Adoptively transferred tumor antigen-specific CD8⁺ T cells persist in the peripheral blood of patients as effector memory T cells. (A) Compared with TIL, the frequency of tetramer or Vβ-positive staining CD8⁺ T cells expressing CD45RA increased in the peripheral blood of all patients more than nearly 2 months after cell infusion, while positive CD45RO expression was maintained. Expression was evaluated on tumor antigen-specific CD8⁺ T cells from patients 9 (▵), 10 (×), 20 (⋄), 21 (○), 23 (x), and 28 (□), and the average of all values is shown (•). (B) CD45RA expression is temporally reacquired with concomitant CD45RO reduction on tumor antigen-reactive T cells in vivo. Representative dot plots show the expression of CD45 isoforms on gated MART-1⁺ CD8⁺ T cells from patient 28 TIL or peripheral blood 63 days after cell administration. (C) TIL and posttransfer PBL-derived tumor antigen-specific CD8⁺ T cells lack expression of the lymphoid homing markers, CD62L and CCR7. Expression of CD62L and CCR7 was not detected. (D) CD62L and CCR7 expression is absent on gated MART-1⁺ CD8⁺ T cells from patient 28 TIL or day-63 posttransfer PBLs and limited to endogenously reconstituted CD8⁺ T cells. TuAg indicates tumor antigen.