Nat. Protoc. 1, 2643–2649 (2007); doi:10.1038/nprot.2006.328; published online 11 January 2007; corrected after print 5 August 2015

In the version of this article initially published, in the Reagent Setup section, it was stated that 50% v/v Percoll should be made by diluting Percoll in 10× PBS at a 1:1 v/v ratio. Percoll should, in fact, be diluted in 2× PBS at a 1:1 ratio. The error has been corrected in the HTML and PDF versions of the article.