Inactivated CD8⁺ memory T cells fail to acquire an effector phenotype on antigen challenge. CD45.1⁺ OT-I effector/memory cells were transferred intravenously to 11c.OVA or nontransgenic (non-tg) controls. Mice were left unchallenged or challenged with OVA/QuilA s.c. at 35 days after transfer and the phenotype of OT-I T cells (CD45.1⁺/CD8⁺) in spleen, liver, and lung analyzed 7 days later. Data are representative of 2 mice per group in more than 2 independent experiments. Numbers on graphs are the percentages of cells in each gate for that plot.