Progressive loss of renal function is associated with a dysregulation of circulating T cells that may underlie their impaired T-cell immunity. Here we tested whether end-stage renal disease (ESRD)-related T-cell alterations are compatible with the concept of premature immunological aging. Younger patients (25-45 years old) with ESRD were found to resemble older healthy controls (60-80 years old) as they had a significant loss of naive T cells and a relative increase of memory T cells showing progressive terminal differentiation. A significant decrease in the content of T-cell receptor excision circles and telomere length in patients with ESRD confirmed these phenotypic data. The loss of naive T cells in patients with ESRD was associated with an excessive age-related decrease of recent thymic emigrants, indicating a premature decline in thymic function. Additionally, increased homeostatic proliferation of naive T cells was found in patients with ESRD, similar to that of older healthy individuals, with an increased susceptibility for activation-induced apoptosis. Therefore, both decreased thymic output and increased susceptibility of naive T cells for apoptosis may play a role in the loss of naive T cells in ESRD patients. Thus, our results are compatible with premature aging of the T-cell system of patients with ESRD comparable with that of healthy individuals 20-30 years older.

BackgroundEnd-stage renal disease (ESRD) patients treated with renal replacement therapy (RRT) have premature immunologically aged T cells which may underlie uremia-associated immune dysfunction. The aim of this study was to investigate whether uremia was able to induce premature ageing of the T cell compartment. For this purpose, we examined the degree of premature immunological T cell ageing by examining the T cell differentiation status, thymic output via T cell receptor excision circle (TREC) content and proliferative history via relative telomere length in ESRD patients not on RRT.ResultsCompared to healthy controls, these patients already had a lower TREC content and an increased T cell differentiation accompanied by shorter telomeres. RRT was able to enhance CD8+ T cell differentiation and to reduce CD8+ T cell telomere length in young dialysis patients. An increased differentiation status of memory CD4+ T cells was also noted in young dialysis patients.ConclusionBased on these results we can conclude that uremia already causes premature immunological ageing of the T cell system and RRT further increases immunological ageing of the CD8+ T cell compartment in particular in young ESRD patients.

SummaryThe uremia-induced inflammatory environment in end-stage renal disease (ESRD) patients is associated with premature T-cell aging resulting in a defective T-cell immunity. As kidney transplantation (KTx) reduces the pro-inflammatory environment, we hypothesized that KTx would rejuvenate the aged T-cell system. As aging parameters, we determined in 70 KTx recipients the differentiation status by immunophenotyping, thymic output by the T-cell receptor excision circle (TREC) content together with CD31 + na€ ıve T-cell numbers and the relative telomere length (RTL) as a measure for proliferative history at pre-KTx, 3, 6 and 12 months post-KTx. In addition, T-cell function was determined by measuring the proliferative capacity and percentages of cytokine-producing cells. Directly post-KTx, memory T-cell numbers were diminished but restored to pre-KTx values at 12 months, except for CD4 + EM T cells. The RTL of (memory) CD4 + and CD8 + T cells did not change. In contrast, TREC content and CD31 + na€ ıve T-cell numbers were stable post-KTx although the RTL of na€ ıve CD4 + and CD8 + T cells decreased implying homeostatic proliferation of na€ ıve cells, in response to a temporary decrease in memory cells. The T-cell function was not improved post-KTx. Our findings demonstrate that the uremia-associated aged phenotype is stably imprinted in the T-cell system and not reversed by KTx.

Advanced ESRD-related T-cell dysregulation that is associated with a relative increase of terminally differentiated CD8 Temra cells protects against AR after kidney transplantation.

The age- and cytomegalovirus (CMV)-seropositivity-related changes in subsets and differentiation of circulating T cells were investigated in end-stage renal disease (ESRD) patients (n = 139) and age-matched healthy individuals. The results show that CMV-seropositivity is associated with expansion of both CD4+ and CD8+ memory T cells which is already observed in young healthy individuals. In addition, CMV-seropositive healthy individuals have a more differentiated memory T cell profile. Only CMV-seropositive healthy individuals showed an age-dependent decrease in CD4+ naïve T cells. The age-related decrease in the number of CD8+ naïve T cells was CMV-independent. In contrast, all ESRD patients showed a profound naïve T-cell lymphopenia at every decade. CMV-seropositivity aggravated the contraction of CD4+ naïve T cells and increased the number of differentiated CD4+ and CD8+ memory T cells. In conclusion, CMV-seropositivity markedly alters the homeostasis of circulating T cells in healthy individuals and aggravates the T cell dysregulation observed in ESRD patients.

SummaryCytomegalovirus (CMV) infection has been implicated in accelerated T cell ageing. End-stage renal disease (ESRD) patients have a severely immunologically aged T cell compartment but also a high prevalence of CMV infection. We investigated whether CMV infection contributes to T cell ageing in ESRD patients. We determined the thymic output by the T cell receptor excision circle (TREC) content and percentage of CD31+ naïve T cells. The proliferative history of the T cell compartment by determination of the relative telomere length (RTL) and the T cell differentiation status was determined by immunophenotyping. It appeared that CMV infection did not affect thymic output but reduced RTL of CD8+ T cells in ESRD patients. Moreover, increased T cell differentiation was observed with higher percentages of CD57+ and CD28null CD4+ and CD8+ memory T cells. These CD28null T cells had significantly shorter telomeres compared to CD28+ T cells. Therefore we concluded that CMV infection does not affect the decreased thymic output but increases T cell differentiation as observed in ESRD-related premature T cell ageing.

SummaryDetection and isolation of viable alloreactive T cells at the single-cell level requires a cell surface marker induced specifically upon T cell receptor activation. In this study, a member of the tumour necrosis factor receptor (TNFR)-family, CD137 (4-1BB) was investigated for its potential to identify the total pool of circulating alloreactive T cells. Optimal conditions for sensitive and specific detection of allogeneic-induced CD137 expression on circulating T cells were established. Thereafter, CD137+ alloreactive T cells were phenotypically and functionally characterized by multi-parameter flow cytometry. Alloantigen-induced CD137 expression identified both alloreactive CD8 + T cells (mean ± standard error of the mean: 0·21 ± 0·07%) and alloreactive CD4 + T cells (0·21 ± 0·05%). CD137 + alloreactive T cells were detected in different T cell subsets, including naive T cells, but were found preferentially in CD28+ T cells and not in the terminally differentiated T cell subset. Upon allogeneic (re-)stimulation, the cytokine-producing as well as proliferative capacity of T cells resided mainly within the CD137-expressing fraction. About 10% of the CD137 + alloreactive T cells produced any combination of interferon (IFN)-γ, interleukin (IL)-2 and TNF-α. Polyfunctional alloreactive T cells, defined by multiple cytokine expression, were observed infrequently. In conclusion, activation-induced CD137 expression is a fast assay allowing for detection and functional analysis of the total alloreactive T cell compartment at the single-cell level by multiparameter flow cytometry.

Introduction: An unusual population of pro-inflammatory CD4 + T cells that have lost the co-stimulatory molecule CD28 (CD4 + CD28null T cells) is expanded in patients with end-stage renal disease (ESRD). CD4 + CD28null T cells are associated with cardiovascular disease and may cause atherosclerotic plaque instability by their highly proinflammatory nature. In this study we tested the hypothesis that expansion of CD4 + CD28null T cells in ESRD poses a risk factor for an atherosclerotic vascular event (AVE) after kidney transplantation. Methods: In a prospective study the number of circulating CD4 + CD28null T cells was established in 295 ESRD patients, prior to receiving a kidney allograft. All patients were screened for a history of symptomatic atherosclerotic disease and routinely evaluated for cardiovascular disease (CVD) by a cardiologist before kidney transplantation. Besides age and gender, the traditional risk factors for atherosclerotic disease were recorded. During the first year after transplantation, patients were followed for the occurrence of an AVE. Results: In 31% of all ESRD patients a medical history of CVD was present (CVDpos). The percentage (10.3% vs 5.6%, p=0.002) and absolute number (38 versus 22 x 10 3 /mL, p=0.01) of CD4 + CD28null T cells were increased in CVDpos patients compared to patients without documented CVD (CVDneg). Within the first year after transplantation, an AVE occurred in 20 patients, 5 cases (2.3 %) in the CVDneg group and 15 cases (18.3 %) in the CVDpos group. Over 80% of all AVEs occurred within 3 months after transplantation with a median time from transplantation to event of 5 days. Univariate analysis showed that besides CVDpos (HR 8.1, p< 0.001), age (HR 1.04, p=0.02), dylipidaemia (HR 8.8, p=0.004) and the % of CD4 + CD28null T cells (1.04 per % increase, p=0.01) were significantly associated with the occurrence of a post-transplantation AVE. In a multivariate analysis, only CVDpos remained a significant risk factor with a significant and positive interaction between the terms CVDpos and the % of CD4 + CD28null T cells (HR 1.05, p< 0.001). Within the CVDpos group, the incidence of an AVE was 13% in the lowest tertile compared to 25% in the highest tertile of % of CD4 + CD28 null T cells. Conclusion:The expansion of circulating CD4 + CD28null T cells is highly associated with the presence of CVD in ESRD patients and increases the risk for a cardiovascular event shortly after kidney transplantation.