A 60-kDa Thymic Epithelial Cell Surface Protein as a Potent Molecule Mediating the Cellular Interaction with Immature T Cells

A unique 60-kDa surface protein expressed on the thymic epithelial cells was characterized as a potent molecule participating in the interaction between thymic stromal cells (TSC) and immature T cells. Previously, we reported an athymic mouse-derived T cell clone, N-9F, which proliferates on TSC. In the present study, we established a TSC clone, SL10.3, from a BALB/c mouse. SL10.3 has an epithelial cell nature and supports N-9F and fetal thymocytes growth in vitro . The two rat monoclonal antibodies, AS19 and AS32, directed to the SL10.3 cell surface inhibited N-9F and fetal thymocytes growth on SL10.3, suggesting that the reactive molecule may mediate the cellular interaction between TSC and immature T cells. Both antibodies are directed to the same 60-kDa protein with a pl point of 5.4, but to different epitopes on the protein. The 60-kDa protein is distributed on thymic epithelial cells, fibroblasts, and vascular endothelial cells, but not on the hematopoietic cells tested.