Effect of Coadministration of M-CSF and IFN- α on NK1.1 + Cells in Mice

The purpose of this study was to evaluate the effect of coadministration of macrophage colony-stimulating factor (M-CSF) and interferon-α (IFN-α) on NK1.1⁺ cells in mice. Administration of M-CSF, but not IFN-α, increased the number of NK1.1⁺ cells and CD11b⁺ cells in spleen and blood. Coadministration of the two agents induced a greater increase in NK1.1⁺ cells than did administration of M-CSF alone. Administration of M-CSF or IFN-α augmented the clearance activity of Yac-1 cells in lung, and coadministration of these agents further augmented this effect. The combination of M-CSF and IFN-α effectively reduced the formation of tumor nodules in lung and liver in an experimental metastasis model using B16 melanoma. The combination of M-CSF and IFN-α induced the increase and activation of NK1.1⁺ cells more than either agent alone. These effects may contribute to the antimetastatic reaction by NK1.1⁺ cells in vivo.