Nat. Immunol. 8, 1019–1026 (2007); corrected after print 19 October 2007

In the version of this article initially published, the corresponding author information is incorrect. The correct e-mail addresses should be as follows: Alan.Baxter@jcu.edu.au and hodgkin@wehi.edu.au. The error has been corrected in the HTML and PDF versions of the article.