The two main aims of the present study were (1) to determine if the number of functionally active WT1-specific T cells obtained from healthy donors can be increased in vitro by inhibiting the enzymatic activity of HO-1 and (2) to examine whether HO-1 inhibition makes it possible to generate sufficient cell numbers for adoptive T-cell transfer to effectively augment T-cell immunity in leukemia patients. Here, WT1 is linked to leukemia.