In situ analysis for DNA fragmentation. (Top panel) Wright-Giemsa–stained cytocentrifuged preparations of cells obtained on day 12 of the second phase of (a) macrophage-containing and (b) macrophage-depleted cultures. An erythroblastic island consisting of a central macrophage (M) surrounded by a ring of late erythroblasts (E) is shown in (a). (Middle and bottom panels) Erythroblasts harvested on day 12 of the second phase of each culture were examined by the TUNEL method, (c) macrophage-containing culture, (d) macrophage-depleted culture, (e) macrophage-containing culture in the presence of anti-Emp peptide (p1) antibodies, and (f) macrophage-depleted culture supplemented with macrophage conditioned medium. Apoptotic cells are identified by more dense staining.