IL-7Rα and CD28 are highly expressed by melanoma antigen-specific CD8⁺ T cells in the early aftermath of ACT into lymphoablated metastatic melanoma patients. (A) The frequency of tumor-reactive CD8⁺ T cells with elevated IL-7Rα expression levels is increased nearly 1 week after cell infusion. Representative histograms show IL-7Rα expression by TIL or day-7 posttransfer PBL-derived MART-1⁺ or Vβ-22⁺ CD8⁺ T cells from patients 9 and 21, respectively. (B) Tumor antigen-specific T-cell clones rapidly and continuously express IL-7Rα after adoptive transfer. IL-7Rα expression was detected on tumor antigen-specific CD8⁺ T cells from patients 9 (x), 10 (▧), 20 (⋄), 21 (□), 23 (○), and 28 (▵), and the average of all values is shown (•). Expression by persistent tumor antigen-specific CD8⁺ T cells was assessed about 1, 4, and 8 or more weeks after ACT. (C-D) CD28 expression was immediately enhanced on melanoma-reactive CD8⁺ T cells from most patients after cell transfer. Although low, CD28 expression was shown to temporally increase on Vβ-7⁺ CD8⁺ T cells from patient 10 in vivo in 4 independent flow cytometric analyses.