Immunotransplantation of CD8 T cells is both necessary and sufficient for tumor protection. (A) Donor mice received CpG/CTX vaccination, and splenocyte cell subsets were purified from CpG/CTX vaccinated donors using mAb-conjugated ferromagnetic beads to either positively select or deplete specific populations. (B) Resulting populations were gated on live lymphocytes, and purity was assessed by flow cytometry. (C) CpG/CTX donor splenocyte subsets were used in immunotransplantation as described. Recipient mice received high-dose tumor challenge on day 3 after transplantation and were followed for bidimensional tumor size. Proportions of tumor-free mice are indicated. One mouse in the “CD4⁺CD8” group died within a week after transplantation but still had palpable tumor.