Mice carrying a loxP-flanked caspase-8 allele (Casp8fl) and Villin-Cre mice were described earlier27 (link)-29 (link). IEC-specific caspase-8 knockout mice were generated by breeding Casp8fl mice to Villin-Cre or Villin-CreERT2 mice. Experimental colitis was induced with 1-1.5% dextrane sodium sulfate (DSS, MP Biomedicals) in the drinking water for 5-10 day. Colitis development was monitored by analysis of weight, rectal bleeding and colonoscopy as previously described30 (link). In some experiments, mice were injected intravenously with TNF-α (200 ng/g body weight, Immunotools) plus/minus necrostatin-1 (1.65 μg/g body weight, Enzo). Histopathological analysis was performed on formalin-fixed paraffin embedded tissue after H&E staining. Immunofluorescence of cryosections was performed using the TSA-Kit as recommended by the manufacturer (PerkinElmer). For electron microscopy, glutaraldehyde fixed material was used. Ultrathin sections were cut and analyzed using a Zeiss EM 906 (Zeiss). Paraffin-embedded patient specimens were obtained from the Institute of Pathology and endoscopic biopsies were collected in the Department of Medicine 1 (Erlangen University). The collection of samples was approved by the local ethical committees and each patient gave written informed consent. For organoid culture, intestinal crypts were isolated from mice and cultured as previously described11 (link). Organoid growth was monitored by light microscopy. IEC were isolated as previously described5 (link). For gene chip experiments, total RNA of IEC was isolated using the RNeasy Mini Kit (Qiagen) and hybridised to the Affymetrix mouse 430 2.0 chip (Affymetrix, Santa Clara, CA). Gene ontology based analyses were performed using the online tool Database for Annotation, Visualization and Integrated Discovery (DAVID). Caspase-3/-7 activity was measured using the Caspase-Glo3/7 Assay (Promega) according to the manufacturer's instructions.