Early appearance of a lymphoid arming factor and cytotoxic lymph‐node cells after tumor induction

An arming factor which collaborates with non‐sensitized lymphoid cells to produce specific killing of tumor cells in vitro appears in the serum within 24‐48 after initiation of a tumor by inoculation of Moloney Sarcoma Virus or a transplant of syngeneic sarcoma cells. Lymph‐node cells taken 1 or 2 days after tumor induction are also specifically cytotoxic in a microcytotoxicity assay. The production of this arming factor and the appearance of cytotoxic lymphoid cells are thus temporally related and are among the early responses to syngeneic sarcomas in BALB/c mice.