Glia maturation factor produced by thymic epithelial cells plays a role in T cell differentiation in the thymic microenvironment

Abstract

In order to determine molecules on thymic epithelial cells which play an important role in the process of T cell differentiation, mAb recognizing thymic epithelial cells were made using stromal cells of the embryonic thymus at 15-gestation date. Among many mAb, a specific one was selected in terms of its inhibition of T cell development in an in vitro culture system of the embryonic thymus. cDNA of the protein recognized by one of the mAb was obtained by a panning method. Sequence analysis revealed that the protein was identical to glia maturation factor (GMF)-β. Northern blot analysis confirmed the expression of GMF-β mRNA in the thymus and brain. Furthermore, immunoblotting analysis identified the production of GMF-β protein in the thymus, the brain and a thymic epithelial cell line. GMF-β protein prepared by a glutathione-S-transferase gene fusion system greatly influenced T cell development in the in vitro culture system of the embryonic thymus in favor of a significant increase of CD4+ T cells with expression of TCRPβ. These data taken together suggest that GMF-β protein is produced by thymic epithelial cells and plays a role in T cell development in favor of CD4+ T cells.