Clonal characterization of a bipotent T cell and NK cell progenitor in themouse fetal thymus

We recently described a population of fetal thymocytes with a CD117(+)NK1.1 (+)CD90(low)CD25(-) phenotype, which were shown to contain committed T cell and NK cell progenitors, However, the characterization of a single cell wi th a restricted T and NK cell precursor potential was lacking, Here, using an in vitro model for T and NK cell differentiation, we provide conclusive evidence demonstrating the existence of a clonal lineage-restricted T and N K cell progenitor. These results establish that fetal thymocytes with a CD1 17(+)NK1.1(+)CD90(low)CD25(-) phenotype represent bipotent T and NK cell pr ogenitors.