Expression of tenascin in thymus and thymic nonlymphoid cells

Tenascin (TN) is an extracellular matrix glycoprotein that is widely expressed in fetal tissues and tumor matrices but is absent from most normal adult tissues. It is transiently expressed at sites of wound healing and has been shown to inhibit some types of T cell activation. We have examined the expression of TN in rat and human thymic tissue. Our results indicate that TN is expressed in both neonatal and adult rat thymus, and that in human thymus TN is present in a meshlike network at the corticomedullary junction. In addition, cultured human thymic non-lymphoid cells grown in serum-containing medium synthesize TN, whereas under serum-free conditions these cells secrete TN in response to transforming growth factor-beta.