Differentiation in Vitro of T 3 + Large Granular Lymphocytes with Characteristic Cytotoxic Activity from an Isolated Hematopoietic Progenitor Colony by Nagahiro Minato , * Masakazu Hattori , § Tetsuo Sudo

Large granular lymphocytes (LGL)' represent a population of lymphoid cells morphologically and functionally distinct from conventional T and B lymphocytes (1), but their exact progenitors as well as differentiation pathway remain largely unclear . We have recently observed that continuous LGL lines could be efficiently generated in vitro by IL-2 from the spleen cells of mice infected with Moloney murine leukemia virus (Mo-MLV) (2). Further analysis revealed that it was IL-3 induced by the retrovirus infection rather than virus itself that was responsible for the phenomenon (2). Thus, it was indicated that the sequential stimulation of normal spleen cells with IL-3 followed by IL-2 in vitro resulted in the selective and continuous proliferation of LGL (2). These observations facilitated our investigation of the role of IL-3 in the early differentiation of LGL . IL-3 is shown to have a number of biological activities, including mast cell growth-promoting activity (3), granulocyte (G)/macrophage (M) colony-stimulating activity (3), pre-B cell-stimulating activity (4), and activity to induce an enzyme 20a-hydroxysteroid dehydrogenase in T-lineage lymphocytes (5). Furthermore, evidence indicates that IL-3 is also involved in the proliferation of pluripotential hematopoietic progenitor cells . It was reported by Suda et al . (6) that IL-3 induced a new class of murine multipotential hematopoietic colonies, termed blast colonies, which had extremely high secondary plating efficiencies in vitro . In the present study, a direct attempt has been made to generate lymphoid cells from such multipotential hematopoietic colonies . The results definitely indicated that LGL with characteristic cytotoxic activity could directly be generated from the isolated hematopoietic progenitor cell colonies . Genetic analysis of TCR genes of the LGL revealed that both y and ,Q chain genes of TCR were rearranged with abundant mRNA for the y chain gene and much