Fig. 1

Pathological images. Endoscopic biopsy specimens obtained from the colorectum of a 16-year-old boy exhibit endothelial cell swelling (A, arrows). An intraluminal thrombus is focally present (B, arrow). The colorectal and ileal mucosa of a 65-year-old woman displays glandular epithelial apoptosis (C, arrows), while the presence of inflammatory cell infiltration in the interstitium is sparse. Intestinal GVHD is characterized by extensive, diffuse lymphocyte infiltration within the mucosa (D) and the infiltration of CD8 + T lymphocytes into the epithelium (E). Gastrointestinal infection with cytomegalovirus was diagnosed based on positive immunostaining for cytomegalovirus (F). The pathological images in D and E, and F are presented as representative examples of intestinal GVHD and CMV infection, not the target patients of this study