BACKGROUND: Dendritic cells (DCs) are professional antigen-presenting cells whose function is to present antigen to naive T cells and play a cental role in the induction of T- cell and B-cell immunity in vivo. Immunotherapy using DCs loaded with tumor antigens may represent a potentially effective method of inducing antitumor immunity in patients with cancer. We evaluated the possibility of adoptive immunotherapy using in vitro-generated dendritic cells (DCs) and activated mononuclear cells (mainly T lymphocytes) with cytotoxic activity against autologous malignant cells in patients with Philadelphia chromosome and chimeric p210 bcr-abl fusion protein positive chronic myelogenous leukemia (CML). METHODS: DCs were cultured from peripheral blood adherent cells in the presence of GM-CSF and interleukin-4 and the morphology and immunophenotype of the cultured DCs were determined by light micro- scope and flow cytometry. As functional assays of DCs, the stimulatory function of mononuclear cells against allogeneic mononuclear cells and autologous tumor cell lysat-es were studied in co-culture reaction. Also, the cytotoxic activity of mononuclear cells against autologous malignant cells were examined using LDH release test. RESULTS: The cultured cells have higher levels of CD40, CD80, CD86, and MHC class II fluorescence intensity, which are markers of DCs, after culture as compared with those before culture. These cells were potent stimulators in the proliferative response of mononuclear cells in allogeneic co-culture reaction and in the proliferative response against autologous tumor lysates. Also, autologous mononuclear cells stimulated with in vitro-generated DCs pulsed with autologous tumor lysates displayed cytotoxic activity against autologous tumor cells. CONCLUSION: We concluded that in vitro- generated DCs can be effectively utilized as inducer of antitumor immune reaction in CML and further in vivo applications with DCs- based antitumor immunotherapy seems to be feasible.