Nat. Immunol. 17, 1075–1083 (2016); published 11 July 2016; corrected online 24 October 2016

In the version of this article initially published, S. Ley was not included in the Acknowledgments section. That section should begin: “We thank S. Ley for critical reading of the manuscript....” This error has been corrected for the PDF and HTML versions of this article.