Suppression of apoptosis by overexpression of IL5R in TF-1 cells. (A) Microscopic measurement. Cells were grown in indicated culture media for 24 hours and the percentage of apoptotic cells in the whole population was calculated from the photomicrographs (see Materials and Methods). Each number represents the average of two independent measurements. For each measurement, 300 cells were counted in cytokine-free cultures (□); 500 cells were counted in GM-CSF– (▪) and IL-5–containing (▨) medium. (B) Histone-releasing assay. Cells were treated as described in (A), and were lysed to release the cytoplasmic contents. The bound nucleosomes were detected with ELISA as described in Materials and Methods. A representative set of data of three independent duplicated experiments is shown and each number is the average of two measurements. (C) DNA fragmentation analysis. Cells grown in the cultures as described in (A) were harvested and the genomic DNA was prepared and analyzed as described in Fig 3A and Materials and Methods. A molecular weight marker (1 kb ladder from Life Technology, Gaithersburg, MD) is loaded at the left-hand side of the figure.