Compartmentalized Eph receptor and ephrin expression in the thymus.

The maturation of T cells is an intricate process involving the interaction of developing thymocytes with discrete microenvironments within the thymus. Numerous studies have indicated that distinct thymic compartments provide signals required for each stage of thymocyte maturation. In this study we performed a comprehensive analysis of the expression patterns of Eph-A receptors and ephrins-A in the thymus using in situ hybridization and reverse transcription-polymerase chain reaction, and show that expression of these molecules is highly compartmentalized. Based on these expression patterns and the known mechanisms of action of Eph receptor/ephrin interactions in other organs, these data suggest that differential Eph receptor expression on discrete subsets of thymic stromal cells may be important in establishing compartment boundaries and preventing intermingling of stromal cell subtypes. Further, together with chemotactic signals such as those provided by chemokines, regulated Eph receptor/ephrin expression on thymocytes may play a role in thymocyte migration.