% of cells recovered after granulocyte-macrophage colony-stimulating factor and interleukin-4 stimulation expressed all surface markers typical of immature dendritic cells and demonstrated a high capacity of uptaking soluble antigens as shown by the FITC-dextran assay. Subsequent exposure to maturation stimuli induced the downregulation of CD1a and upregulation of CD83, HLA-DR, costimulatory molecules and induced the secretion of large amounts of interleukin-12. Mature CD83(+) cells showed a diminished ability of antigen uptake whereas they proved to be potent stimulators of allogeneic T cells in a mixed lymphocyte reaction. Monocyte-derived dendritic cells, pulsed before the addition of maturation stimuli, were capable of presenting soluble proteins such as keyhole limpet hemocyanin and tetanus toxoid to autologous T cells for primary and secondary immune response, respectively. Conversely, pulsing of mature (CD83(+)) dendritic cells was less efficient for the induction of T-cell proliferation. More importantly, CD14(+) cells-derived dendritic cells stimulated autologous T-cell proliferation in response to a tumor antigen such as the patient-specific idiotype. Moreover, idiotype-pulsed dendritic cells induced the secretion of interleukin-2 and gamma-interferon by purified CD4(+) cells. T-cell activation was better achieved when Fab immunoglobulin fragments were used as compared with the whole protein. When dendritic cells derived from CD14(+) cells from healthy volunteers were analyzed, we did not find any difference with samples from myeloma patients as for cell yield, phenotypic profile, and functional characteristics. These studies demonstrate that mobilized purified CD14(+) cells represent the optimal source for the production of a homogeneous cell population of mature CD83(+) dendritic cells suitable for clinical trials in multiple myeloma.

Shortage of circulating naive CD8(+) T cells provides new insights on immunodeficiency in aging

Clinical observations indicate that elderly people are prone to severe, often lethal infectious diseases induced by novel pathogens. Since the ability to mount primary immune responses relies on the availability of naive T cells, the circulating naive T-cell reservoir was evaluated throughout the human life span. Naive T cells were identified as CD95(-) T lymphocytes for their phenotypic and functional features. Indeed, the lack of CD95 marker is sufficient to identify a population of naive T cells, as defined by coincidence with previously characterized CD45RA(+) CD62L(+) T cells. Naive CD95(-) T cells, as expected, require a costimulatory signal, such as CD28, to optimally proliferate after anti-CD3 stimulation. Cytofluorimetric analysis of circulating T lymphocytes from 120 healthy subjects ranging in age from 18 to 105 years revealed that naive T cells decreased sharply with age. The younger subjects had a naive T-lymphocyte count of 825 +/- 48 cells/microL, and the centenarians had a naive T-lymphocyte count of 177 +/- 28 cells/microL. Surprisingly, the naive T-cell count was lower in CD8(+) than in CD4(+) subsets at any age, and the oldest individuals were almost completely depleted of circulating naive CD8(+) T cells (13 +/- 4 cells/microL). Concomitantly, a progressive expansion of CD28(-) T cells occurs with age, which can be interpreted as a compensatory mechanism. These data provide new insights into age-related T-cell-mediated immunodeficiency and reveal some analogies of T-cell dynamics between advanced aging and human immunodeficiency virus (HIV) infection. In conclusion, the exhaustion of the naive CD8(+) T-cell reservoir, which has never been reported before, suggests that this T-cell pool is a major target of the aging process and may define a parameter possibly related to the life span of humans. (Blood. 2000;95:2860-2868)

Do men and women follow different trajectories to reach extreme longevity? Italian Multicenter Study on Centenarians (IMUSCE)

Gender accounts for important differences in the incidence and prevalence of a variety of age-related diseases. Considering people of far advanced age, demographic data document a clear-cut prevalence of females compared to males, suggesting that sex-specific mortality rates follow different trajectories during aging. In the present investigation, we report data from a nationwide study on Italian centenarians (a total of 1162 subjects), and from two studies on centenarians living in two distinct zones of Italy, i.e., the island of Sardinia (a total of 222 subjects) and the Mantova province (Northern Italy) (a total of 43 subjects). The female/male ratio was about 2:1 in Sardinia, 4:1 in the whole of Italy, and about 7:1 in the Mantova province. Thus, a complex interaction of environmental, historical and genetic factors, differently characterizing the various parts of Italy, likely plays an important role in determining the gender-specific probability of achieving longevity. Gender differences in the health status of centenarians are also reported, and an innovative score method to classify long-lived people in different health categories, according to clinical and functional parameters, is proposed. Our data indicate that not only is this selected group of people, as a whole, highly heterogeneous, but also that a marked gender difference exists, since male centenarians are less heterogeneous and more healthy than female centenarians. Immunological factors regarding the age-related increase in pro-inflammatory status, and the frequency of HLA ancestral haplotypes also show gender differences that likely contribute to the different strategies that men and women seem to follow to achieve longevity. Concerning the different impact of genetic factors on the probability of reaching the extreme limits of the human life-span, emerging evidence (regarding mtDNA haplogroups, Thyrosine Hydroxilase, and IL-6 genes) suggests that female longevity is less dependent on genetics than male longevity, and that female centenarians likely exploited a healthier life-style and more favorable environmental conditions, owing to gender-specific cultural and anthropological characteristics of the Italian society in the last 100 years.

C4, BF, C3 allele distribution and complement activity in healthy aged people and centenarians

The aim of this study was to examine the complement system and the distribution of some human leukocyte antigen (HLA) class III alleles (C4, BF) in healthy aged people (77 centenarians and 89 elderly subjects). We have also studied the alleles of C3, a complement component genetically unrelated to HLA, the immunochemical levels of C4 and C3 and serum functional hemolytic activity for classical (CH50) and alternative (AP50) complement pathway. The levels of C3 and C4 and the CH50 and AP50 were found to be within the normal range. The frequencies of C3, BF, and C4A alleles were similar in the cohorts that have been studied. For C4B null allele (C4BQ0) a trend toward an increase in the older cohort was observed, although the differences were not significant after statistical correction. Our data suggest that the complement system is well preserved in centenarians and elderly subjects and class III HLA antigens are equally distributed in aged cohorts and in young healthy individuals.

Soil textural classification by a photosedimentation method

A photosedimentation technique is used to analyze the size composition of soil samples. The number and size of the particles are determined, respectively, by the Stokes formula and the Beer-Lambert law, measuring time-of-flight and laser light attenuation simultaneously and hence evaluating solution turbidity. A simple software procedure has been developed to obtain fractional volume size distribution, taking into account the particle's optical properties depending mainly on its size and refractive index. Laboratory measurements on calibrated particulates, showing their reproducibility and validation as well as a classification of ground samples, are presented. Size distribution data can then be utilized to obtain a textural classification of the soil samples for agricultural applications.

T lymphocyte proliferative capability to defined stimuli and costimulatory CD28 pathway is not impaired in healthy centenarians

It is generally assumed that T cell proliferation is impaired in aged individuals. We report data on the proliferative capability of peripheral blood mononuclear cells (PBMC) and T lymphocytes from 40 healthy people of different ages, (19-107 years), including 14 centenarians, to defined mitogenic stimuli. We observed no age-related proliferative impairment both in PBMC and in purified T cells stimulated by anti-CD3 mAb or phorbol myristate acetate (PMA). Furthermore, T cells stimulated by anti-CD3 mAb or PMA and costimulated by CD28 mAb did not proliferate differently among young, middle aged subjects and centenarians. Thus, short term T cell proliferation is not affected even at extreme age when well defined stimuli are used on cells deriving from carefully selected healthy subjects.

Gene polymorphisms predicting high plasma levels of coagulation and fibrinolysis proteins. A study in centenarians

Gene polymorphisms associated with the plasma levels of fibrinogen, factor VII, and plasminogen activator inhibitor 1 (PAI-1)-hemostasis proteins that help to predict the risk of atherothrombotic disease-were compared in 124 healthy individuals > or = 100 years old and 130 young, healthy individuals to identify genetic influences on extreme longevity. We investigated the restriction fragment length polymorphism G/A-455 located in the promoter of the beta-fibrinogen gene, the guanine insertion/deletion polymorphism 4G/5G in the promoter of the PAI-1 gene, and the R353Q substitution polymorphism in exon 8 of the factor VII gene. Alleles and genotypes associated with elevated plasma levels of fibrinogen and factor VII were found with similar frequencies in centenarians and in the comparison group. However, in centenarians there was a significantly higher frequency of the 4G allele and of the homozygous 4G4G genotype associated with high PAI-1 levels. Since high PAI-1 is considered a predictor of recurrent myocardial infarction in young men, it is intriguing that the corresponding genetic marker is more frequent in centenarians who have escaped major age-related atherothrombotic disease and reached the extreme limits of human life. Homozygosity for the 4G allele, despite its association with impaired fibrinolysis, is compatible with successful aging.

DNA multiallelic systems reveal gene/longevity associations not detected by diallelic systems. The APOB locus

To identify possible genetic factors affecting human longevity we compared allele pools at two candidate loci for longevity between a sample of 143 centenarians (S) and a control sample of 158 individuals (C). The candidate loci were APOB and TPO, which code for apolipoprotein B and thyroid peroxidase, respectively. Both restriction fragment length (RFL) (XbaI2488 and EcoRI4154) and variable number of tandem repeat (VNTR) (3'APOB-VNTR) polymorphisms were analysed at the APOB locus; the TPO-VNTR polymorphism (intron 10) was analysed at the TPO locus. The main result of the investigation was that there is an association between the APOB locus and longevity that is revealed only when multiallelic polymorphisms are considered. In particular: (i) the frequency of 3'APOB-VNTR alleles with fewer than 35 repeats is significantly lower in cases than in controls; (ii) the linkage disequilibrium between the XbaI-RFLP and the EcoRI-RFLP is significantly different from 0 in cases but not in controls; (iii) the EcoRI-RFLP and XbaI-RFLP allele frequencies do not discriminate between cases and controls. The differences observed between case and control allele pools are specific to the APOB locus, since no significant difference was observed at the TPO locus.

Expansion of cytotoxic CD8+ CD28- T cells in healthy ageing people, including centenarians

Ageing is associated with complex remodelling in the phenotypic and functional profiles of T lymphocytes. We investigated whether expression of CD28 antigen on T cells is conserved throughout adulthood and ageing in humans. For this purpose we analysed T cells obtained from peripheral blood of 102 healthy people of ages ranging from 20 to 105 years. We found an age-related increase of CD28- T cells in percentage and absolute number, predominantly among CD8+ T cells. CD28- T cells from aged donors analysed by flow cytometry appeared as resting cells (not expressing CD25, CD38, CD69, CD71, DR), bearing markers of cytotoxic activity (CD 11b and CD 57) and with a phenotype compatible with 'memory' cells (up-regulated CD2 and CD11a; CD62L absent). At the functional level, freshly isolated purified CD28- CD8+ T cells showed high anti-CD3 redirected cytotoxic activity against Fc-bearing P815 cells. The same activity tested on freshly isolated bulk T lymphocytes was significantly augmented with age. We found a positive correlation between age, number of CD8+ CD28- T cells and anti-CD3 redirected cytotoxicity by freshly isolated T cells. These data suggest that an activation of unknown nature within the cytotoxic arm of the immune system occurs with age. We speculate that these cytotoxic T lymphocytes (CTL) in vivo may constitute armed effector cells for immediate killing of targets bearing peptides from pathogens of intracellular origin.

CD45 isoforms expression on CD4+ and CD8+ T cells throughout life, from newborns to centenarians: implications for T cell memory

CD4+ and CD8+ peripheral blood T lymphocytes show mutually exclusive expression of CD45RA or CD45R0, two isoforms of the common leukocyte antigen that seem to recognize so-called virgin/unprimed and memory/activated T cells. The expression of these isoforms has been studied by three colour cytofluorimetric analysis on CD4+ or CD8+ peripheral blood CD3+ cells from 22 healthy centenarians, analyzed in a context of 202 healthy donors 0-110 years old. An age-related unbalance of virgin and memory cells was found between CD4+ and CD8+ subsets. As expected, at birgh 95-99% of the CD3+ lymphocytes expressed the CD45RA isoform. A rapid increase of CD45R0+ cells was observed in the first 2-3 decades of life, this phenomenon being much more pronounced on CD4+ cells. Subsequently, the increase of the 'memory' compartment was much less rapid, so that in centenarians a consistent reservoire of CD45RA+ among CD4+ cells was still present (about 20%). In these exceptional individuals the percentage of CD45RA+ cells among CD8+ T lymphocytes was even higher (about 50%), and only slightly lower than that of young donors (about 55-60%). Thus, the main changes occurred at a different rate in CD4+ (about 20%). In these exceptional individuals the percentage of CD45RA+ cells among CD8+ T lymphocytes was even higher (about 50%), and only slightly lower than that of young donors (about 55-60%). Thus, the main changes occurred at a different rate in CD4+ and in CD8+ T cells, at an age of between 0 and 30 years, when the thymus is still functionally active. Interestingly, no difference in the usage of CD45 isoforms was observed within T cells bearing four different V beta-T cell receptor (TCR). The significance of this age-related unbalance is unknown. However, the presence of a great number of CD45RA+ T lymphocytes within the CD4+ and the CD8+ T cell subsets even in the peripheral blood of centenarians poses the problem of their origin (thymus? extrathymic sites?), of their functional role and of their lifespan. Moreover, the data on centenarians suggest that they may represent a very selected population where a slowing of immunosenescence occurs.