Demonstration of immunogenicity with the poorly immunogenic B16 melanoma

Animal tumors of spontaneous origin have consistently been found to be less immunogenic than are tumors induced by chemical carcinogens or oncogenic viruses. Spontaneous tumors rarely demonstrate significant immunogenicity in classical transplantation rejection tests. This study demonstrates a novel approach to the question of tumor immunogenicity using viable tumor cells in diffusion chambers. Classical transplantation rejection was induced to the poorly immunogenic, spontaneous B16 murine melanoma by implantation of diffusion chambers containing viable B16 melanoma tumor cells. Implantation of B16 chambers i.p. for at least 4 weeks induced specific, long-term resistance to subsequent live B16 tumor cell challenge. In contrast, immunization with irradiated tumor cells for the same time interval resulted in a delay of tumor growth but had no effect on survival. These studies demonstrate the possibility that a significant anti-tumor immune response against the B16 melanoma may be induced without the presence and negative regulatory influences of a progressively growing B16 tumor. In addition, the diffusion chamber sensitization technique may detect the antigenicity of some tumors which are not detectable by classical transplantation rejection tests. Thus, the diffusion chamber technique provides another avenue for testing the immunogenicity of tumors, especially those of spontaneous origin.