Early alloresponses mediated by memory T cells from unprimed mice. Sorted T-cell subsets were cultured with irradiated allogeneic stimulators. All experiments were repeated at least twice and yielded similar results. Results represent mean + SD of triplicate wells. (A) Kinetics of proliferative response. Cells were harvested at different times after the initiation of culture. Proliferation was determined by 3H-thymidine incorporation. Proliferation rates in the syngeneic controls were less than 10%, 5%, and 1% of the experimental groups for 2-, 3-, and 4-day cultures, respectively. (B) IL-2 production. Frequencies of IL-2–producing cells were determined by ELISPOT assay. IL-2 indicates interleukin-2; ELISpot, enzyme-linked immunosorbent spot assay. *P < .05, memory versus other groups; #P < .05, memory versus naive.
