Nat. Immunol. 7, 763–772 (2006); published online 28 May 2006; corrected after print 19 October 2007

In the version of this article initially published, the sentence on page 763, column 2, line 12 is incorrect. The correct sentence should end “...and these mice show increased susceptibility to typhlocolitis and infection with Leishmania major but are resistant to experimental autoimmune encephalomyelitis and asthma14–17.” The error has been corrected in the PDF version of the article.