Because CD8 T lymphocytes are the major type of cells responsible for killing tumor cells, we assessed the number of CD8 T cells in the peritoneal cavity on days 3-4, 5-6, and 12 after immunization and compared it with the level of cytotoxic T lymphocytes (CTLs) in peritoneal lavage of the intact mice (both Tg and WT mice that were not immunized with EL-4 cells, 0d after immunization). This evidence concerns the gene CD8A and neoplasm.