CD70 contributes to age-associated T cell defects and overwhelming inflammatory responses

Abstract

Aging is associated with immune dysregulation, especially T cell disorders, which result in increased susceptibility to various diseases. Previous studies have shown that loss of co-stimulatory receptors or accumulation of co-inhibitory molecules play important roles in T cell aging. In the present study, CD70, which was generally regarded as a costimulatory molecule, was found to be upregulated on CD4⁺ and CD8⁺ T cells of elderly individuals. Aged CD70⁺ T cells displayed a phenotype of over-activation, and expressed enhanced levels of numerous inhibitory receptors including PD-1, 2B4 and LAG-3. CD70⁺ T cells from elderly individuals exhibited increased susceptibility to apoptosis and high levels of inflammatory cytokines. Importantly, the functional dysregulation of CD70⁺ T cells associated with aging was reversed by blocking CD70. Collectively, this study demonstrated CD70 as a prominent regulator involved in immunosenescence, which led to defects and overwhelming inflammatory responses of T cells during aging. These findings provide a strong rationale for targeting CD70 to prevent dysregulation related to immunosenescence.

Keywords: CD70; T cell aging; co-inhibitory molecules; immunosenescence; overwhelming inflammatory responses.

Figure 1

CD70-expressing T cells accumulate with age. Flow cytometry analysis of CD70 expression on PBMCs from healthy controls of different ages. (A) Representative flow cytometric plots show the expression of CD70 gated on CD4⁺ and CD8⁺ T cells from five healthy donors in different age groups. (B–C) Box plots of the frequencies of CD70⁺ cells among CD4⁺ and CD8⁺ T cells from healthy donors in different age groups (n = 34-56 in each group). Values given are the median frequencies ± the interquartile range and 10 and 90 percentile whiskers. The p-values were obtained by Kruskal-Wallis test followed by Dunn’s multiple comparisons test. (D–E) Correlation analysis of age and surface CD70 expression on CD4⁺ T cells (D) and CD8⁺ T cells (E) from all healthy individuals. Spearman’s non-parametric test was used to test for correlations. *p < 0.05, **p < 0.01, ***p < 0.001.

Figure 2

CD70 is preferentially expressed on memory CD4⁺ and CD8⁺ T cells. Expression of CD70 on each subset (T_N, T_CM, T_EM, and T_EMRA) of CD4⁺ and CD8⁺ T cells. Representative flow data (A, C) and box plots (B, D) of the percentage of CD70 expression on each subset of CD4⁺ (A–B) and CD8⁺ (C–D) T cells from five different age groups (n = 34-56 in each group). Data are shown as the median ± 95% confidence interval (CI). The p-values were obtained by Kruskal-Wallis test followed by Dunn’s multiple comparisons test. *p < 0.05, **p < 0.01, ***p < 0.001.

Figure 3

Aged CD70⁺ T cells show a phenotype of over activation. Flow cytometry analysis of percentage of HLA-DR⁺ CD38^hi cells (A–B), and expression of CD28 (C–D) and CD27 (E–F) on CD70^- vs. CD70⁺ CD4⁺ and CD8⁺ T cells from elderly individuals (61-80 years, n = 17). Representative flow data or histograms (left) and plots (right) display the expression of the above receptors on CD70^- vs. CD70⁺ cells (gated with CD4⁺ or CD8⁺ T cells). The p-values were obtained by paired t-test (HLA-DR⁺CD38^hi [CD4⁺ T cells], CD28, CD27) or Wilcoxon matched-pairs signed rank test (HLA-DR⁺CD38^hi [CD8⁺ T cells]). ***p < 0.001.

Figure 4

CD70 expression is associated with the phenotypic profile of exhaustion. Flow cytometry analysis of expression of PD-1 (A–B), 2B4 (C–D), LAG-3 (E–F) and CD160 (G–H) on CD70^- vs. CD70⁺ CD4⁺ and CD8⁺ T cells from elderly individuals (61-80 years, n = 17 [2B4, CD160], n = 34 [PD-1, LAG-3]). Representative histograms (left) and plots (right) display the expression of the above receptors on CD70^- vs. CD70⁺ cells (gated with CD4⁺ or CD8⁺ T cells). The p-values were obtained by paired t-test (PD-1 [CD4⁺ T cells], 2B4, CD160 [CD8⁺ T cells]) or Wilcoxon matched-pairs signed rank test (PD-1 [CD8⁺ T cells], LAG-3, CD160 [CD4⁺ T cells]). ***p < 0.001.

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⁺CD38^hi 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.

Figure 6

Aged CD70⁺ T cells secrete increased levels of inflammatory cytokines that can be reversed by blocking CD70. (A–F) Intracellular staining for TNF-α, IFN-γ, and IL-2 in CD70^- and CD70⁺ T cells from elderly individuals (61-80 years, n = 17) after in vitro anti-CD3/anti-CD28 stimulation. Representative flow data (left) and plots (right) for TNF-α, IFN-γ, and IL-2, respectively. The p-values were obtained by paired t-test (TNF-α, IFN-γ [CD8⁺ T cells], IL-2 [CD4⁺ T cells]) or Wilcoxon matched-pairs signed rank test (IFN-γ [CD4⁺ T cells], IL-2 [CD8⁺ T cells]). (G–L) Purified CD4⁺ and CD8⁺ T cells from healthy individuals (n = 6) were cultured with antagonist anti-CD70 antibody or IgG at a concentration of 10 μg/mL as indicated. After culturing in vitro for 24 h and stimulating with anti-CD3/anti-CD28, the cytokine production was measured by flow cytometry. Representative histogram (left) and plot (right) of TNF-α, IFN-γ, and IL-2 expression in CD4⁺ and CD8⁺ T cells. The p-values were obtained by paired t-test. *p < 0.05, **p < 0.01, ***p < 0.001.