The manipulation of autologous CLL cells to express a functional ligand for the CD40 molecule (i.e. CD40L or CD154) has shown to upregulate costimulatory factors on leukemic cells and to induce the generation of cytotoxic T lymphocytes capable of specifically recognizing parental non-modified leukemic cells in vitro (241). This evidence concerns the gene CD40LG and B-cell chronic lymphocytic leukemia.