CTL clone RDR173 lyses LB-ECGF-1H–positive tumor cells. HLA-B7–expressing CML cells were labeled with CFSE and incubated with CTL clone RDR173. Melanoma cells were transduced with HLA-B7 and tested for recognition by CTL clone RDR173 (▪) in a CFSE-based cytotoxicity assay. Control cells were transduced with retroviral construct containing only the marker gene. Target cells were labeled with CFSE and incubated for 48 hours with CTL clone RDR173 (E/T ratio, 1:1). Target cells were also incubated with an HLA-B7–specific alloreactive T-cell clone (□) to demonstrate functional HLA-B7 expression.