Protective immunity against tumour cannot be generated in the persisting antigen environment. Purified HA-specific effector CD8 T cells from rVV-HA infected B10.D2-BALB/c F1 mice were transferred into B10.D2-BALB/c F1 (rVV-HA (r) B10.D2, n = 10) or C3-HAhi-BALB/c F1 (rVV-HA (r) C3-HAhi, n = 10), and those effector cells from C3-HAhi-BALB/c F1 mice were transferred into B10.D2-BALB/c F1 (C3-HAhi (r) B10.D2, n = 10) or C3-HAhi-BALB/c F1 (C3-HAhi (r) C3-HAhi, n = 10). After 42 days, these mice along with naive B10.D2-BALB/c F1 mice (Naive B10.D2, n = 10) were challenged with A20-HA lymphoma intravenously. The graph indicates the percentage of tumour-free survival over time from tumour inoculation. Representative results of two independent experiments are shown.