Tumor target cells can also be used to activate NK cells in a manner analogous to IL-2, as we have previously demonstrated using the acute lymphoid leukemia cell line CTV-1, which generated NK cells that are able to lyse NK-resistant tumor cell lines, primary leukemias, and solid tumors, in HLA-matched, allogeneic or autologous settings (30). This evidence concerns the gene IL2 and neoplasm.