Nature Reviews Gastroenterology & Hepatology (2019) https://doi.org/10.1038/s41575-018-0093-7 Published online 12 December 2018

In the version of this article published online and in print, the intestinal epithelial barrier depicted in Fig. 1 was drawn incorrectly with the cells oriented in the wrong direction. This error has been corrected for the HTML and PDF versions of the article.