Fig. 1

The highest frequency of CD8 + senescent T cells in middle-age population was analyzed by FACS. a Representative flow cytometric analyses of senescent T cells (CD3 + CD45RA + CCR7-CD27-CD28-CD57 + KLRG1 +) in CD8 and CD4 T cells (top quadrant) and representative flow cytometric analyses of CD27-CD28-CD57 + KLRG1 + subsets, gated on CD3 + CD4 + /CD8 + CD45RO + CCR7-(Tem) population (bottom quadrant). The frequency of CD8 + senescent T cells (b) and CD4 + senescent T cells (c) at young group, middle-age group and elderly group. The percentage of CD57 + KLRG1 + expression on CD3 + CD8 + CD45RO + CCR7-CD27-CD28-population (d) and CD3 + CD4 + CD45RO + CCR7-CD27-CD28-population (e) at different age groups. Expressed as the mean ± SEM. *P < 0.05, **P < 0.01; Mann– Whitney test (two-tailed) and nonpaired Student’s t-test. Tem, effector memory T cell