Adoptive transfer of T cells from treated mice can protect naive recipients against lymphoma growth. BALB/c mice were inoculated with tumor and treated with 5 Gy TBI and anti-CD40 mAb (100 μg intravenously) as before. Four days after treatment just prior to the peak of the primary immune response, splenocytes were harvested, CD19⁺ cells depleted by MACS, and remaining T cells coinjected into naive recipients together with fresh lymphoma cells at an E/T ratio of 100:1 (CD8⁺ cells/T). Controls received either PBS or tumor plus CD19-depleted splenocytes from untreated mice. Survival was recorded daily. Mice that received adoptively transferred “peak” T cells showed a significant enhancement in protection over controls (P < .01).