Telomere shortening in aGVHD patients. (A) Representative confocal microscopy images of the 2 gut biopsies from an aGVHD patient analyzed by Q-FISH. The upper panels represent the initial biopsy, and lower panels the follow-up biopsy. Telomeres were stained with Tel-Cy3 peptide nucleic acid probe, and chromatin was stained with 4,6 diamidino-2-phenylindole (DAPI). Black-and-white images of the telomere signal are shown to improve comparability. Micrograph magnification is ×100. (B) Longitudinal analysis shows that TL is significantly reduced in aGVHD patients but not in controls. One circle corresponds to 1 biopsy. One connecting line corresponds to 1 individual patient. (C) Telomere shortening is shown for the enterocytes of aGVHD patients with a mean telomere loss rate of −0.19 per week compared with enterocytes of the control.