Tumor-specific T cell clones can be generated from repeated antigen-specific stimulation of patient-derived (autologous) or donor-derived (allogeneic) T cells in vitro.30 For example, a recent pilot study explored the use of allogeneic CD8+ T cells with activity against the Wilms tumor antigen 1 (WT1) in leukemia patients who relapsed after HSCT.31 Clones were generated by leukophoresis of human leukocyte antigen (HLA)-matched donor cells and repeated stimulation with peptide-pulsed, autologous dendritic cells over several months. Here, WT1 is linked to leukemia.