T cell subsets in young and old graft recipients treated with Rapamycin. Allograft recipients were treated daily with PBS or Rapamycin. By day 7, splenic frequencies of (A) CD4+CD62L+CD44- (naïve), CD4+CD62L+CD44+ (central memory) and CD4+CD62L-CD44+ (effector memory) T cells in addition to (B) CD8+CD62L+CD44-, CD8+CD62L+CD44+ and CD8+CD62L-CD44+ T cells were assessed by flow cytometry. Representative plots are given for each group. (n=5-6 animals/group; data represent mean ± SD; *, <0.05; **, p<0.01; ***, p<0.001)