Nat. Immunol. 13, 1145–1154 (2012); published online 16 November 2012; corrected after print 29 November 2012

In the version of this article initially published, the label 'TH2 cell' in Figure 4b was incorrectly positioned below 'TH1 cell'. It should be directly beneath the label 'TFH cell' (in the row with the cDC). The error has been corrected in the HTML and PDF versions of the article.