Accumulation of memory T cells from childhood to old age: Central and effector memory cells in CD4+ versus effector memory and terminally differentiated memory cells in CD8+ compartment

Immunosenescence and organ transplantation

Increasing numbers of elderly transplant recipients and a growing demand for organs from older donors impose pressing challenges on transplantation medicine. Continuous and complex modifications of the immune system in parallel to aging have a major impact on transplant outcome and organ quality. Both, altered alloimmune responses and increased immunogenicity of organs present risk factors for inferior patient and graft survival. Moreover, a growing body of knowledge on age-dependent modifications of allorecognition and alloimmune responses may require age-adapted immunosuppression and organ allocation. Here, we summarize relevant aspects of immunosenescence and their possible clinical impact on organ transplantation.

The inverted CD4/CD8 ratio and associated parameters in 66-year-old individuals: the Swedish HEXA immune study

The Swedish OCTO and NONA immune longitudinal studies were able to identify and confirm an immune risk profile (IRP) predictive of an increased 2-year mortality in very old individuals, 86-94 years of age. The IRP, was associated with persistent cytomegalovirus infection and characterized by inverted CD4/CD8 ratio and related to expansion of terminally differentiated effector memory T cells (TEMRA phenotype). In the present HEXA immune longitudinal study, we have examined a younger group of elderly individuals (n = 424, 66 years of age) in a population-based sample in the community of Jönköping, Sweden, to examine the relevance of findings previously demonstrated in the very old. Immunological monitoring that was conducted included T cell subsets and CMV-IgG and CMV-IgM serology. The result showed a prevalence of 15 % of individuals with an inverted CD4/CD8 ratio, which was associated with seropositivity to cytomegalovirus and increases in the level of TEMRA cells. The proportion of individuals with an inverted CD4/CD8 ratio was significantly higher in men whereas the numbers of CD3+CD4+ cells were significantly higher in women. In conclusion, these findings are very similar to those previously found by us in the Swedish longitudinal studies, suggesting that an immune profile previously identified in the very old also exists in the present sample of hexagenerians. Therefore, it will be important to examine clinical parameters, including morbidity and mortality, to assess whether the immune profile also is a risk profile associated with higher mortality in this sample of hexagenerians.

Understanding the immune response to seasonal influenza vaccination in older adults: a systems biology approach

Annual vaccination against seasonal influenza is recommended to decrease disease-related mortality and morbidity. However, one population that responds suboptimally to influenza vaccine is adults over the age of 65 years. The natural aging process is associated with a complex deterioration of multiple components of the host immune system. Research into this phenomenon, known as immunosenescence, has shown that aging alters both the innate and adaptive branches of the immune system. The intricate mechanisms involved in immune response to influenza vaccine, and how these responses are altered with age, have led us to adopt a more encompassing systems biology approach to understand exactly why the response to vaccination diminishes with age. Here, the authors review what changes occur with immunosenescence, and some immunogenetic factors that influence response, and outline the systems biology approach to understand the immune response to seasonal influenza vaccination in older adults.

CCR7+ central and CCR7- effector memory CD4+ T cells in human cutaneous leishmaniasis

PURPOSE

The profile of central (=T(CM)) and effector (=T(EM)) memory CD4(+) T cell subsets and the possible role as surrogate markers of protection is studied in the volunteers with history of cutaneous leishmaniasis (HCL).

METHODS

Profile of T cell subsets based on CCR7/CD45RA expressions and phenotypic changes after soluble Leishmania antigen (SLA) stimulation were analyzed. Then, sorted CD4(+)CD45RO(-)CD45RA(+) naïve T, CD4(+)CD45RO(+)CD45RA(-)CCR7(-) T(EM,) CD4(+)CD45RO(+)CD45RA(-)CCR7(+) T(CM) subsets were cultured with SLA for proliferation, cytokine production and intracellular cytokine assays.

RESULTS

In the HCL and control volunteers, the mean frequencies of CD4(+)CD45RA(+)CCR7(+) naïve T cells and CD4(+)CD45RA(-)CCR7(-) T(EM) cells were higher than the other subsets before culture. Frequency of naïve T cells and CD4(+)CD45RA(-)CCR7(+) T(CM) cells was significantly decreased (P=0.01 for naïve T and P<0.05 for T(CM) cells) and frequency of T(EM) cells was significantly increased after SLA stimulation compared to before culture (P<0.001). By CFSE labeling, CD4(+)CD45RO(+)CD45RA(-)CCR7(+) T(CM) cells showed more proliferation potential than CD4(+)CD45RO(+)CD45RA(-)CCR7(-) T(EM) cells. Stimulation of the T(EM) cells in HCL volunteers induced a significantly higher IFN-γ production (P=0.04) with higher number of intracellular IFN-γ positive cells (P=0.032) than the same cells from controls. A significantly higher number of T(CM) cells produced IL-2 in HCL volunteers compared with controls (P<0.05). Most of the intracellular IFN-γ positive T(EM) cells were proliferating CFSE-dim populations (P<0.05).

CONCLUSIONS

A combination of Leishmania-reactive IFN-γ producing CD4(+)CD45RO(+)CD45RA(-)CCR7(-) T(EM) and Leishmania-reactive IL-2 producing CD4(+)CD45RO(+)CD45RA(-)CCR7(+) T(CM) are identified in individuals with history of CL which might play a role in protective recall immune response against Leishmania infection.

High-dimensional analysis of human CD8(+) T cell phenotype, function, and antigen specificity

Antigen-specific T cells are critical initiators and orchestrators of the adaptive immune response. Categorizing antigen-specific T cell subsets is not a simple task given the diversity of these cells and the large number of parameters that can be considered. Here, we focus on human CD8(+) T cells and discuss the utility of high-dimensional mass cytometric analysis techniques for the concurrent identification and characterization of antigen-specific T cells involved in immunological homeostasis and disease. We first provide an overview of previously identified T cell subsets. We then discuss the segregation of antigen-specific T cells based on protein expression through surface and/or intracellular staining, on functional capacity through measurement expression of cytokines or other inducible markers, and on the antigen-specificity of the cell assessed using peptide-major histocompatibility complex multimers. High-dimensional mass cytometry enables a deeper and more integrated view of all three aspects of antigen-specific T cell diversity than do traditional techniques. Use of mass cytometry for precise measurement of the status of antigen-specific immune responses should result in better prediction of vaccine efficacy and disease outcomes.

The dominant human conjunctival epithelial CD8αβ+ T cell population is maintained with age but the number of CD4+ T cells increases

The conjunctiva is a highly specialized ocular mucosal surface that, like other mucosa, houses a number of leukocyte populations. These leukocytes have been implicated in age-related inflammatory diseases such as dry-eye, but their phenotypic characteristics remain largely undetermined. Existing literature provides rudimentary data from predominantly immunohistochemical analyses of tissue sections, prohibiting detailed and longitudinal examination of these cells in health and disease. Using recovered cells from ocular surface impression cytology and flow cytometry, we examined the frequency of leukocyte subsets in human conjunctival epithelium and how this alters with age. Of the total CD45+ leukocyte population within the conjunctival epithelium, 87% [32-99] (median) [range] comprised lymphocytes, with 69% [47-90] identified as CD3 + CD56- T cells. In contrast to peripheral blood, the dominant conjunctival epithelial population was TCRαβ + CD8αβ + (80% [37-100]) with only 10% [0-56%] CD4+ cells. Whilst a significant increase in the CD4+ population was seen with age (r = 0.5; p < 0.01) the CD8+ population remained unchanged, resulting in an increase in the CD4:CD8 ratio (r = 0.5;p < 0.01). IFNγ expression was detectable in 18% [14-48] of conjunctival CD4+ T cells and this was significantly higher among older individuals (<35 years, 7[4-39] vs. >65 years, 43[20-145]; p < 0.05). The elevation of CD4+ cells highlights a potentially important age-related alteration in the conjunctival intra-epithelial leukocyte population, which may account for the vulnerability of the aging ocular surface to disease.

NF-κB controls Il2 and Csf2 expression during T cell development and activation process

Aging and dysregulation of immune responds are closely associated through a complicated but unclear mechanism. Although many theories have been proposed as overall dysregulation involved in aging, mechanisms such as efficiency of DNA repairing, over-expression of transcription factors (such as NF-κB family), and shift of cell types, are among many factors that contribute to and affect aging process. It is of great interests to understand the possible mechanism that is involved in aging immune system. Here, we report that the inducible genes Il2 and Csf2 are increased as T cells undergo activation and aging. Of particular note were the findings that the relative composition of the circulating CD4(+) T cell population changes as animals mature with an increased percentage of the population being memory/effector type cells. In addition, mRNA levels of NF-κB family genes that are essential elements for cytokine activation in adult mice and activated T cells are significantly increased. We have demonstrated that the expression of inducible genes is accompanied by increased memory/effector type cells and by increased expression level of NF-κB family genes during cell activation and development.

Upregulation of miR-24 is associated with a decreased DNA damage response upon etoposide treatment in highly differentiated CD8(+) T cells sensitizing them to apoptotic cell death

The life-long homeostasis of memory CD8(+) T cells as well as persistent viral infections have been shown to facilitate the accumulation of highly differentiated CD8(+) CD28(-) T cells, a phenomenon that has been associated with an impaired immune function in humans. However, the molecular mechanisms regulating homeostasis of CD8(+) CD28(-) T cells have not yet been elucidated. In this study, we demonstrate that the miR-23∼24∼27 cluster is up-regulated during post-thymic CD8(+) T-cell differentiation in humans. The increased expression of miR-24 in CD8(+) CD28(-) T cells is associated with decreased expression of the histone variant H2AX, a protein that plays a key role in the DNA damage response (DDR). Following treatment with the classic chemotherapeutic agent etoposide, a topoisomerase II inhibitor, apoptosis was increased in CD8(+) CD28(-) when compared to CD8(+) CD28(+) T cells and correlated with an impaired DDR in this cell type. The reduced capacity of CD8(+) CD28(-) T cell to repair DNA was characterized by the automated fluorimetric analysis of DNA unwinding (FADU) assay as well as by decreased phosphorylation of H2AX at Ser139, of ATM at Ser1981, and of p53 at Ser15. Interleukin (IL)-15 could prevent etoposide-mediated apoptosis of CD8(+) CD28(-) T cells, suggesting a role for IL-15 in the survival and the age-dependent accumulation of CD8(+) CD28(-) T cells in humans.

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

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

Constitutive activation and accelerated maturation of peripheral blood T cells in healthy adults in Burkina Faso compared to Germany: the case of malaria?

OBJECTIVE

It is not exactly known how frequent exposure to Plasmodium falciparum shapes the peripheral blood T-cell population in healthy West Africans.

METHODS

The frequency of peripheral blood CD4(+) lymphocytes responding to Plasmodium falciparum merozoite surface protein 1 (PfMSP-1) by production of interferon-gamma (IFN-γ), interleukin-2 (IL-2) or tumor necrosis factor-alpha (TNF-α) was determined using a commercially available flow cytometric activation assay (FastImmune) in 17 healthy adults in Nouna, Burkina Faso. T-cell activation and maturation in peripheral blood of healthy adults in Burkina Faso (n=40) and Germany (n=20) were compared using immunophenotyping and three-colour flow cytometry.

RESULTS

Significant numbers of PfMSP-1 -specific CD4(+) lymphocytes producing IFN-γ, IL-2 and/or TNF-α were detected in 14 healthy adults in Nouna. Cytokine profiles showed predominant production of IFN-γ and TNF-α. Compared to Germans, Burkinabé showed markedly lower proportions of CCR7+ CD45RA+ naive CD4(+) cells and slightly higher frequencies of CD95(+)CD4(+) T-cells and of CD38(+) CD8(+) T-cells. The median antibody-binding capacity of CD95(dim) CD4(+) T-cells in Burkinabé was more than twice the value observed in Germans (263 vs. 108 binding sites per cell, p<0.0001).

CONCLUSIONS

We hypothesize that an IFN-γ-induced increase in the expression level of CD95 on CD4(+) lymphocytes may lower the activation threshold of resting naive CD4(+) T-cells in healthy adults living in Burkina Faso. Bystander activation of these cells deserves further study as a molecular mechanism linking strong IFN-γ responses against Plasmodium falciparum to decreased susceptibility to parasitemia observed in specific ethnic groups in West Africa.

Plasticity of DNA methylation in mouse T cell activation and differentiation

Background

Circulating CD4⁺ T helper cells are activated through interactions with antigen presenting cells and undergo differentiation into specific T helper cell subsets depending on the type of antigen encountered. In addition, the relative composition of the circulating CD4⁺ T cell population changes as animals mature with an increased percentage of the population being memory/effector type cells.

Results

Here, we report on the highly plastic nature of DNA methylation at the genome-wide level as T cells undergo activation, differentiation and aging. Of particular note were the findings that DNA demethylation occurred rapidly following T cell activation and that all differentiated T cell populations displayed lower levels of global methylation than the non-differentiated population. In addition, T cells from older mice had a reduced level of DNA methylation, most likely explained by the increase in the memory/effector cell fraction. Although significant genome-wide changes were observed, changes in DNA methylation at individual genes were restricted to specific cell types. Changes in the expression of enzymes involved in DNA methylation and demethylation reflect in most cases the changes observed in the genome-wide DNA methylation status.

Conclusion

We have demonstrated that DNA methylation is dynamic and flexible in CD4+ T cells and changes rapidly both in a genome-wide and in a targeted manner during T cell activation, differentiation. These changes are accompanied by parallel changes in the enzymatic complexes that have been implicated in DNA methylation and demethylation implying that the balance between these opposing activities may play a role in the maintaining the methylation profile of a given cell type but also allow flexibility in a cell population that needs to respond rapidly to environmental signals.

Paediatric reference values for the peripheral T cell compartment

Immunophenotyping of blood lymphocyte subpopulations is an important tool in the diagnosis of immunological and haematological diseases. Paediatric age-matched reference values have been determined for the major lymphocyte populations, but reliable reference values for the more recently described T lymphocyte subpopulations, like different types of memory T lymphocytes, recent thymic emigrants, regulatory T cells and CXCR5(+) helper T lymphocytes, are not sufficiently available yet. We determined reference values for the absolute and relative sizes of T lymphocyte subpopulations in healthy children using the lysed whole blood method, which is most often used in diagnostic procedures. When the absolute numbers of some or all T lymphocyte subpopulations fall outside these reference ranges, this may indicate disease. The reference values show the course of T lymphocyte development in healthy children. Absolute T lymphocyte numbers increase 1.4-fold during the first months of life, and after 9-15 months, they decrease threefold to adult values; this is mainly caused by the expansion of recent thymic emigrants and naive cells. Helper and cytotoxic T lymphocytes show the same pattern. Regulatory T cells increase in the first 5 months of life and then gradually decrease to adult values, although the absolute numbers remain small. The relative number of CXCR5(+) cells within the CD4(+) CD45RO(+) T lymphocytes increases during the first 6 months of life and then remains more or less stable around 20%.

Phenotyping of circulating CD8⁺ T cell subsets in human cutaneous leishmaniasis

Recovery from CL is usually accompanied with long-lasting protection and induction of strong immune response. The phenotypes, generation and maintenance of central (=T(CM)) and effector (=T(EM)) memory T cell subsets in human leishmaniasis are not well known. Profile of T cell subsets were analyzed on peripheral CD8⁺ T cells from volunteers with history of cutaneous leishmaniasis (HCL). In HCL and control groups, mean frequencies of CCR7⁺CD45RA⁺CD8⁺ naïve and CCR7⁻CD45RA⁻CD8⁺ T(EM) cells were higher than other subsets before culture, but after stimulation with soluble Leishmania antigen, the frequency of naïve T cells was significantly decreased and the frequency of T(EM) cells was significantly increased. T(EM) phenotype composed the highest portion of proliferating Carboxy Fluorescein diacetate Succinimidyl Ester (CFSE)-dim population which was significantly higher in HCL volunteers than in control group. Stimulation of isolated CD8⁺ memory T cells, but not naïve T cells, from HCL volunteers induced a significantly higher IFN-γ production compared with that of healthy controls. Intracellular IFN-γ staining provided the same result. Memory population is shown to be responsible for Leishmania-induced IFN-γ production. Leishmania-reactive proliferating T(EM) cells were identified as the most frequent subset which may play a role in recall immune response and protection against Leishmania infection.

Immune Reconstitution During the First Year of Antiretroviral Therapy of HIV-1-Infected Adults in Rural Burkina Faso

There are no data on the outcome of highly active antiretroviral therapy (HAART) in HIV-infected adults in rural Burkina Faso. We therefore assessed CD4⁺ T-cell counts and HIV-1 plasma viral load (VL), the proportion of naive T-cells (co-expressing CCR7 and CD45RA) and T-cell activation (expression of CD95 or CD38) in 61 previously untreated adult patients from Nouna, Burkina Faso, at baseline and 2 weeks, 1, 3, 6, 9 and 12 months after starting therapy. Median CD4⁺ T-cell counts increased from 174 (10^th-90^th percentile: 33-314) cells/µl at baseline to 300 (114- 505) cells/µl after 3 months and 360 (169-562) cells/µl after 12 months of HAART. Median VL decreased from 5.8 (4.6- 6.6) log10 copies/ml at baseline to 1.6 (1.6-2.3) log10 copies/ml after 12 months. Early CD4⁺ T-cell recovery was accompanied by a reduction of the expression levels of CD95 and CD38 on T-cells. Out of 42 patients with complete virological follow-up under HAART, 19 (45%) achieved concordant good immunological (gain of ≥100 CD4⁺ T-cells/µl above baseline) and virological (undetectable VL) responses after 12 months of treatment (intention-to-treat analysis). Neither a decreased expression of the T-cell activation markers CD38 and CD95, nor an increase in the percentage of naive T-cells reliably predicted good virological treatment responses in patients with good CD4⁺ T-cell reconstitution. Repeated measurement of CD4⁺ T-cell counts during HAART remains the most important parameter for immunologic monitoring. Substitution of repeated VL testing by determination of T-cell activation levels (e.g., CD38 expression on CD8⁺ T-cells) should be applied with caution.

Influence of age, gender and lifestyle in lymphocyte subsets: report from the Spanish Gait-2 Study

INTRODUCTION

Flow cytometry analysis of lymphocyte subsets in peripheral blood is a common technique in diagnostic laboratories. Abnormal values have been identified in prevalent infections, autoimmune disorders and neoplastic diseases. Reference ranges for lymphocyte subsets of a healthy population from Spain are scarce.

METHODS

The study was performed on 319 healthy subjects, aged 4-88 years, from 709 individuals enrolled in the GAIT-2 Project (Genetic Analysis of Idiopathic Thrombophilia). Health status, age, sex, fertility, BMI and lifestyle (physical activity, cigarette smoking and ethanol intake) were assessed using standardized criteria. The percentage of lymphocyte subsets was determined using flow cytometry (Lymphogram™). Percentages of CD3+, CD4+, CD8+, CD19+, CD3-CD56+, CD3+CD4-CD8- double-negative (DN) T cells, CD3+CD4+CD8+ double-positive T cells and the CD4+/CD8+ ratio were recorded for each case.

RESULTS

Children had a significantly higher percentage of CD19+ and DN cells than adults. Women had a significantly higher percentage of CD3+ and CD4+ and a lower percentage of natural killer cells than men. Increases in BMI were inversely associated with the percentage of DN cells. Physical activity increased the percentage of lymphocytes and DN cells. Alcohol consumers had a lower percentage of CD19+ and DN cells, and a higher percentage of CD4+.

CONCLUSION

This study provides reference ranges for lymphocyte subsets of healthy children and adults in a Mediterranean population (Spain) and determines the influence of lifestyle factors on these values.

Activation and maturation of peripheral blood T cells in HIV-1-infected and HIV-1-uninfected adults in Burkina Faso: a cross-sectional study

Background

We wanted to explore to what extent environmental exposure to immune stimulants, which is expected to be more present in rural than in urban settings, influences T cell activation and maturation in healthy and in HIV-1-infected individuals in Burkina Faso in west Africa.

Methods

The proportion of circulating naïve T cells and the expression of the T cell activation markers, CD95 and CD38, were analyzed by immunophenotyping and three-colour flow cytometry in 63 healthy individuals and 137 treatment-naïve HIV-1-infected subjects from Ouagadougou (urban setting) and 26 healthy adults and 61 treatment-naïve patients from Nouna (rural).

Results

A slightly higher activation level of CD4⁺ and CD8⁺ peripheral blood T cells was seen in healthy adults living in Nouna than in those living in Ouagadougou. The percentages of naïve CD45RA^bright CCR7⁺ T cells were not significantly different between both study sites. Taking into consideration that relatively more HIV-1-infected patients in Nouna were in an advanced disease stage, no relevant differences were seen in T cell activation and maturation between patients at both study sites. As expected, the percentage of CD95⁺ CD4⁺ and CD38⁺ CD8⁺ T cells and the respective antigen density on these cells was significantly higher in patients than in controls in both settings. The percentage of naïve CD8⁺ T cells was lower in HIV-1-infected subjects than in healthy controls irrespective of the study site, while a lower proportion of naïve CD4⁺ T cells in patients compared with controls was seen only in Nouna.

Conclusions

Environmentally triggered immune activation may contribute to the increased expression of the activation markers CD95 and CD38 on peripheral blood T cells from healthy adults living in rural versus urban settings in Burkina Faso. T cell activation is further increased in HIV-1-infected individuals due to T cell loss and high plasma viral load levels. The observed variations in T cell activation levels or the proportion of naïve T cells in our study patients, however, are not explained by differences in CD4⁺ T cell counts or HIV-1 plasma viral load levels alone.

Age-related differences in naturally acquired T cell memory to Plasmodium falciparum merozoite surface protein 1

Naturally acquired immunity to Plasmodium falciparum malaria in malaria holoendemic areas is characterized by the gradual, age-related development of protection against high-density parasitemia and clinical malaria. Animal studies, and less commonly, observations of humans with malaria, suggest that T-cell responses are important in the development and maintenance of this immunity, which is mediated primarily by antibodies that slow repeated cycles of merozoites through erythrocytes. To advance our rather limited knowledge on human T-cell immunity to blood stage malaria infection, we evaluated CD4 and CD8 T-cell effector memory subset responses to the 42 kDa C-terminal fragment of Merozoite Surface Protein 1 (MSP1₄₂), a malaria vaccine candidate, by 49 healthy 0.5 to ≥18 year old residents of a holoendemic area in western Kenya. The proportion of individuals with peripheral blood mononuclear cell MSP1₄₂ driven IFN-γ ELISPOT responses increased from 20% (2/20) among 0.5–1 year old children to 90% (9/10) of adults ≥18 years (P = 0.01); parallel increases in the magnitude of IFN-γ responses were observed across all age groups (0.5, 1, 2, 5 and ≥18 years, P = 0.001). Less than 1% of total CD4 and CD8 T-cells from both children and adults produced IFN-γ in response to MSP1₄₂. However, adults had higher proportions of MSP1₄₂ driven IFN-γ secreting CD4 and CD8 effector memory (CD45RA⁻ CD62L⁻) T-cells than children (CD4: 50.9% vs. 28.8%, P = 0.036; CD8: 52.1% vs. 18.3%, respectively P = 0.009). In contrast, MSP1₄₂ driven IFN-γ secreting naïve-like, transitional (CD45RA⁺ CD62L⁺) CD4 and CD8 cells were the predominant T-cell subset among children with significantly fewer of these cells in adults (CD4: 34.9% vs. 5.1%, P = 0.002; CD8: 47.0% vs. 20.5%, respectively, P = 0.030). These data support the concept that meaningful age-related differences exist in the quality of T-cell immunity to malaria antigens such as MSP1.

Chronic resveratrol intake reverses pro-inflammatory cytokine profile and oxidative DNA damage in ageing hybrid mice

Thymic involution and shrinkage of secondary lymphoid organs are leading causes of the deterioration of the T-cell compartment with age. Inflamm-aging, a sustained inflammatory status, has been associated with chronic diseases and shortened longevity. This is the first study to investigate the effect of treating aging hybrid mice with long-term, low-dose resveratrol (RSV) in drinking water by assessing multiple immunological markers and profiles in the immune system. We found that hybrid mice exhibited marked age-related changes in the CD3+CD4+, C3+CD8+, CD4+CD25+, CD4M and CD8M surface markers. RSV reversed surface phenotypes of old mice to that of young mice by maintaining the CD4+ and CD8+ population in splenocytes as well as reducing CD8+CD44+ (CD8M) cells in the aged. RSV also enhanced the CD4+CD25+ population in old mice. Interestingly, pro-inflammatory status in young mice was transiently elevated by RSV but it consequently mitigated the age-dependent increased pro-inflammatory cytokine profile while preserving the anti-inflammatory cytokine condition in the old mice. Age-dependent increase in 8OHdG, an oxidative DNA damage marker was ameliorated by RSV. Immunological-focused microarray gene expression analysis showed that only the CD72 gene was significantly downregulated in the 12-month RSV-treated mice compared to age-matched controls. Our study indicates that RSV even at low physiological relevant levels is able to affect the immune system without causing marked gene expression changes.

Persistent viral infections and immune aging

Immunosenescence comprises a set of dynamic changes occurring to both, the innate as well as the adaptive immune system that accompany human aging and result in complex manifestations of still poorly defined deficiencies in the elderly population. One of the most prominent alterations during aging is the continuous involution of the thymus gland which is almost complete by the age of 50. Consequently, the output of naïve T cells is greatly diminished in elderly individuals which puts pressure on homeostatic forces to maintain a steady T cell pool for most of adulthood. In a great proportion of the human population, this fragile balance is challenged by persistent viral infections, especially Cytomegalovirus (CMV), that oblige certain T cell clones to monoclonally expand repeatedly over a lifetime which then occupy space within the T cell pool. Eventually, these inflated memory T cell clones become exhausted and their extensive accumulation accelerates the age-dependent decline of the diversity of the T cell pool. As a consequence, infectious diseases are more frequent and severe in elderly persons and immunological protection following vaccination is reduced. This review therefore aims to shed light on how various types of persistent viral infections, especially CMV, influence the aging of the immune system and highlight potential measures to prevent the age-related decline in immune function.

Imbalance in T-cell and cytokine profiles in patients with relapsing-remitting multiple sclerosis

Multiple sclerosis (MS) is characterized by autoimmune attack leading to demyelination of the white matter in the central nervous system with devastating clinical consequences. Several immune-mediated destruction mechanisms were previously proposed including different T-cell subsets but complex view on immune system function in patients with MS is missing. In the present study, T-lymphocyte populations and pro-inflammatory as well as suppressive cytokine profiles were evaluated in detail in previously untreated patients with relapsing-remitting MS (RRMS). CD4(+) and CD8(+) naïve, central memory (Tcm), effector memory (Tem), terminal effector memory (Ttem), CD4(+) regulatory T-cells (Treg) and CD8(+) T-suppressor cells (Ts) were analysed using flow cytometry, and levels of ten plasma cytokines were determined using fluorescent bead-based immunoassay. We evaluated two groups of RRMS with minor (n=33) and major (n=25) clinical impairment and compared them with healthy controls (n=40) in order to detect any correlation between severity of MS clinical symptoms and immune disturbances. Significant differences were noted in CD4(+)CD45RA(+)CCR7(+) naïve T-cells, CD4(+)CD45RO(+)CCR7(-) and CD8(+)CD45RO(+)CCR7(-) Tem cells, while no differences were recognized in Tcm, Ttem, Treg and Ts cells in RRMS patients. Nine out of ten studied cytokines were disturbed in plasma samples of patients with RRMS. In conclusion, we demonstrate complex immune dysbalances in untreated MS patients.

Regulatory and activated T cells in human Schistosoma haematobium infections

Acquired immunity against helminths is characterised by a complex interplay between the effector Th1 and Th2 immune responses and it slowly manifests with age as a result of cumulative exposure to parasite antigens. Data from experimental models suggest that immunity is also influenced by regulatory T cells (Treg), but as yet studies on Treg in human schistosome infections are limited. This study investigated the relationship between schistosome infection intensity and the two cell populations regulatory T cells (TREG: CD4(+(dim))CD25(+(high))FOXP3(+)CD127(low)), and activated (Tact: CD4(+)CD25(+)FOXP3(-)) T cells in Zimbabweans exposed to Schistosoma haematobium parasites. Participants were partitioned into two age groups, young children (8-13 years) in whom schistosome infection levels were rising to peak and older people (14+ years) with declining infection levels. The relationship between Tact proportions and schistosome infection intensity remained unchanged with age. However Treg proportions rose significantly with increasing infection in the younger age group. In contrast Treg were negatively correlated to infection intensity in the older age group. The relative proportions of regulatory T cells differ significantly between young individuals in whom high infection is associated with an enhanced regulatory phenotype and older infected patients in whom the regulatory response is attenuated. This may influence or reflect different stages of the development of protective schistosome acquired immunity and immunopathogenesis.

Development of cytomegalovirus and adenovirus-specific memory CD4 T-cell functions from birth to adulthood

Age-related changes in memory CD4 T cells (CD4) are poorly known. To address this issue, CD4 proliferative and cytokine responses to an anti-CD3 monoclonal (CD3), to cytomegalovirus (CMV), and to adenovirus (AdV) were assessed in 57 children (age, 0.07-17.16 y) and 17 adults. Results showed i) accumulation of memory CD4 with aging, with 2-3 times more central-memory T cell (TCM; CD45RA/CD62L) than effector-memory T cell (TEM; CD45RA/62L) CD4 at any age. ii) In children older than 2 y, CMV-specific CD4-secreting IFNγ alone predominated over CD4-secreting IL2 + IFNγ and a continuous increase, with aging, in IFNγ responses to the virus was observed. In contrast, in AdV infection, CD4-secreting IL2 + IFNγ predominated and IFNγ responses to the virus reached adult levels from 3 y of age. iii) In children aged 0-2 y, lower total IFNγ responses to CMV (p < 0.02), AdV (p = 0.05), and CD3 (p < 0.01) and lower IFNγ + IL2-responses (p = 0.1, p < 0.02, p < 0.05, respectively) contrasted with no decrease in CD4-secreting IFNγ alone. Defective proliferative responses to AdV (p = 0.03) were also observed. In conclusion, the development of memory CD4 differed in acute AdV and persistent CMV infections. Young age seemed to depress mostly polyfunctional (IL2 + IFNγ secreting) CD4 in both infections.

Identification of human T-cell responses to Mycobacterium tuberculosis resuscitation-promoting factors in long-term latently infected individuals

The Mycobacterium bovis BCG vaccine is the only tuberculosis (TB) vaccine available, yet it provides limited protection against pulmonary TB in adults and fails to protect against TB reactivation. We hypothesized that immunity against Mycobacterium tuberculosis "resuscitation-promoting factors" (Rpfs), which are small bacterial proteins that promote proliferation of dormant mycobacteria, may be relevant in the human immune response to M. tuberculosis. In previous unpublished work, we found that Rpfs Rv0867c and Rv2389c induced gamma interferon (IFN-γ) production in the blood of TB patients' healthy household contacts in several different African populations. Here we examine these two dominant Rpf antigens in more detail and define the nature of the responding T-cell subsets. Multiparameter cytokine profiling showed that Rv2389c and, to a lesser extent, Rv0867c were recognized by mycobacterium-responsive healthy Dutch individuals; peptide-scanning revealed several epitopes, including a single immunodominant epitope in Rv2389c. Rv0867c and, to a lesser extent, Rv2389c Rpf-specific T-cell responses were maintained for decades in long-term M. tuberculosis nonprogressors. Prominent Rv0867c-specific double- and single-cytokine-producing CD8(+) T-cell subset responses were found, including a large population of CD8(+) effector memory and effector T-cell subsets. We conclude that M. tuberculosis Rpf antigens are important targets in the human immune response to M. tuberculosis and represent interesting TB vaccine candidate antigens.

Gain and loss of T cell subsets in old age--age-related reshaping of the T cell repertoire

The immune system is affected by the aging process and undergoes significant age-related changes, termed immunosenescence. Different T cell subsets are affected by this process. Alterations within the bone marrow and thymus lead to a shift in the composition of the T cell repertoire from naïve to antigen-experienced T cells, thereby compromising the diversity of the T cell pool. Additional infection with latent pathogens such as cytomegalovirus aggravates this process. In this review, we focus on the major age-related changes that occur in the naïve and the antigen-experienced T cell population. We discuss the mechanisms responsible for the generation and maintenance of these subsets and how age-related changes can be delayed or prevented by clinical interventions.

Cytomegalovirus infection induces the accumulation of short-lived, multifunctional CD4+CD45RA+CD27+ T cells: the potential involvement of interleukin-7 in this process

The relative roles that ageing and lifelong cytomegalovirus (CMV) infection have in shaping naive and memory CD4+ T-cell repertoires in healthy older people is unclear. Using multiple linear regression analysis we found that age itself is a stronger predictor than CMV seropositivity for the decrease in CD45RA+ CD27+ CD4+ T cells over time. In contrast, the increase in CD45RA⁻ CD27⁻ and CD45RA+ CD27⁻ CD4+ T cells is almost exclusively the result of CMV seropositivity, with age alone having no significant effect. Furthermore, the majority of the CD45RA⁻ CD27⁻ and CD45RA+ CD27⁻ CD4+ T cells in CMV-seropositive donors are specific for this virus. CD45RA+ CD27⁻ CD4+ T cells have significantly reduced CD28, interleukin-7 receptor α (IL-7Rα) and Bcl-2 expression, Akt (ser473) phosphorylation and reduced ability to survive after T-cell receptor activation compared with the other T-cell subsets in the same donors. Despite this, the CD45RA+ CD27⁻ subset is as multifunctional as the CD45RA⁻ D27+ and CD45RA⁻ CD27⁻ CD4+ T-cell subsets, indicating that they are not an exhausted population. In addition, CD45RA+ CD27⁻ CD4+ T cells have cytotoxic potential as they express high levels of granzyme B and perforin. CD4+ memory T cells re-expressing CD45RA can be generated from the CD45RA⁻ CD27+ population by the addition of IL-7 and during this process these cells down-regulated expression of IL-7R and Bcl-2 and so resemble their counterparts in vivo. Finally we showed that the proportion of CD45RA+ CD27⁻ CD4+ T cells of multiple specificities was significantly higher in the bone marrow than the blood of the same individuals, suggesting that this may be a site where these cells are generated.

Immunologic basis for revaccination of HIV-infected children receiving HAART

With increasing access to antiretroviral therapy for children infected with HIV, especially in sub-Saharan Africa, better understanding of the development and maintenance of memory T- and B-cell responses to pathogens after immune reconstitution is needed to assess the risk of infection. Knowledge of long-term immune responses after starting HAART is of particular importance for policies on revaccination of HIV-infected children, who may lose protective immunity to prior infections and immunizations. We review normal development of T- and B-cell memory responses to viruses and vaccines against viral pathogens, and contrast the immunological effects of perinatal HIV transmission with HIV infection acquired later in life. We then explore the potential benefits of antiretroviral therapy and revaccination, using measles virus as a model.

Tim-3 expression on PD-1+ HCV-specific human CTLs is associated with viral persistence, and its blockade restores hepatocyte-directed in vitro cytotoxicity

Having successfully developed mechanisms to evade immune clearance, hepatitis C virus (HCV) establishes persistent infection in approximately 75%-80% of patients. In these individuals, the function of HCV-specific CD8+ T cells is impaired by ligation of inhibitory receptors, the repertoire of which has expanded considerably in the past few years. We hypothesized that the coexpression of the negative regulatory receptors T cell immunoglobulin and mucin domain-containing molecule 3 (Tim-3) and programmed death 1 (PD-1) in HCV infection would identify patients at risk of developing viral persistence during and after acute HCV infection. The frequency of PD-1-Tim-3- HCV-specific CTLs greatly outnumbered PD-1+Tim-3+ CTLs in patients with acute resolving infection. Moreover, the population of PD-1+Tim-3+ T cells was enriched for within the central memory T cell subset and within the liver. Blockade of either PD-1 or Tim-3 enhanced in vitro proliferation of HCV-specific CTLs to a similar extent, whereas cytotoxicity against a hepatocyte cell line that expressed cognate HCV epitopes was increased exclusively by Tim-3 blockade. These results indicate that the coexpression of these inhibitory molecules tracks with defective T cell responses and that anatomical differences might account for lack of immune control of persistent pathogens, which suggests their manipulation may represent a rational target for novel immunotherapeutic approaches.

The effect of ageing on human lymphocyte subsets: comparison of males and females

Background

There is reported to be a decline in immune function and an alteration in the frequency of circulating lymphocytes with advancing age. There are also differences in ageing and lifespan between males and females. We performed this study to see if there were differences between males and females in the frequency of the different lymphocyte subsets with age.

Results

Using flow cytometry we have examined different populations of peripheral blood leukocytes purified from healthy subjects with age ranging from the third to the tenth decade. We used linear regression analysis to determine if there is a linear relationship between age and cell frequencies. For the whole group, we find that with age there is a significant decline in the percentage of naïve T cells and CD8⁺ T cells, and an increase in the percentage of effector memory cells, CD4⁺foxp3⁺ T cells and NK cells. For all cells where there was an effect of ageing, the slope of the curve was greater for men than for women and this was statistically significant for CD8⁺αβ⁺ T cells and CD3⁺CD45RA^-CCR7^- effector memory cells. There was also a difference for naïve cells but this was not significant.

Conclusion

The cause of the change in percentage of lymphocyte subsets with age, and the different effects on males and females is not fully understood but warrants further study.

Decreased circulating CD28-negative T cells in patients with rheumatoid arthritis treated with abatacept are correlated with clinical response

OBJECTIVE

To verify the hypothesis that blockade of CD28 costimulation by treatment with abatacept in patients with rheumatoid arthritis (RA) might induce a reduction in the number of CD28- T cells, as well as other effector T cell populations. We evaluated whether these variations correlate with clinical response.

METHODS

Peripheral blood T cell subsets were longitudinally evaluated by flow cytometry through the analysis of CD28, CD45RA, and CCR7 expression in 16 patients with RA who were treated with abatacept.

RESULTS

After 48 weeks of treatment, the proportion and the absolute number of circulating CD8+CD28- T cells decreased (p = 0.008, p = 0.055, respectively, compared with baseline), as well as the proportion of the CD8+CD45RA+CCR7- cells, thought to represent terminally differentiated effector T cells (p = 0.03). Reductions of percentages of circulating CD4+CD28- and CD8+CD28- T cells, and (CCR7-) CD8+ total effector T cells were directly correlated with the reduction of Disease Activity Score 28 C-reactive protein (r = 0.58, p = 0.014; r = 0.47, p = 0.059; r = 0.59, p = 0.012, respectively).

CONCLUSION

After therapy with abatacept, circulating CD28- T cells and other effector populations decrease in patients with RA. This decrease is correlated with clinical response.

Leukocyte function in the aging immune system

Aging is associated with a progressive dysregulation of immune responses. Whether these changes are solely responsible for the observed increased mortality and morbidity amongst the elderly is uncertain. Recent advances have highlighted the age-associated changes that occur beyond T and B lymphocytes. Additionally, multiple human and animal studies have identified a relationship between chronic low-grade inflammation and geriatric syndromes, such as frailty, suggesting that the phenomenon of "inflamm-aging" may provide a rationale for the increased vulnerability to chronic inflammatory diseases in older adults. In the present review, we broadly summarize our current understanding of age-dependent changes in leukocyte function and their contribution to aging-related disease processes.

Numerical defects in CD8+CD28- T-suppressor lymphocyte population in patients with type 1 diabetes mellitus and multiple sclerosis

Type 1 diabetes mellitus (T1D) and multiple sclerosis (MS) are organ-specific autoimmune diseases leading to an attack of auto-aggressive lymphocytes against the pancreatic beta-cells and central nervous system, respectively. Using four-colour flow cytometry, T-lymphocyte populations having an important function in autoimmune processes were analyzed. T-regulatory cells (Treg) CD4(+)CD25(+)CD127(low), T-suppressor cells (Ts) CD8(+)CD28(-), activated helper CD4(+)CD25(+)CD127(+) and cytotoxic CD8(+)CD25(+) T-cells and also naive CD4(+)CD45RA(+) and memory T-cells CD4(+)CD45RO(+) were compared in the group of patients with T1D (n=30), MS (n=31) and in the group of healthy controls (n=29). Significant differences in Ts cells, activated helper and cytotoxic cells and also memory T-cells were recognized in the group of T1D patients compared to healthy controls. Ts population was significantly lowered in MS patients as well. However, no significant differences were noticed in Treg population. The observed data demonstrate significant differences among patients with T1D and MS in comparison to healthy individuals.

Low numbers of CD8+ T lymphocytes in hereditary haemochromatosis are explained by a decrease of the most mature CD8+ effector memory T cells

Low CD8(+) T lymphocyte numbers have long been described in hereditary haemochromatosis (HH). Recently, two conserved haplotypes localized near the microsatellite D6S105 at the major histocompatibility complex (MHC) class I region were described predicting the clinical expression of HH and the CD8(+) T lymphocyte numbers. The A-A-T haplotype was associated with a severe clinical expression of HH and low CD8(+) T lymphocyte numbers, while the G-G-G haplotype was associated with a milder clinical expression of HH and high CD8(+) T lymphocyte numbers. As CD8(+) T lymphocytes are a very heterogeneous population, in this study we analysed the CD8(+) subpopulations of naive, central memory (T(CM)) and effector memory (T(EM)), and further subsets of CD8(+) T(EM) cells in 47 HH patients and 68 controls. In addition, association studies were conducted between the conserved haplotypes and the CD8(+) T cell subpopulations in HH. Variations of the numbers of naive and central memory cells with age were similar between HH patients and controls. For T(EM) cells and the T(EM) CD27(-)CD28(-) subset no effect of age was observed in HH [R(2) = 0.001, not significant (n.s.) and R(2) = 0.01, n.s., respectively] contrasting with the increasing of these subpopulations with age in controls (R(2) = 0.09, P = 0.017 and R(2) = 0.22, P = 0.0005, respectively). Interestingly, patients homozygous for the A-A-T haplotype have lower numbers of CD8(+) T(EM) cells due especially to lower numbers of T(EM) CD27(-)CD28(-) (0.206 +/- 0.119 and 0.066 +/- 0.067 x 10(6) cells/ml, respectively) than patients carrying the G-G-G haplotype (0.358 +/- 0.195 and 0.246 +/- 0.202 x 10(6) cells/ml, respectively). This may suggest an inability of HH patients to differentiate the CD8(+) T cells into the most mature phenotype.

Effect of ageing on CMV-specific CD8 T cells from CMV seropositive healthy donors

BACKGROUND

Ageing is associated with changes in the immune system with substantial alterations in T-lymphocyte subsets. Cytomegalovirus (CMV) is one of the factors that affect functionality of T cells and the differentiation and large expansions of CMV pp65-specific T cells have been associated with impaired responses to other immune challenges. Moreover, the presence of clonal expansions of CMV-specific T cells may shrink the available repertoire for other antigens and contribute to the increased incidence of infectious diseases in the elderly. In this study, we analyse the effect of ageing on the phenotype and frequency of CMV pp65-specific CD8 T cell subsets according to the expression of CCR7, CD45RA, CD27, CD28, CD244 and CD85j.

RESULTS

Peripheral blood from HLA-A2 healthy young, middle-aged and elderly donors was analysed by multiparametric flow cytometry using the HLA-A*0201/CMV pp65(495-504) (NLVPMVATV) pentamer and mAbs specific for the molecules analysed. The frequency of CMV pp65-specific CD8 T cells was increased in the elderly compared with young and middle-aged donors. The proportion of naïve cells was reduced in the elderly, whereas an age-associated increase of the CCR7(null) effector-memory subset, in particular those with a CD45RA(dim) phenotype, was observed, both in the pentamer-positive and pentamer-negative CD8 T cells. The results also showed that most CMV pp65-specific CD8 T cells in elderly individuals were CD27/CD28 negative and expressed CD85j and CD244.

CONCLUSION

The finding that the phenotype of CMV pp65-specific CD8 T cells in elderly individuals is similar to the predominant phenotype of CD8 T cells as a whole, suggests that CMV persistent infections contributes to the age-related changes observed in the CD8 T cell compartment, and that chronic stimulation by other persistent antigens also play a role in T cell immunosenescence. Differences in subset distribution in elderly individuals showing a decrease in naive and an increase in effector-memory CD8 T cells may be relevant in the age-associated defective immune response.

Refined characterization and reference values of the pediatric T- and B-cell compartments

Work in the past years has led to a refined phenotypical description of functionally distinct T- and B-cell subsets. Since both lymphocyte compartments are established and undergo dramatic changes during childhood, redefined pediatric reference values of both compartments are needed. In a cohort of 145 healthy children, aged 0-18 years, the relative and absolute numbers of the various T- and B-cell subsets were determined. In addition, we found that besides thymic output, naive (CD27(+)CD45RO(-)) T-cell proliferation contributed significantly to the establishment of the naive T-cell compartment. At birth, regulatory (CD25(+)CD127(-)CD4(+)) T cells (Tregs) mainly had a naive (CD27(+)CD45RO(-)) phenotype whereas 'memory or effector-like' (CD45RO(+)) Tregs accumulated slowly during childhood. Besides the CD27(+)IgM(+)IgD(+) memory B-cell population, the recently identified CD27(-)IgG(+) and CD27(-)IgA(+) memory B-cell populations were already present at birth. These data provide reference values of the T- and B-cell compartments during childhood for studies of immunological disorders or immune reconstitution in children.

Intrinsic defect of the immune system in children with Down syndrome: a review

Down syndrome (DS) is the most frequent cause of mental retardation in man. Immunological changes in DS have been observed since the 1970s. The neurological system appears to be ageing precociously, with early occurrence of Alzheimer disease; until now, the observed immunological differences have been interpreted in the same context. Looking back at past and present results of immunological studies in DS children in relation to the clinical consequences they suffer, we conclude that it is more likely that the DS immune system is intrinsically deficient from the very beginning.

Antigenic experience dictates functional role of glycogen synthase kinase-3 in human CD4+ T cell responses

Signals induced by the TCR and CD28 costimulatory pathway have been shown to lead to the inactivation of the constitutively active enzyme, glycogen synthase kinase-3 (GSK3), which has been implicated in the regulation of IL-2 and T cell proliferation. However, it is unknown whether GSK3 plays a similar role in naive and memory CD4(+) T cell responses. Here we demonstrate a divergence in the dependency on the inactivation of GSK3 in the proliferative responses of human naive and memory CD4(+) T cells. We find that although CD28 costimulation increases the frequency of phospho-GSK3 inactivation in TCR-stimulated naive and memory CD4(+) T cells, memory cells are less reliant on GSK3 inactivation for their proliferative responses. Rather we find that GSK3beta plays a previously unrecognized role in the selective regulation of the IL-10 recall response by human memory CD4(+) T cells. Furthermore, GSK3beta-inactivated memory CD4(+) T cells acquired the capacity to suppress the bystander proliferation of CD4(+) T cells in an IL-10-dependent, cell contact-independent manner. Our findings reveal a dichotomy present in the function of GSK3 in distinct human CD4(+) T cell populations.

An attempt to prevent senescence: a mitochondrial approach

Antioxidants specifically addressed to mitochondria have been studied to determine if they can decelerate senescence of organisms. For this purpose, a project has been established with participation of several research groups from Russia and some other countries. This paper summarizes the first results of the project. A new type of compounds (SkQs) comprising plastoquinone (an antioxidant moiety), a penetrating cation, and a decane or pentane linker has been synthesized. Using planar bilayer phospholipid membrane (BLM), we selected SkQ derivatives with the highest permeability, namely plastoquinonyl-decyl-triphenylphosphonium (SkQ1), plastoquinonyl-decyl-rhodamine 19 (SkQR1), and methylplastoquinonyldecyltriphenylphosphonium (SkQ3). Anti- and prooxidant properties of these substances and also of ubiquinonyl-decyl-triphenylphosphonium (MitoQ) were tested in aqueous solution, detergent micelles, liposomes, BLM, isolated mitochondria, and cell cultures. In mitochondria, micromolar cationic quinone derivatives were found to be prooxidants, but at lower (sub-micromolar) concentrations they displayed antioxidant activity that decreases in the series SkQ1=SkQR1>SkQ3>MitoQ. SkQ1 was reduced by mitochondrial respiratory chain, i.e. it is a rechargeable antioxidant. Nanomolar SkQ1 specifically prevented oxidation of mitochondrial cardiolipin. In cell cultures, SkQR1, a fluorescent SkQ derivative, stained only one type of organelles, namely mitochondria. Extremely low concentrations of SkQ1 or SkQR1 arrested H(2)O(2)-induced apoptosis in human fibroblasts and HeLa cells. Higher concentrations of SkQ are required to block necrosis initiated by reactive oxygen species (ROS). In the fungus Podospora anserina, the crustacean Ceriodaphnia affinis, Drosophila, and mice, SkQ1 prolonged lifespan, being especially effective at early and middle stages of aging. In mammals, the effect of SkQs on aging was accompanied by inhibition of development of such age-related diseases and traits as cataract, retinopathy, glaucoma, balding, canities, osteoporosis, involution of the thymus, hypothermia, torpor, peroxidation of lipids and proteins, etc. SkQ1 manifested a strong therapeutic action on some already pronounced retinopathies, in particular, congenital retinal dysplasia. With drops containing 250 nM SkQ1, vision was restored to 67 of 89 animals (dogs, cats, and horses) that became blind because of a retinopathy. Instillation of SkQ1-containing drops prevented the loss of sight in rabbits with experimental uveitis and restored vision to animals that had already become blind. A favorable effect of the same drops was also achieved in experimental glaucoma in rabbits. Moreover, the SkQ1 pretreatment of rats significantly decreased the H(2)O(2) or ischemia-induced arrhythmia of the isolated heart. SkQs strongly reduced the damaged area in myocardial infarction or stroke and prevented the death of animals from kidney ischemia. In p53(-/-) mice, 5 nmol/kgxday SkQ1 decreased the ROS level in the spleen and inhibited appearance of lymphomas to the same degree as million-fold higher concentration of conventional antioxidant NAC. Thus, SkQs look promising as potential tools for treatment of senescence and age-related diseases.

CD7(-) T cells are late memory cells generated from CD7(+) T cells

CD7(-) T cells constitute a distinct subset within the CD4(+) and CD8(+) T cell populations; their developmental and functional relationship to the majority of CD7(+) T cells, however, remained so far unresolved. We here elucidate that CD7(-) cells represent aging T cells in late memory cell development characterized by a high activation threshold, low effector capacities, and high sensitivity to activation-induced cell death (AICD). In this regard, CD7(-) T cells highly express killer cell lectin-like receptor G1 (KLRG-1), harbor telomeres of shorter lengths, a decreased telomerase expression per cell, and less amounts of T cell receptor rearrangement excision circles (TRECs) compared to CD7(+) cells. CD7(-) T cells are generated in vitro from naive CD7(+) T cells upon repetitive TCR/CD28 engagement, a process that is unidirectional and requires multiple cell divisions. Consequently, clonal expansions of CD7(-) T cells in vivo are less frequent than of CD7(+) T cells, the former can be traced back to those of CD7(+) T cells.

The immune risk profile is associated with age and gender: findings from three Swedish population studies of individuals 20-100 years of age

Earlier we identified an Immune Risk Profile (IRP) of very old individuals, 86-94 years of age, characterised by an inverted CD4/CD8 ratio and associated with persistent cytomegalovirus infection and an increase in the numbers of CD3+CD8+CD28- cells. In the present study we included data from a population-based sample in the age range of 20-79 years to examine the prevalence of individuals with an inverted CD4/CD8 ratio relative to age and gender across the entire adult lifespan. Immunological monitoring that was conducted included analysis of the numbers of T-cells in the subsets CD3+, CD3+CD4+, and CD3+CD8+ as well as CD3+CD8+CD28+, CD3+CD8+CD28-, and CD8+CD45RA+CCR7+. There was found to be a significant lowering of the numbers of CD3+, CD3+CD4+, and CD3+CD8+, and of the CD8+CD45RA+CCR7+ cells across the adult life-span. Notably, the prevalence of individuals with an inverted CD4/CD8 ratio increased from about 8% in the age range of 20-59 years to about 16% in the age range of 60-94 years. The mortality rate in individuals with an inverted CD4/CD8 ratio also increased significantly above the age of 60. Interestingly, the proportion of individuals with an inverted CD4/CD8 ratio was found to be significantly higher in men, whereas the numbers of CD3+CD4+ helper and CD8+CD45RA+CCR7+ naïve cells and the CD4/CD8 ratio were found to be significantly higher in women. These results highlight the importance of functioning of the thymus in the development of IRP and may partly account for the differences between sexes in terms of longevity.

Age-matched lymphocyte subpopulation reference values in childhood and adolescence: application of exponential regression analysis

BACKGROUND

Normal values of lymphocyte subpopulations for healthy children and adults have been published in defined age groups exclusively, which results in difficult data interpretation for patients close to the limit of contiguous age group ranges. In addition, normal values for a number of lymphocyte subpopulations have not been established to date.

OBJECTIVE

The aim of this study was to develop a model which provides continuous age-dependent reference values. This model was applied for lymphocyte subpopulations such as naïve and memory T cells as well as their activation profile with diagnostic relevance in children and adults.

STUDY DESIGN

A total of 100 blood samples, obtained from 80 healthy children and 20 adults were analysed by means of four colour-flow cytometry. Continuous age-dependent reference values were computed based on the residual values in an exponential regression model.

RESULTS

We calculated a continuous age-related regression model for both, absolute cell counts and percentages of CD3(+)CD4(+) T helper (T(H)) cells, CD3(+)CD8(+) cytotoxic T cells, CD56(+)CD3(-) natural killer (NK) cells, CD56(+)CD3(+) T cells, CD3(+)CD4(+)CD45RA(+) naïve T(H) cells, CD3(+)CD4(+)CD45RO(+) memory T(H) cells, CD3(+)CD8(+)CD45RA(+)CD28(+) naïve cytotoxic T cells, CD3(+)CD8(+)CD45RO(+) memory cytotoxic T cells, CD3(+)CD8(+)CD69(+) early activated cytotoxic T cells and CD3(+)CD8(+)HLA-DR(+) late activated cytotoxic T cells, respectively, to obtain reference values.

CONCLUSION

Based on an exponential regression model, the obtained reference values reflect the continuous maturation of lymphocyte subsets during childhood.