Lysis of different tumor cell lines by CTLs derived from mice surviving the P815 tumor cells challenge. Mice were injected s.c. with 3 x 10⁵ CD40L-activated DCs loaded with the P1A peptide on days 21 and 7 prior to the challenge with an i.p. injection of 4 x 10⁵ P815 tumor cells. At day 60, surviving mice (89%) were sacrificed and their spleen cells were stimulated in vitro with P815 tumor cells. After 6 days, these cultures were tested for their ability to lyse the indicated ⁵¹Cr-labeled target cells. Chromium release was assessed after three hours and half. Each curve represents the lytic activity obtained with the spleen cells of one mouse. Data are from one representative experiment of 3 performed.