Nat. Immunol. 15, 439–448 (2014); published online 30 March 2014; corrected after print 6 June 2014
In the version of this article initially published, Lisa Göschl's surname was spelled incorrectly. The error has been corrected in the HTML and PDF versions of the article.
The online version of the original article can be found at 10.1038/ni.2864