CD8 effector T cell–mediated tumor protection. (A) Serum from A20 tumor cell–protected mice was transferred into naive mice 3 days before tumor challenge. (B) Passive transfer of serum from protected mice resulted in a 4-day increase in median survival of naive mice. (C) T-cell depletion using anti-CD4 (n = 10) and anti-CD8 (n = 30) mAbs was carried out 2 days before tumor challenge. Mice immunized with PBS (black line), ADX40-A20+MPC (dashed line), or ADX40-A20+MPC with cell depletion (gray line). (D) CD4 depletion did not affect median or overall survival. (E) CD8 depletion significantly reduced median and overall survival. Graph shows pooled data from 3 independent challenge experiments (n = 30). (F) Depletion of CD4 and CD8 cells significantly reduced median and overall survival (n = 10). *P < .05; **P < .005.