International Immunology Advance Access published online on May 9, 2007
International Immunology, doi:10.1093/intimm/dxm041
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The perivascular space as a path of hematopoietic progenitor cells and mature T cells between the blood circulation and the thymic parenchyma
1 Department of Immunology and Microbiology, Meiji University of Oriental Medicine, Hiyoshi-cho, Nantan, Kyoto 629-0392, Japan
2 Horizontal Medical Research Organization, Faculty of Medicine and Graduate School of Medicine, Kyoto 606-8501, Japan
Correspondence to: Correspondence to: T. Amagai; E-mail: t_amagai{at}meiji-u.ac.jp
It is known that selected populations of lymphoid cells migrate into and from the adult thymus through blood vessels at the cortico-medullary junction and in the medulla. Here, we show that in the perivascular spaces (PVS) of mice surrounding large blood vessels, CD117-positive hematopoietic progenitor cells, CD4 single-positive (SP) and CD8SP T cells are located. However, developing thymocytes, CD25-positive cells and CD4 and CD8 double-positive cells, are not detectable in the PVS. After intravenous (i.v.) injection of CD117-positive bone marrow (BM) cells from C57BL/6 mice into non-irradiated RAG2 mutant mice i.v., donor-derived cells first preferentially migrate into the PVS within 30 min, and then the number of donor-derived cells in the thymic parenchyma increases. Likewise, newly developed mature T cells in the thymic parenchyma of RAG2 mutant mice transferred with wild-type BM cells migrate to the PVS, before leaving the thymus to the circulation. Accumulation of mature T cells was observed after treatment with sphingosine-1 phosphate receptor agonist FTY720 not only in the medulla but also in the thymic PVS. These results suggest that the PVS is a transit pathway for progenitor cells to immigrate into the thymus and for mature T cells to emigrate from the thymus.
Keywords: Organization, cell trafficking, mature T cells, mouse, thymus, T progenitor
* These authors contributed equally to this study.
Transmitting editor: M. Miyasaka
Received 24 November 2006, accepted 9 March 2007.