Splenocytes from combination therapy kill lymphoma cells. BALB/c mice received BCL₁ lymphoma (10⁶ intravenously, day 0) and were treated on day 15 with anti-CD40 (100 μg intravenously) and 5 Gy TBI as before. Five days later splenocytes were harvested and used as effectors against ⁵¹Cr-labeled targets. (A) Cytotoxic activity of splenocytes from control, 5 Gy–irradiated, anti-CD40, or combination therapy–treated mice against πBCL₁ lymphoma cells. The effector-target (E/T) ratio used was as indicated. Only splenocytes from mice given combination therapy were able to kill lymphoma cells. (B) Cytotoxic activity of slenocytes from therapy mice against πBCL₁ in the presence (•) or absence (□) of blocking anti–MHC I mAb (25 μg/mL) or against A31 lymphoma cells (▵). As a positive control bispecific (anti–MHC II × anti-CD3)²⁵  monoclonal antibody (⋆) was included (10 μg/mL) to confirm target cell sensitivity (E/T 100:1; A31 targets). The E/T ratio was as shown. For both figures each point is the mean and SD of triplicate samples. Shown is 1 of 2 separate experiments.