Both pE CD8⁺ T subsets display the same distinctive replicative history. (A) Real-time PCR quantification of TRECs was performed on sorted RA⁺CCR7⁺27⁺28⁺ (N), RA⁺CCR7^–27⁺28⁺ (pE₁), RA⁺CCR7^–27⁺28^– (pE₂), and RA⁺CCR7^–27^–28^– (E) CD8 subsets from 4 healthy individuals (< 35 years old). Asterisk indicates not detectable (sorted cell number was 10⁵, lower quantification limit = 0.01%). (B) Telomere fluorescence analysis in sorted N, pE₁, pE₂, and E CD8⁺ T cells. The telomere fluorescence was converted to kilobase as described in “Materials and methods.” (C) Telomerase activity in cell extracts of sorted 28⁺DR⁺, 28⁺DR^–, N, pE₁, pE₂, E, pE₁ (28⁺DR⁺), pE₂ + E (28^–DR⁺), and EM₁ (28⁺DR⁺) CD8⁺ T cells. As positive control, we used cell extracts of in vitro PHA-activated CD8⁺ T cell (act. CD8⁺). Data are representative of 4 healthy individuals.