Sorted CMV-specific IL-7Rα⁺cells proliferate better than IL-7Rα^-cells. From PBMCs, IL-7Rα⁺ and IL-7Rα CMV-specific (tetramer⁺) CD8⁺ T cells were sorted by fluorescence-activated cell sorter (FACS) analysis. (A) CFSE profiles of sorted IL-7Rα^- or IL-7Rα⁺ CMV-specific CD8⁺ T cells on stimulation with IL-7, IL-15, specific CMV peptide, or CMV peptide in combination with CMV antigen on day 3 (top 2 rows) and day 6 (bottom 2 rows). Numbers indicate the calculated precursor frequency that indicates the percentage of cells from the original population that proliferated. Italic numbers indicate the calculated mean number of divisions of the divided cells and the amount of divisions that the proliferating cells underwent. Representative data are shown from 4 independent experiments with cells from 3 different donors. (B) Means of the precursor frequencies after 6 days of culture, calculated from 4 independent experiments (2 experiments for IL-15). ^*Significant difference (P = .029). ▦ indicates IL-7Rα^-; ▪, IL-7Rα⁺.