Effect of macrophage colony-stimulating factor on mouse NK 1.1+ cell activity in vivo

Abstract The effect of recombinant human macrophage colony-stimulating factor (rhM-CSF) on NK 1.1 + cell activity in vivo and in vitro was studied. An intravenous injection of rhM-CSF increased the numbers of NK 1.1 + cells in mouse spleen and blood and augmented the clearance of Yac-1 cells in vivo. Using a magnetic cell sorter (MACS), we purified NK 1.1 + cells from vehicle-injected and rhM-CSF-injected mouse spleen cells. More than 95% of the collected cells were NK 1.1 antigen-positive. NK 1.1 + cells purified from rhM-CSF-injected mouse spleen cells exhibited (a) higher cytotoxic activity against Yac-1 cells, (b) higher proliferative responsiveness to interleukin (IL)-2 and (c) a greater production of interferon (IFN)- γ in response to IL-2 and IL-12 compared to cells purified from vehicle-injected mouse spleen cells in vitro. These results suggest that the administration of rhM-CSF increases NK 1.1 + cell numbers and activates the cells in vivo.