Figure 5. Aged CD70+ T cells exhibit high susceptibility to apoptosis that can be reversed by blocking CD70. (A–D) Percentage of apoptotic cells (Annexin V+ 7AAD-) (A–B) and expression of CD95 (C–D) in CD70- and CD70+ T cells from elderly individuals (61-80 years, n = 17). Representative histograms (left) and plots (right) of the percentage of apoptotic cells are shown. The p-values were obtained by paired t-test (Annexin V) or Wilcoxon matched-pairs signed rank test (CD95). (E–F) Correlation analysis of percentage of HLA-DR+CD38hi cells and percentage of Annexin V+ 7AAD- cells (E) or CD95 expression (F) on CD4+ T cells (left) and CD8+ T cells (right) from all healthy donors. Spearman’s non-parametric test was used for correlation analysis. (G–J) Purified CD4+ and CD8+ T cells from elderly individuals (n = 8) were cultured in vitro with anti-human CD70 antibody or isotype IgG at a concentration of 10 μg/mL. After culturing for 24 h, the susceptibility to apoptosis was evaluated by flow cytometry. Representative histogram (left) and plot (right) of percentage of Annexin V+ 7AAD- (G–H) and Annexin V+ CD95+ cells (I–J) in CD4+ and CD8+ T cells. The p-values were obtained by paired t-test (Annexin V+ 7AAD- [CD8+ T cells], Annexin V+ CD95+ [CD8+ T cells]) or Wilcoxon matched-pairs signed rank test (Annexin V+ 7AAD- [CD4+ T cells], Annexin V+ CD95+ [CD4+ T cells]). *p < 0.05, **p < 0.01, ***p < 0.001.