[Augmentation of cytotoxic activity by combination with interleukin 2 and interferon gamma]

The synergy of cytotoxic activity by Interleukin 2 (IL-2) and Interferon gamma (IFN-gamma) was evaluated in human peripheral blood mononuclear cells (PBMC) and spleen cells. PBMC incubated with IL-2 (10 IU/ml) and IFN-gamma (200 IU/ml) for 4 days showed the maximum cytotoxic activity against K562, MOLT-4 and Daudi cells. Combination with IL-2 and IFN-gamma induced stronger activity than IL-2 or IFN-gamma alone. In order to investigate the sequential roles of IL-2 and IFN-gamma in the synergy of killer cell function, IFN-gamma was stimulated after washing-out IL-2 or stimulated at various timing and duration without washing-out IL-2. IL-2 was essential to induce the synergistic effect of IL-2 and IFN-gamma to killer activity. The similar augmentation of killer activity was observed by the addition of IFN-gamma at any incubation period with IL-2, compared with that of stimulations IL-2 and IFN-gamma stimulation. The phenotypes of the killer cells by stimulation of IL-2, IFN-gamma alone or IL-2 and IFN-gamma were mainly CD2+, CD16+, namely, the phenotype of activated natural killer cells.