Effect of repletion with recombinant murine IFN-gamma on tumor immunity in IFN-gamma^-/- animals. Groups of 5-7 wild type and IFN-gamma^-/- mice were immunized with hTRP-2. The IFN-gamma^-/- mice were divided into three groups: One group received no repletion, one group was repleted with recombinant murine IFN-gamma from the first day of immunization through the end of the tumor challenge (days 1-56), and one group was repleted with recombinant murine IFN-gamma during the effector phase only (days 41-56). Syngeneic tumor challenge with intravenous B16 melanoma was performed and lung metastases were counted twelve days after tumor injection.