B6-into-BALB/c BMT was performed (850 cGy host irradiation). Cohorts received donor marrow alone ("BMT"); marrow and TS/A tumor cells ("TSA"); marrow, tumor cells, and additional donor T cells ("GVHD"); or marrow, tumor cells, donor T cells, and IL-2 therapy (“GVHD+IL-2”; 50,000 I.U., B.I.D. from day 14 to day 18 post-BMT). Other cohorts received marrow, tumor cells, donor T cells, and donor Th2 cells on day 14 post- BMT either alone ("Th2”) or with IL-2 infusion (“Th2+IL-2”). On day 19 post-BMT, spleen cells were isolated and the absolute number of donor CD8+ T cells (a) and CD4+ T cells (b) were calculated from flow cytometry data (cells per spleen, × 106). Data shown are mean ± SEM (n = 5 per cohort).