Nature Immunology 6, 1236–1244 (2005); corrected online 13 November; corrected after print 9 December 2005.

In the print version of this article and the version initially published online, some labels for Tbx21 in Figure 7b are incorrect. They should read as presented here. The error has been corrected in the HTML and PDF versions of the article. This correction has been appended to the PDF version.