Up-Regulation of a Thymic Epithelial Ligand after Contact with Thymocytes

Thymic medullary epithelial cells of the E-5 line were shown to form in vitro complexes with thymocytes resulting in no apparent modification to the thymocytes participating in the complex, but in lyrosine phosphorylation on a glycoprotein associated with the epithelial adhesion molecule. Because signal transduction from lymphocytes to stromal cells is poorly documented, we examine in this work events which follow epithelial cell activation. Our findings indicate that one chain of the epithelial adhesion molecule (gp23), after complex formation with thymocytes, undergoes a rapid and transient tyrosine kinase-dependent up-regulation.