[Experimental and selected clinical aspects of active immunotherapy in leukemia]

The aim of the review is to summarize current knowledge concerning active immunotherapy in leukemia. The molecular mechanisms and selected clinical implications of different cancer vaccines used in pediatric and adult leukemias are discussed. Escape of neoplasmatic cells from elimination by host cells can be caused by immunological disturbances, such as the production of immunosuppressive cytokines and downregulation of costimulatory and adhesion molecules. Cells of acute lymphoblastic leukemia and chronic lymphocytic leukemia can be induced into antigen-presenting cells with the CD40 ligation system. After CD40 stimulation, leukemic cells achieve the phenotypic and functional characteristics of dendritic cells. In many studies it was confimed that these cells stimulate auto- and/or allogeneic T-cell response. Immunological response can be of cellular and humoral origin and is extensively examined. Similar effects using different cytokines such as GM-CSF, TNF-alpha, and IL-4 can be observed in acute myeloid leukemia and myelodysplastic syndromes. Clinical experience with such vaccines is limited, but the results of some preliminary reports are quite promising. Cancer vaccines are safe, result in host response, and probably prolong patients survival.