[Effects of environmental changes around tumor cells on immunogenicity, and its mechanisms].

I studied alterations in the tumorigenicity and immunogenicity of cultured rat fibrosarcoma clone in different growth environments. When the fetal calf serum concentration in a medium was lowered from 10% to 1%, the tumorigenicity was diminished while the immunogenicity was enhanced, accompanied by a prolongation of the in vitro doubling time in a reversible manner. These phenomena were not associated with the quantities of the tumor-associated antigen and/or the rat major histocompatibility complex, but were associated with the appearance of a unique antigen (s), which consist of glycoprotein and exist as a crypt-antigen (s). Our observations indicate that the in vitro growth environment modifies the surface of tumor cells and causes a reduction in their tumorigenicity and an enhancement of their immunogenicity.