Specificity of antitumor immune reactions mediated by xenogeneic immune RNA.

Evidence that xenogeneic immune RNA (I-RNA) mediated specific cytotoxic immune responses against human tumor-associated antigens was obtained from in vitro studies in two autologous melanoma systems. In these systems, malignant melanoma target cells, matching normal fibroblast target cells, lymphocyte effector cells, and melanoma and normal skin tissue used to immunize RNA donor animals were derived from the same autochthonous hosts. When incubated with autologous lymphocytes, I-RNA extracted from the lymphoid organs of donor animals immunized with melanoma tissue mediated immune reactions against autologous melanoma target cells in vitro. I-RNA from animals immunized with normal skin tissue from autochthonous hosts did not increase the cytotoxicity of autologous lymphocytes for autologous melanoma cells. Using autologous fibroblasts as target cells, we detected no increase in cytotoxicity when autologous lymphocytes were incubated with RNA from animals immunized either with melanoma tissue or normal skin tissue from the autochthonous host. By contrast, when allogeneic lymphocytes were used as effector cells, RNA extracted from animals immunized either with melanoma tissue or normal skin mediated cytotoxic immune reactions against melanoma target cells and normal fibroblast target cells derived from the same patient.