The question of how T cells escape the thymus and enter the circulation to fight infections has finally been answered. "These findings will be taught in textbooks down the road," Kristin Hogquist from the University of Minnesota, who was not involved in the research, wrote in an email. "This is a fascinating study," she added.
A T cell exiting the thymus
Image: Courtesy of Jessica Huppi
Scientists have long wondered how T cells exit the thymus, where they mature. The thymus is threaded with both blood vessels and lymphatic vessels (containing lymphocytes suspended in a clear fluid), so researchers didn't know which exit route T cells took. New findings published this week in __Science__ have settled the debate: Mature T cells escape the thymus via blood vessels rather than lymphatic vessels. Marcus Zachariah and Jason Cyster from the University of California in San Francisco investigated the question by looking at...
M.A. Zachariah, J.G. Cyster, "Neural Crest-Derived Pericytes Promote Egress of Mature Thymocytes at the Corticomedullary Junction," __Science__, published online April 22, 2010, doi:10.1126/science.1188222.

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