The authors and the journal wish to retract the 20 January 2011 paper cited above, because it contains multiple instances of duplicate (redundant) publication of data, text, and images that are nonessential to the paper. The redundancies are between the above-cited Blood article and the following 12 November 2010 article, published in the Journal of Biologic Chemistry (JBC): Jiang S, Zagozdzon R, Jorda MA, et al. Endocannabinoids are expressed in bone marrow stromal niches and play a role in interactions of hematopoietic stem and progenitor cells with the bone marrow microenvironment. J Biol Chem. 2010;285(46):35471-35478.

The authors apologize to the readers, reviewers, and editors of both journals for publishing duplicate data.