A High Frequency of Cytotoxic Precursor Cells for a Syngeneic Tumour

Abstract
The average frequency of cytotoxic precursor cells in DBA/2 [mouse] lymph node cell preparations reactive to the syngeneic tumor P815 [mastocytoma] was determined as 1 in 2000. This frequency is similar to precursor frequency for an allogeneic tumor EL-4 [lymphoma]. The normal lack of response of DBA/2 lymph node cells to the syngeneic tumor P815 in vitro cannot be attributed to lack of cytotoxic precursor cells. In this tumor-host system non-immunogenicity reflects a defect at the inductive step.