Nat. Med. 21 92–98 (2015); doi:10.1038/nm.3730; published online 15 December 2014; corrected after print 20 February 2015

In the version of this article initially published, the ferritin linker region was incorrectly described as HA-tagged. It was FLAG-tagged. Thus, the descriptions of its detection in the study and of the protocol used for its detection in the Online Methods were incorrect (including an incorrect reference for the associated antibody used). Also, the description of the development of the tag was missing from the Online Methods. The errors have been corrected in the HTML and PDF versions of the article.