Number of FOXP3⁺ Tregs per 100 CD8⁺ lymphocytes in healthy controls, and patients without GvHD, with acute and chronic GvHD, with CMV-colitis, and with diverticulitis. Paraffin-embedded intestinal biopsies of healthy controls (n = 13), and patients after allogeneic transplantation without GvHD (n = 33), with acute GvHD (n = 44), with chronic GvHD (n = 18), with CMV-colitis (n = 6), and with diverticulitis (n = 6) were immunohistochemically stained for CD8 and costained with anti-CD3/anti-FOXP3. The number of CD8⁺ cells and CD3⁺/FOXP3⁺ cells was counted per 10 high-power fields. Results are expressed as mean ± SEM. The ratio of FOXP3⁺ Tregs per 100 CD8⁺ lymphocytes was significantly increased in samples without GvHD versus acute and chronic GvHD.