The invention relates to macrophages which have at least one of the following properties: their cytotoxic activity without IFN-.gamma. is increased by about 20 to 30% with respect to standard macrophages, and is preferably of about 70%; their cytotoxic activity with IFN-.gamma. is increased by about 20 to about 40% with respect to standard macrophages, and is preferably of about 93%; the extension of the deactivation of the cytotoxic activity in reply to an activation of IFN-.gamma. is in a ratio such that after 60 h of activation with IFN-.gamma., the cytotoxic activity is higher than or equal to 30%, preferably of about 55%, compared to the maximum cytotoxic activity presented by the macrophages due to IFN-.gamma. activation, with said cytotoxic activity being measured as the percentage of inhibition of 3-H thymidine incorporation by target tumoral cells, particularly U 937 cells.