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A number of mouse lymphomas induced by the Moloney agent were compared with regard to 1) their sensitivity to the rejection response of syngeneic mice preimmunized with Moloney virus-containing materials (“immunosensitivity in vivo”), 2) their susceptibility to the cytotoxic action of sera from resistant syngeneic animals (“immunosensitivity in vitro”), 3) their ability to release virus, estimated by the mouse antibody production test, and 4) their concentration of tumor-specific cell surface antigen, judged by the indirect fluorescent-antibody test and by absorption and inhibition experiments. The different parameters studied varied between different lymphomas, whereas individual lymphomas showed characteristic and well-reproducible patterns of behavior. All lymphomas examined carried the specific transplantation antigen characteristic for this system, though in different quantities. With one notable exception, there was a rough parallelism between immunosensitivity in vitro and in vivo. Immunosensitivity appeared related to the concentration of surface antigen, as judged by Ruorescence and absorption. Immunoresistant tumors do exist that carry specific surface antigens, as measured by the fluorescence and absorption tests, which emphasizes the necessity to distinguish between antigenicity and immunosensitivity. The amounts of infectious virus released from known numbers of irradiated cells in vivo appeared to be independent of the concentration of surface antigen in the same tumor. These results do not critically distinguish between the possibility that cellular antigenicity is due to the release of infectious virus, or, alternatively, that a new cellular antigen appears independently of virus maturation, as in other antigenic virus-induced tumor systems. Passage of antigenic tumors in preimmunized mice did not lead to the selection of antigenic-loss variants or immunoresistant sublines.
Klein et al. (Fri,) studied this question.