Nat. Immunol. 16, 859–870 (2015); published online 22 June 2015; corrected after print 12 October 2015

In the version of this article initially published, reference 44 (Farrell, G.A. Responding to aggression; the role of significant others for student psychiatric nurses, an ethnographic study. Nurse Educ. Today 9, 335–340 (1989)) was incorrect. The correct reference is as follows: Sica, A. & Mantovani, A. Macrophage plasticity and polarization: in vivo veritas. J. Clin. Invest. 122, 787–795 (2012). The error has been corrected in the HTML and PDF versions of the article.