TUNEL-positive epithelial cells in the intestine of healthy and S. Typhimurium–infected neonatal mice. (A) Immunostaining for TUNEL (red) and S. Typhimurium (GFP, green) in small intestinal tissue sections at day 4 p.i. Counterstaining with WGA (white) and DAPI (blue). Bar, 10 μm. (B) Immunostaining for TUNEL (red) in a small intestinal tissue section of a 5-day-old healthy C57BL/6 mouse. Counterstaining with WGA (white) and DAPI (blue). Bar, 50 μm.