SELECTION OF ANTIBODIES TO CELL-SURFACE DETERMINANTS ON MOUSE THYMIC EPITHELIAL-CELLS USING A PHAGE DISPLAY LIBRARY

The network of thymic epithelium contributes significantly to the thym ic stromal cell environment, which plays a vital role in the generatio n and maturation of thymocytes. Monoclonal antibodies (mAb) have revea led considerable heterogeneity within this epithelial component of the mouse thymic microenvironment, but many of these antibodies recognize epitopes that are located inside the cell and so cannot be used in fu nctional studies. As an alternative approach to isolate antibodies spe cific to thymic epithelium, we used a phage display library expressing single chain Fv antibodies. For selection, a thymic cell suspension w as incubated with the phage display library, and major histocompatibil ity complex class II positive cells, the majority of which are epithel ial, were then specifically selected. Phage bound to these cells were eluted and the selection procedure was repeated for a further five rou nds. Immunohistochemical analysis revealed that these phage antibodies show differential staining of thymic epithelial subsets. Flow cytomet ric analysis of a thymic epithelial cell line using a panel of these a ntibodies demonstrated that they recognize epitopes on the cell surfac e. Furthermore, some of these antibodies also labelled human thymic ep ithelium, suggesting that the epitopes recognized by these antibodies are conserved between human and rodent thymus. Our approach therefore provides a rapid method to select antibodies specific for thymic epith elial cell surface determinants in their native configuration.