Loss of T antigen by cells derived from a hamster tumour induced by adenovirus type 12

Cells from a second transplantation of an adenovirus type 12‐induced hamster tumour were cultured and, at the seventh subculture, frozen in liquid nitrogen with 10% DMSO. Later, these cells were cultured in the same conditions as the parent cells. They kept the morphological and growth characteristics and the tumorigenicity of the cells from the former culture. The synthesis of surface antigen was maintained but T antigen and tumour‐specific transplantation antigen were not detectable. The possibility of a relation between the antigen loss and the freezing treatment is discussed.