Expression of T cell antigen receptor β-chains on subsets of mouse thymocytes

The expression on adult mouse thymocytes of a T cell antigen receptor β-chain epitope, recognized by the antibody F23.1, has been studied by three-color flow cytometry. Low density F23.1 staining was found mainly on CD4⁺8⁺ thymocytes. High density staining was mainly on CD4⁺8^- and CD4^-8⁺ cells. Variable proportions of CD4^-8^- cells were also F23.1⁺. Among CD4^-8⁺ cells, F23.1 was expressed only on the J11d^- subset with mature T cell function. We conclude that many subpopulations of thymocytes express antigen receptors and are candidates for the population subject to thymic selection, but at present no single subpopulation makes a convincing claim.