Brain tumor was induced with Rous sarcoma virus (RSV) in adult inbred mice of A/J as a model of human malignant brain tumor. This brain tumor could not be transplanted to allogenic mice of C3H/He and BALB/c. Moreover, the syngeneic animals which had undergone surgical removal, did not take the secondary challenge of the same tumor cells. These results suggest the presense of the tumor specific transplantation antigen (TSTA) associated with major histocompatibility complex (MHC). The tumor

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... ic cytotoxic T cells were induced against this brain tumor using 51Cr release assay. Cytotoxic T cells were also induced when the tumor cells were inoculated intracranially, and their cytotoxic activity was higher in spleen cells than in lymph node cells. The brain has no lymphatic tissues. It may be possible that soluble tumor antigens shedding from cell surfaces may induce the cytotoxic T cells. More precise analysis of immune responses against the brain tumor may be necessary for the sake of immunological therapy.