Evidence for the presence of Thy-1 on cultured thymic epithelial cells of mice and rats.

Thymic tissue of C57BL/6 mice and DA rats was cultured. After 6--8 weeks, cultures were analyzed for their capacity to absorb anti-Thy-1 serum, and for the expression of Thy-1 on the surface of different cell types by means of the indirect peroxidase labeling method. Three main cell types were identified: epithelium-like cells, fibrocyte-like cells and macrophages, but no lymphocytes were found. The presence of Thy-1 on cultured nonlymphocytic thymus-derived cells was demonstrated by their ability to absorb the cytotoxic activity of the appropriate anti-Thy-1 sera. Electron microscopical analyses of labeling experiments revealed that Thy-1 was predominantly expressed on epithelium-like cells with preference for their cell protrusions. The possible role of Thy-1 expression, both on thymocytes and thymus epithelium for cellular interaction, is discussed.