Biopsies of the inflamed and non-inflamed colon of patients suffering from CD, UC, infectious colitis and controls were double immunolabelled with anti GFAP (A,D,G,J,M,P red) and anti-GDNF (B,E,H,K,N,Q green) antibodies and were analyzed by optical sectioning using a confocal microscope. The dotted ovals indicate the position of epithelial crypts. Both antigens, GFAP (A) and GDNF (B) can be detected highly in the intestinal wall of the inflamed colon of UC (A,B)-, infectious colitis (M,N)- and to a smaller extent in CD patients (G,H). The merged images (C,I,O) reveal an almost complete overlap of both immunoreactivities (yellow). Only few GFAP-positive cells (G) display no GDNF immunoreactivity (H, I) in the non-inflamed colon of CD patients and the control section (P-R), whereas in non-inflamed tissue of UC patients GFAP-positive EGCs (D) showing slight GDNF expression (E). GFAP-positive EGCs (A,D,G,J,M,P) are positioned in the mucosal plexus in close vicinity to the epithelium of the colon. Scale bars, 50 μm.