Splenic cytotoxicity in WT, CD8-depleted, NK-depleted, and NK/CD8-depleted mice. Spleen cells were prepared from mice 24 hours after initial transfusion and used as cytotoxic effectors against chromium-labeled (A) P815 and (B) EL-4 target cells in a 6-hour assay. Percent lysis at the indicated effector-to-target ratios was calculated by the following formula: cpm_test - cpm_min/cpm_max - cpm_min × 100. The results are expressed as the mean (± SD) percent lysis from 10 mice per group. • indicates WT; ○, CD8-depleted; □, NK-depleted; ⋄, NK/CD8-depleted. All cytotoxicities were inhibited by addition of 100 μM aminoguanidine (AMG) to the assays.