FIG. 4.

B6 and B6.lpr mice were immunized with 10⁶ B.GV tumor cells. At 14 days later, B6 (experiment 1) or B6.lpr (experiment 2) responder spleen cell populations, which were either unfractionated or CD4 or CD8 depleted, were reconstituted to their original numbers with immune B6.lpr CD4⁺ or CD8⁺ (experiment 1)- or B6 CD4⁺ or CD8⁺ (experiment 2)-enriched spleen cells, respectively, and mixed with E♂G2 tumor stimulator cells without or with AKR.H-2^b inhibitor cells, as indicated. The effector-to-target-cell ratios shown are 50:1 and 20:1 for experiments 1 and 2, respectively. The values for spontaneous release by E♂G2 tumor target cells ranged from 5.1 to 10.8%.