Generation of TS1 memory cells. TS1 T_N were stimulated in vitro with HA peptide and irradiated T cell-depleted splenocytes for 3 days. Cells were then transferred into RAG^−/− mice and allowed to rest for 2-3 months (design, A). Shown are representative flow cytometry showing the phenotypes before culture (B), after 3 days in culture (C) and after resting in RAG^−/− mice (D). Data are representative of > 10 experiments. IFN-γ production in T_N, T_CM and T_EM post stimulation with PMA and ionomycin is shown in panel E (data are from 1 experiment).