Adoptively transferred HIV-specific CD8⁺ T cells that express CD28 are capable of proliferation after specific Ag exposure in the absence of supplemental exogenous cytokines. All plots are gated on pentamer⁺ T cells or as otherwise indicated. (A-B) PBMCs from patients 7701 and 7702 collected, respectively, 14 and 3 days after the first infusion and PBMCs from patients 7703 and 7705 collected, respectively, 21 and 3 days after the first infusion were stained with CFSE and incubated in the presence of cognate peptide (B*0801/GEIYKRWII-HIV-GAG for 7701-7703 and B*0702/IPRRIRQGL-HIV-ENV for 7705). Expression of CD28 on pentamer⁺CD8⁺ T cells (plots in the top row) is shown. Plots in the second and third rows show CFSE dilution after 5 and 7 days ex vivo (x-axis) relative to CD28 expression (y-axis). Dilution of CFSE after 7 days ex vivo is shown (histogram, bottom row). (C) Pentamer⁺CD8⁺ T cells in PBMCs from patient 7707 collected 3 days after the second infusion and after 7 days of ex vivo stimulation with cognate peptide (A*0301/QVPLRPMTYK-HIV-NEF; left panel). The same experiment performed with the addition of exogenous IL-2 50 IU/mL (right panel). (D) CFSE dilution of detected pentamer⁺CD8⁺ T cells PBMC from patient 7707 collected 84 days after the second infusion and after 7 days of ex vivo stimulation with cognate peptide with (right panel) or without IL-2 (left panel).