http://www.sciencemag.org/content/vol296/issue5576/news-summaries.shtml
Jennifer Couzin
Two teams have found that a tiny subset of cells from a mouse embryo can be grown into a full-blown thymus and beget a healthy immune system in the recipient mice. The finding suggests that it might be relatively easy, as far as regenerating organs goes, to give a failing thymus a boost.
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