Specificity of the anti-CD137 SAD approach. Day 21 MLTC responder cells were obtained by stimulating CD8 T cells of donor 203 against haploidentical MZ1257-RCC cells (for HLA types see Table 1). (A) After 24 hours of incubation with K562-B*0702 transfectant cells followed by anti-CD137/CD65 SAD, the CD137/CD65^neg subset, the CD137/CD65^pos subset, and undepleted MLTC control cells stimulated exclusively with MZ1257-RCC were analyzed for cytolytic activity against MZ1257-RCC (▪), K562-B*0702 (○), K562-A*0301(▴), and K562 parental cells ([×]) in ⁵¹chromium-release assay. (B) After 24 hours of incubation with MZ1257-RCC cells followed by anti-CD137 SAD, the CD137^neg fraction (white bars), the CD137^pos fraction (gray bars), and the MLTC control stimulated exclusively with MZ1257-RCC (black bars) were analyzed for reactivity in IFN-γ ELISPOT assay. (C) After 24 hours of incubation with K562-B*0702 transfectant cells, allodepletion was performed using anti-CD134/CD65 instead of anti-CD137/CD65 reagents. IFN-γ ELISPOT results are illustrated as described in panel B.