Nat. Immunol. 16, 618–627 (2015); published online 4 May 2015; corrected after print 21 May 2015

In the version of this article initially published, the filled circles in Figure 3b were incorrectly labeled 'A20+/flCD4-Cre'. The correct label is 'A20fl/flCD4-Cre'. The error has been corrected in the HTML and PDF versions of the article.