Selective expression of CD8 alpha (Ly-2) subunit on activated thymic gamma/delta cells.

Although most cells of the T cell receptor (TcR) gamma/delta lineage are CD4-CD8-, some gamma/delta cells express CD8. We show here that mouse thymic gamma/delta cells express CD8 following in vitro activation by concanavalin A. Staining with monoclonal and polyclonal antibodies to the CD8 alpha (Ly-2) and CD8 beta (Ly-3) subunits indicates that only CD8 alpha is expressed by these activated TcR gamma/delta cells. Furthermore, immunoprecipitation and reduced/nonreduced gel analysis reveals that thymic gamma/delta cells express CD8 alpha as a homodimer. In contrast, similarly activated TcR alpha/beta cells express a conventional CD8 alpha/CD8 beta heterodimer.