Proliferation and protection from apoptosis in M07Sb and TF1β cells following incubation with SMFs. M07Sb (A) and TF1β (B) cells that had been starved of GM-CSF for 24 hours were cocultured for 96 hours with SMFs and subjected to proliferation analysis. Parallel cultures were continuously incubated with neutralizing mAbs recognizing the GM-CSFRα, GM-CSFRβ, IL-15Rβ, IL-15Rα chains, and IL-15. Cells were counted in an electronic Coulter counter and the data are expressed as percentages of difference in proliferative potential with respect to control-untreated samples. The data presented are representative of 3 independent experiments. Treatment with the different neutralizing mAbs significantly reduced SMF-induced proliferation in M07Sb cells (*P < .05 compared with the SMF group). In contrast, in TF1β cells, only treatment with anti-GM-CSFRα and β neutralizing mAbs decrease their proliferation (*P < .05 compared with the SMF group). M07Sb (C) and TF1β (D) cells that had been starved of GM-CSF starved for 24 hours were cocultured for 24 hours with SMFs and analyzed for protection from apoptosis. Parallel cultures were continuously incubated with neutralizing mAbs recognizing the GM-CSFRα, IL-15Rβ, IL-15Rα chains, and IL-15. The percentage of apoptotic cells was determined by flow cytometry using the fluorescent DIOC63 probe to detect cells with a dissipated transmembrane mitochondrial potential (ΔΨm). The data presented are representative of 3 independent experiments. In both cell lines, treatment with the different neutralizing mAbs significantly reduced SMF-antiapoptotic effects (*P < .05 compared with the SMF group). (E) Flow cytometry analysis of IL-15R α, β, and γc subunit surface expressions in NKPs and TF1β and MO7Sb cells. These data are representative of 3 different experiments. Values are means ± SD (n = 3).
