GVT effect is maintained after ECP treatment. (A) Specific killing of target (T) tumor cell lines A20 (left) and Bcl1 (right) by effector CD8⁺ T cells (E) is shown. CD8⁺ T cells were isolated from ECP-treated (ECP) or nontreated (Tcon) mice 10 days after BMT and were added to ⁵¹Cr-labeled target cells at an E:T ratio of 20:1 and 5:1. Specific killing occurred in both target cells, but with reduced efficiency in ECP-treated mice. (B) GVT effects in vivo are maintained in ECP-treated mice in a Bcl1 tumor model. Recipients were injected with 5 × 10³luc⁺Bcl1 cells 9 days prior to BMT. Tumor-bearing recipients were transplanted with Tcon alone (blue, ▲), or additionally received ECP-treated splenocytes from healthy mice (red, ▼) 48 hours prior to BMT. Results are done in triplicates and are representative of 2 individual experiments (A) or are compiled from 2 experiments with 10 mice per group (B).