Analysis of interleukin 2 and various effector cell populations in adoptive immunotherapy of 9L rat gliosarcoma: allogeneic cytotoxic T lymphocytes prevent tumor take. Recombinant interleukin 2 (rIL-2) and various effector cell populations were used for adoptive immunotherapy in the Fischer strain 9L rat gliosarcoma model. The in vivo cytotoxicities of nonspecifically activated lymphocytes and specifically activated cytotoxic T lymphocytes (CTLs) were assessed in a modified in vivo neutralization (Winn) assay. Effector cells (10(6)) and 9L tumor cells (10(5] were combined with 10(4) units of rIL-2 and stereotactically implanted into the right frontal centrum semiovale of the Fischer (F344) rat. At 7 and 14 days, additional effector cells (10(6] and rIL-2 (10(4) units) were administered through the same burr hole. Nonspecifically activated splenocytes were lymphokine-activated killer (LAK) cells, both plastic-adherent and nonadherent, whereas specifically activated CTLs were either syngeneic (genetically identical) or allogeneic (genetically dissimilar). Syngeneic CTLs were T lymphocytes from Fischer rats primed in vivo with 9L cells and restimulated in vitro. Allogeneic CTLs were generated by exposing DA rat lymphocytes either to irradiated Fischer lymph node cells or to 9L Fisher tumor cells in vitro. Control groups included rats bearing 9L tumor who were untreated, those who received peripheral (i.p. or s.c.) administration of rIL-2, or those who received syngeneic unstimulated T lymphocytes and rIL-2. For a set of animals given the same inoculum of 9L tumor, significantly improved survival was shown for groups treated with nonadherent or adherent LAK cells (P less than or equal to 0.0003), syngeneic CTLs (P = 0.0327), or allogeneic CTLs (P = 0.0025) over untreated control animals by using Mantel-Haenzel nonparametric logrank equations. Only treatment with allogeneic CTLs prevented tumor take. 