Organizing the Thymus Gland

The Role of Eph and Ephrins


Address for correspondence: Dr. Agustín G. Zapata, Department of Cell Biology, Faculty of Biology, Complutense University of Madrid, C/ José Antonio Nováis 2; Ciudad Universitaria, C.P. 28040, Madrid, Spain. Voice: +34 91 394 49 79; fax: +34 91 394 49 81.


Eph receptors and their ligands, ephrins, are molecules involved in the morphogenesis of numerous tissues, including the central nervous system in which they play a key role in determining cell positioning and tissue domains containing or excluding nerve fibers. Because common features have been suggested to occur in the microenvironmental organization of brain and thymus, a highly compartmentalized organ central for T cell differentiation, we examined the expression and possible role of Eph/ephrins in the biology of the thymus gland. We reviewed numerous in vivo and in vitro results that confirm a role for Eph and ephrins in the maturation of the thymic epithelial cell (TEC) network and T cell differentiation. Their possible involvement in different steps of early thymus organogenesis, including thymus primordium branching, lymphoid colonization, and thymocyte–TEC interactions, that determine the organization of a mature three-dimensional thymic epithelial network is also analyzed.