Costimulation through baCD3/CD28 generates TK⁺ human lymphocytes with a CM phenotype. At day 10, aCD3- or baCD3/CD28-TK⁺ lymphocytes were compared with the corresponding PBLs for memory phenotype. (A) After gating for CD3 in the case of PBLs and for LNGFR in the case of TK⁺ cells, cells were analyzed by flow cytometry for CD45RA and CCR7 expression (dot plots). Quadrants were set according to isotype-control staining. The inserts report the percentages of cells for each quadrant. Results with cells from one representative donor of 5 are shown. Averages ± SD of the relative distribution of CD45RA⁺CCR7⁺, CD45RA^-CCR7⁺, or CD45RA^-CCR7^- cells are reported for CD4⁺ (top histograms) or for CD8⁺ cells (lbottom histograms) in PBLs, aCD3- or baCD3/CD28-TK⁺ lymphocytes. (B) Cells were also analyzed by flow cytometry for CD27 and CD28 expression (dot plots). Quadrants were set according to isotype-control staining. The inserts report the percentages of cells for each quadrant. Results with cells from one representative donor of 5 are shown. Averages ± SD of the relative distribution of CD28⁺CD27⁺, CD28^-CD27⁺, or CD28^-CD27^- cells are reported for CD4⁺ (top histograms) or CD8⁺ cells (bottom histograms) in PBLs or saCD3- or baCD3/CD28-TK⁺ lymphocytes. Symbols overlying saCD3- or baCD3/CD28-TK⁺–related bars are for statistical comparison with the corresponding PBL-related bars (^*P < .05; ^**P < .01; ^***P < .005).