Erythroblast apoptosis in normal bone marrow. Sections from bone marrow biopsies were fixed in paraformaldehyde and paraffin and double-labeled for TUNEL reaction with BCIP (black) and anti–glycophorin-A or anti-CD68 with AEC (red). (A) Control section treated with irrelevant IgG Abs and TUNEL reaction without TdT. (B) Section stained with anti–glycophorin-A and TUNEL reaction showing an immature apoptotic erythroblast (arrowhead). (C and D) Sections treated with anti-CD68 and TUNEL reaction representing macrophages surrounding and phagocytosing apoptotic cells are indicated by arrows. Representative sections from one donor out of four are shown.