FACS analyses of blood samples during aging. (A) Memory CD8 T-cell accumulation in representative animals from the 4 genotypes at 10 months. DM indicates Cdkn1b^+/−/MTCP1^TG; Tg, MTCP1 transgenics; Htz, Cdkn1^+/−; and WT, wild type. (Left) Dot plots of CD4-PE and CD8-APC gated on the lymphocyte population and (right) CD44-FITC and CD122-PE-Cy5 gated on the CD8⁺ cells. (B) Percentage of CD8m (CD8⁺CD44^HICD122^HI) among total CD8 (CD8_T) cells at 7, 10, and 14 months in mice with the 4 different genotypes (DM represented by black diamond; Tg, black circle; Htz, empty diamond; and WT, empty circle). Means are indicated as empty squares; ± SDs are indicated as lines. Significance of between-group analyses (brackets) determined by Student t test is indicated as follows: NS, nonsignificant difference; *P < 5.10⁻²; **P < 5.10⁻³; and ***P < .001. At 10 months, a group of 4 DM mice with higher CD8m accumulation is identified by a rectangle. (C) Vβ repertoire in CD8⁺ cells in the different genotypes at 10 months. The distribution of 9 TCR Vβ in CD8m (CD8⁺CD44^HI) is represented by black rectangle; and in CD8n (CD8⁺CD44^LOW) by gray rectangle, in representative animals from 1 wild-type (WT1), 1 MTCP1 transgenic (TG10), and 4 DM mice.