Nat. Immunol. 14, 509–513 (2013); published online 31 March 2013; corrected online 8 April 2013

In the version of this article initially published, a label in Figure 2b and the scale size for Figure 5a were incorrect. The left label under the left image in Figure 2b should be CXCL9 (in red); the legend for Figure 5a should end “Scale bars, 20 μm.” The errors have been corrected in the HTML and PDF versions of this article.