E.G7 tumor growth is not due to antigen loss. C57BL/6 mice were immunized with irradiated E.G7 cells. One week later, they were challenged with 2.5 x 10⁶ live E.G7 cells. At a tumor diameter of more than 20 mm, tumor cells from individual mice (6 mice, designated A-F) were isolated and used as targets in a ⁵¹Cr release assay with or without sensitization by ova257-264. Spleen cells from VSV-OVA infected mice stimulated in vitro with ova257-264 for 5 days were used as effector cells.