TNF and Arthritis: It is striking that the intestinal epithelium is sensitive to TNF‐induced damage: Transgenic TNF overexpression, via a myriad of mechanisms, clearly leads to inflammatory bowel disease and/or arthritis, and injection of TNF in mammals has shown that intestinal toxicity is a major dose‐limiting issue (Piguet et al, 1998; Kontoyiannis et al, 1999).