The intestinal epithelium has a surface area of 300m2, separating the gut lumen from the interior of the human body. This critical barrier serves a dual function: to absorb nutrients but at the same time prevent the entry of pathogens. How does the gut epithelium coordinate these two seemingly paradoxical functions? Professor Frank Ruemmele describes the cells, signaling pathways and molecules that orchestrate these processes, focusing his attention on TGF. In order to appreciate the importance of TGB, Ruemmele takes a journey along the gut epithelium, outlining its immune functions.Starting with the process of immune maturation, Ruemmele describes the innate and adaptive immune systems, leading to the onset of disease. How can we induce immune tolerance and thereby avoid uncontrolled activation of the immune system? The disrupted homeostasis leading to inflammation can be modulated by dietary factors, including TGF. Ruemmele concludes with an overview of how to harness the anti-inflammatory potential of TGF for the treatment of chronic ailments such as Crohn’s disease.