Karin Hähnel

Hallmark Features of Immunosenescence Are Absent in Familial Longevity

Seropositivity for CMV is one of the parameters of the “immune risk profile” associated with mortality in longitudinal studies of the very elderly and may accelerate immunosenescence. Thus, any genetic factors influencing human longevity may be associated with susceptibility to CMV and CMV-accelerated immunosenescence. To test this, we analyzed long-lived families in the Leiden Longevity Study (LLS) in which offspring enjoy a 30% reduced standardized mortality rate, possibly owing to genetic enrichment. Serum C-reactive protein levels and the frequency of different T cell subsets were compared between 97 LLS offspring and 97 controls (their partners, representing the normal population). We also determined the capacity of T cells to respond against immunodominant Ags from CMV in a smaller group of LLS subjects and controls. CMV infection was strongly associated with an age-related reduction in the frequency of naive T cells and an accumulation of CD45RA–re-expressing and late-differentiated effector memory T cells in the general population, but not in members of long-lived families. The latter also had significantly lower C-reactive protein levels, indicating a lower proinflammatory status compared with CMV-infected controls. Finally, T cells from a higher proportion of offspring mounted a proliferative response against CMV Ags, which was also of greater magnitude and broader specificity than controls. Our data suggest that these rare individuals genetically enriched for longevity are less susceptible to the characteristic CMV-associated age-driven immune alterations commonly considered to be hallmarks of immunosenescence, which might reflect better immunological control of the virus and contribute to their decreased mortality rate.

Pretreatment frequency of circulating IL-17+CD4+ T-cells, but not Tregs, correlates with clinical response to whole-cell vaccination in prostate cancer patients

The aim of this study was to determine the prognostic implications of the pretreatment level of Th17 cells compared with regulatory T‐cell status in prostate cancer patients receiving active whole cell immunotherapy. Ten‐color flow cytometry was used to analyze IL‐17‐producing CD4+ T‐cells in the peripheral blood of hormone‐resistant non‐bone metastatic prostate cancer patients prior to immunotherapy with an allogeneic whole‐cell vaccine. Surface expression of the chemokine receptors CCR4 and CCR6 was used to further subdivide IL‐17‐producing cells into subsets with distinct homing properties. The frequency of circulating regulatory T‐cells (Tregs), defined as CD3+CD4+CD127loFoxp3+CD25+ was compared in the same patients. The frequency of CCR4−IL‐17+CD4+ T‐cells prevaccination inversely correlated with time to disease progression (TTP) in 23 prostate cancer patients. Furthermore, responder (R) patients with statistically significant reductions in PSA velocity (PSAV) in response to the immunotherapy (n = 9), showed a Th17 profile similar to healthy male controls and significantly different from non‐responder (NR) patients (n = 14) (i.e., those without any significant reduction in PSAV). In contrast, the frequency of Tregs in peripheral blood in PSA‐R (n = 11) and ‐NR (n = 14) patients was similar (but in both cases, significantly higher than in age‐matched healthy men). Accordingly, there was no significant correlation between frequency of Tregs and TTP in these late‐stage prostate cancer patients undergoing active immunotherapy. These data imply an important role for IL‐17‐producing helper T‐cells in cancer immunology and highlight their potential use as a pretreatment screen to ensure appropriate treatment is offered to hormone‐resistant prostate cancer patients.

Cytomegalovirus-associated accumulation of late-differentiated CD4 T-cells correlates with poor humoral response to influenza vaccination

Influenza vaccination is less effective in the elderly compared to the young. Studies that have attempted to identify immune parameters correlating with satisfactory vaccine responses have yielded inconclusive results. Here, we correlate the distribution of different circulating CD4+ and CD8+ T-cell phenotypes with the humoral response to vaccination with Intanza, an intradermal seasonal vaccine, in 54 individuals of different ages. Subjects were stratified according to age (below or over 60) and presence of a latent infection with Cytomegalovirus (CMV). CMV-seropositivity was significantly associated with a lower response rate to the vaccine in people over but not below 60 yr of age. Unlike reported data, late-differentiated (CD45RA+CCR7-CD27-CD28-) CD4+, but not CD8+ T-cells associated with a poorer vaccine response. Thus, latent CMV infection has a deleterious effect on influenza antibody responses in the elderly, which might be mediated through CD4 T-cells lacking CCR7, CD27 and CD28 and re-expressing CD45RA.

Latent Infection with Cytomegalovirus Is Associated with Poor Memory CD4 Responses to Influenza A Core Proteins in the Elderly

Influenza remains a major pathogen in older people. Infection with CMV and the accumulation of late-differentiated T cells associated with it have been implicated in poor Ab responsiveness to influenza vaccination in the elderly, most of whom are CMV positive. However, whether CMV infection also affects memory T cell responses to influenza remains unknown. To investigate this, we assessed T cell responses to influenza A matrix protein and nucleoprotein ex vivo in 166 Dutch individuals (mean age 62.2 y, range 42–82) and validated the results in a second cohort from North America (mean age 73.1 y, range 65–81, n = 28). We found that less than half of the CMV-infected older subjects mounted a CD4 T cell response to influenza Ags, whereas ∼80% of uninfected elderly did so. A similar proportion of younger subjects possessed influenza A virus–responsive CD4 T cells, and, interestingly, this was the case whether they were CMV-infected. Thus, the effect of CMV was only seen in the older donors, who may have been exposed to the virus for decades. The percentage of donors with CD8 responses to influenza A virus was lower than those with CD4; this was not influenced by whether the subjects were CMV seropositive or seronegative. CMV-seropositive responders had significantly higher frequencies of late-differentiated CD4 T-cells (CD45RA+/−CCR7−CD27−CD28−) compared with CMV-infected nonresponders. These data add to the accumulating evidence that infection with CMV has profound but heterogeneous effects on responses to the products of other viruses and have implications for the design of influenza vaccines, especially in the elderly.

In vitro senescence models for human T lymphocytes.

Immunosenescence is an age-associated dysregulation of immune function which may contribute to the increased susceptibility of the elderly to infectious disease. Although age-associated changes are measurable in the innate immune system, it is the adaptive arm of the immune system which is particularly susceptible to the deleterious effects of ageing, especially the T cell compartment. In this review, the characteristics of longitudinal ageing in cultured monoclonal human T cell populations will be summarized. It will be argued that parallels between this in vitro model and T cell senescence in vivo suggest the use of such models to screen for interventions ameliorating immunosenescence in vivo.

Extrathymic T cell differentiation in vitro from human CD34+ stem cells

Although it is well established that T cells are derived from CD34+ stem cells in vivo, and that T cells can develop in the absence of a functioning thymus, it has not proven possible thus far to generate human T cells in vitro from CD34+ cells in the absence of any thymic influence. We now present a limiting dilution cloning culture system that supports the differentiation of highly purified human CD34+ cells to CD3+ T cells in vitro in the complete absence of any thymic components. The culture system features the use of a serum‐free medium supplemented with a cocktail of cytokines including flt‐3 ligand, interleukin‐3 (IL‐3), stem cell factor (SCF), and IL‐2. CD4+ T cell clones capable of mitogen‐stimulated proliferation and response to IL‐2, and expressing a varied TCR‐Vβ repertoire were obtained under these conditions. This culture system therefore supports human T lymphopoiesis in the absence of any thymic influence and may prove useful for the evaluation of extrathymic T cell differentiation in vitro. J. Leukoc. Biol. 64: 733–739; 1998.

CCR4+ Regulatory T Cells Accumulate in the Very Elderly and Correlate With Superior 8-Year Survival

CD4(+) regulatory T cells (Tregs) are a distinct population of T cells involved in maintaining peripheral tolerance to self-antigens. Several studies have shown increased frequency and number of Tregs in the elderly. Whether such an increase has any clinical relevance has not been addressed. Here, we have analyzed circulating Tregs in 114 donors between the ages of 18 and 89 years and assessed their implications for survival of the very elderly. In line with previously published data, we observed higher proportions of Tregs in the elderly. Expression of chemokine receptor 4 (CCR4) by Tregs has been shown to characterize antigen-primed activated Tregs with immediate suppressive function. Thus we further analyzed Tregs expressing or lacking this chemokine receptor. There were more CCR4(+) and CCR4(-) Tregs in the elderly than the young. Finally, using a subset of 48 elderly donors participating in the Leiden 85-plus study we documented that people with greater median frequencies of CCR4(+) Tregs enjoyed a better 8-year survival rate than those with lower frequencies of these cells. Our data, demonstrating for the first time a positive correlation between increased frequency of Tregs and survival in the elderly, imply an increasing importance of controlling inappropriate immune responses and inflammation as we grew old.