In vitro cytotoxic assays demonstrated that the cytolytic activity of Cd38+/+ NK cells was superior to that of Cd38−/− NK cells against not only B16F10 but also YAC-1 and EL4 murine lymphoma cell lines (Fig. 7b), indicating that Cd38+/+ NK cells exhibited a broad spectrum of natural cytotoxicity. The gene discussed is CD38; the disease is lymphoma.