The effect of passage in vitro and in vivo on the properties of murine fibrosarcomas I. Tumorigenicity and immunogenicity.

Cloned cell lines of chemically-induced murine fibrosarcomas maintained in tissue culture usually fail to grow when transplanted to normal syngeneic mice. They grow, however, in various categories of T cell deficient mice and after such passage grow readily in normal mice. Both cultured and mouse-passaged lines possess strong TATA. Three alternative explanations are suggested which might account for these findings. Emergence during the initial passage of a population of tumour cells resistant to NC cells. Acquisition during the initial passage of a protective surface molecule that interferes with the efferent side of the immune response when the tumour cells are subsequently transplanted to a normal host. Loss during the initial passage of a Class I MHC molecule which prevents dual recognition of the tumour cells by T cells when they are transplanted to a normal host. New experiments are proposed to distinguish between these possibilities.