Establishment and characterization of mouse thymic epithelial cell lines.

Primary stromal cell cultures from fetal day-16 thymuses of Swiss mice were developed using a combination of D-valine-containing DMEM and Ham's F-12 medium supplemented with epidermal growth factor, insulin and cortisone. Using cloning cylinders and subsequent limiting dilution techniques, we obtained two clones, MTE-1 and MTE-2. The presence of cytokeratin filaments established their epithelial origin. These cells expressed class I and class II MHC antigens after induction by gamma-interferon, and lacked conventional lymphoid cell-surface markers. Their ability to form rosettes with thymocytes should allow us to identify cell-surface antigens involved in thymocyte-epithelial cell interaction. Moreover, these lines will be used to set up in vitro thymocyte maturation assays.