The primary granule proteins (PGP) of myeloid cells are a source of multiple antigens with immunotherapeutic potential formyeloid leukemias.Therefore, we developed a method to induceT-cell responses to PGP protein sequences.We found that gene-transfected antigen-presenting cells efficiently expand functionally competent PGP-specific CD4 and CD8 Tcells. The system was optimized using T-cell responses to autologous CD40-activated B cells (CD40-B) transfected with a cytomegalovirus pp65-encoding expression vector. To generate leukemiaspecificTcells, expression vectors encoding the PGP proteinase 3 (PR3) human neutrophil elastase, and cathepsin-G were transfected into CD40-B cells to stimulate postallogeneic stem cell transplantation T cells from five patients with myeloid and three with lymphoid leukemias. T-cell responses to PGP proteinase 3 and human neutrophil elastase were observed in CD8+ and CD4+ T cells only in patients with myeloid leukemias. T-cell responses against cathepsin-G occurred in both myeloid and lymphoblastic leukemias. T cells from a patient with chronic myelogenous leukemia (CML) and from a posttransplant CML patient, expanded against PGP, produced IFN-γ or were cytotoxic to the patient’s CML cells, demonstrating specific antileukemic efficacy. This study emphasizes the clinical potential of PGP for expansion and adoptive transfer of polyclonal leukemia antigen-specific T cells to treat leukemia.