Demonstration of host resistance against sarcomas induced by implantation of cellophane films in isologous (syngeneic) recipients.

Whether it is possible to build up host resistance against sarcomas induced by the implantation of cellophane films was studied by pretreating autochthonous and isologous (syngeneic) hosts with heavily irradiated cells of the same tumor. In the ten available autochthonous hosts, whose tumors had been operatively removed, no resist ance could be demonstrated after pretreatment with irradiated cells followed by chal lenge with low numbers of viable cells from the same tumor. After similar pretreatment isologous mice could be rendered slightly resistant. This resistance was manifested only when low cell doses were inoculated and was considerably weaker than the previously demonstrated resistance with methylcholanthrene-induced sarcomas. The threshold dose of cells that could grow out into tumors was lower in animals that received 350-400 r total-body irradiation than in untreated mice. Lymph node cells of preimmunized hosts that were resistant against low cell doses showed a certain neutralizing effect when admixed to target cells. Thus at least some of the film-induced tumors are weakly antigenic in isologous hosts even though their antigenicity in the autochthonous host remains to be demonstrated.