Cellular characteristics of EM and EM_CD45RA+ IL-7Rα^high and IL-7Rα^low CD8⁺ T cells in elderly and young subjects. (A-C) PBMCs from healthy elderly and young subjects were stained with antibodies to CD8, CCR7, CD45RA, IL-7Rα, CD27, CD28, CD57, perforin, or isotype antibodies. Expression of CD27, CD28, CD57 (shaded histograms, B), perforin (shaded histograms, C) and isotype (open histograms, B-C) antibodies by naive, CM, EM IL-7Rα^high, EM IL-7Rα^low, EM_CD45RA+ IL-7Rα^high and IL-7Rα^low CD8⁺ T-cell subsets was determined by gating on each cell subset. Numbers in dot plots (A) indicate the percentage of positive cells in each quadrant. Results are representative data from 5 separate subjects in each group. (D-E) PBMCs from a healthy elderly subjects were stained with antibodies to CD8, CD45RA, and CCR7 and were sorted into naive, EM, EM_CD45RA+ IL-7Rα^high, and IL-7Rα^low. (D) Cells were stained with CFSE and stimulated for 6 days with antibodies to CD3 and CD28. Stimulated cells were stained with antibodies to CD57. Numbers in histograms indicate the percentages of proliferating cells. Results are representative data from 3 young and 2 elderly subjects. (E) Sorted cells were incubated for 6 days in the presence of IL-7 (100 ng/mL) and were stained with annexin V and 7-AAD. Numbers in dot plots indicate the percentage of cells in each quadrant. Results are representative data from 2 young and 2 elderly subjects.