Nat. Immunol. 8, 514–521 (2007); published online: 8 April 2007; corrected after print 24 May 2007

In the version of this article initially published, two labels in the key to Figure 6c are reversed. The blue line is “Ins(1,3,4,5)P4 (300 μM)” and the green line is “Ins(1,4,5,6)P4 (300 μM).” The error has been corrected in the HTML and PDF versions of the article.