Nat. Immunol. 18, 541–551 (2017); published online 13 March 2017; corrected after print 17 April 2017

In the version of this article initially published, the second sentence in the first subsection of Results incorrectly described an experimental group as “...seven additional patients with UC...”. The correct description is “...seven additional UC patient cohorts...”. The error has been corrected in the HTML and PDF versions of the article.