Nature Immunology 7, 40–48 (2005); published online 13 November 2005; corrected after print 10 March 2006

In the version of this article initially published, the GEO database accession number is missing. This should be the final subsection of Methods, as follows:

Accession code. GEO: microarray data, GSE4171.

The error has been corrected in the PDF version of the article.