Figure 3: Colonic biopsy from patients with clinical features of GVHD. A: H&E section shows classic histopathological features of GVHD with numerous apoptotic cryptic cells (arrows) (40x original magnification). B: one of the patients with histological features of GVHD shows negative C4d staining (20x original magnification); C and D: two separate patients with histological features of GVHD show focal (3C) and diffuse (3D) intramucosal vascular C4d staining (20x original magnification; arrows in 3C highlight the vascular structures). E: one patient without histological features of GVHD shows diffuse intramucosal vascular C4d staining (20x original magnification). F: higher magnification of 3E to highlight the accentuated C4d vascular staining (40x magnifications).