Immunofluorescence staining of caspase-3 in jejunal epithelium at 1 dpi. Apoptotic cells are presented by cells being positive for cleaved caspase-3 (as depicted in green). Nuclei (DAPI staining) are presented in blue. (A) When the jejunal epithelium was affected by TGEV infection, only the villus lining was apoptotic, while the crypt epithelium stayed intact. Scale bar = 100 μm. (B) Under Znlow diet, most of jejunal enterocytes were cleaved caspase-3-positive and their shape was distorted, whereas under Znmed treatment, the amount of cleaved caspase-3 signals was reduced and the cell shape was not affected. Under Znhigh, apoptotic cells were extremely rare and cell morphology was not impaired. Scale bar = 20 μm.