T cells that migrated through endothelium are capable of lysing autologous leukemia cells. (A) Anti–leukemia-specificity of input cells was assessed by using as targets primary autologous leukemia cells (▩), autologous CD40-stimulated leukemia cells (•), autologous PHA blasts (▴), allogeneic CD40-stimulated leukemia cells (▵), and K562 cells (⧫). Target cells were labeled with DiOC₁₈(3) and used at the effector/target ratios displayed. (B) Migrated T cells were recovered after the 6-hour chemotaxis assay and used for the cytotoxicity assay. Primary leukemia cells were labeled with DiOC₁₈(3) and used as targets at the effector/target ratios displayed. Input cells (▴) and T cells that migrated through BMEC (□) were compared as effectors. Cell-mediated cytotoxicity was measured by flow cytometry as described in Materials and Methods.