Specific “arming” of normal lymph‐node cells by sera from tumor‐bearing mice

Lymph‐node cells of non‐sensitized mice were “armed” (i.e. made specifically cytotoxic) by exposure in vivo to passively transferred sera from tumor‐bearing mice. Four hours after an intraperitoneal injection of antitumor serum, the lymph nodes were removed from recipient mice and the activity of the lymph‐node cells was tested on tumor cells in an in vitro microcytotoxicity test. Specific cytotoxicity was demonstrated to the respective target tumors (Moloney virus or 3‐methylcholanthrene‐induced sarcoma) carried by the tumor‐bearing serum donors.