In addition, when day 10 tumor cultures were tested in cytotoxicity against fresh IL-2 activated primary NK cells, those that were obtained from tumor implanted and sNK or sNK+CDDP injected mice had much lower susceptibility to NK cell mediated cytotoxicity when compared to those cultured from tumor alone implanted mice, indicating the increased differentiation and acquisition of MHC-class I antigens in these cultures. The gene discussed is IL2; the disease is neoplasm.