Percent mortality by tumor relapse of lethally irradiated (DBA/2 × B10.D2)F1 mice grafted with B10.D2 cells from day-0 NBB either alone (––) or mixed with splenocytes (NBB+Spl, – –) or from TCD BM (–··–) alone. Naive F1 mice served as controls (–·–). All recipient mice were injected intravenously with 10³ P815 tumor cells 2 to 3 months after grafting. Mortality was recorded daily and mice were examined for the presence of tumor metastasis (number of live mice/total number of mice).