EphB2-mediated interactions are essential for proper migration of T cell progenitors during fetal thymus colonization.

The ephrin-Eph ligand receptor pair is known to control the repulsion/adhesion process in different tissues, including the immune system. Herein, we evaluated the role of EphB2 receptors in T cell progenitor migration during in vitro thymus colonization and to ECM or chemokine stimuli. EphB2 and their ligands, ephrin-B1 and ephrin-B2, are expressed in BM-derived progenitors, and EphB2(-/-) cells had diminished thymus colonization capacity.

EphrinB1-EphB signaling regulates thymocyte-epithelium interactions involved in functional T cell development.

The Eph and ephrin families are involved in numerous developmental processes. Recently, an increasing body of evidence has related these families with some aspects of T cell development. In the present study, we show that the addition of either EphB2-Fc or ephrinB1-Fc fusion proteins to fetal thymus organ cultures established from 17-day-old fetal mice decreases the numbers of both double-positive (CD4(+)CD8(+)) and single-positive (both CD4(+)CD8(-) and CD4(-)CD8(+)) thymocytes, in correlation with increased apoptosis.