IFN-γ secretion. CD3⁺ T cells from patient 5 were stimulated twice with WT1-A (native), WT1-A1 (analog) (A), 122A (native), or 122A1 (analog) (B) peptides. IFN-γ–secreting T cells were measured by ELISPOT assay after challenge with the indicated peptides. Controls were: no peptide (only CD14⁺ APCs) or with irrelevant Ewing sarcoma–derived peptide (EW) (A) or JAK-2 derived peptide (JAK-2 DR) (B). Data are mean ± SD from quadruplicate cultures from prevaccine (i), postvaccine 3 (ii), and postvaccine 6 (iii). Results indicate that a WT1-A–specific response can be generated not only by the HLA-A0201 restricted peptide but also by the HLA-DR peptide (WT1 122A1) that contains the embedded short sequence, demonstrating the processing and presentation of the WT1-A epitope.