Because TREC content is related reliably and linearly with age, measuring the TREC content in blood can be used as a tool for age determination for forensic purposes . In both ESRD patients and elderly healthy individuals a decreased thymic output of naive T cells based upon TREC analysis Selleck Regorafenib was observed. Next to the TREC content, an alternative technique to identify recent thymic emigrants is to measure the CD31 expression on naive T cells , which corroborates the findings of the TREC content. In addition, activation and increased numbers
of proliferating Ki-67+ naive T cells were observed. Homeostatic proliferation occurs in response to this decreased thymic output to maintain the naive T cell compartment. Our findings do not support a role for CMV in the decreased output of naive T cells or their peripheral proliferation in the periphery, as both the TREC content and the percentage of CD31+ and Ki-67+ cells were not affected by CMV serostatus. This also suggests that the expansion and differentiation of memory T cells in CMV-seropositive patients does not change the number or homeostatic proliferation of naive T cells. This may have been expected, as it is assumed that increased turnover of this compartment would also accelerate the turnover of naive T cells. Another parameter to assess the immunological age of T cells is to determine
the telomere length of CD4+ and CD8+ T cells, which is indicative of the proliferative history of the cells. Similarly to TREC content, overall there is a VX-809 order clear inverse
correlation between RTL and age in both healthy individuals and ESRD patients. However, the CD8+ T cells of CMV-infected ESRD patients have substantially shorter telomeres than age-matched CMV-seronegative ESRD patients, resulting in an immunological age OSBPL9 difference of almost 20 years. This finding indicates a higher burden by CMV on CD8+ T cells of ESRD patients during ageing. We could not detect this CMV-related effect in RTL for the CD4+ T cells. The absence of additional CMV-induced telomere attrition within total CD4+ T cells in ESRD patients in contrast to that within total CD8+ T cells can therefore be explained by the difference in differentiation status of the T cell compartment. To examine whether the telomere shortage in CD8+ T cells is caused by a possible inhibitory effect on the activity of the telomerase enzyme (responsible for extending the telomere length), we analysed the activity of this enzyme in both CD8+ and CD4+ T cell populations. No differences were found between the CMV-seronegative and CMV-seropositive patients, indicating that altered telomerase activity is not a probable cause for the decreased RTL in CD8 T cells of CMV-seropositive ESRD patients. This indicates that the shorter telomeres for the CD8+ T cell compartment is caused by the higher proliferation and differentiation status in CMV-seropositive patients.