Thymocyte Egress

Science Signaling  01 Jun 2010:
Vol. 3, Issue 124, pp. ec165
DOI: 10.1126/scisignal.3124ec165

A critical step during the development of the immune system is the egress of developing T lymphocytes, or thymocytes, from the thymus to peripheral organs, where they can defend against infectious microorganisms. Egress requires detection of the lipid mediator, sphingosine 1-phosphate (S1P), by thymocytes, but whether S1P detection is sufficient for egress, the source of S1P, and the location where T lymphocytes exit the thymus are unknown. Zachariah and Cyster found that selective expression of a transgene for the S1P receptor-1 in mouse thymocytes was sufficient for thymocyte egress. Thymocyte egress occurred at corticomedullary junctions via blood vessels rather than via lymphatics. Pericytes, neural crest–derived cells that ensheath blood vessels, provided the S1P for exiting thymocytes

M. A. Zachariah, J. G. Cyster, Neural crest–derived pericytes promote egress of mature thymocytes at the corticomedullary junction. Science 328, 1129–1135 (2010). [Abstract] [Full Text]