Cloning of human thymic subcapsular cortex epithelial cells with T-lymphocyte binding sites and hemopoietic growth factor activity

The thymic microenvironment involves complex cell interactions among different types of epithelial cells, macrophages, tissue histiocytes, and immature and maturing T cells. We describe the isolation of a subset of thymic epithelial cells by selective primary culture followed by cotransfection with a simian virus 40 replication-origin-defective mutant and pSV2neo plasmid. The cloned cells have the composite immunophenotype that is unique to thymic subcapsular epithelial cells, suggesting that they may provide a model system in vitro for analyzing the earliest steps in T-cell differentiation. This possibility is supported by the finding that these epithelial cells express LFA-3-associated binding sites for T cells, secrete a macrophage hemopoietic growth factor, and synergize with macrophages in the production of interleukin 1.