Antigenic Heterogeneity in Cell Populations of Cloned Polyoma, Virus-induced Tumour Lines

WALLS and Negroni1 isolated in tissue culture two cell clones from a polyoma virus-induced fibrosarcoma of H3B Bi mice. One (malignant cell line 71) produced transplantable tumours in adult syngeneic mice; the other (transformed non-malignant line 72) was not tumorigenic but induced resistance to the growth of the malignant cells. We have now confirmed these results and extended them to show that other malignant cells (tissue culture clones C4 and C5) from a polyoma virus-induced parotid tumour of syngeneic mice are also inhibited by pre-immunization with a non-malignant line (72). The number of cells required to induce tumours in 50% of the animals is ten times higher in the preimmunized mice than in the controls, for both fibrosarcoma and parotid malignant lines (Table 1).