Nat. Med. 21 81–85 (2015); published online 22 December 2014; corrected after print 18 August 2016

In the version of this article initially published, the article did not mention some restrictions on the availability of reagents. The following text has been added to the HTML and PDF versions of the paper: “The retroviral vectors containing BCL-6 and BCL-xL have been generated by a for-profit company, AIMM Therapeutics, which makes the plasmids available. Obtaining the plasmids requires an MTA (http://www.aimmtherapeutics.com/partnering/academic-collaboration/) that includes financial obligations.” The error has been corrected in the HTML and PDF versions of the article.