The Murine Epithelial Thymic Microenvironment Is Governed by Eph/Ephrin Signalling

Although the relevance of thymic epithelial cell-thymocyte interactions for thymus function has long been emphasised, the mechanisms that govern the biology of thymic epithelial cells (TECs) are not fully understood. In other epithelial tissues, erythropoietin-producing hepatocellular carcinoma (Eph) receptors and their ligands, the Eph receptor-interacting proteins (ephrins), have been demonstrated to be important regulators of epithelial homeostasis. Accordingly, we have studied the function of Eph/ephrin signalling in the organisation, phenotypes and function of mouse thymic epithelial cells, as well as its effects on T-cell differentiation, for over 20 years. This review provides a detailed description of these results, concluding that the absence of certain EphA/B receptors or ephrins B generates specific phenotypes that affect T-cell differentiation and immunological function in different ways. This suggests that the proper histological organisation of the epithelial thymic stroma is not essential for normal T-cell maturation, or that at least some aspects of the process are preserved.