Synergistic antiapoptotic activity of SCF and IL-5 in TF-1 cells. (A) DNA fragmentation assay. The genomic DNA was prepared from TF-1 cells treated with various combinations of cytokines as indicated in the figure and was subjected to agarose gel electrophoresis. The dose of cytokines used in these experiments was identical to those used in Fig 1. (B) Histone releasing assay. TF-1 cells were cultivated in the indicated cytokines and the released cytosolic contents were subjected to histone measurement according to the manufacturer’s instruction. Data shown are the averages of two independent duplicated experiments. The difference between the values in columns SCF and IL5 + SCF was statistically significant (P<< .001). The relative antiapoptotic activities for cells cultured in various conditions are referred to that of cells in cytokine-free medium (set as 0%) and in GM-CSF–containing medium (set as 100%) and are shown underneath the bar graph.